Growth in mid-monsoon dry phases over the Indian region: prevailing influence of anthropogenic aerosols

Chakraborty, Rohit; Guha, Bijay Kumar; Talukdar, Shamitaksha; Ratnam, Madineni Venkat; Maitra, Animesh

A detailed investigation on the potentially drought-prone regions over India is presented in this study based on the balance between precipitation and potential evapotranspiration (PET) during the southwest Asian mid-monsoon season. We introduce a parameter named dry day frequency (DDF) which is found suitable to present the drought index (DI) in mid-monsoon season, hence strongly associated with the possibility of drought occurrences. The present study investigates the probable aspects which influence the DDF over these regions, revealing that the abundance of anthropogenic aerosols especially over urbanized locations has a prevailing role in the growth of DDF during the last few decades. The prominent increasing trend in DDF over Lucknow (26.84 N, 80.94 E), a densely populated urban location situated in the Indo-Gangetic Plain, strongly reflects the dominant association of anthropogenic aerosols with the increasing dry phase occurrences. Increase in DDF (∼90 %) during the last 60 years is observed over this urban area compared to a broader region in its surroundings. In addition, periodic impacts of large-scale phenomena like ENSO (El Niño–Southern Oscillation) or SSN (sunspot number) become weaker when the study location is downscaled towards an urbanized region. Finally, when long-term projections of DDF are drawn using the high urbanization scenario of RCP 8.5, a huge rise in dry days is seen during mid-July to mid-September (reaching up to 50 dry days by the year 2100 over Lucknow), which will be a crucial concern for policymakers in future.

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Chakraborty, Rohit / Guha, Bijay Kumar / Talukdar, Shamitaksha / et al: Growth in mid-monsoon dry phases over the Indian region: prevailing influence of anthropogenic aerosols. 2019. Copernicus Publications.

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Rechteinhaber: Rohit Chakraborty et al.

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