Articles | Volume 16, issue 16
Research article
22 Aug 2016
Research article |  | 22 Aug 2016

Tropospheric ozone variability during the East Asian summer monsoon as observed by satellite (IASI), aircraft (MOZAIC) and ground stations

Sarah Safieddine, Anne Boynard, Nan Hao, Fuxiang Huang, Lili Wang, Dongsheng Ji, Brice Barret, Sachin D. Ghude, Pierre-François Coheur, Daniel Hurtmans, and Cathy Clerbaux

Abstract. Satellite measurements from the thermal Infrared Atmospheric Sounding Interferometer (IASI), aircraft data from the MOZAIC/IAGOS project, as well as observations from ground-based stations, are used to assess the tropospheric ozone (O3) variability during the East Asian Summer Monsoon (EASM). Six years 2008–2013 of IASI data analysis reveals the ability of the instrument to detect the onset and the progression of the monsoon seen by a decrease in the tropospheric 0–6 km O3 column due to the EASM, and to reproduce this decrease from one year to the other. The year-to-year variability is found to be mainly dependent on meteorology. Focusing on the period of May-August 2011, taken as an example year, IASI data show clear inverse relationship between tropospheric 0–6 km O3 on one hand and meteorological parameters such as cloud cover, relative humidity and wind speed, on the other hand. Aircraft data from the MOZAIC/IAGOS project for the EASM of 2008–2013 are used to validate the IASI data and to assess the effect of the monsoon on the vertical distribution of the tropospheric O3 at different locations. Results show good agreement with a correlation coefficient of 0.73 (12 %) between the 0–6 km O3 column derived from IASI and aircraft data. IASI captures very well the inter-annual variation of tropospheric O3 observed by the aircraft data over the studied domain. Analysis of vertical profiles of the aircraft data shows a decrease in the tropospheric O3 that is more important in the free troposphere than in the boundary layer and at 10–20° N than elsewhere. Ground station data at different locations in India and China show a spatiotemporal dependence on meteorology during the monsoon, with a decrease up to 22 ppbv in Hyderabad, and up to 5 ppbv in the North China Plain.

Short summary
The Asian Summer Monsoon has implication on the weather and climate system as well as pollutants concentration over the monsoon regions leading to effects on the global air quality. Our results, combining satellite, aircraft and ground station data, show that tropospheric ozone, decrease during the period May–August over East and South Asia due to the Monsoon. The magnitude of this drop depends largely on meteorology and geographic location.
Final-revised paper