Change in letter on GMI NRT GPROF data products
Effective on the date and time above, all the NRY GPROF data product verson numbers were changed by increasing the letter of the data product version. This letter change means that data products were changed but no backward processing is undertaken. Only the products forward of the date/time have been altered. So, for GMI GPROF the vesion changed from V05A to V05B. Other instrument GPROF retrievals had a similar change but appropriate to their starting data product version.
The algorithm itself did not change but some of the database profiles did. The algorithm team provided the following information:
A monthly emissivity class file is used within the surface type assignment to define the GPROF surface class and thus select similar database profiles. While examining IMERG data in a new polar stereographic projection, many areas of erroneous precipitation (very high precipitation rates) were observed. This was found to be caused by incomplete and incorrect assignment of the surface type in Northern Canada and Greenland. Using an Autosnow created climatology, these surface types were changed in the GPROF ancillary files to a new snow class, instead of a open water classification. The result greatly reduced the retrievals of anomalous high precipitation, and occur only over the areas highlighted in the following figure. Precipitation retrievals in ALL other areas are not affected.