Five Minute Dataset

Documentation of the ISFS Five Minute Dataset for PCAPS

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 five minute dataset contains first moments and some second moments of variables measured by the 7 NCAR ISFS stations during PCAPS.

Each measured variable will have a short_name attribute in the NetCDF header. For second moments, such as variances and co-variances, the short_name will contain single quote marks after a variable to indicate it is an average of a deviation.  For example,  a short name of  w'kh2o', indicates the quantity is an average of  (w-mean(w)) * (kh2o-mean(kh2o)), where mean(w) is the 5 minute mean of w. The actual NetCDF variable names will have underscores, '_', in place of the single quotes.

The following second moments are provided:

  u v w tc kh2o
u u'u' u'v' u'w' u'tc' u'kh2o'
v   v'v' v'w' v'tc' v'kh2o'
w     w'w' w'tc' w'kh2o'
tc  u'tc'  v'tc' w'tc' tc'tc'  
kh2o  u'kh2o' v'kh2o'  w'khqo'   kh2o'kh2o'

The missing data value is 1.0 x 10^37, indicating data is not available at the corresponding time for the given variable.

The dataset consists of 93 day-long NetCDF files on the EOL CODIAC site, see PCAPS datasets in CODIAC. 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 "isfs_YYYYMMDD.nc".  The date is also coded in the variable base_time in each file.

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

Dimension name size description
time 288 number of 5 minute periods in a day
station 7 index for each of the 7 ISFS stations

 

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 (See Note 1) m/s time,station V component of wind, from CSAT3, averaged from 60Hz samples
w (See Note 1) m/s time,station W component of wind, corrected for sonic tilt from the plane of mean horizontal flow.
tc degC time,station Virtual temperature from the speed of sound, as measured by a CSAT3
u_u_, u_v_, u_w_, etc varies time,station seconds moments of wind components and fast scalar quantities as shown in the table above.
spd_max m/s time,station Maximum 60Hz wind speed during the five minute period
ldiag (See Note 2)   time,station QC indicator for CSAT3 data, the fraction of time in the 5 minutes that a CSAT3 diagnostic bit was set or a sample was missing.
counts_sonic (See Note 2)   time,station Number of CSAT3 samples averaged. The usual value of 18000 indicates  that all 60 Hz samples were received during the 5 minute period.
sonicHeight m station Approximate measurement height above ground of the CSAT3 anemometer at each station.
kh2o (See Note 3) g/m^3 time,station Water vapor density from Campbell Krypton hygrometer
kh2oV V time,station Raw voltage from Campbell Krypton hygrometer
counts_kh2o   time,station Number of krypton hygrometer samples that were co-incident with CSAT3 samples in the five minute period. This value is usually around 17150, since the krypton was sampled at approximately 57 samples/sec.
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.
Rpile_in W/m^2 time,station Thermopile value of up-looking pyrgeometer, converted to W/m^2
Tcase_in degC time,station Case temperature of up-looking pyrgeometer
Tdome_in* degC time,station Dome temperature of up-looking pyrgeometer
Rpile_out W/m^2 time,station Thermopile value of down-looking pyrgeometer, converted to W/m^2
Tcase_out degC time,station Case temperature of down-looking pyrgeometer
Tdome_out* degC time,station Dome temperature of down-looking pyrgeometer
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 4) 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
Tsoil_0_6cm,
Tsoil_0_6cm_aux
degC time,station Soil temperature at approximately 0.6 cm below surface
Tsoil_1_9cm,
Tsoil_1_9cm_aux
degC time,station Soil temperature at a depth of approx 1.9 cm
Tsoil_3_1cm,
Tsoil_3_1cm_aux
degC time,station Soil temp at a depth of approx 3.1 cm
Tsoil_4_4cm,
Tsoil_4_4cm_aux
degC time,station Soil temp at a depth of approx 4.4 cm
dTsoil_dt_* degC/s time,station Average of [ Tsoil(t) - Tsoil(t-dt) ]  / dt at each of the above depths.
Vheat, Vheat_aux V time,station Hukeseflux TP01 heater voltage
Vpile_off, Vpile_off_aux uV time,station Hukeseflux TP01 thermopile before heating
Vpile_on, Vpile_on_aux uV time,station Hukesflux TP01 thermopile after heating
Tau63, Tau63_aux s time,station TP01 time to decay to 37% of Vpile.on-Vpile.of
Lambdasoil, Lambdasoil_aux W/m/degK time,station TP01 derived thermal conductivity

 

  • 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 the estimated tilt of the sonic with respect to a plane of mean horizontal flow, 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 =18000 +- 1  (60Hz * 300 seconds) 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, often 17999 or 18001 samples will be averaged in a 5 minute period.
  • Note 3: kh2o is the water vapor density, as measured by the Campbell Krypton ultra-violet hygrometer. It has not been corrected for the ultra-violet absorption by O2. kh2oV is the raw voltage output of the detector. If liquid water contaminates the optical path, or if the optics have become scaled with contaminants, the water vapor measurement is compromised. In this case, the raw voltage value will be small, often less than 0.01 V. Until approximately December 1, the krypton optics at all stations were scaled. See the project logbook for details of the krypton cleanings.
  • Note 4: Auxiliary soil measurements, as indicated with an "_aux" suffix, were sampled at stations 1,5 and 6. 

For derived values of the latent, sensible, and surface heat fluxes, see the 30 minute dataset.