Abstract
The impacts of concurrent droughts and heatwaves could be more serious compared to their individual occurrence. Meteorological drought condition is generally characterized by low rainfall, but impact of such an event is amplified with simultaneous occurrence of heatwaves. Positive feedback between these two extremes can worsen the rainfall deficit situation to serious soil moisture depletion due to enhanced evapotranspiration. In this study, the concurrence of meteorological droughts and heatwaves is investigated in India using Indian Meteorological Department (IMD) high resolution gridded data over a period of 60 years. Significant changes are observed in concurrent meteorological droughts and heatwaves defined at different percentile based thresholds and durations during the period 1981–2010 relative to the base period 1951–1980. There is substantial increase in the frequency of concurrent meteorological droughts and heatwaves across whole India. Statistically significant trends in the spatial extent of droughts are observed in Central Northeast India and West Central India; however, the spatial extent affected by concurrent droughts and heatwaves is increasing across whole India. Significant shifts are identified in the distribution of spatial extent of concurrent drought and heatwaves in India compared to the base period.
Highlights
India has witnessed severe droughts in the recent past and heatwaves have been occurring frequently across many parts of the country
Slight increase in the frequency of 3-day heatwaves is observed along Eastern Ghats and in some regions of West Central India (Telangana, Chhattisgarh, Maharashtra and Madhya Pradesh) (Fig. 1a)
Analysis of concurrent droughts and heatwaves over India during 1951–2010 is presented in this study, with a view to quantify the changes in their frequency and spatial extent
Summary
India has witnessed severe droughts in the recent past and heatwaves have been occurring frequently across many parts of the country. Significant long term increasing trends are observed in the frequency of heatwaves over India during recent 50 years (1961–2010), with 2001–2010 being the warmest decade for the country[2]. Total duration and maximum duration of heatwaves is observed over central and north-western parts of the country[3]. Number of consecutive days with maximum temperature above 90th percentile is generally taken as three or five[23] for defining a heatwave. 3-day, 5-day and 10-day heatwave events defined above 85th, 90th and 95th percentiles of maximum daily temperature are considered in this study. Droughts are classified as moderate (SPI < −1.3), severe (SPI < −1.6) and extreme (SPI < −2) following the World Meteorological Organisation guidelines for using SPI26
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