Contrasting aerosol trends over South Asia during the last decade based on MODIS observations
D. G. Kaskaoutis1, S. K. Kharol2,3, P. R. Sinha4, R. P. Singh5, K. V. S. Badarinath2, W. Mehdi*, and M. Sharma11Research and Technology Development Centre, Sharda University, Greater Noida, NCR 201306, India 2Atmospheric Science Section, Oceanography Division, National Remote Sensing Centre, Dept. of Space-Govt. of India, Hyderabad 500 625, India 3Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Canada 4National Balloon Facility, Tata Institute of Fundamental Research, Hyderabad 500 062, India 5School of Earth and Environmental Sciences, Schmid College of Science and Technology, Chapman University, Orange, CA 92866, USA *formerly at: Department of Civil Engineering, Indian Institute of Technology-Kanpur, Kanpur 201608, India
Received: 14 Jun 2011 – Accepted for review: 12 Aug 2011 – Discussion started: 16 Aug 2011
Abstract. Atmospheric aerosols over south Asia constitute a major environmental and climate issue. Thus, extensive land and cruise campaigns have been conducted over the area focusing on investigating the aerosol properties and climate implications. Except from the ground-based instrumentation, several studies dealt with analyzing the aerosol properties from space, focusing mainly on the spatial distribution of the aerosol optical depth (AOD) and possible feedbacks of aerosols on the monsoon system. However, except from some works using ground-based instrumentation or satellite observations over a specific region, there is lack of studies dealing with monitoring of the aerosol trend over south Asia. The present work analyzes the variations and trends in aerosol load over south Asia using Terra-MODIS AOD550 data in the period 2000–2009. Overall, an increasing trend of 10.17 % in AOD is found over whole south Asia, which exhibits large spatio-temporal variation. More specifically, the AOD550 increasing trend is more pronounced in winter, and especially over northern India. The present study shows an evidence of a decreasing AOD550 trend over the densely-populated Indo-Gangetic Plains (IGP) during the period April–September, which has never been reported before. This decreasing trend is not statistically significant and leads to an AOD change of −0.01 per year in June, when the dust activity is at its maximum. The AOD decrease seems to be attributed to weakness of dust activity in the northwest of India, closely associated with expansion of the vegetated areas and increase in precipitation over the Thar desert. Similarly, GOCART simulations over south Asia show a pronounced decreasing trend in dust AOD in accordance with MODIS. However, much more analysis and longer dataset are required for establishing this evidence.
Kaskaoutis, D. G., Kharol, S. K., Sinha, P. R., Singh, R. P., Badarinath, K. V. S., Mehdi, W., and Sharma, M.: Contrasting aerosol trends over South Asia during the last decade based on MODIS observations, Atmos. Meas. Tech. Discuss., 4, 5275-5323, doi:10.5194/amtd-4-5275-2011, 2011.