Late on March 2, 2016, the GPM NRT system will begin using V04 algorithms for:

• Level 1B GMI
• Level 1C GMI
• Level 1 Radar
• Level 2 Radar
• Level 2 Combined

V04 is the first version that uses GPM as the calibrator for the constellation rather than TRMM. The GPROF database is built using the combined observations. GMI is extremely well calibrated and the brightness temperatures in 1B and 1C are an important improvement over those in V03.

V04 also made improved retrievals in the Ku, Ka, and DPR Level 2 products. Combined has also made retrieval improvements in this version.

GPROF the algorithm used for radiometer retrievals will remain at V03 until approximately April 15. This was necessary because of late bug fixes  to combined that impacted the database creation the GPROF uses and was built 
using an earlier version of the combined retrievals.

The IMERG product will be affected by the conversion to V04 as it will not update its version for another 3 months.  To minimize the impact of changes. 1C for partner constellation radiometers remains at the current version and are not yet inter-calibrated to GMI. The GPROF also remains at the current version.  Because the combined product is used for calibration as part of the IMERG system, it will not be updated during the period in which GPROF remains at V03.  Intercalibrating GPROF V3 with combined V04 could lead to major retrievals biases. Hopefully these measures will minimize the impact of GPROF remaining at V03 until mid-April
while the radar and combined as well as GMI 1B/1C will be updated to V04. IMERG is not scheduled for V04 until June/July timeperiod.

No major file modifications were made to any of the V04 products. So your existing software should continue to be able to read V04 without changes.