CERES/ARM Validation Experiment (CAVE)

CAVE Clouds & Radiation Swath (CRS) files contain a modified version of the official CERES CRS data product that one may access from the NASA Langley Atmospheric Sciences Data Center These files contain footprint by footprint observations and radiation transfer calculations for every other CERES footprint and every other CERES scan. For our purposes the files here contain only those footprints whose radiometric center lies within a 25km radius of surface validation sites (list of surface validation sites) which are observing radiation coming down at the surface of the Earth.

The following table contains links to details explaning the files.

Summary

The CERES instruments on board TRMM, Terra, and Aqua satellites observe emitted and reflected radiation at the top of the Earth's atmosphere. Beyond these observations CERES produces "higer order" data products that synthasize other inputs, for instance MODIS radiances collocated within a given CERES footprint observation. The first higher order product, the Single Satellite Flux (SSF product) provides, along with CERES observed radiances and fluxes, cloud, aerosol and surface properties defined to be contained within the bounds of the CERES footprint, ~20km to ~30km at the Earth's surface, in length, near nadir viewing angles. Utilizing the CERES SSF product, the Surface & Atmospheric Radiation Budget (SARB) group, adds in yet more ancillary data (for instance gridded meteorological profile data supplying temperature, pressure, and humidity data) and then execute a fast radiation transfer code under a number of different scenarious. (See table below.) Radiation transfer results are output at 5 atmosperhic pressure levels, though the model is run at much higher vertical resolution. After the 4 scenarios are run the model TOA results are compared to the CERES observed TOA fluxes and radiances. Depending on scene conditions, various inputs are carefully adjusted and the model is run again. This provides constrained (or "tuned") model calculations and it is these tuned values, along with the amount by which they were adjusted, which are reported in the CRS files. These tuned fluxes and adjustments and a number of RT inputs are basically added to the SSF record for each footprint and released as the next higher order data product, the Clouds & Radiative Swath or CRS data product.

CERES Clouds & Radiation Swath (CRS) - The CAVE Version

The CAVE CRS file is a binary (big-endian) file of fixed record length. It consists of a Header record that contains information regarding the surface site and a list of variables contained in each file. The remainder of a file contains one record for each available variable where each record is one month's worth of data for that variable. Figure 1 below shows this schematically.

Figure 1. Graphic showing Surface Aerosol Meteorology (SAM) file structure.

File Naming Conventions

File names are based on a set of unique 3-letter identifiers. The following table connects the 3 letter identifier to the data site and gives the prefix of the file names found in the data base. See Site List for a global map and listing of all surface sites.