Numerical analysis of extreme heat in Nagpur city using heat stress indices, all-cause mortality and local climate zone classification

Abstract

Spatio-temporal investigation of heat-related impacts forms the basis for planning resources and formulating possible countermeasures. The present study aims to examine the effect of temperature extremes on all-cause mortality in Nagpur, a tropical Indian city and investigates (i) long-term (1969–2015) daily air temperature trend (ii) long-term (1985–2015) heat stress pattern using heat stress indices (iii) relationship between heat stress indices and all-cause mortality, and (iv) role of local climate zones to estimate intra-urban variation in mortality. The findings reveal a steady rise in maximum temperature, heat wave, severe heat wave, and hot nights. It was observed that during 1985–2015, heat index and humidex increased by 4 °C and 1 °C respectively. A cubic spline regression revealed a strong influence (R2 > 0.75) between heat stress indices and all-cause mortality. The results indicate that large low-rise and sparsely built areas (i.e., local climate zones 8, 9 and 93) present higher levels of heat stress indicating greater susceptibility to mortality. In contrast, compact/open low-rise developments with vegetation cover showed lower susceptibility to heat stress. The findings provide potential evidence to develop hyperlocal thresholds, and strengthen early warning systems by selecting appropriate indices for a given climate zone.