Study of Observed Precipitation and Temperature Extreme Indices over India

The Global Climate Model (GCM) projections of precipitation and temperatures reveal that earth is becoming warmer. There will be direct impact on drought and flood occurrences and consequent serious impacts on water resources management, agriculture and environment. The most prevailing consequence of climate change is not the changes in mean conditions but the overall increase in the behaviour of extreme events. A slight change in the frequency of extreme events such as floods, droughts, heat waves will have severe impact on both human society and natural environment. An increase in the number and magnitude of extreme climate events is observed in the recent past in most parts of the world causing huge loss of lives, extensive damages to crops, properties and immeasurable misery to millions of people. Therefore, it is crucial to understand the behaviour of extreme climate events which can be further utilised for urban planning, flood design and management etc.

Many studies have been performed to determine the change in intensity and frequency of extreme precipitation and temperature at different spatial and temporal scales all over the world. Being the second most populous country in the world and diverse socio-economic condition, India is being affected severely by natural calamities linked to climate extremes. The climate extreme trend analysis in the recent years is very much essential for throughout India. To this end, the study of climate extremes has progressed enormously over the last few decades due to the international coordinated efforts led by the Expert Team on Climate Change Detection and Indices (ETCCDI) to standardise the extreme climate indices agreeable to the research community. The ETCCDMI recommended a total of 27 core extreme indices such as the hottest or coldest days of a year, frost days or tropical nights, or the annual maximum 1-day or 5-day precipitation rates and percentile based threshold indices, which estimate the exceedance rates above or below a threshold derived from the considered base period of 1961-1990. The present study considered the gridded daily precipitation data from India Meteorological Department (IMD) available for the period of 1901 to 2015 at 0.25^o X 0.25^o resolution precipitation datasets and the gridded daily maximum and minimum temperatures at a resolution of 1^o X 1^o resolution are used in the study of extreme indices over India. The study reports the trends in extreme precipitation and temperature indices estimated with the observed data sets about 4964 grids over India. Mann-Kendall trend test and Sen’s slope method have been applied to determine significant trends in extreme precipitation indices and magnitude of change respectively for each station. The heterogeneous trends in the extreme precipitation and temperatures are observed over India.