Nitric acid in the stratosphere based on Odin observations from 2001 to 2007 ? Part 1: A global climatology

Joanna M Urban (1) , M. Pommier (1) , D. P. Murtagh (1) , M. L. Santee (2) , Y. J. Orsolini (3)

1 Chalmers University of Technology [Göteborg]
2 JPL - Jet Propulsion Laboratory
3 NILU - Norwegian Institute for Air Research

The Sub-Millimetre Radiometer (SMR) on board the Odin satellite, launched in February 2001, observes thermal emissions of stratospheric nitric acid (HNO₃) originating from the Earth limb in a band centred at 544.6 GHz. Height-resolved measurements of the global distribution of nitric acid in the stratosphere between ~18?45 km (~1.5?60 hPa) were performed approximately on two observation days per week. An HNO₃ climatology based on roughly 6 years of observations from August 2001 to December 2007 was created. The study highlights the spatial and seasonal variation of nitric acid in the stratosphere, characterised by a pronounced seasonal cycle at middle and high latitudes with maxima during late fall and minima during spring, strong denitrification in the lower stratosphere of the Antarctic polar vortex during winter (the irreversible removal of NO_y by the sedimentation of cloud particles containing HNO₃), as well as high quantities of HNO₃ formed every winter at high-latitudes in the middle and upper stratosphere. A strong inter-annual variability is observed in particular at high latitudes. A comparison with a stratospheric HNO₃ climatology based on UARS/MLS measurements from the 1990s shows a good consistency and agreement of the main morphological features in the potential temperature range ~465 to ~960 K, if the different characteristics of the data sets such as altitude range and resolution are considered.

Domaines: Océan, Atmosphère

Joanna M Urban, M. Pommier, D. P. Murtagh, M. L. Santee, Y. J. Orsolini. Nitric acid in the stratosphere based on Odin observations from 2001 to 2007 ? Part 1: A global climatology. Atmospheric Chemistry and Physics Discussions, 2008, 8 (3), pp.9569-9590. ⟨hal-00304186⟩