MEASUREMENTS OF WATER-VAPOR DISTRIBUTIONS BY THE IMPROVED STRATOSPHERIC AND MESOSPHERIC SOUNDER - RETRIEVAL AND VALIDATION

The Improved Stratospheric and Mesospheric Sounder (ISAMS) measured em issions from the 6.3-mu m band of water vapor using the pressure modul ation technique, The particular form of the technique employed by ISAM S produces two signals: a pressure-modulated signal and a wideband sig nal. Water vapor retrievals from the wideband signal are presented her e since data from the former are still under investigation, The data a re also restricted to nighttime because of the significant nonthermal emission processes which govern the daytime water vapor emissions at t his wavelength, In this paper the retrieval method for the wideband wa ter vapor retrievals is discussed in detail and an internal error budg et is derived based on results for version 9 of the ISAMS data set. Co mparisons are also made with available coincident measurements during the ISAMS period of observations from September 1991 to July 1992, inc luding data from other instruments on the Upper Atmosphere Research Sa tellite.