CERES/ARM Validation Experiment (CAVE)

For validation of CERES/SARB radiation transfer modeling, observed surface radiation data are collected at over 60 locations around the globe. The following table contains links details explaning the files.

Summary

CAVE surface observations consist of a host of radiometric, meteorological, and aerosol observations taken at a number of sites around the globe.  A number of organizations and people have generously made their data available for dissemination through this web site.  That data, generally arrives at 1 minute temporal resolution and for our purposes is averaged to 15 minute means. The data is rewritten as binary files, each file contains a header and all available data for a single site for a single month. These are then released via anonymous ftp along with programs to read the files. See the links above for lists of files at surface sites and an on-line plotting tool that prints summary tables of all variables available at a given site.

There are three types of files in the surface observation data base. The Surface flux Aerosols & Meteorology (SAM) file contains the surface observations averaged to 15 minute temporal resolution. The "SYN" or Synoptic files have the same data averaged to 1-hourly, 3-hourly, 24-hours (daily), and monthly means.

Surface Flux Aerosol & Meteorology (SAM) File Format

The SAM 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.	Figure 2. List of commonaly available data in SAM files.

Figure 2 lists the first 22 variables in every SAM file (identical in each SAM whether the surface site has recorded the data or not.) Most sites do not record all these varialbes. Some observe more. If a site has more data of interest, UV data at SURFRAD sites for instance, these data are include as "Extra" variables in records beyond #22. The number of extra variables in a file is recorded in the file header. For quickly determining available data at a site go to the SAM PLOT page where a summary table for all sites in the data base can be quickly accessed.

Synoptic (SYN) File Format

    (744 - 72)
    ---------- * 100 = 90.3
       744

Figure 3. Graphic showing synoptic (SYN) file structure.

File Naming Conventions

SAM and SYN files can be downloaded via a web tool found here: Data Base. File names are dependent upon a unique 3-letter identifier for each site. See Site List for a global map and listing of all surface sites. Or just continue down to see a list of sites, their 3-Lette identifier and the file name/source.

Surface Flux Aerosol & Meteorology (SAM) Statistics Files

Most data coming into our data base arrive as 60 second averages of 1Hz observations. For our purposes we average these data to 15 minutes (minutes 0 throug 14, 15 through 29, etc...) Often too, data might be missing. So, statistic files containing the standard deviation of the data over each 15 minute time period and the number of points that go into each 15 minute average are also maintained and made available for interested parties. The naming convention is the same execept instead of "avg" they have "sts" before the version number.

Please contact David Rutan if you would like to access these files. The format of these files is nearly identical to the average file except that for each variable there are two records, the standard deviation and count.