Lidar measurements of stratosphere-mesosphere thermal structure at a low latitude: comparison with satellite data and models

Abstract

Making use of 240 nights of Rayleigh lidar data collected over March 1998 to July 2001, we present the general characteristics of low-latitude middle atmospheric temperature structure over Gadanki (13.5°N, 79.2°E). The height-monthly mean temperature contour plot shows two distinct maxima in the stratopause region (~45-55 km), occurring over February-March and September-October, a seasonal dependence quite different from that reported for midlatitudes and high latitudes. The statistical distributions of stratopause and its temperature show the most probable values to be 47-48 km and 262-264 K, respectively. A comparison with the satellite (UARS Halogen Occultation Experiment) data shows a fairly good agreement, but for the mesospheric inversion region of 70-80 km, where the lidar measurements are about 5-10 K warmer than those of the satellite. A comparison with the models, CIRA-86 and Mass Spectrometer Incoherent Scatter Extended-1990 (MSISE-90), showed that the agreement with differences less than 3 K is the best for CIRA-86 over ~40-55 km and MSISE-90 over 55-65 km. Below 40 km, both models overestimate by 3-9 K, with deviations somewhat larger for MSISE-90. For 70-80 km both models deviate significantly, with differences exceeding 10 K, particularly during equinoctial periods when the mesospheric inversion occurs most frequently.