Cardington Data Description
This document describes the file format and contents of the processed data from the Cardington instrumentation site.

1. File names

Data files are named using the following convention: 
 card_YYYYMMDD_xx.dat
where YYYY is the year, MM is the month, DD is the day and xx the averaging period of the data in minutes (eg. 01, 10 or 30).

2. File Format

The datasets are ascii files, which begin with a header section. This consists of a list of the variables contained within the file. Each line in the variable list is made up of three elements - a data prefix, a variable label, and a long-hand description of the parameter.

The prefix refers to the source of the data within the logging system. For instance, variables with a 50m prefix refers to instruments on the 50m sonic mast, and rad refers to the radiation instrumentation data logger. Some parameters, which are measured at more than one height, may be allocated the same variable label, but have different data prefixes. A full list of parameters available in the files, is given below.

Data is then aligned in columns, beneath the relevent variable labels and prefixes. Each data element is preceded by a symbol, representing the quality control status of the instrument. Possible values for the quality control flags are as follows:- 

    |  = data OK
    X  = data flagged as bad
    m  = data missing
    ?  = possibly suspect data
    c  = calibration suspect 
    D  = sonic orientation bad for wind direction
    H  = wind coming from hangar direction
A dummy value (1x1011) is substituted for any data which has been assigned an 'X' flag. 'D' and 'H' flags are applied to data derived from the sonic anemometers only, and indicate that the wind, and turbulence data in particular, may not be reliable.

To read in data from a single file, the PVWAVE/IDL function read_proc_file.pro, may be used. This program returns an unnmamed structure consisting of a 2-d data array, and arrays containing the labels, prefixes and QC flags.

3. Parameter List

The table below, shows a list of the parameters currently contained within the datasets:-

Parameter Label Prefix Notes
Time [hrs] HOUR time Midpoint of averaging period
Mean wind speed [m/s] UTOT 10m, 25m, 50m Magnitude and direction of the mean wind vector
Wind direction [deg] DIR 10m, 25m, 50m
* Maximum gust [m/s] UMAX 10m, 25m, 50m Peak scalar windspeed during averaging period
* Variance U wind component [m2/s2] UU 10m, 25m, 50m Turbulence statistics

The three wind components are defined as follows:-
- U is the horizontal wind in the direction of the mean wind vector.
- V is the horizontal wind perpendicular to the mean wind vector.
  (mean V = 0)
- W is the vertical wind component.
  (upwards positve)

T is the sonic-derived temperature

Q is the specific humidity derived from either the LICOR (10m) or humicaps (25m and 50m)

CO2 concentration is derived from the LICOR

* Variance V wind component [m2/s2] VV 10m, 25m, 50m
* Variance W wind component [m2/s2] WW 10m, 25m, 50m
* Variance Sonic Temperature [K2] TT 10m, 25m, 50m
* Covariance U and W [m2/s2] UW 10m, 25m, 50m
* Covariance V and W [m2/s2] VW 10m, 25m, 50m
* Covariance U and V [m2/s2] UV 10m, 25m, 50m
* Covariance W and T [K.m/s] WT 10m, 25m, 50m
* Covariance W and Q [kg/m2/s] WQL 10m
* Covariance W and Q [kg/m2/s] WQH 25m, 50m
* Covariance W and CO2 [kg/m2/s] FCO2 10m
Temperature [oC] TEMP screen, 10m, 25m, 50m 'screen' temperature and humidity sensors located at 1.2m above gorund level
Relative humidity from Humicap [%] RHHU screen
Dewpoint from Michell hygrometer [oC] DEWP screen
Specific humidity from Michell hygrometer [%] QMIC screen
Relative humidity from Michell hygrometer [%] RHMI screen
Relative humidity from Humicap [%] MRH 25m, 50m  
Specific humidity [g/kg] QLIC 10m from LICOR
C02 concentration [ppm] MCO2 10m
Global solar irradiance [W m-2] SWDN rad  
* Maximum global solar irradiance [W m-2] SWMX rad  
Diffuse solar irradiance [W m-2] SWDF rad  
Reflected solar irradiance [W m-2] SWUP rad  
Downwelling LW irradiance [W m-2] LWDN rad  
Upwelling LW irradiance [W m-2] LWUP rad  
Surface radiation temperature [oC] IRTG rad  
Visibilty [km] VISI screen  
Nephelometer scattering coefficient [km-1] NEPH rad  
Barometric pressure [hPa] PRES screen 1.2m above ground level
* Rainfall [mm] RAIN screen Accumulation over averaging period
* Soil Moistures (south site) [%vol] SMxx subsoil_s xx is depth of the sensor:
10 = 10cm
22 = 22cm
57 = 57cm
2M = 1.6m
* Soil Moisture (west site) [%vol] WMxx screen
* Soil Temperature (south site) [oC] STxx subsoil_s xx is depth of the sensor (cm):
01,04,07,10,17,35 or 65
* Water table depth (west site) [mm] WTWE screen Depth below ground level
* Water table depth (south site) [mm] WTSO subsoil_s


* Note that the parameters indicated above are not output in the 1 minute datasets. This includes the various turbulence quantities derived from the sonic anemometers, plus the slow response measurements (ie soil moistures and temperatures.)

Some of the parameter labels are common to more than one data prefix and so reference must be made to both the variable label and the prefix when extracting the desired data from the file. For example, to access the mean windspeed at 25m, the variable labelled 'UTOT', and having a prefix '25m' should be accessed. Other variables on the other hand, are unique to a single data prefix, and so reference need only be made to the variable label (eg. 'VISI' for the visibility)

Cardington Instrumentation Facility

Last Modified:- 6th November 2006
By:- james.mcgregor@metoffice.gov.uk