The objective of this project is to generate a 20-year tropospheric wind data set covering both polar regions, poleward of approximately 65 degrees latitude, using the historical Advanced Very High Resolution (AVHRR) Global Area Coverage (GAC) data from NOAA satellites. The winds data set will extend the record back 20 years, providing an invaluable product for the verification of, and assimilation in, climate prediction models.
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| An example of winds produced from NOAA-11 AVHRR on August 5, 1993 at 1800 utc. The background is the AVHRR 11 micron brightness temperature image. Wind vectors are grouped into three height categories (for illustration only): below 700 hPa (yellow), from 400 to 700 hPa (cyan), and above 400 hPa (magenta). |
GAC data are navigated and calibrated with software developed at the Colorado Center for Astrodynamics Research (CCAR) at the University of Colorado-Boulder (Dan Baldwin). Although multiple NOAA satellites are typically in orbit, only one satellite is employed at any given time. The European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-40 Reanalysis data serves as the model background for the wind processing. The ERA-40 data are 2.5 by 2.5 degree GRIB files that contain temperature, humidity, geopotential height, mean sea-level pressure and u,v wind profiles. They are converted into 1 degree resolution for wind retrievals. The MODIS polar winds procedure has been adapted for use with the AVHRR data. However, winds are derived only through cloud tracking as the AVHRR does not have a water vapor channel.
Winds for the period 1982-2002 have been generated. The data are available with conditions. Data access and format is described here as a web page or here as a PDF file. The historical AVHRR polar winds are only available in BUFR format via FTP at CIMSS.
This research is being performed by Richard Dworak, Jeff Key, Dave Santek, and Chris Velden. Support was provided by NOAA and NASA.