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Overview of data products

The UWM/COADS data set is a collection of global raw and analyzed gridded fields covering the period from January 1945 to December 1989. These fields have been derived primarily from individual observations in COADS (see section 3), with additional corrections as described in section 6. Our quality control procedure uses a more stringent criterion over regions climatologically covered by sea ice; the climatological ice mask used was derived from the sea surface temperature and sea ice data set by Alexander and Mobley (1976). In the calculation of buoyancy fluxes (section 7) we use the recent estimates of monthly mean salinity by Levitus et al. (1994). These two data sets are included in UWM/COADS for the sake of completeness.

The data set is organized in 5 main subsets:

Directly Observed Quantities.
This subset contains the most basic surface marine parameters entering our calculations. Although monthly mean nonlinear fluxes cannot be directly derived from the monthly means of these parameters, many of the qualitative features in the fluxes can be traced to the seasonal and interannual characteristics of these basic fields. See Table 1 for a list of these quantities.

Heat and Momentum Fluxes.
This subset includes estimates of wind stress, sensible and latent heat fluxes, as well as radiational fluxes at the ocean surface. The wind speed entering these calculations has been corrected according to our revised Beaufort equivalent scale (section 5). This correction eliminates much of the bias and artificial trends associated with the erroneous WMO Code 1100 scale used in COADS Release 1. Transfer coefficients are based on Large and Pond (1981, 1982). The estimates of heat and radiational fluxes, when combined to form the net heat flux at the ocean surface, do not yield a physically plausible implied oceanic heat transport. This problem is circumvented by a simple linear inverse calculation which provides a systematic way to fine tune parameters in the bulk formulas (section 9). Gridded sensitivity parameters are included in this subset to allow users to experiment with different ways of constraining the surface fluxes.

Fresh Water Fluxes.
This subset includes estimates of evaporation, precipitation, and the corresponding buoyancy fluxes based on Levitus et al. (1994) climatological sea surface salinity.

Miscellaneous Derived Quantities.
This subset contains several derived quantities of general interest, most of which are available in the original COADS Monthly Mean Summaries. Refer to Table 1 for a list of these parameters.

Number of Observations.
The distribution of surface marine data is highly variable in space and time. The surface marine observing system is clearly not adequate to truly resolve global anomalies, especially in the decade following World War II. Even today, large portions of the tropics and the southern oceans are extremely under-sampled. However, there is no simple way to determine the validity of our analysis over the oceans. Some regions of the tropics that were void of data in the early years have experienced an increase in coverage throughout the years. In order to assist users determining the reliability of our analyses we have included files with the number of observations for some of the basic quantities. Some issues related to sampling and fair weather bias are addressed in section 10.

The data is stored using Unidata's Network Common Data Format (NetCDF) described in Rew et al. (1993). NetCDF is self-describing and system-independent software for storing scientific data and is currently available for most Unix workstations, supercomputers and personal computers. A description of the UWM/COADS data formats, FORTRAN subroutines needed to read the data, and a description of NetCDF commands can be found in Appendices C-E. FORTRAN access software and examples of how to read the data are also included in the data distribution.

The objectively analyzed anomaly and climatology files are listed in Table 1. The companion raw (non-analyzed) monthly mean files appear in Table 2. Table 3 lists files with analyzed climatological statistics such as means, standard deviations and number of observations (see section 8 for definitions of these statistics).



Next: Data source and Up: Atlas of Surface Previous: Introduction


Fri Oct 20 12:28:33 EDT 1995