MODIS/Terra Clear Radiance Statistics Indexed to Global Grid 5-Min L2 Swath 10km V006Entry ID: MODCSR_G
Abstract: The MODIS Level 2 Clear Sky Radiance product (MODCSR_G) provides a variety of, statistical measures that characterize observed top-of-atmosphere clear sky radiances at a 25-km spatial resolution. Clear radiances are collected for all earth scenes and separated by day and night. The following statistical quantities are included:
total number of observations
number of clear observations
sum of ... clear values
minimum clear value
maximum clear value
sum of viewing zenith angles
sum of clear-sky values squared
sum of observed clear minus calculated clear values (for clear-sky bias calc.)
sum of observed minus calculated clear values squared
In addition, total counts (clear and cloudy radiances) are separated into land and water and day and night categories for better target discrimination.
MODCSR_G serves as input to the downstream Level 3 aggregation processes that culminate with the production of the 1-degree Zonal Bias Product (MODCSR_B) used as input to PGE06 (MODIS Cloud Product).
MODCSR_G data are collected for bands 1-7 and 17-36 for all but the last two statistics. Calculated clear-sky radiances are produced for bands 20, 22-25, and 27-36 and subtracted from observed values. Differences in bands 31 and 33-36 are summed and used to create the clear-sky biases used in generating the PGE06 cloud top pressure field. Numbers of observations from land vs. water are also kept for each 25-km region. Biases are used to quantify the difference between instrument observed radiances and a calculated radiance. This difference is especially important for the cloud top properties retrieval which utilizes an atmospheric transmittance model as a means of calculating radiances in different layers of the atmosphere and matching that to observations.
The biases contained in MODCSR_G are the difference between the calculated radiance and the observed radiance for all clear-sky grid cells which fall within the given granule. Several different ways of determining the bias were studied, including an attempt to interpolate observed biases across grid boxes where no clear sky scenes could be found for a given day. This procedure worked well for relatively cloud free regions, but large areas of cloud cover produced unrealistic interpolated values. It was finally determined that compositing eight days of clear sky
radiance values would work logistically and produce scientifically robust results. The MODCSR_G files are in Hierarchical Data Format (HDF).
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Data Set Citation
Start Date: 1999-12-18
ATMOSPHERE > ATMOSPHERIC RADIATION > INCOMING SOLAR RADIATION
ATMOSPHERE > ATMOSPHERIC RADIATION > LONGWAVE RADIATION
ATMOSPHERE > ATMOSPHERIC RADIATION > REFLECTANCE
ATMOSPHERE > ATMOSPHERIC RADIATION > SHORTWAVE RADIATION
ATMOSPHERE > ATMOSPHERIC RADIATION > SOLAR RADIATION
SPECTRAL/ENGINEERING > INFRARED WAVELENGTHS > INFRARED RADIANCE
SPECTRAL/ENGINEERING > ULTRAVIOLET WAVELENGTHS > ULTRAVIOLET RADIANCE
Data Set Progress
Extended Metadata Properties
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