Tropospheric ozone maxima observed over the Arabian Sea during the pre-monsoon

摘要

An enhancement of the tropospheric ozone column (TOC) over Arabian Sea (AS)during the pre-monsoon season is reported in this study. The potentialsources of the AS spring ozone pool are investigated by use of multiple datasets (e.g., SCIAMACHY Limb-Nadir-Matching TOC, OMI/MLS TOC, TES TOC, MACCreanalysis data, MOZART-4 model and HYSPLIT model). Three-quarters of the enhanced ozoneconcentrations are attributed to the 0–8 km height range. The main sourceof the ozone enhancement is considered to be caused by long-range transportof ozone pollutants from India (∼  50 % contributions to the lowest4 km,  ∼  20 % contributions to the 4–8 km height range), theMiddle East, Africa and Europe (∼  30 % in total). In addition, thevertical pollution accumulation in the lower troposphere, especially at4–8 km, was found to be important for the AS spring ozone pool formation.Local photochemistry, on the other hand, plays a negligible role in producingozone at the 4–8 km height range. In the 0–4 km height range, ozone isquickly removed by wet deposition. The AS spring TOC maxima are influenced bythe dynamical variations caused by the sea surface temperature (SST) anomalyduring the El Niño period in 2005 and 2010 with a  ∼  5 DU decrease.