QuestionHow do I calibrate GOES AREA files provided by CLASS?
Satellites measure upwelling radiation from the Earth. Visible radiation is generally what our eyes see. Infrared radiation is sensitive to the temperature of the surface (e.g., clouds, oceans, etc). The satellites sensor converts radiation falling on the sensor to a voltage which is generally reported in counts (often ranging from 0-255 counts for 1-byte data or 0-1023 for 10-bit data). Satellite image calibration is the conversion of this count value to a radiance, which is then often converted to a temperature (for infrared) or reflectance (for visible).
The satellite format converter developed at NCDC will convert CLASS-netCDF and Area files to netCDF format (applying a calibration and navigation as needed).
The weather and climate toolkit developed at NCDC will calibrate and remap CLASS-Area files to various output formats, some of which can be used with GIS software.
Image formats: GIF/JPGFor imagery data from CLASS, there is little to do. GIF and JPG imagery are not calibrated, but are simply displayed in a scale appropriate for visual analysis.
netCDFThe netCDF files raw provide satellite data from the Area files. So data in netCDF files must first be converted from 16-bit to 10-bit data by dividing by 32. Then use this result to calibrate the IR observations to radiance or brightness temperature and the visible observations to radiance or scaled reflectance.
Information on the conversion from 10-bit data to radiance/brightness temperature/reflectance can be found at:
McIDAS Area Files - GVARThese files are Area files which originate from GVAR data. This includes the following satellites: GOES-8,9,10,11,12,...
The user will need to read the data from the files, then calibrate the data using the information provided by the links above.
McIDAS Area Files - Mode dataThese files are Area files which originate from mode A/AA/AAA data. This includes the following satellites: GOES-1,2,3,4,5,6,7
A description of the calibration will be included here at a later date.
RawRaw data from GVAR files are calibrated in the same manner as described in the links above.