One Second Dataset

These data contain surface meteorological measurements of the Integrated Surface Flux System (ISFS) during the Persistant Cold-Air Pool Study (PCAPS) in the Salt Lake basin, during the winter of 2010, 2011.

For general information about the operations of the ISFS during PCAPS click here.

The ISFS one second dataset contains averages and single point values of many variables measured by the 7 NCAR ISFS stations during PCAPS.

The data are stored in 93 day-long NetCDF files, which are available for download at

Information on the NetCDF file format and software is available at

Time Representation

The first ISFS measurements were recorded on Nov 10, 2010, the last on Feb 10, 2011.

Each file contains data for one day, from 00:00 UTC to 24:00 UTC.  The file names contain the date,  formatted as "", where YYYY, MM and DD are the numeric year, month and day.

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.  There are 288 5 minute periods per day, so the time dimension is 288.

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 0.5 (00:00:00.5 UTC), 1 (00:00:01), etc, up to 86399.5 (23:59:59.5 UTC).

Time-series variables and variables associated with multiple stations have one or both of the following dimensions:

Dimension name size description
time 86400 number of seconds in a day
station 7 index for each of the 7 ISFS stations

Variables that were recorded at rates faster than 1 Hz, namely u, v and spd from sonic anemometers, have been averaged to 1 second. Radiation and soil variables that were recorded at approximately 1/5 Hz will have missing values interspersed with measured values.

The missing data value is 1.0 x 10^37, indicating the sensor was not reporting at the corresponding time and station for the given variable, or that the data value did not meet QC criteria during post-project analysis.

The variables in the NetCDF files are:

Variable name units dimensions description
latitude degrees-north station Latitude of each station
longitude degrees-east station Longitude of each station
base_time seconds   POSIX time, non-leap seconds since 1970-01-01 00:00:00 00:00 UTC
time seconds time Middle of each sampling period, in seconds since base_time.
P_2m mb time,station Barometric pressure at 2 meters
T_2m degC time,station Ambient air temperature at 2 meters
RH_2m % time,station Relative humidity at 2 meters
Rainr mm/hr time,station Liquid water precipitation rate, measured by ETI weighing precipitation gauge, at stations 3,4 and 6
u (See Note 1) m/s time,station U component of wind, as measured by Campbell CSAT3 sonic anemometer, averaged from 60Hz samples.
v m/s time,station V component of wind, from CSAT3, averaged from 60Hz samples
spd m/s time,station Wind speed, average of CSAT3 60Hz wind speeds, calculated from components: spd=sqrt(u^2+v^2)
spd_max m/s time,station Maximum 60Hz wind speed during the second
ldiag (See Note 2)   time,station Fraction of non-zero CSAT3 diagnostic values for the second. 0=all OK.
counts_sonic (See Note 2)   time,station Number of CSAT3 samples averaged. The usual value of 60 indicates  that all 60 samples were received during the second.
sonicHeight m station Approximate measurement height above ground of the CSAT3 anemometer at each station.
U_10m m/s time,station U component of wind speed, as measured by RMYoung prop-vane anemometer at 10 meters at stations 1 and 6.
V_10m m/s time,station V component of wind speed from RMYoung at 10 meters.
Rlw_in W/m^2 time,station Incoming long wave (infra-red) radiation, as measured by pyrgeometer
Rlw_out W/m^2 time,station Outgoing long wave radiation
Rsw_in Wm^2 time,station Incoming short wave (solar) radiation, as measured by pyranometer
Rsw_out W/m^2 time,station Outgoing short wave radiation
Rsw_dfs W/m^2 time,station Incoming, diffuse (indirect) solar radiation, measured by Licor pyranometer with a manually adjustable shadowband
Rsw_global W/m^2 time,station Incoming global solar radiation, Licor pyranometer without shadowband
Rsw_dfs_spn1 Wm^2 time Incoming, diffuse solar radiation, as measured by SPN1 sunshine pyranometer at station 7
Rsw_global_spn1 W/m^2 time Total incoming solar radiation, as measured by SPN1 at 7
Gsoil_5cm, Gsoil_5cm_aux (See Note 3) W/m^2 time,station Soil heat flux at approximately 5 cm below surface.
Qsoil, Qsoil_aux vol% time,station Soil moisture content, at approximately 2.5 cm below surface
degC time,station Soil temperature at approximately 0.6 cm below surface
degC time,station Soil temperature at a depth of approx 1.9 cm
degC time,station Soil temp at a depth of approx 3.1 cm
degC time,station Soil temp at a depth of approx 4.4 cm
Lambdasoil. Lambdasoil_aux W/m/degK time,station Soil thermal conductivity, computed from measurements of Hukseflux TP01.
asoil, asoil_aux m^2/s time,station Soil diffusivity from TP01
Cvsoil, Cvsoil_aux J/(m^3 K) time,station Soil heat capacity from TP01
  • Note 1: u and v wind components from CSAT3 sonic anemometers are in standard meteorological coordinates, where a positive u is wind TO the east, positive v is wind TO the north. The original 3D wind vectors have been corrected for sonic tilt, as described here.
  • Note 2: Signal levels of CSAT3 sonic anemometers are strongly influenced by liquid water. The ldiag and counts_sonic variables provide a quality indicator for the wind measurements, where ldiag=0 and counts_sonic >= 59 indicate that no signal problems were detected during the second.  Note that due to oscillator clock drift of the sonic relative to the data system, sometimes 59 or 61 samples will be averaged in a second.
  • Note 3: Auxiliary soil measurements, as indicated with an "_aux" suffix, were sampled at stations 1,5 and 6. 

For values of the surface heat flux, derived from the soil heat flux at 5 cm and the heat storage in the soil from 0 to 5 cm, see the 30 minute dataset.