What does NCEP use for the gravity constant in Reanalysis processing?
[5/5/2000] In nearly all processing, NCEP uses 9.8 exactly as the gravity constant. The only exceptions are that a value of 9.81 is used to compute mass weight variables on isentropic surfaces and to compute pressure levels of the isentropic surfaces. • Is the field called geopotential height of the earth’s surface always the same throughout the entire Reanalysis period?[5/5/2000] The geopotential height of the earth’s surface that is stored in the grbsanl file on the Gaussian grid is derived from the spectral sigma file and the code that does this derivation has changed three times. There was a change on 21 September 1994 and a change on 27 January 1998 which have no effect on the values. A change made on 22 January 1998 did cause some differences and fields before this date will be different from fields after this date. Otherwise this field is the same throughout the period. This change only affects this particular field and only in the grbsanl file. The same field on the 2.5×2.5 lat
