---------------------------------------------------------------------- Interpolated T and S from World Ocean Atlas 2001 1/4 deg Climatology ---------------------------------------------------------------------- Barry Klinger, 7/29/05, 7/12/07 George Mason University Climate Dynamics Dept and Center for Ocean-Land-Atmosphere Studies Introduction ------------ The National Ocean Data Center has created a number of data products describing the global distribution of ocean temperature, salinity, and other fields. The World Ocean Atlas is a gridded climatology which has been created over the years in different versions (WOA 1994, WOA 1998, WOA 2001, and WOA 2005) and is available from www.nodc.noa.gov/OC5/indprod.html. Sometimes the climatologies are referred to as "Levitus" after Sydney Levitus, who has lead the effort to create them. The data here is from the WOA 2001 1/4 degree climatology (henceforth WOA01-1/4). Other versions of WOA are very highly smoothed, so that each grid point is based on a weighted average of nearby points. The weighting function for including points is a Gaussian with a full width at half maximum (FWHM) of at least 220 km. This tends to severely smooth features that are less than about 200 km wide, such as features associated with western boundary currents, equatorial features, and coastal upwelling. WOA01-1/4 uses a FWHM of 107 km and does a much better job of revealing important narrow oceanographic features. WOA01-1/4 does not resolve features well which are smaller than about 100 km, so the 1/4 degree resolution of the data set is not really necessary. The data set in this directory is averaged to 1/2 degree resolution, which makes files smaller and hence easier to work with. The files here are also smaller than the original because data is converted from ascii to binary format. Data Files ---------- All data is in /data/overturning/NODC/WOA01 on the COLA computer system. If you do not have access to these computers and would like to use the data, please email me and I will be happy to make the data available to you. T = in situ temperature S = salinity GrADS format files: *b.dat (floating point format) Matlab format files: *.dat (int16 format) "ann": annual average climatology (33 levels) "03" "06: etc: monthly climatology (24 levels) I have provided a few sample .ctl files: Tannb.ctl, Sannb.ctl, T03b.ctl. Currently I have .dat files for annual and months 3,6,9,12. I may include all 12 months for T and S if there is strong interest. Contents of Files ----------------- Files are derived from data downloaded from: www.nodc.noa.gov/OC5/WOA01/qd_ts01.html Original data was in O(200 Mbyte) long ascii files on a 1/4 degree global grid. Data was averaged to 1/2 deg grid (using ocean-points only) and written to Matlab files with createhalf.m. Data was converted from Matlab format to GrADS format with converthalf.m. In theory the Matlab format files should be readable by GrADS because they are simply binary files (see Tann.ctl and Tannxy.ctl) but I had trouble making this work. To save space, the Matlab files store integer variables (T',S'). To convert to actual values (T,S), use these formula: T = T'/1000 S = 30 + S'/1000. A script for reading a subset of the data into Matlab and making the above conversion is provided: gethalf.m. See gethalf.m for documentation. Each file consists of 25 or 33 levels of 359X720 gridpoints. Lat coordinates are -89.5 to 89.5, lon coordinates are .5 to 360, and z levels are standard WOA01 levels (see for instance Tannb.ctl or gethalf.m for values).