Why there is an extra “A” in 3B42 and 3B43 file names after May 2007?
Due to changes in the AMSU calibration, all 3B42 and 3B43 granules starting in May 2007 and continuing for the remainder of the Version 6 processing cycle will now have the designation “6A” to indicate this change. Full announcement for TRMM Data Users – Due to changes in the AMSU calibration, all 3B42 and 3B43 granules starting in May 2007 and continuing for the remainder of the Version 6 processing cycle will now have the designation “6A” to indicate this change. One of the inputs to 3B42 and 3B43 is AMSU-B data processed by NOAA. NOAA began processing with a new version of their algorithm May 31, 2007 around 1800 UTC. 3B42 and 3B43 had to change to use the new AMSU-B. Since both 3B42 and 3B43 use data from the entire month, all 3B42 and 3B43 for May 2007 forward have the filename version 6A and the algorithm version 6.43. Additional info can be found at the link below: ftp://precip.gsfc.nasa.gov/pub/trmmdocs/3B42_3B43_doc.
