In an effort to keep users informed, below is the current status of the IMERG V04 products.
1. As of 02:20 UTC on 9 May 2017, IMERG Early and Late are running in V04 with backward compatibility adjustments to V05 inputs.
2. From that point to about 11:30 UTC on 12 May 2017, there are long, thin streaks of artifacts in IMERG Early and Late due to GPROF-ATMS.
3. From that point to about 15:00 UTC on 30 May 2017, there are unrealistically large areas of light rain in moist tropical ocean areas in IMERG Early and Late due to GPROF-ATMS and GPROF-MHS. Thereafter, the content of microwave data is somewhat reduced.
These artifacts will remain in the V04 Early and Late products, and be resolved in the expected upgrade to V05 later this summer.
- At 02:20 UTC on 9 May 2017, Version 04 processing was shut down for GPM core products and subsequently started as Version 05. At this point IMERG Early and Late continued to run in V04, with backward compatibility adjustments to V05 inputs. This might introduce some additional uncertainty in the results. IMERG Final will be computed with a few-month lag up through April 2017, but then must be halted until V05 is instituted because we wish to keep this research data record as consistent as possible.
- At about 11:30 UTC on 12 May 2017, the Version 05 GPROF-ATMS Level 2 precipitation estimates were turned off because the scan positions were slghtly misnavigated, which caused frequent unreasonable values in the last 6 footprints. A corrected version was restarted about 23:00 UTC on 15 May. The IMERG Early and Late products from the start of Version 05 processing for core products (9 May) up to this correction include the erroneous data (long, thin streaks of high values).
- At about 15:00 UTC on 30 May 2017, the Version 05 GPROF-ATMS and GPROF-MHS Level 2 precipitation estimates were given quality flags of 3 in the outer swath regions, suggesting that users (in particular IMERG) should not use these footprints due to unrealistic areas of widespread light rain in moist tropical oceanic cases. [Diagnosis of the problem is on-going by the GPROF team. It is not obvious that these footprints yield unrealistic values outside of moist tropical ocean areas, but at present not enough is known to do a more sophisticated screening.] As a result, the swaths are narrowed by footprints 1-18 and 79-96 for ATMS and 1-15 and 76-90 for MHS. This should increase the frequency of morphed and IR-based input data. The IMERG Early and Late results from the start of Version 05 processing for core products (9 May) up to this correction have erroneous data in these footprints, at least in moist tropical oceanic conditions.
Please contact us for any questions.