The MCD18A1 Version 6 is a Moderate Resolution Imaging Spectroradiometer (MODIS) Terra and Aqua combined Downward Shortwave Radiation (DSR) gridded Level 3 product produced daily at 5 kilometer pixel resolution with estimates of DSR every 3 hours. DSR is incident solar radiation over land surfaces in the shortwave spectrum (300-4,000 nanometers) and is an important variable in land-surface models that address a variety of scientific and application issues. The MCD18 products are based on a prototyping algorithm that uses multi-temporal signatures of MODIS data to derive surface reflectance and then calculate incident DSR using the look-up table (LUT) approach. The LUTs consider different types of loadings of aerosols and clouds at a variety of illumination/viewing geometry. Global DSR products are generated from MODIS and geostationary satellite data. Additional details regarding the methodology used to create the data are available in the Algorithm Theoretical Basis Document (ATBD).
Provided in the MOD18A1 product are layers for instantaneous DSR array for each individual MODIS overpass and 3-hour DSR array along with a View Zenith Angle layer.
|File Size||~1.1 MB|
|Temporal Extent||2001-01-01 to Present|
|Geographic Dimensions||1200 km x 1200 km|
|Number of Science Dataset (SDS) Layers||12|
|Columns/Rows||240 x 240|
|Pixel Size||5600 m|
|SDS Name||Description||Units||Data Type||Fill Value||No Data Value||Valid Range||Scale Factor|
|DSR||Instantaneous total DSR at MODIS overpass||W/m²||32-bit floating point||-1||N/A||0 to 1400||N/A|
|Direct||Instantaneous direct DSR at MODIS overpass||W/m²||32-bit floating point||-1||N/A||0 to 1400||N/A|
|Diffuse||Instantaneous diffuse DSR at MODIS overpass||W/m²||32-bit floating point||-1||N/A||0 to 1400||N/A|
|GMT_0000_DSR||Total DSR at GMT 00:00||W/m²||32-bit floating point||-1||N/A||0 to 1400||N/A|
|GMT_0300_DSR||Total DSR at GMT 03:00||W/m²||32-bit floating point||-1||N/A||0 to 1400||N/A|
|GMT_0600_DSR||Total DSR at GMT 06:00||W/m²||32-bit floating point||-1||N/A||0 to 1400||N/A|
|GMT_0900_DSR||Total DSR at GMT 09:00||W/m²||32-bit floating point||-1||N/A||0 to 1400||N/A|
|GMT_1200_DSR||Total DSR at GMT 12:00||W/m²||32-bit floating point||-1||N/A||0 to 1400||N/A|
|GMT_1500_DSR||Total DSR at GMT 15:00||W/m²||32-bit floating point||-1||N/A||0 to 1400||N/A|
|GMT_1800_DSR||Total DSR at GMT 18:00||W/m²||32-bit floating point||-1||N/A||0 to 1400||N/A|
|GMT_2100_DSR||Total DSR at GMT 21:00||W/m²||32-bit floating point||-1||N/A||0 to 1400||N/A|
|ViewZenithAngle||View Zenith Angle of each MODIS overpass||Degree||32-bit floating point||-1||N/A||0 to 90||N/A|
See Table 1 in the User Guide for additional information on band dimensions.
For information about MCD18A1 product quality please refer to the MODIS Product Quality Documentation.
Known issues for MCD18A1 are available on the MODIS Land Quality Assessment website.