Downwelling Surface Radiation/Photosynthetically Active Radiation (MCD18)

sample thumbnail of DSR/PAR image

Incident solar radiation over land surfaces, either photosynthetically active radiation (PAR) in the visible spectrum (400-700nm) or downward shortwave radiation (DSR) in the shortwave spectrum (300-4000nm), is a key variable required by almost all land surface models. Satellite DSR and PAR products are needed to address a variety of issues related to climate trends, hydrologic, bio-physical and bio-chemical modeling, solar energy applications, and agriculture.

Currently, global satellite radative flux products only exist at coarser resolutions of hundreds of kilometers to a degree. Few land surface global PAR products exist because most global radiative flux datasets do not include PAR, leaving users to empirically convert DSR to PAR. The conversion itself is a source of much uncertainty.

A suite of global high-resolution (5km) DSR and PAR products over land surfaces are generated from MODIS Terra and Aqua data. The new product suite consists of two gridded Level 3 products: MCD18A1 (Downward Shortwave Radiation) and MCD18A2 (Photosynthetically Active Radiation). MCD18A1 and MCD18A2 are combined Aqua and Terra MODIS products.




Product PIs: Dongdong Wang, Shunlin Liang

User Guide - C6.1



See links below to the Product Description pages posted at the LP DAAC (product details, data access links, and more....)


Product Name

Downwelling Surface Radiation Daily L3 Global 5km

Photosynthetically Active Radiation Daily L3 Global 5km

Combined Aqua & Terra Product ID





   Wang, D., Liang, S., Zhang, Y., Gao, X., Brown, M., & Jia, A. (2020). A new set of MODIS land products (MCD18): Downward shortwave radiation and    photosynthetically active radiation. Remote Sensing, 12(1), 168, doi:10.3390/rs12010168.