MODAPS PCR 16-010
| PCR Number | 16-010 |
|---|---|
| Date | 2016-03-28 |
| Initiator | Zhuosen Wang |
| Abstract | PGE23 v6.0.34. (1) Using the MOD35 snow flag embedded in the MO/YD09GA product to determine snow status. In the previous code both the MOD35 snow flag and the MO/YD09GA internal snow algorithm flag were used to determine snow status. (2) No longer need the inputs of MOD10A1. Now the package calculates NDSI from surface reflectance. Snow fraction is then calculated from NDSI. |
| Problem Statement | MCD43 products contained significant non-retrievals from false snow. PGE23 combined the snow flag from the cloud mask product and the surface reflectance product. The C6 snow flag in the surface reflectance product was found to be unreliable with large number of commission error from snow-cloud confusion. |
| Description of Change | Updated the PGE23 to use the snow flag from the cloud mask product only and implemented the snow algorithm used in the land C6 snow PGE to derive the fraction of snow cover. |
| Products Affected | MCD43A |
| Software Affected | MOD_PR23 |
| Processing String to Receive the Change | Terra and Aqua Reprocessing |
| Downstream Product Effects | None. |
| Data Granules to be Used for Science Testing | Process 2 two-month period from year 2003 and also generated 1-year of global data from year 2010.2010-059 |
| Justification | A Large number of commission errors was found in C6 surface reflectance product snow flag due to snow-cloud confusion. This commission error is much worse in C6 compared to C5 surface reflectance product. BRDF/Albedo product relies on snow flag from both the cloud mask product and the surface reflectance product that results in lots of snow BRDF/Albedo retrievals during growing season and significant non-retrievals in C6 caused by the contamination of snow flag. This contamination can be significantly reduced by using the snow flag from the cloud mask product only. Snow cover fraction is used in BRDF/Albedo retrieval to capture rapid snowmelt. In this version we implemented the snow algorithm used in the land C6 snow PGE to derive the fraction of snow cover. Putting this change into operational processing, we can calculate the snow cover fraction for each observation instead of one best observation per day in the snow product and also reduce the input data loading. |
| Effective Date for Implementation of Change | Completed. |
| Status | Major algorithm development completed. Sadashiva Devadiga approved on 04/11/2016. Michael King approved on 04/11/2016. Gang Ye approved on 04/12/2016. |
