Using a combination of satellite observations and computer modelling, researchers of the Max Planck Institute for Chemistry have studied nitrogen oxides pollution over the Indian Ocean. They showed that the central Indian Ocean in the southern hemisphere is not always as pristine as found earlier during the winter monsoon period, but is polluted during the monsoon transition periods by pollution plumes from Africa and Southeast Asia. Generally, the most polluted region is the Bay of Bengal, which is influenced by Indian and south-east Asian outflow during most of the year and China during part of the year (Geophysical Research Letters, 30 April 2004 and 11 August 2004). Current knowledge of atmospheric chemistry over the Indian Ocean is still limited due to the scarcity of long-term observations covering all seasons. The region is dynamically and chemically active because of the strong tropical sunlight, high humidity and the increasing anthropogenic emissions. The Indian Ocean Experiment (INDOEX) was an international field campaign during the winter monsoon period in 1999 to study how air pollution affects climate processes over the tropical Indian Ocean. Satellite pictures showed a thick haze - one of the now well-known "Atmospheric Brown Clouds" - which spreads thousands of kilometers south of India during this period. The results contrasted the highly polluted northern hemisphere with the more pristine air of the southern hemisphere (Fig. 1a).
Research on southern Asian pollution at the Max Planck Institute for Chemistry since then has focused on other periods of the year. The field campaign MINOS (Mediterranean Intensive Oxidants Study), led by the institute during the summer of 2001, showed that the same monsoon storms which produce the torrential rains also lift insoluble gases like carbon monoxide into the upper troposp
Contact: Dr. Mark Lawrence