MODAPS PCR 16-008
| PCR Number | 16-008 |
|---|---|
| Date | 2016-04-05 |
| Initiator | Bill Ridgway |
| Abstract | PGE03 v5.3.15 -- Added thresholds.dat.terra.v13nrt and destripe_config_terra.dat.v5nrt for nrt. Matched with the logic used by C6 for chosing destripe_config file. PGE03 v6.0.47 -- Use destripe_config_terra.dat.v5nrt in NRT. PGE06 v51.0.18 -- Added destripe_config_terra.dat.v5nrt for nrt. Matched with the logic used by C6 for chosing destripe_config file. PGE06 v6.0.91 -- Use destripe_config_terra.dat.v5nrt in NRT. |
| Problem Statement | Recovery from the Feb 19, 2016 safe-hold resulted in degraded radiances in Terra Bands 27 & 29 (both bad and noisy detectors). Cloud mask, atmospheric profiles and some downstream products were seriously impacted by bad radiances in these thermal bands. |
| Description of Change | Updated PGE03 threshold tests for these bands. Two cloud detection tests (8.6-11 micron BTD and 6.7 micron BT) in the Terra MODIS cloud mask algorithm have been effectively eliminated by modifying the test thresholds. The new thresholds are set in such a way as to prevent the corresponding tests from reporting any cloud, whether or not clouds actually exist in the scene, i.e., 1-km MODIS pixel. The 6.7 micron BT thresholds are set to non-physically low values, while the 8.6-11 micron BTD thresholds are made unreasonably high. This change restores cloud mask quality to near pre-safe-hold levels. Updated the de-striper that previously used Band 27 Detector 9 as a reference. This detector is no longer in family and is vulnerable to producing negative radiances (reason not yet clear). The de-striper has replaced detector 9 with detector 4 as the reference. This changes minimizes striping in the profile product. |
| Products Affected | PGE03 products MOD35_L2 and MOD07_L2 and downstream products |
| Software Affected | PGE03 v5.3.15, PGE03 v6.0.47, PGE06 v51.0.18, PGE06 v6.0.91 |
| Processing String to Receive the Change | Terra Forward, Terra Reprocessing |
| Downstream Product Effects | None |
| Data Granules to be Used for Science Testing | Science Testing Required: Single day science tests were run for Terra 2016 Day 061. See AS 1393/1399. |
| Justification | Avoids unacceptable level of false positives in cloud detection, particularly over ocean. Avoids striping and bad average values in profile products. |
| Effective Date for Implementation of Change | ASAP Terra forward processing starting at 2016 day 059 or thereafter. |
| Status | Major algorithm development completed. Steve Platnick approved 04/06/2016; Sadashiva Devadiga approved 04/06/2016. Gang Ye approved on 04/07/2016. |
