In the Arctic Region, the monthly fields were created by fitting the Winter and Summer PHC 3.0 fields to a cycloid-sinusoid function. Outside of the Arctic Region, the monthly fields mimic those found in NODC's WOA. You'll find more details about how we created these fields by clicking on the PHC 2.1 link found on the PHC Technical Details page of this site.Field Depths
A Special Note About These Monthly Fields
Note that in PHC 3.0, the average of the monthly fields March, April, and May is not necessarily identical to the seasonal MAM fields. Why is this?
PHC2.0: The winter Tmin/Smax is set at mid-April. This means that the average of the monthly fields M, A, and M is not necessarily the same as the seasonal winter MAM field.
PHC 2.1: This was corrected by iterating the monthly cycloid function until monthly and seasonal fields were identical. Unfortunately, this sometimes involves a freezing point correction (see link HERE) which can lead to a rather sharp temporal discontinuity between months, e.g., very rapid and discontinuous warming from May to June.
PHC 3.0: These discontinuities are more troublesome to us than maintaining strict consistency between monthly and seasonal fields, so we modified the PHC 2.1 method slightly in PHC 3.0: We corrected to freezing when the iteration creates sub-freezing values, but we did not then make corrections so that monthly averages equal the seasonal fields.
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