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[Ａ−３.７　Stratospheric denitrification and composition of polar stratospheric clouds inferred from 3D simulations and ILAS data]

[Contact person]

[Total Budget for FY1999-2000]

　2,000,000 Yen
　(FY 2000; 1,000,000 Yen)

［Abstract］

　Polar stratospheric clouds (PSCs) form in winter of both hemispheres at an altitude varying between 12 and 30 km. The key role played by these clouds in the Antarctic 《 ozone hole 》 phenomenon and in the substantial ozone loss often observed during the Arctic winter is now well recognized. However, the mechanism of formation of PSCs, as well as the physical nature of their particles, is still relatively poorly known. This uncertainty has important implications on our ability to predict their occurrence and their future impact on the ozone layer. This study uses a state-of-the-art three-dimensional model of the stratospheric chemistry to analyse the observations of the ILAS satellite-borne sensor developed by the Environmental Agency of Japan. In particular, vertical profiles of nitric acid (HNO₃) are compared to coincident model calculations in order to derive information on the composition of PSCs and their impact on the vertical distribution of nitrogen species.

［Key Words］

　stratosphere, ozone, nitric acid, polar stratospheric cloud (PSC), denitrification