Handout (128.8 kB)
A number of input data streams are needed to produce the CERES land surface albedo. Higher resolution, narrowband Moderate resolution Infrared Spectrometer (MODIS) pixels are collocated within the larger broadband CERES footprints. Cloud properties are derived which are consistent with the broadband radiation. Global Modeling and Assimilation Office (GMAO) Goddard Earth Observing System (GEOS) GEOS-4 supplies atmospheric profiles; global ozone is from National Centers for Environmental Prediction (NCEP); and microwave based snow and ice maps are from National Snow and Ice Data Center. For aerosols, we use MODIS aerosol optical depth data along with the Model for Atmosphere and Chemistry (MATCH) data to supply aerosol constituent types and their vertical distribution. A surface model based on International Geosphere and Biosphere Programme (IGBP) scene types is used to supply underlying spectral shapes for both albedo and emissivity. Initial broadband surface albedo is either retrieved directly from clear sky footprints or taken from a history map of pre-processed clear sky data for cloudy skies. Over ice-free ocean, a validated coupled ocean atmosphere radiation transfer model is used to specify the surface albedo. Fast, 2-stream radiative transfer calculations are done for each footprint; and compared with CERES TOA observations.
While we use narrowband measurements like MODIS for guidance, radiative transfer calculations for land albedo are anchored to direct CERES measurements at TOA which are spectrally integrated (the same, solar broadband envelope that heats the earth). Data is collected over each month at satellite observation time (~1030 LST for Terra and ~1330 LST for Aqua) and spatially averaged within 1-degree equal angle grid boxes. These data are subsequently averaged in time providing a monthly mean. We supply a diurnal model based on a single "d-value" (following Dickinson's theory, which we assign as a function of surfacetype); this gives the albedo for any sun angle or sky condition.
Supplementary URL: http://www-cave.larc.nasa.gov/
![](images/flag.png)
![](images/blue_ribbon.png)