We assembled daily precipitation records, initially for 3838 stations, throughout India and ultimately identified 129 stations with reasonably complete records over the period 1910 to 2000. From these daily records, we generated annual time series of seven different indices of extreme precipitation events, including total precipitation, largest 1, 5, and 30 day totals, and the number of daily events above the amount that marks the 90th, 95th, and 97.5th percentiles of all precipitation at each station. Of the 903 different time series (seven variables for 129 stations), 114 had a significant upward trend and 61 had a significant downward trend; overall, 61% of the time series showed an upward trend. The standard regression coefficients showing the strength and sign of the trend were highly correlated across the network. They generally showed increasing values in a contiguous region extending from the northwestern Himalayas in Kashmir through most of the Deccan Plateau in the south and decreasing values in the eastern part of the Gangetic Plain and parts of Uttaranchal. Our results are in general agreement with the prediction from numerical models for an increase in extreme precipitation events in India given the ongoing build-up of greenhouse gases.

[1] India has one of the most intensive and spatially extensive irrigation systems in the world developed during the1960s under the agricultural Green Revolution (GR). Irrigated landscapes can alter the regional surface energy balance and its associated temperature, humidity, and climate features. The main objective of this study is to determine the impacts of increased irrigation on long-term temperature trends. An analysis of the monthly climatological surface data sets at the regional level over India showed that agriculture and irrigation can substantially reduce the air temperature over different regions during the growing season. The processes associated with agriculture and irrigation-induced feedback are further diagnosed using a column radiation-boundary layer model coupled to a detailed land surface/hydrology scheme, and 3-D simulations using a Regional Atmospheric Modeling System. Both the modeling and observational analysis provide evidence that during the growing season, irrigation and agricultural activity are significantly modulating the surface temperatures over the Indian subcontinent. Therefore irrigation and agricultural impacts, along with land use change, and aerosol feedbacks need to be considered in regional and global modeling studies for climate change assessments.

This study investigates changes in temporal trends and spatial patterns of precipitation in Beijing over the last six decades. These changes are discussed in the context of rapid urbanization and the growing imbalance between water supply and demand in Beijing. We observed significant decreases in precipitation amounts from 1950 to 2012, with the annual precipitation decreasing by 32% at a decadal rate of 28.5 mm. In particular, precipitation decrease is more pronounced in the summer and warm seasons when water use is at its seasonal peak. We further analyzed hourly precipitation data from 43 rain gauges between 1980 and 2012 to examine the spatiotemporal characteristics of both precipitation amount and intensity across six distinct subregions in Beijing. No significant spatial variations in precipitation changes were identified, but slightly greater amounts of precipitation were noted in the urban areas (plains) than in the surrounding suburbs (mountains), due to the effect of urbanization and topography. Precipitation intensity has increased substantially, especially at the hourly duration, as evidenced by the more frequent occurrence of extreme storms. The observed decreased water availability and the increase in extreme weather events require more integrated water management, particularly given the expectation of a warmer and more variable climate, the continued rapid growth of the Beijing metropolis, and the intensifying conflict between water supply and demand.

[1] We assembled data at a 1°latitude by 1°longitude resolution for 285 cells across India and analyzed the seasonal trends in the maximum and minimum temperature, diurnal temperature range (DTR), and cloud cover for the time period 1931 -2002. Significant increases in maximum and minimum temperature have occurred over the Deccan plateau, but in general, trends in DTR were not significant except for a decrease in northwest Kashmir in summer. The effect of cloud cover on the DTR was expectedly negative for most of the country for winter and summer seasons with significant increase in summer cloud cover in Kashmir.Citation: Roy, S. S., and R. C. Balling Jr. (2005), Analysis of trends in maximum and minimum temperature, diurnal temperature range, and cloud cover over India, Geophys. Res. Lett., 32, L12702,

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