MODAPS PCR 21-023
| PCR Number | 21-023 |
|---|---|
| Date | 2021-07-30 |
| Initiator | Starry Manoharan |
| Abstract | PGE03 6.1.4; PGE06 6.1.9 Updated valid ranges on cloud optical thickness (to read from 0 to 15000) and cloud effective radius (to read from 400 to 6000) datasets in order to properly reflect the actual stored data. |
| Problem Statement | On October 5, 2020 at 15:21:12, Terra MODIS experienced a Printed Wire Assembly (PWA) failure that resulted in an operational data acquisition decision that caused an ongoing reduction and irregularity in the overall Terra daytime coverage over high latitudes in both hemispheres. In many polar and some subpolar sunlit scenes, L1B visible and near infrared (VNIR) and shortwave (SWIR) reflectances are missing. The lack of VNIR reflectance data means the Normalized Difference Snow Index (NDSI) cannot be computed and the daytime L1B scans are marked as "night". This has caused degraded results in cloud mask and cloud top properties. |
| Description of Change | For daytime mapped National Snow and Ice Data Center (NSIDC) NISE (Near-Real-Time SSM/I-SSMIS EASE-Grid Daily Global Ice Concentration and Snow Extent) data is substituted for the missing NDSI. To address the incorrect scan mode day vs night designation a fix is submitted to make the decision according to the solar zenith angle (SZA) alone |
| Products Affected | |
| Software Affected | PGE03 6.1.4; PGE06 6.1.9 |
| Processing String to Receive the Change | Terra Forward Processing and Terra Reprocessing. NRT |
| Downstream Product Effects | MOD35_L2, MOD07_L2, MOD04_L2, MOD05_L2, MOD06_L2, MOD08_D3, MOD08_E3, MOD08_M3 |
| Data Granules to be Used for Science Testing | Science test generated a month of L2 and L3 Atmosphere data and the data were verified for correctness. |
| Justification | The fix will improve the quality of L2 and L3 cloud mask and cloud top properties. The updated PGEs is to be put in forward processing for MODIS Terra from August 9, 2021. And products for the period of Terra PWA failure between October 5, 2020 and August 8, 2021 will be reprocessed. This reprocessed data will replace the errored data (that are already processed) in the AS61. (Justification amended 11/12/2021.) |
| Effective Date for Implementation of Change | August 9, 2021 |
| Status | Major algorithm development completed. Steve Platnick approved 08/02/2021; amended 11/12/2021. Michael King approved 08/03/2021. Gang Ye implemented 08/03/2021. |
