In this scientific research report, monthly, seasonal and annual area weighted rainfall time series for all-India, 5 homogeneous regions and 30 meteorological subdivisions for the period 1871-2016 are constructed on the basis of a fixed and well distributed network of 306 rain gauge stations over India.

Over India, heat waves occur during the summer months of April to June. A gridded daily temperature data set for the period, 1961–2013 has been analyzed to examine the variability and trends in heat waves over India. For identifying heat waves, the Excess Heat Factor (EHF) and 90th percentile of maximum temperatures were used. Over central and northwestern parts of the country, frequency, total duration and maximum duration of heat waves are increasing.

The present report is a collection of research results presented, by IITM scientists and other experts at the IITM Monsoon Discussion Forums (IMDF) during conspicuous boreal summer of 2015.

The Indian summer monsoons of 2013 and 2014 had contrasting onset and progression phases. The onset was timely and the progression of 2013 monsoon was the fastest in the last 70 years, whereas 2014 had a delayed onset and a very lethargic progression phase compared to 2013.

A 'reliability ensemble averaging (REA)' technique is proposed to provide a quantitative estimate of associated uncertainty range and reliability of future climate change projections for Indian summer monsoon (June-September), simulated by the state-of-the-art Coupled General Circulation Models (CGCMs) under Coupled Model Intercomparison Project 5 (CMIP5).

In the present study, the observed variability of monsoon droughts over India has been examined using a drought monitoring index, namely the Standardized Precipitation Evapo-transpiration Index (SPEI). For calculating the SPEI over different time periods, long term (1901–2010), high resolution, monthly gridded temperature and rainfall data sets have been used. The drought time series shows significant interannual, decadal and long term trends. The analysis suggests a general increase in the intensity and percent area affected by moderate droughts during the recent decades.

In this communication, we discuss the development of a very high resolution (0.5

In this study, using 104 years (1901–2004) of high resolution daily gridded rainfall data, variability and long-term trends of extreme rainfall events over central India have been examined. Frequency of extreme rainfall events shows significant inter-annual and inter-decadal variations in addition to a statistically significant long term trend of 6% per decade. Detailed analysis shows that inter-annual, inter-decadal and long-term trends of extreme rainfall events are modulated by the SST variations over the tropical Indian Ocean. The present study supports the hypothesis that the increasing trend of extreme rainfall events in the last five decades could be associated with the increasing trend of sea surface temperatures and surface latent heat flux over the tropical Indian Ocean. In the global warming scenario, the coherent relationship between Indian Ocean SST and extreme rainfall events suggests an increase in the risk of major floods over central India.

This paper, discusses the development of a very high resolution (0.50 x 0.50 degree) daily rainfall data set for mesoscale meteorological studies over the Indian region. The data set was developed using quality controlled rainfall data from more than 6000 rain-gauge stations over India. The analysis consists of daily rainfall data for all the seasons for the period 1971-2005.

Sub-seasonal rainfall fluctuations, characterized as active and weak spells during the Indian monsoon season (June to September) is an important component of the variability of the Indian monsoon rainfall.