Comparative Analysis of the 2013 and 2022 Record-Breaking Heatwaves over the Yangtze River Basin

Abstract

The Yangtze River Basin (YRB) experienced record-breaking heatwaves (HWs) during the summers of 2013 and 2022. A comparative analysis of their variations and physical causes was undertaken using ERA5 reanalysis data to determine the similarities and differences between their characteristics and mechanisms. The results show that the duration of the 2013 and 2022 HWs rank as the second and first longest, respectively, since the 1950s. Both HWs were associated with anomalous high pressure and descending motions over the middle and lower reaches of the YRB in conjunction with a westward shift of the Northwestern Pacific subtropical high in summer. These high-pressure anomalies over the YRB led to decreases in total precipitation, soil moisture, and cloud cover and increases in surface solar radiation and air temperature, favoring the 2 HWs. However, high-pressure anomalies associated with the 2013 HWs peaked in July, while those associated with the 2022 HWs peaked in August. The 2022 HWs were of longer duration and higher intensity than those in 2013, which was primarily due to the stronger anticyclonic circulation anomalies induced by more intense Rossby wave trains in the mid to high latitudes in 2022. Notably, the zonal sea surface temperature gradient in the tropical Pacific, which was larger in 2022 than in 2013, played a crucial role in triggering the high-pressure anomalies and extreme HWs over the YRB through forcing distinct patterns of northeastward propagating wave trains over East Asia in the 2 years.