MODAPS PCR 17-011
| PCR Number | 17-011 |
|---|---|
| Date | 2017-05-24 |
| Initiator | Dongdong Wang |
| Abstract | PGE140 v6.0.2 developed to generate L2G of the MODIS Atmosphere product MxD05 and combine with the MAIAC intermediate product to generate the MxD18PI, the intermediate for the DSR/PAR process. PGE141 v6.0.7 New PGE141 developed to generate the L3 MCD18A1/A2 products. |
| Problem Statement | Generate the new Terra and Aqua combined MODIS Land products – the daily L3 tiled DSR (MCD18A1: Daily Surface Radiation) and PAR (MCD18A2: Photosynthetic Active Radiation) at MODAPS in C6 using the science algorithms developed by the science team at UMD. |
| Description of Change | MCD18A1 and MCD18A2 are two new MODIS land products. The MCD18A1/A2, the combined Terra and Aqua MODIS DSR/PAR algorithm is a LUT-based method to directly estimate surface shortwave radiative fluxes without need of comprehensive atmospheric parameters as input. The LUTs consider different types and loadings of multiple aerosols and clouds at a variety of illumination/viewing geometry. The algorithm uses MODIS top-of-atmosphere radiance/reflectance and surface reflectance as the major input to calculate diffuse PAR, direct PAR, diffuse insolation and direct insolation for each individual MODIS overpass. The instantaneous results are then temporally interpolated to intervals of 3-hour. |
| Products Affected | MOD181PGD, MYD18IPGD, MCD18A1, MCD18A2 |
| Software Affected | PGE140 v6.0.2, PGE141 6.0.7 |
| Processing String to Receive the Change | Terra and Aqua Forward Processing and Terra and Aqua Reprocessing |
| Downstream Product Effects | None. |
| Data Granules to be Used for Science Testing | Generate daily global product for 8-day periods starting data day 2003001 and 2003193 |
| Justification | The new products of incident PAR and shortwave radiation are needed to address a variety of scientific and application issues related to climate trends, hydrologic, bio-physical and bio-chemical modeling, solar energy applications, and agriculture. For example, the high-quality and high-resolution products of PAR and shortwave radiation are inputs of other MODIS land products, such as GPP/NPP and evapotranspiration products. However, few land surface global PAR products exist because most global radiative flux datasets do not include PAR, so users have to empirically convert insolation to PAR. The current insolation products do not have the accuracy and spatial resolution required for land surface applications. The new products were designed for such land applications. The new product has been validated using field measurements of incident PAR and shortwave radiation at SURFRAD, BSRN and FLUXNET stations. |
| Effective Date for Implementation of Change | Completed |
| Status | Major algorithm development completed. Sadashiva Devadiga approved on 05/30/2017. Michael King approved 06/12/2017. Gang Ye implemented 06/13/2017. |
