Tropopause-Level NO x in the Asian Summer Monsoon.

Deep convection within the Asian summer monsoon (ASM) transports surface level air into the upper troposphere-lower stratosphere (UTLS). This work aims to understand the distribution of NO 2 , NO, and NO x in the UTLS ASM anticyclone from satellite measurements. Observations of NO 2 from the Optical Spectrograph and InfraRed Imager System, the Atmospheric Chemistry Experiment - Fourier Transform Spectrometer (ACE-FTS), and the Stratospheric Aerosol and Gas Experiment III on the International Space Station are considered. The PRATMO photochemical box model is used to quantify the NO x photochemistry, and to derive the NO x concentration using OSIRIS NO 2 and O 3 observations. The satellite data show a relative minimum in NO 2 over the ASM in the summer months, while the corresponding NO and NO x anomalies are elevated, mainly due to low O 3 and cold temperatures within the ASM. The observations within the ASM show reasonable agreement to simulations from the Whole Atmosphere Community Climate Model.