ISFS Variable Names
Updated 2022

 

ISFS variable names and naming convention. Applicable to all ASTER/PAM/ISFF/ISFS projects. Some additional parameters may be included based on the project needs.

Many meteorological variables are sampled using both slow response and fast response sensors. The slow response sensors provide a mean value for state variables, while fast measurements are used in eddy correlation calculations.

Names of slowly sampled variables (usually once per second or less) begin with an upper case character, for example P, T, RH, Dir, Spd, U, and V.

Lower case is used for more rapidly sampled (usually 10/sec or more) eddy correlation variables,for example: t, u, v, w, spd.

Derived fluxes use the abbreviation commonly used in the literature, which may be upper or lower case, for example, H for sensible heat flux.

Met Variables



Variable Name Full Name Usual Units Usual Source Notes
P Barometric pressure mb Barometer  
T Air temperature degC Thermometer, TRH sensor  
RH Relative humidity % Hygrometer, TRH sensor  
Spd Wind Speed m/s Prop vane or 2D sonic aneomometer  
Dir Wind Direction deg Prop vane or 2D sonic anemometer 0=from North, 90=East
U U wind vector component m/s Prop vane or 2D sonic + is from West
V V wind vector component m/s Prop vane or 2D sonic + is from South
Tc Sonic temperature degC 2D sonic  

 

3D Sonic Anemometer Winds

Variable Name Full Name Usual Units Usual Source Notes
u U wind component m/s Sonic anemometer May be in instrument, geographic or special coordinate system
v V wind component m/s Sonic anemometer May be in instrument, geographic or special coordinate system
w W wind component m/s Sonic anemometer May be in instrument, geographic or special coordinate system
spd Wind speed m/s Sonic anemometer May be in instrument, geographic or special coordinate system
dir Wind direction deg " 0=along +u axis
diagbits CSAT3 diagnostic sum   CSAT3 Sonic anemometer Sum of: 1(low signal),2(high signal), 4(no lock), 8(path difference),16(skipped sample)
ldiag CSAT3 logical diagnostic   CSAT3 Logical value, 0=all diagbits are zero, 1=one or more non-zero diabits

Fast Scalar


Variable Name Full Name Usual Units Usual Source
tc Virtual Temp degC Sonic anemometer, speed of sound
t Air Temperature degC Platinum wire
kh2o Water vapor density g/m^3 Krypton hygrometer, not corrected for absorption by O2
h2o water vapor density g/m^3 EC150 H2O/CO2 infrared gas analyzer or fast hygrometer
co2 carbon dioxide density g/m^3 EC150 H2O/CO2 infrared gas analyzer or fast hygrometer
Tirga CSI IRGA temperature deg C EC150 H2O/CO2 infrared gas analyzer
irgadiag diagnostic flag   EC150 H2O/CO2 infrared gas analyzer
Pcell, Pirga Gas analyzer pressure mb Li7500, EC150; will have dynamic pressure error due to poor port placement

Radiation Parameters

Variable Name Full Name Usual Units Usual Source Notes
Rsw.in Incoming short wave radiation W/m^2 Pyranometer  
Rsw.out Outgoing short wave radiation W/m^2 Pyranometer  
Rpile.in Upward-looking pyrgeometer thermopile measurement W/m^2 Pyrgeometer thermopile Not corrected for sensor temperature
Rpile.out Downward-looking pyrgeometer thermopile W/m^2 Pyrgeometer thermopile Not corrected.
Tcase Radiometer case temperature degC Thermistor  
Rlw.in Incoming long wave radiation W/m^2 Pyrgeometer Derived from Rpile.in, Tcase
Rlw.out Outgoing long wave radiation W/m^2 Pyrgeometer Derived from Rpile.out, Tcase
Wetness Surface wetness indicator mV Decagon sensor Can detect water source from shape of signal; flat=dry

Soil and Surface Variables



Variable Name Full Name Usual Units Usual Source
Tsoil Soil temperature degC 4-prong NCAR-built probes
Qsoil Soil moisture %vol CS615, EC-20, EC-5 probes
Gsoil Heat flux at at depth W/m^2 REBS HFT
Vheat heater voltage V Hukseflux TP01
Vpile thermopile voltage microV Hukseflux TP01
Tau63 soil heating time constant s Hukseflux TP01
Lambdasoil soil thermal conductivity W/m K Hukseflux TP01

Rain Parameters

Variable Name Full Name Usual Units Usual Source
rainr, Rainr Rain rate mm/hr Tipping bucket, Ott Parsival2
raina, Raina Rain accumulation mm Derived from raina, Ott Parsival2
WX Present weather code   Ott Parsival2
Z Radar reflectivity (derived) dBz Ott Parsival2
Vis MOR visibility m Ott Parsival2
KE Particle kinetic energy J/m^2h Ott Parsival2
Sig Signal amplitude   Ott Parsival2
N Number of particles   Ott Parsival2
Stat Sensor status   Ott Parsival2

Eddy Correlation Covariances


Variable Name Usual Units Usual Source
w't' m/s degC Covariance of w with t from fast temperature probe
w'tc' m/s degC Covariance of w with sonic temperature
w'h2o' m/s g/m^3 Covariance of w with fast water vapor
w'kh2o' m/s g/m^3 Covariance of w with kh2o from krypton hygrometer, not corrected for absorption by O2
w'co2' m/s g/m^3  
Names of Variances, Covariances and Higher Moments:
  • variance: varname'varname'. Examples: u'u', h2o'h2o', P'P'
  • covariance: varname1'varname2'. Examples: u'v', v'h2o', w'tc'
  • 3rd order moments: varname1'varname2'varname3'. Examples: u'u'u', u'v'w', w'w'tc'
  • How to combine long names into a covariance in a netcdf file:
    • Covariance of h2o.3m and h2o.3m: h2o_h2o__.3m
    • Covariance of w.3m and tc.3m: w_tc__.3m
    • Covariance of u.3m, v.3m, and w.3m: u_v_w__.3m

Engineering Variables


Variable Name Full Name Usual Units
Iload, Icharge Power supply current mA
Ifan Current consumption of TRH sensor's fan mA
Vbatt, Vcharge, Vmote Power supply input voltage V
GPSnsat Number of satellites acquired by GPS  
GPSstat Status of GPS (1 is okay)  
Stratum Status of time service (1 is best)  
Timeoffset Error in data system clock us

Other Derived Quantities

Variable Name Full Name Usual Units Usual Source
H Sensible heat flux W/m^2 Derived from sonic anemometer + gas analyzer
LE Latent heat flux W/m^2 Derived from sonic + gas analyzer

 

Full Format of ISFS Variable Names

If a variable is sampled at multiple locations (i.e. heights on a tower) at a site or with multiple sensors, additional fields can be appended to the variable names to make them unique. These additional fields to the variable names keep the variables distinct, for example at site s2, the variable u can take the name "u_s2", or "u_s2_5m" of multiple sonics mounted on a tower.

Full format of variable names: variable [_ site ] [_ height_depth ]

variable : conventional name for variable being measured, from tables above. Note that temperature measurements of substances other than air, or measured from a different sensor, should have the substance in the measurement name, like Tsoil, Tirga so that it won't be confused with an air temperature.

sensor : (optional) use sensor name if measurement is not unique, e.g.: u & u.gill

height_depth : (optional) height or depth, e.g. 3m, 10m, 3.1cm. Use height if otherwise the name is not unique or if it helps clarify the name.

site : (optional) tower or site name. This is usually only needed if there are multiple towers at a station doing redundant measurements. In NetCDF files, variables from multiple stations will have a station dimension, rather than different names.