MODAPS PCR 17-018
| PCR Number | 17-018 |
|---|---|
| Date | 2017-08-15 |
| Initiator | Bill Ridgway |
| Abstract | PGE03 6.1.1 - Updated MOD_PRLCAT; Use of new destripe_config_terra files (revision 2) PGE04 6.1.3 - Updated MOD_PR04DB to version 6.1.3 PGE06 6.1.2 - Updated MOD_PR04DB to version 6.1.3; Use of new destripe_config_terra files (revision 2) PGE85 6.1.0 - Release of Collection 6.1 version PGE93 6.1.0 - Produces products with filenames and metadata appropriate for Collection 6.1 PGE90 6.1.0_5 - Updated metadata for Collection 6.1; Corrected to resolve Bug 1674. PGE108 6.1.0 - Release of Collection 6.1 version PGE83 6.1.0 - Release of Collection 6.1 version PGE69 6.2.0 - Release of Collection 6.1 version PGE56 6.2.0 - Release of Collection 6.1 version PGE57 6.2.1 - Updated template file to version 620 PGE70 6.2.0 - Release of Collection 6.1 version PGE55 6.1.0 - Release of Collection 6.1 version PGE81 6.1.0 - Release of Collection 6.1 version PGE89 6.1.0 - Release of Collection 6.1 version PGE92 6.1.0 - Release of Collection 6.1 version |
| Problem Statement | Crosstalk in Terra IR Bands 27-30 compromised C6 products including cloud mask (MOD35), cloud fraction and cloud top properties (MOD06) as well as total precipitable water (MOD07/MOD05). Most notable were cloud cover artifacts (spurious clouds) over tropical ocean and faulty cloud phase diagnostics as B29-B31 cirrus threshold tests became unreliable starting about 2013. |
| Description of Change | The C6.1 L1B crosstalk correction fix uses band averaged influence coefficients based upon monthly lunar views by Terra MODIS (Wilson et al. 2017). The fix restores the cloud and water vapor products to acceptable quality with minimal trending over the mission. PGE03/PGE06 IR band destriper configuration tables were updated to be consistent with updated L1B. PGE04 Dark Target retrievals: Corrected a bug found during code conversion to CentOS-7. Created a new SDS called BowTie_Flag, which is set to 0 when the bowtie effect is detected. Dark Target over Ocean only: added reflectance, standard deviation, aerosol cloud fraction, and number of pixels for retrievals when optical depth is zero or very small. All earlier PGE04 Versions (Collections) reported only optical depth in these cases. Also modified the sediment mask to make it more robust. Dark Target over Land only: Degraded the quality of retrievals to zero if there are more than 50% coastal pixels or 20% of water pixels in 10x10 km grid. Modified 3km algorithm for Aerosol retrieval over land surface when urban percentage is larger than 20% using a revised surface characterization (Gupta et al., 2016). MODIS land cover type data set is used to identify urban pixels. The revised surface ratios for urban regions were created using MYD09 spectral surface reflectance product. PGE04 Deep Blue retrievals: Applied latest Ocean Biology Processing Group calibration corrections. Improved internal smoke detection masks. Applied new surface reflectance models for elevated terrain types in order to remove systematic biases. Updated uncertainty estimates, reported an estimate of the uncertainty of the retrieved AOD at 550 nm for each retrieval at Level 2.PGE06 Cloud Optical Properties: C6.1 uses updated surface albedo data based on MODIS BRDF/Albedo Product MCD43. Actual MCD43 data are used for processing of the period 2000-2016. Current-year (2017) production will use 2016 model data. PGE57: Aerosol L3 Aggregation Change: In C6.1 the logic for the monthly level 3 (L3) product (MxD08_M3) has been changed to require valid retrievals from at least 3 days from the month for a grid cell to be populated. This change applies only to the monthly product (i.e. not the daily or 8-day products), for both Deep Blue and Dark Target. |
| Products Affected | All Atmosphere L2 and L3 products are impacted. These PGEs are updated: PGE03 - 6.1.1 (Cloud Mask) PGE04 - 6.1.3 (Aerosol) AM1M_C61_A1mc 6.1.8 PGE06 - 6.1.2 (Cloud Optical and Top Properties) AM1M_C61_A1mc 6.1.8 PGE85 - 6.1.0 (L2 CSR statistics) AM1M_C61_A1bmc 6.1.0 PGE93 - 6.1.0 (L1B sub-sampler - MOD02SSH) AM1M_C61_1mc 6.1.5 PGE90 - 6.1.0_5 (Atmosphere AERONET subsetting) AM1M_C61_A1cmc 6.1.5 PGE108 - 6.1.0 (global L2 browse) AM1M_C61_ABRcmc 6.1.0 PGE83 - 6.1.0 (Atmosphere L2 subsetter browse) AM1M_C61_A1mc 6.1.8 PGE69 - 6.2.0 (daily L3) AM1M_C61_A2mc 6.2.0 PGE56 - 6.2.0 (daily L3) AM1M_C61_A3mc 6.2.0 PGE57 - 6.2.1 (monthly L3) AM1M_C61_A5mc 6.2.1 PGE70 - 6.2.0 (8-day L3) AM1M_C61_A4mc 6.2.0 PGE55 - 6.1.0 (L3 Daily Clear Sky radiance Statistics) AM1M_C61_A6mc 6.1.0 PGE81 - 6.1.0 (Level 3 8-day Clear Sky radiance Statistics) AM1M_C61_A7mc 6.1.0 PGE89 - 6.1.0 (Atmosphere L3 browse image composite) AM1M_C61_ABRcmc 6.1.0 PGE92 - 6.1.0 (CERES L1B sub-sampler) AM1M_C61_1mc 6.1. |
| Software Affected | All Atmosphere L2 and L3 products are impacted. |
| Processing String to Receive the Change | Terra and Aqua Forward Reprocessing. Terra and Aqua Reprocessing. NRT |
| Downstream Product Effects | Only Atmosphere products through Level 3. |
| Data Granules to be Used for Science Testing | Extensive Science testing was done to evaluate the success of the calibration updates as well as Level 2 changes. Reference: https://modis-images.gsfc.nasa.gov/PGE_Test_Archive |
| Justification | Serious calibration issues (B1/B2 calibration flaws and B26-30 Terra instrument crosstalk) resulted in degraded C6 atmosphere product quality, particularly for the period 2013 to present. Product trends were found to have limited usability for climate studies. Calibration fixes combined with L2 bug fixes and enhancements have restored acceptable product quality. |
| Effective Date for Implementation of Change | Forward Processing: Aqua and Terra C6.1 forward processing to begin on or about 9/1/2017. Re-Processing: Terra reprocessing to begin immediately with products released on or after 8/15/2017. NRT Processing: NRT processing to begin on or about 9/1/2017. |
| Status | Major algorithm development completed. Michael King approved on 08/28/2017. Gang Ye implemented 08/28/2017. |
