T-FLEX MOORINGS

"Tropical Flex" moorings were developed by the Engineering Division at PMEL to replace the Next Generation ATLAS moorings in RAMA and PIRATA as components become obsolete.  T-Flex moorings allow greater flexibility with respect to number and types of instruments that may be deployed, and utilize more commercial off-the-shelf instrumentation. 

T-Flex electronics are housed in drop-in canisters for deployment in a modified ATLAS toroid (filled toroid with 2 wells for canisters; 1 for electronics, the second for an external battery). An iridium modem and antenna are integrated into the T-flex canister. There is also an RF modem on the buoy to enable ship to buoy communications. T-Flex tower modifications include a T-cup handle, cable runs around the lower bars, and an additional mounting pad on top for optional sensors. Eight (8) T-Flex moorings were deployed alongside ATLAS moorings in RAMA and PIRATA between March 2011 and December 2015. A NOAA Technical Memorandum comparing the system performance and data equivalency is in preparation.   The first stand-alone T-Flex was deployed in August, 2015 at 4S 81E. 

Hourly values of all measurements are returned to shore via Iridium satellite, formatted into WMO BUFR code, and placed on the GTS by PMEL. Higher resolution data are logged internally, and downloaded once the mooring is recovered.

TAO REFRESH MOORINGS

TAO Refresh systems were designed by the NOAA's National Data Buoy Center (NDBC) to make observations comparable to legacy ATLAS systems in TAO. All ATLAS moorings in TAO have been replaced with TAO Refresh systems They transmit 10-min data via Iridium, with hourly observations placed on the GTS by NDBC. Additional details on TAO Refresh systems are available at http://tao.ndbc.noaa.gov/proj_overview/mooring_ndbc.shtml.

NEXT GENERATION ATLAS MOORINGS

This effort used as many of the components and procedures of the existing system as possible, thereby minimizing the impact on the infrastructure that supported the array.The first NextGeneration systems were deployed in the array in May 1996. The transition to NextGeneration systems throughout the array was completed in November 2001.

Design of the relatively inexpensive ATLAS (Autonomous Temperature Line Acquisition System) mooring was initiated by PMEL's Engineering Development Division (EDD) in 1984 (see Standard ATLAS Moorings, below). By the mid-1990's, a reengineering effort was underway to modernize the ATLAS mooring with emphasis on: improving data quality adding new sensors increasing temporal resolution of internally recorded data improving reliability to extend system life simplifing fabrication procedures reducing costs

A significant Next Generation ATLAS improvement over the Standard ATLAS is the incorporation of inductively coupled sensors for subsurface data. The sensors clamp onto the wire rope strength member that serves as one of the inductive elements. This simplifies fabrication, eliminating the themistor cable with its labor-intensive assembly and deployment procedures. Addressable modules on the cable allow the system to be expanded for new sensors by adding the appropriate hardware and software interfaces. Flexibility in the design also allows the interface of additional sensors including rainfall, short-wave and long-wave radiation, barometric pressure, ocean salinity and currents. Most measurements are made at a sample rate of 10 minutes, with the exception of barometric pressure (1 hour), short-wave and long-wave radiation (2 minutes), and rainfall (1 minute). These high temporal resolution data are recorded internally and available after mooring recovery.

HISTORICAL STANDARD ATLAS MOORINGS  

After testing and deployment of prototype ATLAS moorings, the first elements of the large scale monitoring TAO array were deployed in the eastern Pacific in November 1984. The full TAO array was eventually completed in December 1994.The standard ATLAS mooring had a design lifetime of one year, and the system proved to be robust and reliable. Over 500 Standard ATLAS moorings were deployed between 1984 and 2001. The final standard ATLAS was recovered in November 2001 and NextGeneration ATLAS moorings are now used exclusively in the TAO array.

Standard ATLAS moorings measured surface winds, air temperature, relative humidity, sea surface temperature, and ten subsurface temperatures from a 500 m long thermistor cable. Daily-mean data were telemetered to shore in near real-time via NOAA's polar-oribiting satellites and Service Argos. A small subset of hourly values (2-3 per day) coinciding with satellite passes were also transmitted in real time. Hourly values of surface data were internally recorded and available after mooring recovery.

SURFACE MOORING HARDWARE

The TAO surface buoy is a 2.3 m diameter fiberglass-over-foam toroid, with an aluminum tower and a stainless steel bridle. When completely rigged, the system has an air weight of approximately 660 kg, a net buoyancy of nearly 2300 kg, and an overall height of 4.9 m. The electronics tube is approximately 1.5 m long, 0.18 m diameter, and weighs 27 kg. The buoy can be seen on radar from 4-8 miles depending on sea conditions.

Non-rotating 3/8" (0.92 cm) diameter wire rope jacketed to 1/2" (1.27 cm) is used in the upper 700 meters to guard against damage from fish bite. Standard ATLAS thermistor cables were fixed to the mooring wire with wire rope clamps. Plaited 8-strand 3/4" (1.9 cm) diameter nylon line is used for the remainder of the mooring. Anchors are fabricated from scrap railroad wheels, and typically weight 1900-2000 kg. All hardware is standard equipment as used in other PMEL taut-line moorings and deployments follow the traditional anchor last routine.

Moorings are deployed in water depths between 1500 and 6000m. To ensure that the upper section of the mooring is nearly vertical a nominal scope of 0.985 (ratio of mooring length to water depth) is employed on the moorings in water depths of 1800m or more. At a few sites, slack moorings with scope 1.35 have been deployed due to either shallow bathymetry or severe current regimes. In these cases, the upper portion of the mooring is keep fairly vertical (but less so than taut-line moorings) by using a reverse catenary design.

NOMINAL HEIGHTS AND DEPTHS OF ATLAS SENSORS

Standard instrument heights for ATLAS mooring meteorological sensors. LWR is Long Wave Radiation sensor, SWR is Short Wave Radiation sensor, Rain is rain gauge, ATRH is air/relative humidity sensor, BP is Barometric Pressure sensor

Meteorological sensor	Wind	LWR	SWR	Rain	ATRH	BP
Height (m)	4 m	3.5 m	3.5 m	3.5 m	3 m	3 m

Standard instrument depths for ATLAS moorings by ocean basin are listed below: SST/C is Sea Surface Temperature and Conductivity sensor. T1, T2, ...., T10 are subsurface thermistors. TP9 and TP10 are subsurface temperature and pressure sensors. TC1,...,TC6 are subsurface temperature and conductivity sensors. TV1 is a velocity measurement made at 10m depth by a Sontek acoustic Doppler current meter. The current meter is cabled to a temperature module at 13m depth, which relays both velocity and temperature data to the surface buoy.

Indian Ocean	SST/C	TC1	TV1	TC2	TC3	TC4	T5	TC6	T7	T8	T9	TP10	TP11
Depths (m), all sites	1	10	10/13	20	40	60	80	100	120	140	180	300	500

CURRENT METER MOORINGS

ACOUSTIC DOPPLER CURRENT METER MOORINGS Subsurface Acoustic Doppler Current Profiler (ADCP) moorings are deployed at a few locations to provide velocity profiles the upper 200-300 m of the water column. ADCP moorings are mostly deployed at equatorial locations where geostrophy breaks down and direct velocity measurements are required. ADCPs are usually deployed in tandem with nearby surface moorings, which may also measure velocity as a backup to the ADCP and/or to provide velocity data near the surface where acoustic backscatter from the sea surface interferes with the ADCP signal. The vertical resolution of the ADCP is about 8 m. ADCP data are available only after the subsurface moorings are recovered.

HISTORICAL CURRENT METER MOORINGS

From the 1980s to the mid-1990s, older style current meter moorings were deployed at a few equatorial sites in the Pacific (0-156E, 0-165E, 0-140W and 0-110W). Upper ocean currents were measured at 4 to 7 discrete depths in the upper 300 m using vector-averaging and vector measuring mechanical current meters. In general, these moorings differed from ATLAS moorings in that no subsurface data were telemetered in real time and in that subsurface data were internally recorded at higher sample rates than Standard ATLAS systems. Between 1990 and 1995, current meter moorings included downward looking Acoustic Doppler Current Profilers (ADCP) mounted in the surface toroidal float and were referred to as PROTEUS (PRofile TElemetry of Upper ocean currentS) moorings. PROTEUS mooring deployments stopped in 1995 because fish backscatter interfered with the acoustic signals and seriously contaminated the velocity measurements.

These older style current meter moorings were eventually replaced by Next Generation ATLAS moorings with paired subsurface ADCP moorings. Instrument depths for the older current-meter moorings were different than for ATLAS moorings and varied over time. For graphical information on these instrument depths, see the TAO data availability page. In NetCDF files used for web displays, temperatures from historical current meter moorings have been regridded to standard ATLAS depths.

TRITON MOORINGS

In October 1999, responsibility for TAO moorings along and to the west of 156E was assumed by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) which has deployed Triangle Trans-Ocean Buoy Network (TRITON) buoys at those locations. Data from both ATLAS and TRITON moorings are merged in a common data base and available from both PMEL and JAMSTEC. M-TRITON moorings, a smaller TRITON mooring also developed by JAMSTEC are deployed in RAMA. Details on TRITON and M-TRITON moorings are available at http://www.jamstec.go.jp/jamstec/TRITON/real_time/overview/ and http://www.jamstec.go.jp/iorgc/iomics/projectoverview/projectoverview_en....

BAILONG MOORINGS

China's First Institute of Oceanography (FIO) has introduced ATLAS-like moorings, known as BaiLong, one of which occupies a RAMA site. A description the mooring system is available at http://rdsea.com/wp-content/uploads/2011/12/Oceans-2011-Final.pdf. Data from this mooring is telemetered to and quality controlled by FIO and made available on the GTMBA data web page.