MODAPS PCR 15-026
| PCR Number | 15-026 |
|---|---|
| Date | 2015-06-05 |
| Initiator | Dr. Zhengming Wan |
| Abstract | PGE23 v6.0.22. Large scale reorganization of the code optimizing the reading of data, fill value updates, updated memory allocation with no change to the science algorithm. Minor science code bug fix implemented to update the backup database for the shallow ocean pixels that were missing in the original backup database, to fix the code to detect the full/fractional snow cover status based on NDSI and to fix software bug affecting the 1km magnitude inversion. |
| Problem Statement | PGE is running too slow and tiles at high latitude are taking unusually long to complete. |
| Description of Change | a. Reorganize the code structure to improve performance optimizing read, fill value updates and memory allocation. b. Update the backup database for the shallow ocean pixels that are missing in the original back up database because of difference in C5 and C6 land water mask. c. Update code to detect the full/fractional snow cover status based on NDSI in MCD43 code for cases with clear MODIS reflectance but fill value in input tiled snow product. d. Fix software bug affecting the 1km magnitude inversion. |
| Products Affected | MCD43A1, MCD43A2, MCD43A3, MCD43A4, MCD43C*, MCD43D* |
| Software Affected | PGE23 v6.0.22 |
| Processing String to Receive the Change | Terra Reprocessing and Aqua Reprocessing |
| Downstream Product Effects | None. |
| Data Granules to be Used for Science Testing | Process 16-day period starting data day 2001345 generating the BRDF-Albedo product for all land tiles for each of the data day using the 16-day input from the C6 archive.2010-059 |
| Justification | The operational version 6.0.15 of PGE23 was performing very poorly in the on-going C6 reprocessing with increasing processing time for tiles at high latitude. The overall processing rate is <15. This variation in processing time with latitude has even worse impact on the downstream LST process which cannot start the processing for a day until the BRDF-Albedo for all tiles for the day is complete. With the proposed changes to the PGE23 in version 6.0.20 the PGE runs at least twice as fast and the overall processing rate is expected to be >30. This improvement in the processing rate is achieved without compromising the product quality. However it was also noticed that the CMG product from the version 6.0.15 quality may have been negatively impacted by the software bug affecting the 1km magnitude inversion. Though this doesn't impact the quality full resolution products (MCD43A*), reprocessing of the full suite of BRDF-Albedo product is required to maintain spatial and temporal consistency across the products in the product suite. The reprocessing is also required to adopt polarization corrected surface reflectance. However, this reprocessing of the early period from beginning of Terra through 2003.001 could be planned after the completion of the on-going reprocessing. |
| Effective Date for Implementation of Change | Completed. |
| Status | Major algorithm development completed. Sadashiva Devadiga approved on 07/22/2015. Michael King approved on 07/24/2015. |
