Anomalous Values in PHC 2.0

Some mildly anomalous values were discovered in the GIN sea region (thanks to Dr. M-N Houssais, Paris), i.e., differences between WOA98 and PHC2.0 of greater than 0.02 (mostly in T, but occasionally in S). The cause is closely spaced input data (owing to the convergence of meridians in WOA98 data) which gives OI difficulty when errors are low. Similar behavior was observed and fixed near Antarctica by increasing WOA98 error values (from 0.001 to 0.01, still quite small). This procedure wasn't as satisfactory in the GIN sea (owing to the presence of complex bathymetry which forces the solution to use input values far from the interpolation point). Instead, we simply replaced GIN sea PHC points that differed from WOA98 values by greater than 0.02 (T and S) with WOA98 values. This was done for all fields at all depths. The GIN sea is here defined by latitudes betwenn 65.5N and 85.5N, and longitudes between 315.5E and 55.5E. For the winter season, the affected points represent 0 to 4.5% of the total number of points at each level within the GIN sea, and may be examined in the difference plots provides here:

Winter Salinity
Winter Temperature

The improved PHC 2.0 fields are available on the Data Download page. They are gzipped, and named exactly like the originals, except that they have an added ".p" in the name to distinguish them. The winter temperature file, for example, is named: Temp13.98.p.obj.gz.

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