Sensitivity of NOx over the Indian Ocean to emissions from the surrounding continents and nonlinearities in atmospheric chemistry responses

The sensitivity of the Indian Ocean atmospheric chemistry to continental NOx emissions is examined using a global chemistry‐transport model (MATCH‐MPIC). NOx responds nonlinearly to changes in emissions, since O3 and OH, which depend on NOx, influence its lifetime. Due to this feedback and the contribution from other NOx sources (e.g., lightning), much of the Indian Ocean lower troposphere (LT) is only weakly sensitive to continental NOx emissions. In contrast to INDOEX (Indian Ocean Experiment) results for aerosols, CO, etc., during the winter monsoon the central Indian Ocean (CIO) is weakly sensitivity to Indian NOx emissions. However, the Bay of Bengal LT is very sensitive to NOx emissions from India (summer) and SE Asia and China (winter). Higher up, NOx over the CIO is most sensitive to African and SE Asian emissions, while the northern regions are influenced by the summer monsoon plume from India, SE Asia and China.