Abstract: Based on daily meteorological data spanning 43 years from 351 stations in Southwest China, we identified compound hot extremes and droughts at the rice growth period (heading-milk stage and milk-maturity stage) based on daily maximum temperatures and the standardized antecedent precipitation evapotranspiration index (SAPEI). We further analyzed the spatiotemporal variations of these compound events. The results showed that there was a significant increasing trend in the number of stations experiencing compound hot extremes and droughts during the rice growth period from 1980 to 2022. The spatial distribution of event duration and frequency was largely consistent, both exhibiting a pattern of lower values in the southwest and higher values in the northeast, with high-value areas concentrated mainly in southern, central, and northeastern Sichuan Basin, as well as most of Chongqing. In terms of the trend rate of event duration, most regions in Southwest China showed an increasing trend, with only Hekou in Yunnan, experiencing a decrease during the milk-maturity stage. Our findings elucidate the spatiotemporal variations of rice-affecting compound hot extremes and droughts at the daily scale, providing guidance for agricultural production.

Key words: Southwest China, rice, standardized antecedent precipitation evapotranspiration index, compound hot extreme and drought event