Spatial and temporal variability of stratospheric HNO₃ from IASI global measurements

Abstract : Nitric acid (HNO₃) plays a crucial role in the stratospheric ozone cycles but its spatial distribution was until recently only accessible from limb satellite measurements, with medium coverage and sampling. IASI provides since 2007 HNO₃ concentration distributions with unprecedented spatial and temporal sampling, which have not yet been exploited. In this presentation, we will first briefly review the characteristics of the HNO₃ profiles retrieved from IASI and we will show results from a validation exercise, in which the HNO₃ profiles and total columns from IASI are compared with those retrieved from ground-based measurements at several sites. We will then show and discuss the spatial distributions of HNO₃ IASI total and stratospheric columns and assess the seasonal and inter-annual variability of HNO₃ using the 8 years of IASI observations available. Preliminary results from a simple multivariable regression model applied to these time series will be shown to support the analysis and to identify the principal processes driving the variability of stratospheric HNO₃. In this discussion focus will be given onto the polar regions, where the relation of HNO₃ to ozone will be investigated in greater details. With these results, the potential of using IASI for studying stratospheric chemistry will be more generally highlighted.