A bispectral approach for temperature determination of semitransparent clouds is taken to identify areas covered by Polar Stratospheric Clouds (PSCs). The method is based upon the information obtained from two satellite pixels and two spectral channels of the passive HIRS instrument onboard the NOAA satellites. Since PSCs form and emit in very cold stratospheric environments (<195 K) solutions of the bispectral method yield low temperatures in a range that clearly differs from those derived for a cold but cloudfree stratosphere. Application of the method to NOAA satellite data gained during the major PSC event on January 31 1989 demonstrates that large areas covered by dense PSCs are found with a horizontal distribution in very good agreement to independent airborne and satellite measurements.
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