With the implementation of the Automated Surface Observing System (ASOS) as the backbone of the NWS surface observing network, the air quality community lost some key data necessary to execute some of the most widely used air dispersion models, particularly the Industrial Source Complex (ISC) suite. Notably missing from the stand-alone, un-augmented ASOS observation is middle and high cloud information required to determine the Pasquill-Gifford (P-G) stability categories in these models. Without the P-G categories, calculating dispersion characteristics would require high frequency wind data. Although ASOS is capable of delivering such data, the cost of reconfiguring the software to collect and store the data and the cost of developing a system to download, QC, and compile the data for the air dispersion models' use is prohibitive. An alternate technique can be employed to determine the P-G category for virtually every ASOS/AWOS site on an hourly basis.
Using techniques developed by scientists at NOAA and the Cooperative Institute for Meteorological Satellite Studies (CIMSS) at the University of Wisconsin, cloud amounts and heights can be inferred from radiance information collected from the Visible Infrared Spin Scan Radiometer Atmospheric Sounder (VAS) aboard the NOAA Geostationary Operational Environmental Satellites (GOES). Past testing shows satisfactory comparisons to traditional human cloud reports.
These cloud data are routinely reported through existing National Weather Service communications on a series of satellite interpretation messages (TCUS40-42 and 51-53 KWBC) and are available to the public. Therefore, these data are available for other traditional application and are not limited to dispersion modeling requirements.
NOAA scientists at the Environmental Protection Agency and state air quality modelers are investigating procedures to implement the use of the METSAT-derived cloud data in air quality models. Expectations are that tests will compare favorably to modeling results which were based on traditional cloud reports.