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====== GERB Station Data ======

===== Introduction =====

At the end of the RMIB GERB processing, the data in the SHI images (3*3 SEVIRI pixel resolution) is extracted over pre-defined pixels. These pixels correspond to the positions of ground measurement stations in the GERB field-of-view such as BSRN sites. This extraction is expected to be useful in the frame of the validation of the GERB processing and to validate surface radiation budget retrieval from GERB data.

===== Listing of stations =====

The extraction is currently performed over the following stations:

    Station       Country               Lat      Lon

    Achern        Germany               48.638   8.066
    Balbina       Brazil                -3.2   -60.0
    Bermuda       USA-sponsored         32.3   -64.3
    Budapest      Hungary               47.8    19.1
    Cabauw        The Netherlands       51.97    4.93
    Cambourne     UK                    50.0    -5.0
    Carpentras    France                44.0     5.0
    Chilbolton    UK                    51.1445 -1.437
    De-Aar        South Africa         -30.7    24.0
    Florianopolis Brazil               -27.5   -48.5
    Hornisgrinde  Germany               48.604   8.204
    Heselbach     Germany               48.539   8.395
    Ilorin        Nigeria                8.5     4.6
    Lindenburg    Germany               52.3    14.1
    Niamey        Niger                 13.477   2.176
    AMMA-anc      Niger                 13.522   2.632
    Palaiseau     France                48.713   2.204
    Payerne       Switzerland           46.8     6.9
    Riyadh        Saudi Arabia          24.7    48.8
    Sede-Boqer    Israel                30.9    34.8
    Tamanrasset   Algerie               22.78    5.85
    Toravere      Estonia               58.3    26.5
    Uccle         Belgium               50.8     4.35
    Valencia      Spain                 39.57   -1.29

===== Files Format =====

For each station, a monthly ASCII file is created (for example //Uccle_200402.txt// for February 2004 at the Uccle station). The file contains a header followed by the 15' data organized in line. The file looks like:

  # Station: Valencia
  # position      : lat=39.570  lon=-1.290   (line=187.822,column=606.480)
  # nearest pixel : lat=39.549  lon=-1.342   (line=    188,column=    606)
  # Viewing zenith angle=46.000000 , viewing azimuth angle=178.000000
  #
  #  time        flux_s  flux_t  rad_s  rad_t c_sw c_lw cc  ca  cp  sz  ra        hdf_file
  20040219075510   81.00  230.75  97.25 371.75   1   3  -1  -1  -1  80 117 # G2_SEV1_L20A_H_20040219_074500_V002.hdf
  20040219081010   94.00  229.25 120.00 369.50   7  -1  -1  -1  -1  77 119 # G2_SEV1_L20A_H_20040219_080000_V002.hdf
  20040219082510  107.00  235.25 144.25 379.25   3   1   0   0   0  74 122 # G2_SEV1_L20A_H_20040219_081500_V002.hdf
  20040219084010  128.00  232.25 178.50 374.25   5   0   0   0   0  72 125 # G2_SEV1_L20A_H_20040219_083000_V002.hdf
  20040219085510  134.00  229.75 194.50 370.50   8  -2   0   0   0  70 128 # G2_SEV1_L20A_H_20040219_084500_V002.hdf
  20040219091010  149.50  228.00 214.25 367.25   5   0  22  14   0  67 131 # G2_SEV1_L20A_H_20040219_090000_V002.hdf
  20040219092510  169.75  234.00 253.00 377.50   5   1  11  11   0  65 134 # G2_SEV1_L20A_H_20040219_091500_V002.hdf
  ...
  ...

The header gives:

  - the positions of the station (lat-lon and coordinates in the ARCH field-of-view)
  - the positions of the nearest pixel (lat-lon and coordinates in the ARCH field-of-view)
  - the viewing angle for the pixel
  - the viewing azimuth angle for this pixel

The different columns of data provide respectively:

  - Time (UTC) of acquisition at the station [YYYYMMDDhhmmss],
  - solar flux [W/m2],
  - thermal flux [W/m2],
  - solar radiance [W/m2/sr],
  - thermal radiance [W/m2/sr],
  - shortwave correction factor [%],
  - longwave correction factor [%],
  - cloud cover [%],
  - cloud amount [%],
  - cloud phase [%],
  - solar zenith angle [°],
  - relative azimuth angle [°],
  - original file name.

Remarks:

  - When a quantity is not available (for example the cloud retrieval during the night) the quantity is set to -1.0.
  - The user must be aware that the data files are not sorted chronologically.
  - For more information about the meaning of these different numbers see [[gerb_content|GERB Content Description]].
  - Details of BSRN sites can be found at: https://bsrn.awi.de/

===== Station data access =====

The station data are available for download on the ROLSS FTP site provided you are a registered GERB data user (you need a //username// and //password// to login). The station files are in the following ROLSS directories:

     cd G2/SEV1/G2_SEV1_L20A_H_STATION       before May 2007
     cd G1/SEV2/G1_SEV2_L20A_H_STATION       after May 2007

===== For more information / addition of station =====

For additional information or to add new locations in the list, please email:

  * To : <Nicolas.Clerbaux@meteo.be>
  * CC : <gerb@oma.be>
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