5 Minute ISFF Data for CASES99
These data contain surface meteorology measurements of the Integrated Surface Flux Facility (ISFF) during the CASES99 field project, in October, 1999. Note: ISFF is now know as ISFS.
For general information about the operations of the ISFS during CASES99 see https://www.eol.ucar.edu/content/integrated-surface-flux-facility-during-cases99.
The 5 minute files contain means, variances and covariances of ISFF variables that were sampled on the main tower and the six outlying towers. We recommend combining these to obtain more statistically-significant averages over longer time periods.
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.
The NetCDF file names are cases.99MMDD.nc, where MMDD is the starting month and day in UTC.
Quality Control
No removal of questionable data has been performed on this data.
Some variables can be used as quality indicators. The Campbell CSAT3 sonic anemometers at 1.5, 5, 30 and 50 meters on the tower provide a diag bit-field variable, which will be zero if the sonic transducer signal levels and measured speed of sound on the 3 axes are within acceptable ranges. Wind vectors and sonic temperature values should not be used when diag is non-zero.
The ATI sonic anemometers on the tower at 10, 20, 40 and 55 meters, and at 5 meters on the outlying stations provide usamples, vsamples and wsamples variables, which contain the number of 200 Hz samples that were averaged within the sonic to create a 20 Hz sample. A value of 10 indicates the sonic was working correctly. Wind vectors and sonic temperature values should not be used when usamples, vsamples and wsamples are less than 10.
The online field logbook logbook has detailed information about sensor issues that were noted in the field.
Corrections
The following corrections have been applied to both datasets
- All horizontal wind components, U and V from 2D anemometers, and u and v from fast 3D anemometers, have been rotated to geographic coordinates, where +U is wind to the east, +V is wind to the north. These rotations are based on compass measurements of the anemometer orientations.
- The 3D sonic anemometers were installed as level as was possible, but not perfectly "bubble" level. The 3D wind vectors have been rotated to a coordinate system where the mean W component is zero, as described in /content/sonic-tilt-corrections
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 of 288, the number of 5 minute periods in a day.
The time variable contains the time to be associated with each sample, in units of seconds since base_time. The values of time are the middle of the 5 minute averaging period, and have values of 150, 450, ... 86250, corresponding to UTC times of 02:30:00, 07:30:00, ... 23:57:30 of the day.
Dimensions
The NetCDF dimensions in each file are:
| Dimension name | size | description |
|---|---|---|
| time | 288 | number of 5 minute samples in a day |
| station | 6 | index for the six ISFF stations at CASES99 |
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.
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.30m
NetCDF 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 v.5m will have a NetCDF variable name of v_5m.
Units and Long Names
Variables have a NetCDF attribute specifying the units of the measurement.
Missing Data
The missing data value is 1037. A missing value indicates that the sensor was not reporting at the given time.