This is the last version of the TRMM-formatted, in HDF4 format, Combined (Radar-Radiometer) product, which is in a state of permanent preservation. New version that is consistently processed with Global precipitation Measurement (GPM) algorithms, and in a concistent with GPM HDF5 format, is available under short name GPM_3CMB_TRMM. Note that new TRMM Daily Combined product has now been made available: GPM_3CMB_TRMM_DAY.
The dataset TRMM_3B31 uses the high quality retrievals done for the narrow swath in 2B31 to calibrate the wide swath retrievals generated in 2A12. For each 0.5 degree box and each vertical layer, an adjustment ratio is calculated for the swath overlap region for one month. Only TMI pixels with 2A12 pixelStatus equal to zero are included in monthly averages, which effectively removes sea ice.