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CR prepress abstract   -  DOI: https://doi.org/10.3354/cr01655

Recent patterns of extreme temperature events over Tamil Nadu, India

R. Rajkumar*, C. S. Shaijumon, B. Gopakumar, Deepak Gopalakrishnan

*Corresponding author:

ABSTRACT: The present study tracks and investigates the time evolution of heat waves and warm nights over the seven agro-climatic zones of Tamil Nadu, India, during the period 1951-2016. The spatiotemporal patterns of concurrent hot day and hot night (CHDHN) episodes and the concurrent warm spells in daytime temperature and drought (CWD) episodes over the region come within the purview of this investigation. The research relied upon gridded temperature and rainfall observations from the India Meteorological Department (IMD). The Heat-wave magnitude index daily (HWMId) was utilized to study the warm spells in daytime and nighttime temperature, while the analysis of droughts was performed using the Standardized Precipitation Evapotranspiration Index (SPEI). We observed a considerable increase in the count, intensity, and duration of heat waves and warm night episodes across Tamil Nadu, between the two epochs 1951-1983 and 1984-2016. Particularly, the number of heat wave events has almost doubled in the second half of the study period. We observed a west - east gradient in the severity of heat waves over Tamil Nadu. The intensity and duration of warm night events have recorded up to a three-fold increase in the second half of the study period, especially over the central Tamil Nadu. The study also recorded a multi-fold increase (α= 0.01) in the number and frequency of CHDHN episodes and the number of CWD episodes during 1984-2016 in comparison with the base period 1951-1983. More importantly, the incidence of compound events that coexisted with anomalous phases of SST registered a statistically significant (α = 0.01) spike in many locations across Tamil Nadu. These changes in the temperature induced extremes pose an exceptional public health threat that can increase morbidity and mortality, disproportionately affecting vulnerable sections of Tamil Nadu’s populace engaged in outdoor work.