MODAPS PCR 17-028
| PCR Number | 17-028 |
|---|---|
| Date | 2017-12-21 |
| Initiator | Alexei I. Lyapustin, Yujie Wang |
| Abstract | PGE113 v6.0.32 -- Code changes to implement: - Polarization correction - Residual trending and MODIS Terra-to-Aqua cross calibration - Retrieve surface BRDF from accumulated multi-angle set of observations - Retrieve surface state – snow, cloud, aerosol, water vapor etc. |
| Problem Statement | Generate the MAIAC (Multi-angle Implementation of Atmospheric Correction) suite of products (MCD19A1, MCD19A2, and MCD19A3) products at MODAPS in the C6 reprocessing and forward processing streams. |
| Description of Change | MAIAC is a new advanced algorithm that uses time series analysis and a combination of pixel- and image-based processing to improve accuracy of cloud detection, aerosol retrievals, and atmospheric correction. Starting with gridded polarization corrected MODIS measurements (L1B data) at 1km resolution data as input, MAIAC implements the sliding window technique by storing from 4 (at poles) to 16 (at equator) days of past observations in operational memory. This helps retrieve surface BRDF from accumulated multi-angle set of observations, and detect seasonal (slow) and rapid surface change. The knowledge of the previous surface state also helps MAIAC’s internal dynamic land-water-snow classification including snow detection and characterization. MAIAC provides a suite of atmospheric and surface products in three HDF4 files: daily MCD19A1 (spectral BRF, or surface reflectance), daily MCD19A2 (atmospheric properties), and 8-day MCD19A3 (spectral BRDF/albedo). |
| Products Affected | MCD19A1, MCD19A2 and MCD19A3 |
| Software Affected | PGE113 v6.0.32 MOD_PR19, MOD_PR19CMP |
| Processing String to Receive the Change | Terra and Aqua Forward Processing. Terra and Aqua Reprocessing. |
| Downstream Product Effects | None. |
| Data Granules to be Used for Science Testing | Run test generating the global data from three 8-day periods 2003001 - 2003024 |
| Justification | A broad community-based and internal analysis puts MAIAC validation status between Level 2 (Regional) and 3 (Global). While covering most of the globe through NCCS releases, Indonesia-Oceania and Australia-New Zealand regions were never processed due to limited disk space, which limits MAIAC to Level 2 validation. The undertaken validation studies showed a considerable increase in accuracy and number of good retrievals overall and very significant improvement over tropics in particular in MAIAC surface reflectance as compared to MOD09 product. Aerosol validation analysis shows that MAIAC is comparable or better than the MODIS Dark Target and Deep Blue algorithms, and significantly outperforms the VIIRS aerosol algorithm. Applications of MAIAC products include 1) air quality and health studies; 2) vegetation analysis, drought monitoring etc.; 3) regional and global climate change research; 4) global model assimilation and others. |
| Effective Date for Implementation of Change | Completed. |
| Status | Major algorithm development completed. Sadashiva Devadiga approved on 12/21/2017. Michael King approved 1/3/2018. Gang Ye implemented 01/5/2018. |
