The present study focuses on analyzing the precipitation trends over six Indian cities during the summer monsoon (June–September) covering the period 1951–2007 and also attempting to investigate possible urban forcing and dynamics by examining the variation in precipitation in the upwind and downwind directions. The analysis shows negative trends in the total number of rainy days over Hyderabad (？10.4%), Kanpur (？7.1%), Jaipur (？10.5%), and Nagpur (？4.8%) and positive trends over Delhi (7.4%) and Bangalore (22.9%). On the other hand, decreases of ？21.3%, ？5.9%, ？14.2%, and ？14.6% in seasonal rainfall are found over Delhi, Hyderabad, Jaipur, and Kanpur, respectively, whereas Bangalore and Nagpur show 65.8% and 13.5% increase. The lesser rainfall and rainy days, along with the mostly declining trend, in the downwind directions of the cities may imply an urban influence in precipitation associated with the increased anthropogenic emissions due to expansion of the urban areas and the increase of population. However, the large spatiotemporal variability of precipitation and the lack of statistical significance in the vast majority of the trends do not allow the extraction of safe conclusion concerning the aerosol-precipitation interactions around Indian cities. 1. Introduction Rainfall is a key physical process that transports water from the atmosphere back to Earth’s surface and links weather, climate, and hydrological cycle [1, 2]. Especially for India, precipitation has serious importance in the regional climate, annual crop, food grains, and local economy and, therefore, analysis of the long-term trends in precipitation was the subject of numerous studies [3–5]. Duhan and Pandey [5] analyzed 102 years of precipitation records in central India (Madhya Pradesh) founding a spatial-averaged decreasing trend of ？2.59%, with a maximum decrease of ~？12%, but only 3 out of the 45 stations exhibited significant decreasing trend in annual precipitation. However, pronounced spatiotemporal differences were observed between the 45 stations on seasonal basis. Analysis of 100 years of surface rainfall observations over India suggested that the mean monsoon rainfall has not been significantly changed, but several locations across the country exhibited an increasing trend in heavy rainfall (>70？mm/day) during the summer monsoon season [6]. Furthermore, the increase in extreme rainfall (>120？mm/day) events during the Indian summer monsoon (ISM) is particularly pronounced during the last 50 years [7]. The extreme rainfall events analysis by Malik et al. [8] suggested that
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