Extreme temperature and rainfall events in National Capital Region of India (New Delhi) in the recent decades and its possible impacts

Abstract

Intergovernmental Panel on Climate Change (IPCC) promulgated a clear message that there have been many extreme weather and climate events observed globally since 1950, and these changes occurred mainly due to anthropogenic causes and emission of greenhouse gases. A computation study was carried out to assess the extreme temperature and rainfall events for the period 1984–2015 at the Indian Agricultural Research Institute, New Delhi by using ETCCDI indices through RClimDex software. The statistical significance of time series data and various calculated indices was done by linear regression as well as by Mann-Kendall test. Results indicated that annual mean maximum temperature decreased significantly at 0.019 °C/year and annual mean minimum temperature showed an increasing trend but without statistical significance. Alteration has happened in atmospheric properties, both physical and chemical over Delhi region during the period because of rapid urbanization and, increased concentration of aerosol. Fossil fuel/biomass waste burning, transportation of sand dust from Thar Desert, and reduction in incoming solar radiation have contributed both for fall in daytime temperature and rise in nighttime temperature. The changes in temperature would affect agricultural production through reduction in the rate of photosynthesis and excessive nocturnal respiration. Frequency and magnitude of coolest day (maximum temperature < 15 °C) and night (minimum temperature < 5 °C) have been rising at IARI, New Delhi. In the case of rainfall-based indices, annual rainfall (PRCPTOT), consecutive wet days (CWD), and number of days with rainfall ≥ 20 mm (R20) showed significant increasing tendency. Increasing trend in simple daily intensity index (SDII), rainy days (R2.5), and declining trend of consecutive dry days (CDD) indicates better distribution of rainfall. Nevertheless, increasing tendency in RX1day, RX5day, and R99p indicates possibilities of heavy rainfall events although the trend has been found insignificant.