Spatio-temporal trend in heat waves over India and its impact assessment on wheat crop

This study presents two aspects of heat waves over India. Firstly, we have analysed the gridded daily temperature data (1° × 1°) for six decades (1951–2015) to understand the changes in heat waves using the heat wave magnitude index daily (HWMId). Secondly, we have post-facto assessed the impact of the March 2010 heat wave on the growth and yield of wheat crop over north India. The study clearly showed the effectiveness of HWMId to capture the heat waves over India. The most-intense heat waves have significantly increased over 56% area of the country, and over the past three decades, it also started occurring in non-conventional heat wave regions of the southern peninsula and northeastern India. Among different categories of HWMId, the rate of spatial spread was highest for the very extreme category. The auto-regressive integrated moving average (ARIMA) intervention technique showed negative impact of the March 2010 extreme heat on yield of wheat over north India. The yield decreased by 4.9%, 4.1% and 3.5% over Punjab, Haryana and Uttar Pradesh, respectively, which were statistically significant (p < 0.1). Though the total production decreased, it was non-significant due to the slight increase in harvested area. Satellite-derived crop phenology parameters also captured the event. The rate of browning increased significantly over the study area. There were inter-district variations in the heat-wave impacts. The results may be used for identification of potential heat wave zones. It may also be used for devising zone-specific adaptation strategies for shielding wheat crop from such events.