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.
Validation at stage 1 has been achieved for the MODIS Surface Radiation products for 2011 through present. Further details regarding MODIS land product validation for the MCD18 data products are available from the MODIS Land Team Validation site. Please note that the MCD18 C6 dataset from year 2000 to 2010 have not been reprocessed and are not appropriate for use in quantitative scientific publications.
|File Size||~1.1 MB|
|Temporal Resolution||< Daily|
|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.
Please note that the MCD18 C6 dataset from year 2000 to 2010 have not been reprocessed and are not appropriate for use in quantitative scientific publications.
Known issues for MCD18A1 are available on the MODIS Land Quality Assessment website.