CN115128364B

CN115128364B - Determination method and determination device for observation stability of satellite-borne microwave radiometer

Info

Publication number: CN115128364B
Application number: CN202211059179.9A
Authority: CN
Inventors: 周武; 林明森; 马超飞
Original assignee: NATIONAL SATELLITE OCEAN APPLICATION SERVICE
Current assignee: NATIONAL SATELLITE OCEAN APPLICATION SERVICE
Priority date: 2022-08-31
Filing date: 2022-08-31
Publication date: 2022-11-22
Anticipated expiration: 2042-08-31
Also published as: CN115128364A

Abstract

The application provides a method and a device for determining observation stability of a satellite-borne microwave radiometer, which relate to the technical field of satellite remote sensing and comprise the following steps: screening out a target area from the observation area by using reference brightness temperature data and reanalysis data of a reference satellite-borne microwave radiometer under the target frequency; determining the target ground object emissivity of each target time point according to target brightness temperature data and reanalysis data of a target area observed by a target satellite-borne microwave radiometer in a target polarization mode under a target frequency; and determining the standard deviation of the emissivity of the target ground object as the observation stability of the target satellite-borne microwave radiometer in a predetermined period under the target frequency and the target polarization mode. Therefore, the screened target area can have more stable ground object emissivity, so that the observation stability determined by the standard deviation of the ground object emissivity of the target area is more stable and credible, the target area can be better used for evaluating the observation stability of the satellite-borne microwave radiometer, and higher evaluation precision is achieved.

Description

Method and device for determining observation stability of satellite-borne microwave radiometer

Technical Field

The application relates to the technical field of satellite remote sensing, in particular to a method and a device for determining observation stability of a satellite-borne microwave radiometer.

Background

The satellite-borne microwave radiometer is influenced by various factors such as signal attenuation caused by aging of on-satellite electronic components and system noise change caused by on-satellite environment change, the observation stability of the satellite-borne microwave radiometer changes, system deviation of the observed brightness temperature of the satellite-borne microwave radiometer slowly changes, and therefore observation and inversion results deviate, and data accuracy of the observation and inversion results is influenced.

At present, in the prior art, the observation stability of the satellite-borne microwave radiometer is usually evaluated by counting the brightness and temperature data observed by the satellite-borne microwave radiometer. However, the light temperature data is extremely susceptible to meteorological conditions, so that the accuracy of evaluating the observation stability of the satellite-borne microwave radiometer is insufficient.

Disclosure of Invention

In view of this, an object of the present application is to provide a method and a device for determining observation stability of a satellite-borne microwave radiometer, which can determine a reference ground object emissivity by using reference brightness-temperature data and reanalysis data of a reference satellite-borne microwave radiometer, and then screen out a target area by using the reference ground object emissivity; and taking the standard deviation of the target ground object emissivity of the target satellite-borne microwave radiometer in the target area as the observation stability. Therefore, the screened target area can have more stable ground object emissivity, so that the observation stability determined by the standard deviation of the ground object emissivity of the target area is more stable and credible, the target area can be better used for evaluating the observation stability of the satellite-borne microwave radiometer, and the target area has higher evaluation precision.

The embodiment of the application provides a method for determining observation stability of a satellite-borne microwave radiometer, which comprises the following steps:

acquiring reference brightness temperature data of a reference satellite-borne microwave radiometer under a target frequency, which is observed in different polarization modes in an observation period and aims at an observation area;

according to the reference brightness temperature data and the reanalysis data, determining the reference surface feature emissivity corresponding to each polarization mode of each observation grid region included in the observation region at each observation time point; each observation grid region included in the observation region and each observation time point included in the observation period are obtained by performing space-time matching on the reference brightness temperature data and the reanalysis data;

screening out a target area from the observation area according to the reference ground object emissivity of each observation grid area corresponding to each polarization mode at each observation time point;

acquiring target brightness temperature data of the target area observed by the target satellite-borne microwave radiometer in a target period in a target polarization mode under the target frequency;

determining the target surface object emissivity of the target area at each target time point according to the target brightness temperature data and the reanalysis data;

and counting the standard deviation of the emissivity of the target ground object in the target area in a preset period, and determining the standard deviation of the emissivity of the target ground object as the observation stability of the target satellite-borne microwave radiometer in the preset period under the target frequency and the target polarization mode.

Further, after the determining the target surface object emissivity of the target area at each target time point according to the target brightness and temperature data and the reanalysis data, the determining method further includes:

fitting to obtain a specific relation between the target ground object emissivity and time determined by the target satellite-borne microwave radiometer under the target frequency and the target polarization mode by using the target ground object emissivity corresponding to each target time point; wherein the specific relation comprises the sum of a part of drift of the emissivity of the ground object towards a fixed direction along with the increase of time, a part of periodic variation of the emissivity of the ground object along with the time and a basic emissivity of the ground object.

Further, the formula of the specific relation is expressed as:

in the formula (I), the compound is shown in the specification,

representing the emissivity of the ground object;

represents time;

representing the target frequency;

indicating the julian day corresponding to the target time point,

represents the total day of the year in which the target time point is locatedCounting;

、

、

、

、

and

respectively obtaining coefficients of the specific relational expression obtained by fitting;

a drift part indicating that the emissivity of the ground object increases towards a fixed direction along with time;

representing the part of the ground object emissivity which changes periodically along with time;

indicating the base emissivity of the terrain.

Further, the determining method further includes:

acquiring historical ground object emissivity determined by the target satellite-borne microwave radiometer under the target frequency and the target polarization mode;

and correcting the historical ground object emissivity based on a part that the ground object emissivity increases along with time and drifts towards a fixed direction in the specific relation.

Further, the determining, according to the reference brightness and temperature data and the reanalysis data, a reference surface feature emissivity corresponding to each polarization mode of each observation grid region included in the observation region at each observation time point includes:

performing space-time matching on the space-time information of the reference brightness temperature data and the space-time information of the reanalysis data to obtain reanalysis data of each observation grid region at each observation time point and reference brightness temperature data corresponding to each polarization mode; the reanalysis data includes: atmospheric temperature data, surface temperature data, air pressure data, humidity data and cloud liquid water profile data;

for each observation grid region and each observation time point, calculating the transmittance of an uplink atmospheric radiation, a downlink atmospheric radiation, a total path from the earth surface to the top of the atmosphere and the transmittance of a total path from the top of the atmosphere to the earth surface of the observation grid region at the observation time point corresponding to each polarization mode by using the atmospheric temperature data, the earth surface temperature data, the air pressure data, the humidity data and the cloud liquid water profile data of the observation grid region at the observation time point through a microwave radiation transmission model;

for each polarization mode, the earth surface temperature data of the observation grid region at the observation time point and the reference bright temperature data, the uplink atmospheric radiation, the downlink atmospheric radiation, the transmittance of the total path from the earth surface to the top of the atmosphere and the transmittance of the total path from the top of the atmosphere to the earth surface corresponding to the polarization mode are used for calculating the reference ground object emissivity of the observation grid region at the observation time point corresponding to the polarization mode through the following formula:

in the formula (I), the compound is shown in the specification,

indicating the emissivity of the reference ground object;

representing reference light temperature data;

representing surface temperature data;

represents the ascending atmospheric radiation;

represents the downstream atmospheric radiation;

indicating the transmission of the total path from the surface to the top of the atmosphere,

represents the transmission rate from the top of the atmosphere to the total path of the earth surface;

indicating cold air background radiation.

Further, screening out a target area from the observation area according to the reference ground object emissivity of each observation grid area corresponding to each polarization mode at each observation time point includes:

for each observation grid region, determining the polarization difference of the reference ground object emissivity of the observation grid region according to the reference ground object emissivity corresponding to each polarization mode of the observation grid region at each observation time point, and judging whether the polarization difference is smaller than a preset polarization difference threshold value;

if the polarization difference is smaller than the preset polarization difference threshold value, determining the observation grid area as a first candidate grid area;

screening a plurality of first candidate areas from the observation area according to each first candidate grid area; each first candidate region is composed of at least one first candidate mesh region;

for each first candidate area, according to the reference surface feature emissivity corresponding to each polarization mode of each first candidate grid area at each observation time point included in the first candidate area, determining the reference surface feature emissivity standard deviation corresponding to each polarization mode of the first candidate area and judging whether the reference surface feature emissivity standard deviation is smaller than a preset standard deviation threshold value or not;

and if the standard deviation of the emissivity of the reference ground object is smaller than a preset standard deviation threshold value, determining the first candidate area as the target area.

Further, the reanalysis data also includes liquid water content; for each observation grid region, determining a polarization difference of the reference surface feature emissivity of the observation grid region according to the reference surface feature emissivity corresponding to each polarization mode of the observation grid region at each observation time point, including:

aiming at each observation grid region, screening out at least one candidate observation time point with the liquid water content smaller than a preset liquid water content threshold value from a plurality of observation time points according to the liquid water content of the observation grid region at each observation time point;

selecting any one candidate observation time point from at least one candidate observation time point, calculating the difference value of the reference surface feature emissivity of the observation grid region corresponding to different polarization modes at the candidate observation time point, and determining the difference value as the polarization difference of the reference surface feature emissivity of the observation grid region.

Further, the reanalysis data also comprises water vapor content and liquid water content; for each first candidate region, determining a standard deviation of the reference ground object emissivity corresponding to each polarization mode of each first candidate grid region at each observation time point according to the reference ground object emissivity corresponding to each polarization mode of each first candidate grid region included in the first candidate region, including:

for each first candidate region, determining a water vapor content average value and a liquid water content average value of each first candidate grid region at each observation time point according to the water vapor content and the liquid water content of each first candidate grid region included in the first candidate region;

screening a plurality of candidate observation time points of which the average water vapor content is smaller than a preset water vapor content threshold value and the average liquid water content is smaller than a preset liquid water content threshold value from the plurality of observation time points according to the average water vapor content value and the average liquid water content value of the first candidate region at each observation time point;

for each polarization mode, calculating a reference ground object emissivity average value of each first candidate area according to the reference ground object emissivity of each first candidate grid area included by the first candidate area at each candidate observation time point, and determining the reference ground object emissivity average value as a reference ground object emissivity corresponding to the polarization mode of the first candidate area at the candidate observation time point;

and determining a standard deviation of the reference surface object emissivity related to the observation time dimension corresponding to the polarization mode of the first candidate region according to the reference surface object emissivity corresponding to the polarization mode of the first candidate region at each candidate observation time point.

The embodiment of the present application further provides a device for determining observation stability of a satellite-borne microwave radiometer, where the device for determining observation stability includes:

the first acquisition module is used for acquiring reference brightness temperature data, observed in different polarization modes in an observation period, of a reference satellite-borne microwave radiometer at a target frequency and aiming at an observation region;

the first determination module is used for determining the reference surface feature emissivity of each observation grid region included in the observation region corresponding to each polarization mode at each observation time point according to the reference brightness and temperature data and the reanalysis data; each observation grid region included in the observation region and each observation time point included in the observation period are obtained by performing space-time matching on the reference brightness-temperature data and the reanalysis data;

the screening module is used for screening out a target area from the observation area according to the reference ground object emissivity of each observation grid area corresponding to each polarization mode at each observation time point;

the second acquisition module is used for acquiring target brightness temperature data of the target area observed by the target satellite-borne microwave radiometer at the target frequency in a target period in a target polarization mode;

the second determining module is used for determining the target ground object emissivity of the target area at each target time point according to the target brightness and temperature data and the reanalysis data;

and the statistical module is used for counting the standard deviation of the emissivity of the target ground object in the target area in a preset period and determining the standard deviation of the emissivity of the target ground object as the observation stability of the target satellite-borne microwave radiometer in the preset period under the target frequency and the target polarization mode.

An embodiment of the present application further provides an electronic device, including: a processor, a memory and a bus, the memory storing machine-readable instructions executable by the processor, the processor and the memory communicating via the bus when the electronic device is running, the machine-readable instructions being executable by the processor to perform the steps of a method of determining the observation stability of a microwave-borne radiometer as described above.

An embodiment of the present application further provides a computer-readable storage medium, where a computer program is stored on the computer-readable storage medium, and when the computer program is executed by a processor, the computer program performs the steps of the method for determining the observation stability of the satellite-borne microwave radiometer.

The method and the device for determining the observation stability of the satellite-borne microwave radiometer provided by the embodiment of the application comprise the following steps: acquiring reference brightness temperature data aiming at an observation region, which are observed by a reference satellite-borne microwave radiometer under a target frequency in different polarization modes in an observation period; according to the reference brightness temperature data and the reanalysis data, determining the reference surface feature emissivity corresponding to each polarization mode of each observation grid region included in the observation region at each observation time point; each observation grid region included in the observation region and each observation time point included in the observation period are obtained by performing space-time matching on the reference brightness-temperature data and the reanalysis data; screening out a target area from the observation area according to the reference ground object emissivity corresponding to each polarization mode of each observation grid area at each observation time point; acquiring target brightness temperature data of the target area observed by the target satellite-borne microwave radiometer in a target period in a target polarization mode under the target frequency; determining the target surface object emissivity of the target area at each target time point according to the target brightness temperature data and the reanalysis data; and counting the standard deviation of the emissivity of the target ground object in the target area in a preset period, and determining the standard deviation of the emissivity of the target ground object as the observation stability of the target satellite-borne microwave radiometer in the preset period under the target frequency and the target polarization mode.

Therefore, the screened target area can have more stable ground object emissivity, so that the observation stability determined by the standard deviation of the ground object emissivity of the target area is more stable and credible, the target area can be better used for evaluating the observation stability of the satellite-borne microwave radiometer, and higher evaluation precision is achieved.

In order to make the aforementioned objects, features and advantages of the present application more comprehensible, preferred embodiments accompanied with figures are described in detail below.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained from the drawings without inventive effort.

FIG. 1 is a flow chart illustrating a method for determining the observation stability of a satellite-borne microwave radiometer according to an embodiment of the present disclosure;

FIG. 2 shows one of the schematic structural diagrams of the device for determining the observation stability of the satellite-borne microwave radiometer according to the embodiment of the present application;

fig. 3 shows a second schematic structural diagram of the device for determining the observation stability of the satellite-borne microwave radiometer according to the embodiment of the present application;

fig. 4 shows a schematic structural diagram of an electronic device provided in an embodiment of the present application.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all the embodiments. The components of the embodiments of the present application, generally described and illustrated in the figures herein, can be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present application, presented in the accompanying drawings, is not intended to limit the scope of the claimed application, but is merely representative of selected embodiments of the application. Every other embodiment that one skilled in the art can obtain without inventive effort based on the embodiments of the present application falls within the scope of protection of the present application.

The research shows that the observation stability of the satellite-borne microwave radiometer is changed under the influence of various factors such as signal attenuation caused by aging of on-satellite electronic components, system noise change caused by change of on-satellite environment and the like, so that the system deviation of the observed brightness temperature of the satellite-borne microwave radiometer is slowly changed, the observed and inverted results are shifted, and the data accuracy of the observed and inverted results is influenced.

Based on this, the embodiment of the application provides a method and a device for determining observation stability of a satellite-borne microwave radiometer, and a screened target area can have more stable ground object emissivity, so that the observation stability determined by the standard deviation of the ground object emissivity of the target area is more stable and reliable, and the method and the device can be better used for evaluating the observation stability of the satellite-borne microwave radiometer and have higher evaluation accuracy.

Referring to fig. 1, fig. 1 is a flowchart illustrating a method for determining an observation stability of a satellite-borne microwave radiometer according to an embodiment of the present disclosure. As shown in fig. 1, an embodiment of the present application provides a determination method, including:

s101, acquiring reference brightness temperature data of a reference satellite-borne microwave radiometer under a target frequency, which are observed in different polarization modes in an observation period and aim at an observation area.

It should be noted that the reference space-borne microwave radiometer is another known stable observation space-borne microwave radiometer, and the target frequency is the frequency to be measured of the target space-borne microwave radiometer under study. Different types of satellite-borne microwave radiometers have a number of different observation frequencies, e.g., 10.7GHz, 18.7 GHz, 23.8GHz, 37.0 GHz and 89.0 GHz, etc. And the polarization mode (P), i.e., the vibration direction of the electromagnetic field, the vibration direction of the radio waves used when the satellite-borne microwave radiometer transmits signals to the ground, e.g., the horizontal polarization mode (H) and the vertical polarization mode (V). The different polarization modes include the target polarization mode to be measured by the target satellite-borne microwave radiometer under study.

The observation period may be determined according to experimental requirements, for example, the observation period may be one year or one month. The observation area is an area with relatively stable reference brightness temperature data, so that the influence of misjudgment of observation data change caused by natural weather in the observation area as the observation stability of the satellite-borne microwave radiometer is avoided.

In specific implementation, amazon rainforest regions can be selected as observation regions, tropical rainforests can be selected as reference ground features, and the type of the ground features is dense vegetation. This is because: firstly, the region is covered by dense vegetation throughout the year, and is not easy to change in a long time scale, so that the ground feature is stable and is suitable for being used as an observation region; secondly, the region is wide, and for a satellite-borne microwave radiometer with a relatively high ground resolution (generally more than 20 kilometers), the space scale of Amazon rainforest is large and relatively uniform; thirdly, the human activity density in the region is low, the influence of electronic interference on the satellite-borne microwave radiometer is low, and data are not easily interfered by human, so that the method is also suitable for carrying out statistical analysis on observation stability.

In the step, firstly, a satellite-borne microwave radiometer which is known to have stable observation and has corresponding target frequency is selected as a reference satellite-borne microwave radiometer, and reference brightness temperature data which are observed by the reference satellite-borne microwave radiometer in different polarization modes in an observation period when the reference satellite-borne microwave radiometer works at the target frequency, for example, reference brightness temperature data which are observed by the reference satellite-borne microwave radiometer in a horizontal polarization mode and a vertical polarization mode in the observation region every day in one year are obtained.

However, it should be noted that even in amazon rainforest regions, the meteorological observation data in the region will be naturally changed by the influence of meteorological factors such as the atmosphere and the earth surface temperature, so that a region with more stable meteorological observation data can be further screened out from the observation region in a certain manner as a target region to perform statistical analysis of observation stability, so as to improve the accuracy of the observation stability of the determined satellite-borne microwave radiometer. The manner of screening the target region will be described in detail below.

S102, determining the reference surface feature emissivity corresponding to each polarization mode of each observation grid region included in the observation region at each observation time point according to the reference brightness temperature data and the reanalysis data.

Wherein each observation grid region included in the observation region and each observation time point included in the observation period are obtained by performing space-time matching on the reference brightness-temperature data and the reanalysis data.

It should be noted that the reanalysis data (reanalysis data) is data obtained by a process of re-fusing and optimally integrating various types and sources of observation data with short-term numerical weather forecast products using a perfect (state-of-the-art) data assimilation system. In specific implementation, the 1 degree x 1 degree longitude and latitude grid reanalysis data of the NCEP can be used, and the data is global atmosphere reanalysis data which is jointly developed by the national environmental prediction center (NCEP) and the national atmospheric research center (NCAR) and is lattice point data formed by reanalyzing meteorological data from 1948 to the present in the world by using observation data, prediction modes and an assimilation system. The reanalysis data can comprise atmospheric temperature data, surface temperature data, air pressure data, humidity data, cloud liquid water profile data, water vapor content, liquid water content and the like.

In one possible implementation, step S102 may include:

s1021, performing space-time matching on the space-time information of the reference brightness temperature data and the space-time information of the reanalysis data to obtain reanalysis data of each observation grid region at each observation time point and reference brightness temperature data corresponding to each polarization mode; the reanalysis data includes: atmospheric temperature data, surface temperature data, barometric pressure data, humidity data, and cloud liquid water profile data.

Here, it is highly probable that the spatiotemporal information of the reference brightness temperature data and the spatiotemporal information of the reanalysis data do not match, for example, there is inconsistency in the temporal coverage, temporal resolution, spatial coverage and spatial resolution of the reference brightness temperature data and the reanalysis data.

Therefore, in this step, by performing space-time matching on the space-time information of the reference bright temperature data and the space-time information of the reanalysis data, reanalysis data (reanalysis data includes atmospheric temperature data, surface temperature data, air pressure data, humidity data, cloud liquid water profile data, and the like) of each observation time point included in each observation grid region included in the observation period and reference bright temperature data corresponding to each polarization mode of each observation time point included in each observation grid region included in the observation period can be obtained. In specific implementation, the spatiotemporal matching of the reference brightness temperature data and the reanalysis data can be performed by any means in the prior art, and the present application does not limit the present invention.

And S1022, for each observation grid area and each observation time point, calculating uplink atmospheric radiation, downlink atmospheric radiation, transmittance of a total path from the earth surface to the top of the atmosphere and transmittance of a total path from the top of the atmosphere to the earth surface of the observation grid area at the observation time point corresponding to each polarization mode by using the atmospheric temperature data, the earth surface temperature data, the air pressure data, the humidity data and the cloud liquid water profile data of the observation grid area at the observation time point through a microwave radiation transmission model.

In specific implementation, any method in the prior art may be used to calculate the transmittance of the ascending atmospheric radiation, the descending atmospheric radiation, the total path from the earth surface to the top of the atmosphere, and the transmittance of the total path from the top of the atmosphere to the earth surface of the observation grid region at the observation time point according to the microwave radiation transmission model, for example, the RTM microwave radiation transmission model. For example, the atmospheric temperature data, the surface temperature data, the air pressure data, the humidity data and the cloud liquid water profile data of the observation grid region at the observation time point may be input into an RTM microwave radiation transmission model, and an RTM microwave radiation transmission model is obtained and output, where the upward atmospheric radiation, the downward atmospheric radiation, the transmittance of the total path from the surface to the top of the atmosphere, and the transmittance of the total path from the top of the atmosphere to the top of the atmosphere at the observation time point correspond to the horizontal polarization mode, and the upward atmospheric radiation, the downward atmospheric radiation, the transmittance of the total path from the surface to the top of the atmosphere, and the transmittance of the total path from the top of the atmosphere to the surface corresponding to the vertical polarization mode.

And S1023, aiming at each polarization mode, calculating the reference ground object emissivity of the observation grid area corresponding to the polarization mode at the observation time point by using the ground surface temperature data of the observation grid area at the observation time point and the reference bright temperature data, the uplink atmospheric radiation, the downlink atmospheric radiation, the transmittance of the total path from the ground surface to the top of the atmosphere and the transmittance of the total path from the top of the atmosphere to the ground surface. For example, taking the horizontal polarization manner as an example, the reference ground object emissivity of the observation grid region in the horizontal polarization manner at the observation time point may be calculated by the following formula:

in the formula (I), the compound is shown in the specification,

indicating the emissivity of a reference ground object;

representing reference light temperature data;

representing surface temperature data;

represents the ascending atmospheric radiation;

represents the downstream atmospheric radiation;

representing cold air background radiation, is a constant and approximately equal in different polarization modes.

Through the analysis, the results show that,

、

、

and

are all susceptible to atmospheric changes, and the emissivity of the ground object

The vegetation is basically influenced by the growth distribution of the vegetation, and in amazon rainforest areas, the ground objects are mostly dense tree-type vegetation, the coverage is basically stable for years, the growth change of trees is extremely slow, so the emissivity of the ground objects is changed in the above variables

Is relatively slow and varies much less in magnitude. Therefore, the embodiment of the application adopts the ground object emissivity

The method is used as a calculation basis for judging the observation stability of the satellite-borne microwave radiometer, and the influence of the atmospheric temperature and the earth surface temperature is eliminated through calculation.

Here, the influence of the atmospheric and surface temperature is excluded by formula calculation, rather than by averaging for long-time data statistics, which not only reduces the amount of statistical data and the statistical time required for accumulating data, but also ensures the accuracy of the statistical data.

S103, screening out a target area from the observation area according to the reference ground object emissivity corresponding to each polarization mode of each observation grid area at each observation time point.

In one possible implementation, step S103 may include:

and S1031, aiming at each observation grid region, determining the polarization difference of the reference ground object emissivity of the observation grid region according to the reference ground object emissivity corresponding to each polarization mode of the observation grid region at each observation time point, and judging whether the polarization difference is smaller than a preset polarization difference threshold value.

In this step, the polarization difference of the reference surface feature emissivity of the observation grid region at the observation time point can be determined by the reference surface feature emissivity corresponding to each polarization mode of the observation grid region at the observation time point.

To be explainedIn amazon rainforest, the earth surface is covered with dense vegetation, and therefore the earth surface has characteristics of radiometric isotropy, and therefore, the polarization characteristics thereof are not obvious. Therefore, the emissivity of the ground object can be judged

Judging whether each observation grid region is an isotropic feature ground object or not according to the polarization difference, and further judging whether the observation grid region is a dense-planted covered uniform region or not. Illustratively, this can be judged by the following formula:

in the formula (I), the compound is shown in the specification,

represents a vertical polarization mode;

represents a horizontal polarization mode;

representing a target frequency; 0.01 is a preset polarization difference threshold.

In particular implementations, the reanalysis data further includes liquid water content; for each observation grid region, determining a polarization difference of the reference surface feature emissivity of the observation grid region according to the reference surface feature emissivity corresponding to each polarization mode of the observation grid region at each observation time point, wherein the polarization difference comprises:

the first step is as follows: and aiming at each observation grid region, screening out at least one candidate observation time point with the liquid water content smaller than a preset liquid water content threshold value from a plurality of observation time points according to the liquid water content of the observation grid region at each observation time point.

The second step: selecting any one candidate observation time point from at least one candidate observation time point, calculating the difference value of the reference surface feature emissivity of the observation grid region corresponding to different polarization modes at the candidate observation time point, and determining the difference value as the polarization difference of the reference surface feature emissivity of the observation grid region.

For the high frequency of a satellite-borne microwave radiometer, such as 89GHz high frequency channel (the channel is divided into two dimensions of frequency and polarization mode, for example, 89GHz high frequency channel comprises 89GHz/V, H), the response to the atmospheric cloud layer is particularly obvious, if the liquid water content is higher, the information of the earth surface is covered by the cloud information to a great extent, so that the uniform characteristic of earth surface ground objects is not reflected, but the non-uniformity of the cloud layer is reflected, so that the high frequency channel needs to judge when the liquid water content of the cloud is relatively lower, and the liquid water content of the cloud is less than 0.1mm; because atmospheric oxygen, nitrogen and water vapor are uniform, the uniformity judgment result is not influenced.

S1032, if the polarization difference is smaller than the preset polarization difference threshold value, determining the observation grid area as a first candidate grid area.

S1032, screening a plurality of first candidate areas from the observation area according to each first candidate grid area. Wherein each first candidate region is composed of at least one first candidate mesh region.

In particular, the geographic location of each first candidate grid area may be analyzed to form a first candidate area from a number of geographically adjacent first candidate grid areas exceeding a threshold.

In one experiment, two first candidate regions were screened from the amazon rainforest region of the observation region in the manner described above, using a GMI satellite-borne microwave radiometer (without a 23.8GHz horizontally polarized channel), for example. The annual average of the polarization differences of the two first candidate areas a and B with reference to the surface emissivity at different frequencies is shown in table 1 below:

TABLE 1 annual average of polarization differences of first candidate areas A and B with reference to surface emissivity

Area/frequency	10.7GHz	18.7GHz	37.0GHz	89GHz
					First candidate region A	0.0041	0.0037	0.0032	0.0059
First candidate region B	0.0054	0.0047	0.0043	0.0073

As can be seen from table 1 above, the first candidate areas a and B both satisfy the requirement of the feature uniformity, and in comparison, the feature of the first candidate area a is more uniform than the feature of the first candidate area B.

In this way, by referring to the polarization difference of the ground object emissivity, a plurality of first candidate regions with uniform dense vegetation coverage can be screened from the observation region.

S1033, for each first candidate region, according to a reference ground object emissivity corresponding to each polarization mode of each first candidate grid region at each observation time point included in the first candidate region, determining a reference ground object emissivity standard deviation corresponding to each polarization mode of the first candidate region and judging whether the reference ground object emissivity standard deviation is smaller than a preset standard deviation threshold value.

In this step, statistics of the reference feature standard deviation may be performed according to the time axis in each first candidate region. For example, after the data of each month are averaged, the standard deviation of the average value of each month is calculated, the amplitude of the fluctuation of the reference ground object emissivity can be judged according to the standard deviation, and then the region with the ground object emissivity being stable in the time dimension is screened out from the first candidate regions again.

For example, when the target frequency is 23GHz or 89GHz, whether the standard deviation of the emissivity of the reference ground object is smaller than the preset standard deviation threshold value can be judged by the following formula:

when the target frequency is not 23GHz or 89GHz, whether the standard deviation of the emissivity of the reference ground object is smaller than a preset standard deviation threshold value can be judged through the following formula:

in the formula (I), the compound is shown in the specification,

representing a target frequency;

represents a polarization mode;

represents a month;

represents the number of months;

representing the mean value of the emissivity of the reference ground object.

S1034, if the standard deviation of the emissivity of the reference ground object is smaller than a preset standard deviation threshold, determining the first candidate area as the target area.

In another possible embodiment, the reanalysis data further comprises a water vapor content and a liquid water content; for each first candidate region, determining a standard deviation of the reference ground object emissivity corresponding to each polarization mode of each first candidate grid region at each observation time point according to the reference ground object emissivity corresponding to each polarization mode of each first candidate grid region included in the first candidate region, including:

the first step is as follows: and for each first candidate region, determining the average value of the water vapor content and the average value of the liquid water content of each first candidate grid region included in the first candidate region at each observation time point according to the water vapor content and the liquid water content of the first candidate grid region.

The second step: and screening a plurality of candidate observation time points of which the average water vapor content is smaller than a preset water vapor content threshold value and the average liquid water content is smaller than a preset liquid water content threshold value from the plurality of observation time points according to the average water vapor content and the average liquid water content of the first candidate region at each observation time point.

The third step: and for each polarization mode, calculating a reference ground object emissivity average value of each first candidate grid area included by the first candidate area according to the reference ground object emissivity of each first candidate grid area at each candidate observation time point, and determining the reference ground object emissivity average value as the reference ground object emissivity corresponding to the polarization mode of the first candidate area at the candidate observation time point.

The fourth step: and determining a standard deviation of the reference ground object emissivity of the first candidate region corresponding to the polarization mode with respect to the observation time dimension according to the reference ground object emissivity corresponding to the polarization mode of the first candidate region at each candidate observation time point.

Here, considering that the weather conditions change due to seasonal changes, the emissivity of the reference ground object changes, especially the change of water vapor and the change of liquid water in different months, and the emissivity of the ground object is easily affected by the atmospheric changes in a high-frequency channel, especially 23GHz sensitive to water vapor and 89GHz sensitive to liquid water. Thus, the observation time points can first be screened for moisture content and liquid water content.

After a plurality of candidate observation time points with the average water vapor content smaller than a preset water vapor content threshold value and the average liquid water content smaller than a preset liquid water content threshold value are screened out from the plurality of observation time points, at each candidate observation time point, according to the reference ground object emissivity of each first candidate grid area included by each first candidate area, calculating the average reference ground object emissivity of the first candidate area, and determining the average reference ground object emissivity as the reference ground object emissivity corresponding to the polarization mode of the first candidate area at the candidate observation time point; and then, counting the standard deviation of the emissivity of the reference ground object relative to the observation time dimension corresponding to the polarization mode of the first candidate region.

Illustratively, for any one first candidate region: firstly, aiming at a certain month in a year, assuming that one day is an observation time point, and screening out the observation time point of 20 days from the month according to the average value of the water vapor content and the average value of the liquid water content; then, for each of the 20 days, determining an average value of the reference ground object emissivity of each first candidate grid area included in the first candidate area based on the reference ground object emissivity of the first candidate grid area; then, according to the average value of the reference surface feature emissivity of each day in 20 days, determining the monthly average value of the reference surface feature emissivity of the month; finally, the standard deviation of the reference surface emissivity at 12 months in the year is determined by the monthly average of the reference surface emissivity at each month in the year.

And then, determining the target area from the plurality of first candidate areas according to the standard deviation of the emissivity of the test ground object and a preset standard deviation threshold.

Specifically, if the standard deviation of the emissivity of the reference ground object is smaller than a preset standard deviation threshold value, determining the first candidate area as the target area; if the standard deviation of the emissivity of a plurality of first candidate areas is smaller than a preset standard deviation threshold, the first candidate area with the smallest standard deviation of the emissivity can be comprehensively selected as the target area. In specific implementation, it may also be specified that, when the standard deviation of the reference surface feature emissivity corresponding to each polarization mode is smaller than a preset standard deviation threshold, the first candidate region is determined as the target region.

In one experiment, taking a GMI satellite borne microwave radiometer (without 23.8GHz horizontal polarization channel) as an example, the mean reference standard deviation of the ground emissivity of the two first candidate areas a and B at 12 months in the year was determined in the manner described above as shown in table 2 below:

TABLE 2 mean reference standard deviation of emissivity of terrain for first candidate area A and B years

Frequency (GHz)/region	First candidate region A	First candidate region B
			10.7V	0.0054	0.0078
10.7H	0.0052	0.0078
			18.7V	0.0068	0.0092
18.7H	0.0066	0.0093
			23.8V	0.0109	0.0139
37.0V	0.0067	0.0103
			37.0H	0.0067	0.0106
89.0V	0.0229	0.0416
			89.0H	0.0236	0.0440

As can be seen from table 2 above, in comparison, the reference ground object emissivity of the first candidate region a is much more stable than that of the first candidate region B in the time dimension, the first candidate region B does not satisfy the stability determination requirement at 89GHz, and the first candidate region a satisfies the stability determination requirement at the full frequency band.

S104, acquiring target brightness temperature data of the target area observed by the target satellite-borne microwave radiometer in a target polarization mode in a target period under the target frequency.

In the step, after a target area is determined, target brightness and temperature data of the target area observed by a target space-borne microwave radiometer at the target frequency in a target period in a target polarization mode are obtained. The target polarization may be a horizontal polarization, a vertical polarization, or the like.

And S105, determining the target surface object emissivity of the target area at each target time point according to the target brightness temperature data and the reanalysis data.

Similarly, firstly, performing space-time matching on the target brightness temperature data and the reanalysis data, and determining the target brightness temperature data and the reanalysis data of each target grid area at each target time point, wherein each target grid area included in the target area and each target time point included in the target period are obtained by performing space-time matching on the target brightness temperature data and the reanalysis data; secondly, calculating the target ground object emissivity of each target grid area at the observation time point aiming at each target grid area and each target time point; finally, for each target time point, determining the average value of the target ground object emissivity of each target grid area at the target time point as the target ground object emissivity of the target time point.

Here, according to the target brightness temperature data and the reanalysis data, the specific implementation of determining the target ground object emissivity of the target area at each target time point may refer to the descriptions in S102 to S103, and may achieve the same technical effects, which is not described herein again.

S106, counting the standard deviation of the emissivity of the target ground object in the target area in a preset period, and determining the standard deviation of the emissivity of the target ground object as the observation stability of the target satellite-borne microwave radiometer in the preset period under the target frequency and the target polarization mode.

In this step, a standard deviation of the emissivity of the target surface object in the target area in a predetermined period may be counted according to the emissivity of the target surface object at each target time point, and the standard deviation of the emissivity of the target surface object is determined as the observation stability of the target space-borne microwave radiometer in the predetermined period under the target frequency and the target polarization mode. The detailed description may refer to the description in S103 and achieve the same technical effect, which is not described herein again. Illustratively, the observed stability of the target satellite-borne microwave radiometer at 10.7GHz/V channel can be determined.

The predetermined period may be a day, a cycle, a month, etc., where the cycle represents a repeating orbit period of the satellite, and is determined according to different satellites, and the repeating period of the satellite in the common sun-synchronized orbit is different from 10 days to 14 days.

Therefore, the target area screened out by referring to the reference brightness temperature data and the re-analysis data of the satellite-borne microwave radiometer can have more stable ground object emissivity, so that the observation stability determined by the standard deviation of the ground object emissivity of the target area is more stable and credible, the target area can be better used for evaluating the observation stability of the satellite-borne microwave radiometer, and the target area has higher evaluation precision.

In a possible implementation manner, after determining the target ground object emissivity of the target area at each target time point in step S106, the determining method further includes:

s107, using the target ground object emissivity corresponding to each target time point to fit to obtain a specific relation between the target ground object emissivity and time determined by the target satellite-borne microwave radiometer under the target frequency and the target polarization mode; wherein the specific relation comprises the sum of a part of drift of the emissivity of the ground object towards a fixed direction along with the increase of time, a part of periodic variation of the emissivity of the ground object along with the time and a basic emissivity of the ground object.

In one possible implementation, the formula of the specific relation can be expressed as:

in the formula (I), the compound is shown in the specification,

representing the emissivity of the ground object;

represents time;

representing the target frequency;

indicating the julian day corresponding to the target time point,

represents the total number of days of the year that the target time point is located;

、

、

、

、

and

respectively obtaining coefficients of the specific relational expressions obtained by fitting;

indicating a drift of the emissivity of the terrain in a fixed direction with increasing time,

is the slope of the straight line, i.e., the drift rate;

represents the aboveThe part of the emissivity of the ground object which changes periodically along with the time;

representing the base emissivity of the terrain.

The emissivity change rules of two different conditions can be judged according to the fitting result, and firstly, the target satellite-borne microwave radiometer shows linear drift towards a fixed direction due to the self-observed drift of the target satellite-borne microwave radiometer; secondly, the emissivity of the ground objects of the amazon rainforest is periodically changed in different seasons, mainly due to the periodic growth change of the vegetation in different seasons, but the overall appearance is stable.

In an experiment, when the target frequency is 10.7GHz and the polarization mode is a horizontal polarization mode, the coefficients of the specific relational expression obtained by fitting are shown in table 3 below:

TABLE 3 coefficient table of specific relations

Frequency/coefficient	a0	a1	a2	a3	a 4	a5
							10.7 V	0.000146	0.00693	1.02316	-2.75152	1.00000	0.93679

Further, after the step S107 is to determine the specific relationship between the emissivity of the target ground object and the time by the target space-borne microwave radiometer under the target frequency and the target polarization mode, the determining method further includes:

s108, obtaining historical ground object emissivity determined by the target satellite-borne microwave radiometer under the target frequency and the target polarization mode.

S109, correcting the historical ground object emissivity based on the part that the ground object emissivity increases along with time and drifts towards a fixed direction in the specific relation.

Specifically, based on an expression that the emissivity of the ground object increases with time and drifts towards a fixed direction in a specific relation, the time corresponding to the emissivity of the historical ground object is substituted into the expression to determine the deviation caused by the drift; and further correcting the historical ground object emissivity according to the deviation.

The method for determining the observation stability of the satellite-borne microwave radiometer provided by the embodiment of the application comprises the following steps: acquiring reference brightness temperature data aiming at an observation region, which are observed by a reference satellite-borne microwave radiometer under a target frequency in different polarization modes in an observation period; according to the reference brightness temperature data and the reanalysis data, determining the reference surface feature emissivity corresponding to each polarization mode of each observation grid region included in the observation region at each observation time point; each observation grid region included in the observation region and each observation time point included in the observation period are obtained by performing space-time matching on the reference brightness temperature data and the reanalysis data; screening out a target area from the observation area according to the reference ground object emissivity corresponding to each polarization mode of each observation grid area at each observation time point; acquiring target brightness temperature data of the target area observed by the target satellite-borne microwave radiometer in a target period in a target polarization mode under the target frequency; determining the target ground object emissivity of the target area at each target time point according to the target brightness temperature data and the reanalysis data; and counting the standard deviation of the target ground object emissivity of the target area in a preset period, and determining the standard deviation of the target ground object emissivity as the observation stability of the target space-borne microwave radiometer in the preset period under the target frequency and the target polarization mode.

Therefore, the screened target area can have more stable ground object emissivity, so that the observation stability determined by the standard deviation of the ground object emissivity of the target area is more stable and credible, the target area can be better used for evaluating the observation stability of the satellite-borne microwave radiometer, and the target area has higher evaluation precision.

Referring to fig. 2 and 3, fig. 2 is a schematic structural diagram of an observation stability determining device of a satellite-borne microwave radiometer according to an embodiment of the present disclosure, and fig. 3 is a second schematic structural diagram of the observation stability determining device of the satellite-borne microwave radiometer according to the embodiment of the present disclosure. As shown in fig. 2, the determination device 200 includes:

the first obtaining module 210 is configured to obtain reference brightness temperature data, which are observed by a reference satellite-borne microwave radiometer at a target frequency in different polarization modes in an observation period and are specific to an observation region;

the first determining module 220 is configured to determine, according to the reference brightness and temperature data and the reanalysis data, a reference surface feature emissivity corresponding to each polarization mode of each observation grid region included in the observation region at each observation time point; each observation grid region included in the observation region and each observation time point included in the observation period are obtained by performing space-time matching on the reference brightness-temperature data and the reanalysis data;

the screening module 230 is configured to screen out a target area from each observation area according to the reference ground object emissivity of each observation grid area at each observation time point corresponding to each polarization mode;

a second obtaining module 240, configured to obtain target brightness temperature data of the target region observed by the target space-borne microwave radiometer at the target frequency in a target period in a target polarization manner;

a second determining module 250, configured to determine, according to the target brightness-temperature data and the reanalysis data, a target ground object emissivity of the target area at each target time point;

and the counting module 260 is configured to count a standard deviation of the emissivity of the target ground object in the target area in a predetermined period, and determine the standard deviation of the emissivity of the target ground object as the observation stability of the target space-borne microwave radiometer in the predetermined period under the target frequency and the target polarization mode.

Further, the determining apparatus 200 further includes: a fitting module 270; the fitting module 270 is configured to:

using the target ground object emissivity corresponding to each target time point to obtain a specific relation between the target ground object emissivity and time determined by the target satellite-borne microwave radiometer under the target frequency and the target polarization mode through fitting; wherein the specific relation comprises the sum of a part of drift of the emissivity of the ground object towards a fixed direction along with the increase of time, a part of periodic variation of the emissivity of the ground object along with the time and a basic emissivity of the ground object.

Further, the formula of the specific relation is expressed as:

in the formula (I), the compound is shown in the specification,

representing the emissivity of the ground object;

represents time;

representing the target frequency;

indicating the julian day corresponding to the target time point,

represents the total number of days of the year in which the target time point is located;

、

、

、

、

and

representing the part of the terrain emissivity which changes periodically with time;

indicating the base emissivity of the terrain.

Further, the determining apparatus 200 further includes a modification module 280; the modification module 280 is configured to:

and correcting the historical ground object emissivity based on the part that the ground object emissivity increases along with time in the specific relation and drifts towards a fixed direction.

Further, when the first determining module 220 is configured to determine, according to the reference brightness and temperature data and the reanalysis data, a reference surface feature emissivity corresponding to each polarization mode of each observation grid region included in the observation region at each observation time point, the first determining module 220 is configured to:

in the formula (I), the compound is shown in the specification,

indicating the emissivity of the reference ground object;

representing reference light temperature data;

representing surface temperature data;

represents the ascending atmospheric radiation;

representing the downstream atmospheric radiation;

indicating cold air background radiation.

Further, when the screening module 230 is configured to screen out a target area from the observation area according to the reference ground object emissivity of each observation grid area at each observation time point corresponding to each polarization manner, the screening module 230 is configured to:

if the polarization difference is smaller than the preset polarization difference threshold value, determining the observed grid area as a first candidate grid area;

screening out a plurality of first candidate regions from the observation region according to each first candidate grid region; each first candidate region is composed of at least one first candidate mesh region;

Further, the reanalysis data also includes liquid water content; for each observation grid region, when the screening module 230 is configured to determine a polarization difference of the reference surface feature emissivity of the observation grid region according to the reference surface feature emissivity of the observation grid region corresponding to each polarization manner at each observation time point, the screening module 230 is configured to:

selecting any one candidate observation time point from at least one candidate observation time point, calculating the difference value of the reference ground object emissivity of the observation grid region corresponding to different polarization modes at the candidate observation time point, and determining the difference value as the polarization difference of the reference ground object emissivity of the observation grid region.

Further, the reanalysis data also comprises water vapor content and liquid water content; for each first candidate region, when the screening module 230 is configured to determine, according to the reference surface feature emissivity corresponding to each polarization manner of each first candidate grid region included in the first candidate region at each observation time point, the reference surface feature emissivity standard deviation corresponding to each polarization manner of the first candidate region, the screening module 230 is configured to:

for each first candidate region, at each observation time point, determining the average value of the water vapor content and the average value of the liquid water content of the first candidate region at the observation time point according to the water vapor content and the liquid water content of each first candidate grid region included in the first candidate region;

for each polarization mode, at each candidate observation time point, calculating an average value of the reference ground object emissivity of each first candidate grid area included by the first candidate area according to the reference ground object emissivity of the first candidate grid area, and determining the average value of the reference ground object emissivity as a reference ground object emissivity corresponding to the polarization mode of the first candidate area at the candidate observation time point;

and determining a standard deviation of the reference ground object emissivity of the first candidate region corresponding to the polarization mode with respect to the observation time dimension according to the reference ground object emissivity corresponding to the polarization mode of the first candidate region at each candidate observation time point.

Referring to fig. 4, fig. 4 is a schematic structural diagram of an electronic device according to an embodiment of the present disclosure. As shown in fig. 4, the electronic device 400 includes a processor 410, a memory 420, and a bus 430.

The memory 420 stores machine-readable instructions executable by the processor 410, when the electronic device 400 runs, the processor 410 communicates with the memory 420 through the bus 430, and when the machine-readable instructions are executed by the processor 410, the steps of the method for determining the observation stability of the satellite-borne microwave radiometer in the method embodiment shown in fig. 1 may be executed.

An embodiment of the present application further provides a computer-readable storage medium, where a computer program is stored on the computer-readable storage medium, and when the computer program is executed by a processor, the step of the method for determining the observation stability of a satellite-borne microwave radiometer in the method embodiment shown in fig. 1 may be executed.

It can be clearly understood by those skilled in the art that, for convenience and simplicity of description, the specific working processes of the above-described systems, apparatuses and units may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.

In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus and method may be implemented in other ways. The above-described embodiments of the apparatus are merely illustrative, and for example, the division of the units is only one logical division, and there may be other divisions when actually implemented, and for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection of devices or units through some communication interfaces, and may be in an electrical, mechanical or other form.

The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.

In addition, functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit.

The functions, if implemented in the form of software functional units and sold or used as a stand-alone product, may be stored in a non-volatile computer-readable storage medium executable by a processor. Based on such understanding, the technical solution of the present application or portions thereof that substantially contribute to the prior art may be embodied in the form of a software product stored in a storage medium and including instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present application. And the aforementioned storage medium includes: various media capable of storing program codes, such as a usb disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk, or an optical disk.

Finally, it should be noted that: the above-mentioned embodiments are only specific embodiments of the present application, and are used for illustrating the technical solutions of the present application, but not limiting the same, and the scope of the present application is not limited thereto, and although the present application is described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: those skilled in the art can still make modifications or changes to the embodiments described in the foregoing embodiments, or make equivalent substitutions for some features, within the technical scope of the present disclosure; such modifications, changes or substitutions do not depart from the spirit and scope of the exemplary embodiments of the present application, and are intended to be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A method for determining observation stability of a satellite-borne microwave radiometer is characterized by comprising the following steps:

acquiring reference brightness temperature data aiming at an observation region, which are observed by a reference satellite-borne microwave radiometer under a target frequency in different polarization modes in an observation period;

according to the reference brightness temperature data and the reanalysis data, determining the reference surface feature emissivity corresponding to each polarization mode of each observation grid region included in the observation region at each observation time point; each observation grid region included in the observation region and each observation time point included in the observation period are obtained by performing space-time matching on the reference brightness-temperature data and the reanalysis data;

screening out a target area from the observation area according to the reference ground object emissivity corresponding to each polarization mode of each observation grid area at each observation time point;

counting the standard deviation of the emissivity of the target ground object in the target area in a preset period, and determining the standard deviation of the emissivity of the target ground object as the observation stability of the target satellite-borne microwave radiometer in the preset period under the target frequency and the target polarization mode;

screening out a target area from the observation area according to the reference ground object emissivity corresponding to each polarization mode of each observation grid area at each observation time point, wherein the screening comprises the following steps:

2. The method of claim 1, wherein after said determining a target surface object emissivity of the target area at each target time point from the target light temperature data and the reanalysis data, the method further comprises:

3. The determination method according to claim 2, characterized in that the formula of the specific relational expression is expressed as:

in the formula (I), the compound is shown in the specification,

expressing the emissivity of the ground object;

represents time;

representing the target frequency;

indicating the julian day corresponding to the target time point,

、

、

、

、

and

a drift portion indicating an increase in emissivity of the terrain over time toward a fixed direction;

indicating the base emissivity of the terrain.

4. The determination method according to claim 2 or 3, characterized in that the determination method further comprises:

5. The method for determining the reference surface feature emissivity of each observation grid region included in the observation region according to the reference brightness and temperature data and the reanalysis data, wherein the determination of the reference surface feature emissivity corresponding to each polarization mode of each observation grid region at each observation time point comprises the following steps:

performing space-time matching on the space-time information of the reference brightness temperature data and the space-time information of the reanalysis data to obtain reanalysis data of each observation grid area at each observation time point and reference brightness temperature data corresponding to each polarization mode; the reanalysis data includes: atmospheric temperature data, surface temperature data, air pressure data, humidity data and cloud liquid water profile data;

in the formula (I), the compound is shown in the specification,

indicating the emissivity of the reference ground object;

representing reference light temperature data;

representing surface temperature data;

represents the ascending atmospheric radiation;

representing the downstream atmospheric radiation;

indicating cold air background radiation.

6. The determination method of claim 1, wherein the reanalysis data further comprises liquid water content; for each observation grid region, determining a polarization difference of the reference surface feature emissivity of the observation grid region according to the reference surface feature emissivity corresponding to each polarization mode of the observation grid region at each observation time point, wherein the polarization difference comprises:

7. The method of determining of claim 1, wherein said reanalysis data further comprises a water vapor content and a liquid water content; for each first candidate region, determining a standard deviation of the reference ground object emissivity corresponding to each polarization mode of each first candidate grid region at each observation time point according to the reference ground object emissivity corresponding to each polarization mode of each first candidate grid region included in the first candidate region, including:

8. A device for determining observation stability of a space-borne microwave radiometer, comprising:

the screening module is used for screening out a target area from the observation area according to the reference ground object emissivity corresponding to each polarization mode of each observation grid area at each observation time point;

the statistical module is used for counting the standard deviation of the emissivity of the target ground object in the target area in a preset period and determining the standard deviation of the emissivity of the target ground object as the observation stability of the target satellite-borne microwave radiometer in the preset period under the target frequency and the target polarization mode;

further, when the screening module is configured to screen out a target area from the observation area according to the reference surface feature emissivity of each observation grid area corresponding to each polarization manner at each observation time point, the screening module is configured to:

9. An electronic device, comprising: a processor, a memory and a bus, the memory storing machine-readable instructions executable by the processor, the processor and the memory communicating via the bus when the electronic device is running, the machine-readable instructions being executable by the processor to perform the steps of the method of determining the observation stability of a microwave-borne radiometer according to any of claims 1 to 7.

10. A computer-readable storage medium, characterized in that the computer-readable storage medium has stored thereon a computer program which, when being executed by a processor, carries out the steps of the method for determining the observation stability of a microwave radiometer on board a satellite, according to any one of claims 1 to 7.