TAO Data Download README

Data available free of charge. User assumes all risks for use of data. NDBC requests user to display citation (“These data were collected and made freely available by NOAA/NDBC.”) in any publication or product using data. User is asked to contact NDBC prior to any commercial use of data.

The temporal resolution of internally recorded data has changed with time due to technological improvements and evolving scientific priorities. Therefore, several choices can be made. For further information see the Sampling) and Sensor pages. High resolution data can include 1-minute, 2-minute, 10-minute, 20-minute, 30-minute and/or hourly data.

Data Time Reference

All dates and times in files are referenced to GMT time, ascii files are specified as two integers, such as "20250831 235000", which means 2025 August 31 at 11:50:00 pm GMT.

Data Quality Codes(Q)

0 = unknown
1 = good data
2 = probably good data
3 = questionable data
4 = bad data
5 = adjusted data
9 = missing data

Data Mode Codes(M)

R = real-time data
P = provisional data
D = delayed mode data
M = mixed real-time and delayed mode data

Measurement Information

Sea Level Barometric Pressure

Sea Level Pressure first became available in the TAO array in April 2000, and is presently available only at East Pacific sites.

Surface Meteorological Data:

Surface met data are delivered in these files as a package for the period after 1989 when relative humidity first became available. Sea surface temperature, air temperature, and winds are available before 1989 at several sites, and since 1980 at 0,110W. Winds use the oceanographic convention. A wind with zonal and meridional components of 1.0 and 1.0 is blowing toward the Northeast. Daily averaged wind speeds and directions are based on daily averaged wind velocity components. Wind speed and wind components are in units of meters per second, direction is in degrees clockwise from true north, air temperature and sea surface temperature are in degrees celsius, and relative humidity is in percent.

ATLAS buoys used in TAO measure meteorological and oceanographic data at the following heights and depths relative to mean sea level:

• Winds: 4.0 meters height
• Relative Humidity: 3.0 meters height
• Air Temperature: 3.0 meters height
• Sea Surface Temperature: 1.0 meters depth

TRITON buoys replaced ATLAS buoys in the Pacific west of 160E beginning in 1999. TRITON buoys measure meteorological and oceanographic data at the following heights and depths relative to mean sea level:

• Winds: 3.5 meters height
• Relative Humidity: 2.2 meters height
• Air Temperature: 2.2 meters height
• Sea Surface Temperature: 1.5 meters depth

In ascii files organized by site, these depth and height differences are explicitly distinguished. The study by Freitag et al ("Calibration procedures and instrumental accuracies for ATLAS wind measurements", NOAA. Tech. Memo. OAR PMEL-119, 2001) discovered a systematic error in standard and NextGeneration ATLAS wind directions of approximately 6.8 degrees in the counterclockwise direction. This error was present possibly as far back as 1984. Modifications were made to the NextGeneration ATLAS system in 2000 to correct this error in subsequent deployments, and archived NextGeneration ATLAS wind directions were corrected (both daily averages and high resolution datasets) on 28 March 2002.

Standard ATLAS wind directions have not been corrected in the archives since the exact time when the error began to affect the measurements is unknown. Standard ATLAS were used exclusively between 1984 and 1996 when NextGeneration ATLAS moorings began to replace them. By November 2001, the standard ATLAS had been phased out and the array was comprised entirely of NextGeneration systems. Expected RMS error for standard ATLAS wind direction is 7.8 degrees (of which 6.8 degrees is a bias) while expected RMS error for NextGeneration ATLAS wind directions is about +/- 5 degrees with no appreciable bias.

Sea Surface Temperature

Sea surface temperature (SST) data begin in 1977 and continue to the present at sites located across the Tropical Pacific and Atlantic.

ATLAS buoys used in TAO measure SST at a depth of 1 m. TRITON buoys replaced ATLAS buoys in the Pacific west of 160E beginning in 1999. TRITON buoys measure SST at depth of 1.5 m. ATLAS and TRITON SST depths are explicitly distinguished in ascii files organized by site.

Upper Ocean Temperatures

Upper ocean temperatures between the sea surface (1 m) and 500 m depth began in 1977 and continue to the present at sites located across the Tropical Pacific. TRITON buoys replaced ATLAS buoys in the Pacific west of 160E beginning in 1999. For TRITON buoys, SST is measured at 1.5 m depth, and the deepest temperature is measured at 750 meters.

Salinity

Salinity data begin in 1987 and continue to the present at sites located across the Tropical Pacific. Salinity is in practical salinity units (PSU).

Density (sigma-theta)

Conductivity and temperature are first used to compute salinity, which is then combined with potential temperature to compute the potential density anomaly (sigma-theta) defined as

sigma-theta = 1/V(S,Theta,P) - 1000 kg m-3

where V is specific volume, S is salinity, Theta is potential temperature, and P is set to zero.

The algorithm used is from "Algorithms for computation of fundamental properties of seawater" by Fofonoff and Millard (UNESCO technical papers in marine science, 44, 1983).

Current

Fixed depth current measurents prior to 2000 were made with mechanical current meters, ie., either Vector Averaging Current Meters (VACM) which employed a Savonious rotor and vane, or Vector Measuring Current Meters (VMCM) which employed orthogonal rotors. After 2000, measurements were made with Sontek Argonaut single-point, acoustic-doppler current meters.

Buoy Position

Time series of buoy latitude and longitude are available for users interested in exact buoy positions. Location accuracies vary from 300 m to 1000 m. GPS is now used for position fixes on Refresh buoys. TAO surface buoys, while anchored to the sea floor, may change location by up to 4 km in response to variable winds and currents. This motion arises because nylon mooring lines stretch when dynamcal forces put stresses on the buoy system. During annual recovery cruises, moorings are typically redeployed within a few kilometers of the previous location, but on occasion they have been relocated by tens of kilometers. In addition, a few moorings have broken free of their anchor and drifted. Environmental data from moorings which have drifted more than 1 degree of latitude or 5 degrees of longitude are excluded from the data base.

TAO NetCDF Files Convention

A TAO station at a site is designated by a string in the format of 'T' + [Site Nominal Location]. For example, the station at the nominal location 0N 110W is named as 'T0N110W'. A TAO deployment is an instrumented platform performing observations for a period of time. Changes to the instrumentation or to the spatial characteristics of the platform or its instruments constitute the end of the deployment. Deployment names starting with 'DM' are for TAO Refresh buoys and others for TAO Legacy buoys. A TAO NetCDF file name follows the format 'TAO' + '_' + [Station Name] + '_' + [Deployment Name-YYYYMMDD] + '_' + [Data Mode] + '_' + *.nc. 'YYYYMMDD' indicates the deployment start year (YYYY) and month (MM) and day (DD). For some historical data files, 'AGGREG' is used in place of the deployment name to indicate it is an aggregated dataset covering multiple deployment periods.