30 Minute ISFS Data for SOAS

These data contain surface meteorology measurements of the Integrated Surface Flux System (ISFS) during the  Southern Oxidant and Aerosol Study (SOAS), at the Alabama Aquatic Biodiversity Center (AABC), during May, June and July of 2013.

For general information about the operations of the ISFS during SOAS see https://www.eol.ucar.edu/field_projects/soas.

The ISFS 30 minute dataset contains some of the first and second moments of variables measured by the NCAR ISFS during SOAS, in addition to derived calculations of the fluxes of sensible and latent heat, friction velocity, surface heat flux and net radiation.

The data are stored in NetCDF files. Information on the NetCDF file format and software is available at http://www.unidata.ucar.edu/software/netcdf/.  Information specfic to ISFS NetCDF files is available at https://www.eol.ucar.edu/content/isfs-netcdf-files.

NetCDF File Names

Each NetCDF file contains one week of data. The file names are of the form "isfs_YYYYMMDD.nc", where YYYYMMDD is the year, month and day in UTC of the start of the data.

NetCDF Variables

See the table at the bottom of this page for a partial listing of the variables in the file.  The second moments are not listed in that table.

See the table at https://www.eol.ucar.edu/content/soas-isfs-page for information on the sensors that were deployed.

Time Representation

The base_time variable contains one value, the time of the start of the file, as a number of POSIX (non-leap) seconds since 1970 Jan 1, 00:00 UTC.

Values for each time-varying measurement will be found in the NetCDF files, as a variable with a time dimension.  The time dimension for a file containing a full week of data will be 336, the number of 30 minute periods in a week.

The time variable contains the time to be associated with each sample, in units of seconds since base_time, or 00:00 UTC of the day.  Each time value is the middle of the averaging period, and will have  values of 900 (00:15:00 UTC), 2700 (00:45:00), etc, up to 86250 (23:45:00 UTC).

Dimensions

The NetCDF dimensions in each file are:

Short Name Attributes

Each measured variable will have a short_name NetCDF attribute. The field before the first period in the short_name is a generic variable name, such as T for temperature, Rsw for short wave radiation, or u for the U component of the wind. For second moments, such as variances and co-variances, the first field of the short_name will contain single quote marks after a variable to indicate it is an average of a deviation.  For example,  a leading short name of  w'tc', indicates the quantity is an average of  (w-mean(w)) * (tc-mean(tc)), where mean(x) is the 5 minute mean of the variable x, w is the vertical wind component, and tc is the temperaure from the speed of sound.

Higher Moments

For each of the  3-D sonic anemometers, the following second moments in u,v,w and tc are provided for the computation of eddy-correlation fluxes. Scalar values such as water vapor density and carbon dioxide were also measured at the same locations. kh2o is a water vapor measurement from a Campbell krypton hygrometer at 2 and 13.9 meters on the AABC tower. h2o and co2 are water vapor and carbon-dioxide measurements from LICOR 7500 gas analyzers at 8, 20, 26, 32 and 43.9 meters, and from a Campbell Scientific EC150 IRGA at 38 meters.

Heights

The height in meters above ground of the measurement, if appropriate, will be indicated in a second field after a period in the short_name, for example RH.26m, or u'tc'.38m.

Variable Names

The actual NetCDF variable names will have underscores, '_', in place of periods and single quotes.  Therefore a variable with a short_name attribute of w'co2'.38m will have a NetCDF variable name of w_co2__38m.

Units and Long Names

Each variable will have NetCDF attributes containing the units of the measurement, and a long name giving more information on the measurement.

Counts Attributes

Variables from sensors used in eddy-covariance flux measurements will have a counts attribute indicating the number of samples that were included in each statistic.

Missing Data

The missing data value is 1x10^37.  A missing value indicates either that nothing was measured at the location indicated in the variable name and station index, or the sensor was not reporting at the given time, or it was detemined that the data value did not meet QC criteria during post-project analysis.

Table of NetCDF Variables

The following is a partial listing of the variables in the NetCDF files. It does not contain the second moments.