Abstract
The Improved Limb Atmospheric Spectrometer (ILAS) was a satellite sensor developed by Global Environment Division, the Environment Agency of Japan, for monitoring the ozone layer. ILAS was onboard the ADEOS (Advanced Earth Observing Satellite) "MIDORI" satellite which was launched on August 17, 1996 by the National Space Development Agency of Japan (NASDA). ILAS measured about 6700 vertical profiles of O3, HNO3, NO2, N2O, CH4, and H2O in the stratosphere both in the Northern and the Southern Hemispheres from November 1996 to June 1997. It provided valuable observational data for investigating the mechanism of ozone loss in high latitude stratosphere. Substantial ozone loss was found from the ILAS O3 data, which were taken in early spring in 1997 in the northern high latitude region. Simultaneously, frequent occurrence of Polar Stratospheric Clouds (PSCs) was observed.
