Cloud Driftwinds Product: data set description page


Data set source
Information on available Data
Data Processing
Quality Control Processing
Data format
References
Data selection page

Data set source

  • GOES EAST geostationary satellite

    • The GOES Cloud driftwinds product was prepared by Chris VELDEN, Univ. of Wisconsin, Madison USA, from the raw data of the NASA geostationary satellite GOES-8 (position 0N - 75W).

    Information on available data in the FASTEX Central Archive

  • between 19970102:14Z and 19970302:06Z
  • data included in the domain 10N-70N, 95W-05W


    • Data Processing

    The method used to deduce winds from geostationary satellite observations is explained in Velden C. and al.(1997).

    Measurements from two Water Vapor channels of the GOES Sounder (channels 10 and 11) and three channels of the Imager (channel 1 (VIS), channel 3 (WV), chanel 4 (IR)) are routinely used as input of an automated wind-extraction algorithms processus during the FASTEX Experiment period.

  • Time resolution: For imager products a 30 minute time interval is used, for sounder products a 60 minute time interval is used.
  • Horizontal resolution: The resolutions depend on the channel, but also on clouds and features being tracked. These are tracked in boxes of 15 by 15 pixels on 4 km resolution images. Boxes were overlapped as well. For rough estimates, 75km horizontal could be used.
  • Vertical resolution: The vertical resolution is not applicable because vector heights are assigned to features tracked, which could be at any level. Practically, there is a good vector coverage in the 200-400 mb layer, and the 700-950 layer, with less coverage in between.


    • Quality Control Processing

  • Data providers validation
    This dataset is the real-time one, with a few data gaps added/modified in delayed time .

    • Data format

    ASCII format Each file name yymmjjhhFXG8 is made by appending the Date/Time of the data, the FX identifier, and the satellite identifier (G8 for GOES-8).

    Each file contains a header of 1 line, and N data records.

    Each data record contains 9 fields, separated by spaces. The contents and sizes of the 9 fields are as follows (Unit for Unit, Form for FORTRAN Format, Miss for Missing value). 

     No Parameter                                          Unit           Form. Miss
 -- ---------                                          ----           ----- ----

  1 Type                                                              a4
      WV10 - Sounder water vapor winds - channel 10
      WV11 - Sounder water vapor winds - channel 11
      WV   - Imager water vapor winds - channel 3
      IR   - Imager cloud drift winds - channel 4
      VIS  - Imager low level visible winds - channel 1
  2 Sat                                                               a6
      GOES8 - Only satellite available for this data set.
  3 Day                                                yymmdd         a6
  4 Collecting Time (UTC)                              hhmi           a4
  5 Latitude of wind vector (positive north)           dec.degrs      f7.2
  6 Longitude of wind vector (positive west)           dec.degrs      f8.2
  7 Pressure - Height of the wind vector               hPa            i5
  8 Speed of the wind vector                           m/s            f6.1
  9 Direction of the wind vector                       degr           i4

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Please note that the LONGITUDE are POSITIVE WEST in the data files,
this is the opposite of the general use in the FASTEX archive files.
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    References

    Velden C. S., C. M. Hayden, S. J. Nieman, W. P. Menzel, S. Wanzong and J. S. Goerss: Upper-Tropospheric Winds Derived from Geostationary Satellite Water Vapor Observations, Bull. Amer. Meteor. Soc., 78, 173-195, 1997.
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    Updated: 29 Jan 1999