Lengthening Dry Spells Intensify Summer Heatwaves

A lengthening of dry spells (DSLs) has been reported by some regional studies, but its linkage with heatwaves via the feedback between soil moisture and air temperature is still not clear on global continental scales. Here we examine increases in length DSLs during summer over continents using situ precipitation records. Globally, average DSL increased 0.46 day/decade since 1970s along high-pressure anomalies which are found to be an important reason for intensification as suggested robust widespread relationships heatwave duration severity northern extratropics. The associated a declined lands, implying strengthening coupling heatwaves. findings this study suggest that variations changes should considered attributions extremes.