ISFF Variable Name Convention

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.

Slowly sampled variables (usually once per second or less) have upper case characters in their names, 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, and q.

Some derived variables have capitalized abbreviated names, using the symbol commonly used in the literature, 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
RH
relative humidity
%
hygrometer
Td
dewpoint temperature
degC
Tw
wet bulb temperature
degC
Q
specific humidity
gr/kg of moist air
MR
water vapor 

mixing ratio
gr/kg of dry air
Spd
wind Speed
m/s
prop vane
Dir
wind Direction
deg
prop vane
0=from North, 

90=East
Spdmax
maximum wind wpeed 
m/s
U
U wind vector

component
m/s
prop vane
+ is from West
V
V wind vector

component
m/s
prop vane
+ is from South


 
Sonic Anemometer Winds
Variable Name
Full Name
Usual Units
Usual Source
Notes
u
U wind
m/s
Sonic anemometer
sonic coordinates
v
V wind
m/s
" "
w
W wind
m/s
" "
spd
wind speed
m/s
" "
dir
wind direction
deg
" "
0=along +u axis
Vazimuth
pointing direction (0=N,90=E)
of sonic +V axis
deg
" "
uflag,vflag,

wflag,tcflag
sonic spikes
none
" "
fraction of points

that are detected

as spikes


 
Fast Scalars
Variable Name
Full Name
Usual Units
Usual Source
tc
virtual Temp
degC
Sonic anemometer,

speed of sound
t
air Temperature
degC
Platinum wire
h2o
water vapor density
gr/m^3
q
specific humidity
gr/kg of moist air
mr
water vapor 

mixing ratio
gr/kg of dry air
co2mr
CO2 mixing ratio
ppmV
o3mr
ozone mixing ratio
ppbV


 
Eddy Correlation Covariances
Variable Name
Full Name
Usual Units
Usual Source
w't'
m/s degC
covariance
w'tc'
m/s degC
"
w'q' 
m/s gr/kg
"
w'h2o'
m/s gr/m^3
"
w'mr'
m/s gr/kg
"
w'co2mr'
m/s ppmV
"
w'o3mr'
m/a ppbV
"


 
Fluxes and Other Derived Quantities
Variable Name
Full Name
Usual Units
Usual Source
H
sensible heat flux
W/m^2
LE
latent heat flux
W/m^2
G
surface heat flux
W/m^2
L
Monin-Obukhov length
m
u*
friction velocity
m/s
z/L
stability


 
Radiation
Variable Name
Full Name
Usual Units
Usual Source
Notes
Rnet
net radiation
W/m^2
Rsw.in
incoming short

wave radiation
W/m^2
Rsw.out 
W/m^2
Rlw.in
incoming long

wave radiation
W/m^2
Rlw.out
W/m^2
Rpile.in
upward-looking

thermopile

measurement
W/m^2
thermopile
Not corrected 

for sensor

temperature
Rpile.out
downward-looking

thermopile
W/m^2
thermopile
Not corrected.
Tcase.in
radiometer case

temperature
degC
thermistor
Tdome.in
radiometer dome

temperature
degC
thermistor
Tcase.out
degC
thermistor
Tdome.out
degC
thermistor
Rsw.sum
signed sum of 

short wave

radiation
W/m^2
in - out

+ve = net

incoming
Rlw.sum
signed sum of 

long wave radiation
W/m^2
Rsum
signed sum of

all radiation
W/m^2
Tsfc
surface temperature
degC
Rpar.in
Rpar.out
Ruv.in
Ruv.out
Rveg
"veggie" meters


 
Soil and Surface Variables
Variable Name
Full Name
Usual Units
Usual Source
Tsoil
soil temperature
degC
Qsoil
soil moisture
%vol
G
heat flux at surface
W/m^2
Gsoil
heat flux at at depth
W/m^2
Tice
ice temperature
degC
Gice
heat flux at at depth
W/m^2


 
Rain
Variable Name
Full Name
Usual Units
Usual Source
rainr
rain rate
mm/hr
tipping bucket
raina
rain accumulation
mm


 
Engineering Variables
Variable Name
Full Name
Usual Units
Usual Source
Tbox
electronics temperature
degC

Full Format of ISFF Variable Names

If a variable is sampled at multiple locations at a site or with multiple sensors, additional fields can be appended to the variable names to make them unique. Adding additional fields to the variable names should only be done to keep the variables distinct. The instrument type, height and site should be documented elsewhere, rather than carried as excess baggage in the variable name. If possible, use simply "u" instead of "u.ati",or "u.ati.5m", or "u.ati.5m.flux".

Full format of variable names: variable [. sensor ][. height_depth ][. site ]

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

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

height_depth : (optional) height or depth, e.g. 3m, 10m, 8cm. 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.

Names of Variances, Covariances and Higher Moments:

variance: varname'varname' u'u'

covariance: varname1'varname2' u'v'

How to combine long names into a covariance:

Covariance of "u.atik.3m" and h2o.csi.3m: u'h2o'.(atik,csi).3m

Covariance of "u.atik.3m" and h2o.3m: u'h2o'.(atik,).3m