Tropopause‐Level NOx in the Asian Summer Monsoon

Abstract

Abstract 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 NO2, NO, and NOx in the UTLS ASM anticyclone from satellite measurements. Observations of NO2 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 NOx photochemistry, and to derive the NOx concentration using OSIRIS NO2 and O3 observations. The satellite data show a relative minimum in NO2 over the ASM in the summer months, while the corresponding NO and NOx anomalies are elevated, mainly due to low O3 and cold temperatures within the ASM. The observations within the ASM show reasonable agreement to simulations from the Whole Atmosphere Community Climate Model.

Keywords

• Asian summer monsoon
• UTLS
• NOx chemistry