Validation of version 5.20 ILAS HNO3, CH4, N2O, O3, and NO2 using ground-based measurements at Arrival Heights and Kiruna

Ground-based measurements of O3 and NO2 columns at Kiruna (68°N) and Arrival Heights (78°S) were used to validate stratospheric profile measurements of the same species by the satellite-based Improved Limb Atmospheric Spectrometer (ILAS) flown between November 1996 and June 1997. In addition, measurements of HNO3, CH4, and N2O made at Arrival Heights are compared with measurements of these species by ILAS. Even though there were no temporal coincidences in the latter comparison, the groundbased data provide a climatological context for the ILAS measurements. ILAS profiles measured within 10° of longitude and 2° of latitude of each site were used. For the species with large tropospheric components (CH4 and N2O), ILAS profiles were integrated upward from 12 km and were compared with ground-based retrievals of partial columns above 12 km. For O3, which is primarily stratospheric but has an appreciable tropospheric component, tropospheric columns (typically to 8–10 km altitude) calculated from ozonesonde climatologies were added to the integrated ILAS profiles to allow comparison with ground-based total column ozone measurements. Tropospheric columns of HNO3 and NO2 were assumed to be sufficiently small so that ILAS profiles integrated above 8 km could be compared directly with ground-based total column measurements.