CEOP/EOP-1 GAPP SGP Hourly Surface Meteorology, Flux, and Radiation Data Set

1.0 Contact Information

1.1 UCAR/JOSS Contact

   Steven F Williams
   Data Specialist
   P.O. BOX 3000
   Boulder, CO, USA, 80307-3000

   Telephone: 303-497-8987
   Facsimile: 303-497-8158

   E-Mail Address:

1.2 ARM EBBR Contact

  David R. Cook
  Argonne National Laboratory
  9700 South Cass Avenue
  Building 203
  Argonne, IL 60439.
  Phone: (630) 252-5840
  FAX: (630) 252-5498

1.3 ARM SMOS Contact

  Michael T. Ritsche
  Scientific Assistant
  Argonne National Laboratory
  Bldg. 203
  Argonne IL 60439
  Phone: (630) 252-1554
  Fax: (630) 252-5498

1.4 ARM SIRS Contact

  Tom Stoffel
  National Renewable Energy Laboratory
  1617 Cole Blvd.
  Golden, CO 80401-3393
  Voice: 303-384-6395
  Fax: 303-384-6391

2.0 General Description

This data set contains the Coordinated Enhanced Observing Period (CEOP)
Enhanced Observing Period 1 (EOP-1) Global Energy and Water Cycle Experiment
(GEWEX) Americas Prediction Project (GAPP) Surface Meteorology, Flux, and
Radiation data. This data set contains hourly data from 24 Department of
Energy (DOE) Atmospheric Radiation Measurement (ARM) Southern Great Plains
(SGP) stations for the CEOP EOP-1 time period (01 July 2001 to 30 September
2001). The University Corporation for Atmospheric Research/Joint Office for
Science Support (UCAR/JOSS) did not perform quality control processing on this
data set.

3.0  Detailed Data Description

The data comprising this data set are also available on-line in native format at
under the heading CEOP EOP-1 "Native Format" Reference Site Data Sets, GAPP.

This composite data set is composed of data from four sources which report
data at different frequencies. It was developed by the merging of radiation
data from the Solar Infrared Radiation Station (SIRS), flux data from the
Energy Balance Bowen Ratio (EBBR), meteorological data from the Surface
Meteorological Observation System (SMOS), and skin temperatures from the
Infrared Temperature (IRT) networks. These stations are located at many of the
ARM SGP Extended Facilities in southern Kansas and northern Oklahoma.

3.1 SGP Algorithms

This hourly data set was formed by extracting the top of the hour observations
from the native format data. The U and V wind components were computed from
wind speed and direction. More information regarding this site can be found
under the CEOP Reference Site Station Characteristics link on the UCAR/JOSS
CEOP Data Management page at

3.1.1 Heat Flux
Heat flux sensors consist of a differential temperature sensor which measures
heat flow. Heat flux is a vector quantity of energy flowing through a 1 meter
square surface in one second. Sensible heat flux is the transfer of sensible
heat between the surface and the air, or vice versa. Latent heat flux is the
transfer of latent heat (heat released or absorbed by water) between the
surface and the air, or vice versa. Ground, or soil, heat flux is the transfer
of sensible heat in the soil, either toward the surface or away from the

3.1.2 Surface Energy Exchange
Energy balance Bowen ratio measure the rates of heat and moisture exchange
between the surface of the Earth and the atmosphere at selected locations.

The Energy Balance Bowen Ratio (EBBR) system is a ground-based system using in
situ sensors to estimate the vertical fluxes of sensible and latent heat at
the local surface. The flux values are representative of the grassy area
within about 50 meters of the EBBR station. Flux estimates are made from
observations of net radiation, soil heat flow, and the vertical gradients of
temperature and relative humidity; these data are used in the Bowen ratio
energy balance technique.

In this composite data set, all energy flux densities have a negative sign
when directed toward the surface and positive when directed away. For example,
a representative value for latent heat flux could be 100-500 watts per meter
squared during the daytime in the summer. ARM EBBR

The components of the energy balance were determined with the
Bowen Ratio Energy Balance (BREB) method. The BREB method is a
combination of the transport and the energy balance equations. The
Bowen ratio, B {a ratio of the gradient equations of sensible
heat, H and latent heat, E} is given by:

      B = H / E (1)


      H = -rho*c(p)*K(h)*dT/dz

      E = -(rho*epsilon / P)*l(v)*K(v)*de/dz

where symbols are defined as:

      e = Air vapor pressure
      epsilon = Ratio of the molecular weights of water vapor and  
                dry air
      c(p) = Specific heat of air at constant pressure
      K(h) = Eddy diffusivity for heat
      K(v) = Eddy diffusivity for water vapor
      p = Atmospheric pressure
      rho = Air density
      T = Air temperature
      z = Height or depth
      l(v) = Latent heat of vaporization

Substituting (1) in the energy balance equation (2) yields the
BREB (3). Q is net radiation and G is soil heat flux density.

      Q + G + H + E = 0 (2)

In this system surface-air interface is considered as a closed
system. Any energy flux coming in is considered positive and going
out is negative.

      E = -(Q + G) / (1 + B) (3)

(FIFE, 1999) 

3.1.3 Radiation

The ARM SIRS provides measurements of upwelling and downwelling hemispherical
solar irradiances, direct-beam solar irradiance, diffuse hemispherical solar
irradiance from the sky and up- and downwelling hemispherical infrared
irradiances via its collection of instruments including the Multifilter
Rotating Shadowband Radiometer (MFRSR), pyranometer, pyrheliometer, and
pyrgeometer at 19 of the ARM extended facilities (including the central

The ARM Solar Infrared Radiation Station (SIRS) provides continuous
measurements of broadband shortwave (solar) and longwave (atmospheric or
infrared) irradiances for downwelling and upwelling components.

3.2 Station Information

The following is a complete description of the station information provided
with this CEOP GAPP SGP data set. Table 1 details the station list parameters.
GAPP SGP values for each parameter are listed in brackets at the end of each
line. The beginning and ending dates for the period of coverage are in
Universal Time Coordinated (UTC). The Identification Type field is network
dependent and indicates the source of the Identification field. The Occurrence
field is an integer value used to indicate co-located stations. Note that when
a particular parameter is unknown for a station, either a blank, a question
mark, or all 9's will appear in that parameter's position. For a complete list
of Country, State, and County values, refer to the document in the references
(Section 5.0). Possible platform types and frequency values are listed in
Tables 2 and 3, respectively. Note that only those platform types present in
the CEOP EOP-1 data have been listed.

Table 1

Parameter                Description
---------                -----------
Identification           ID in data.        [SGP]
Identification Type      Internal ID number type.  [32]
Latitude                 Station Latitude.  [48.31000]
Longitude                Station Longitude. [-105.10000]
Occurrence               Station occurrence. [0]
Lat/Lon Accuracy         Number of digits accuracy 
                         in lat/lon values.  [2]
Name                     Expanded station name. [GAPP:SGP]
Commissioned Flag        `(C)' indicates commissioned station,
                         `(N)' indicates station which is NOT
                         commissioned. [(N)]
Begin Period of Coverage Beginning date of period of coverage
                         (YYYYMMDD). [20010701]
End Period of Coverage   End date of period of coverage
                         (YYYYMMDD). [20010930]
Country                  Country in which station is located. [US]
State                    State code.  [30]
County                   County code. [???]
UTC offset               Hour Offset from UTC time. [0.00]
DST switch               'y' indicates station does switch to
                         Daylight Savings Time (DST). 'n' indicates 
                         station does not switch to DST.   [n]
Platform type            Collection Platform. See Table 2. [264] 
Reporting Frequency      Frequency of data collection.  [30min]
Elevation                Station elevation. [634]
Fixed/Mobile flag        Flag indicating if station has fixed
                         location. 'f' indicates a fixed station.
                         'm' indicates a mobile station. [f]

Table 2

Platform Type  Description
-------------  -----------
264            CEOP Reference Site Platform

Table 3                                            
Reporting Frequency
varies by site

3.3  Detailed Format Description
The CEOP EOP-1 GAPP SGP Hourly Surface Meteorology, Flux, and Radiation Data
Set contains 10 metadata parameters and 22 data parameters.  The metadata
parameters describe the station location and time at  which the data were
collected. The time of observation is reported  both in Universal Time
Coordinated (UTC) Nominal and UTC actual time. Days begin at UTC 0100 and end
at UTC 0000 the following day. Note that  missing parameter values are
indicated by "-999.99".  The table below  details the data parameters in each

Parameters                   Units 
----------                   -----
Date of Observation          UTC Nominal 
Time of Observation          UTC Nominal 
Date of Observation          UTC Actual
Time of Observation          UTC Actual
CSE Identifier               Abbreviation of CSE name
Reference Site Identifier    Abbreviation of Site name
Station Identifier           Reference Site Dependent 
Latitude                     Decimal degrees, South is negative
Longitude                    Decimal degrees, West is negative
Station Elevation            Meters 
Station Pressure             Hectopascals (mb) 
Dry Bulb Temperature         Celsius 
Dew Point                    Celsius 
Relative Humidity            Percent
Specific Humidity            g/kg
Wind Speed                   m/s
Wind Direction               Degrees 
U Wind Component             m/s
V Wind Component             m/s
Total Precipitation          mm
Snow Depth                   cm     
Sensible Heat Flux           W/m2
Latent Heat Flux             W/m2
Incoming Shortwave Radiation W/m2
Outgoing Shortwave Radiation W/m2
Incoming Longwave Radiation  W/m2
Outgoing Longwave Radiation  W/m2
Net Radiation                W/m2
Skin Temperature             Celsius
CO2 Flux                     uMoles/m2/s
Incoming PAR                 uMoles/m2/s
Outgoing PAR                 uMoles/m2/s

4.0  Data Remarks

This data set contains only the hourly observations for the CEOP EOP-1
time period. This data set is also available on-line in native format at under the link "CEOP EOP-1 Reference
Site Data Sets".

4.1 ARM Data Quality Reports

A few problems occurred with instrumentation during CEOP EOP-1 which affected
the quality of the data. Summarized below are the time period within CEOP
EOP-1, as well as the cause and possible resolution. This information was
taken from Data Quality Reports provided by ARM. (ARM, 2003)


START DATE: 06/21/2001  START TIME: 0   END DATE: 07/17/2001  END TIME: 1901
DESCRIPTION: RH% values approximately 10% high at values of 70% and higher.  
Sensor replaced.


START DATE: 07/17/2001  START TIME: 1830   END DATE: 07/17/2001  END TIME: 1901
DESCRIPTION: All data values off-scale during replacement of T/RH probe.


START DATE: 07/25/2001  START TIME: 1424   END DATE: 07/25/2001  END TIME: 1801
DESCRIPTION: All data values off-scale during routine maintenance.


START DATE: 07/25/2001  START TIME: 1726   END DATE: 07/25/2001  END TIME: 1803
DESCRIPTION: All data values off-scale during routine maintenance.


START DATE: 08/10/2001  START TIME: 1936   END DATE: 08/23/2001  END TIME: 1701
DESCRIPTION: T/RH probe began reading high values of temperature and RH 
intermittently.  High RH values noticed above 70% RH compared to neighboring sites.
High temperature values more difficult to determine but very noteceable on 08/10 
from 19:36 - 21:07z.  Probe replaced.


START DATE: 09/18/2001  START TIME: 2109   END DATE: 09/18/2001  END TIME: 2111
DESCRIPTION: All data values off-scale during routine maintenance.

4.2  ARM EBBR Data Quality Reports

4.2.1 ARM_DQR_20010401_20010823.html
4.2.2 ARM_DQR_20010401_20011005.html
4.2.3 ARM_DQR_20010401_20010823.html
4.2.4 ARM_DQR_20010401_20010823.html

       ARM_DQR is the type of file
       20010401 is the start date of the earliest quality report
                in the file
       20010823 is the end date of the latest quality report in 
                the file

4.3 ARM SIRS Data Quality Reports


4.4  Quality Control Processing

UCAR/JOSS performed limited gross limit and visual checks on this data set. No
data values have been changed.

5.0  References

Bolton, D., 1980: The computation of equivalent potential temperature.,
   Mon. Wea. Rev., 108, pp 1046-1053.

Department of Commerce - National Institute of Standards and Technology
   (NIST), 1985: Federal Information Processing Standards Publication)
   10-3 Countries, Dependencies, & Areas of Special Sovereignty.
   Department of Commerce - NIST, Washington, DC.

Energy Balance Bowen Ratio (EBBR),; September 6, 1999

FIFE Bowen Ratio Surface Flux: Smith Data Set Guide Document,;
   September 8, 1999 

Wexler, A., and W. A. Wildhack, 1963:  Humidity and Moisture.
   Vol. 3: Fundamentals and Standards.  Reinhold Publ. Corp., 562 pp.