STRATOSPHERIC NO AND NO2 ABUNDANCES FROM ATMOS SOLAR-OCCULTATION MEASUREMENTS

Using results from a time-dependent photochemical model to calculate t he diurnal variation of NO and NO2, we have corrected Atmospheric Trac e MOlecule Spectroscopy (ATMOS) solar-occultation retrievals of the NO and NO2 abundances at 90 degrees solar zenith angle. Neglecting to ad just for the rapid variation of these gases across the terminator resu lts in potential errors in retrieved profiles of similar to 20% for NO 2 and greater than 100% for NO at altitudes below 25 km. Sensitivity a nalysis indicates that knowledge of the local O-3 and temperature prof iles, rather than zonal mean or climatological conditions of these qua ntities, is required to obtain reliable retrievals of NO and NO2 in th e lower stratosphere. Extremely inaccurate O-3 or temperature values a t 20 km can result in 50% errors in retrieved NO or NO2. Mixing ratios of NO in the mid-latitude, lower stratosphere measured by ATMOS durin g the November 1994 ATLAS-3 mission compare favorably with in situ ER- 2 observations, providing strong corroboration of the reliability of t he adjusted space-borne measurements.