In July and August of 2022, unprecedented and long-lasting heatwaves attacked central and eastern China (CEC); and the most affected area was in the Yangtze River (YR) basin. The extreme heatwaves and associated drought and wildfire had significant social impacts, but the underlying mechanisms remain unknown. Observational analysis indicates that the heatwaves were regulated by anomalous anticyclone in the mid-upper troposphere over northern CEC. Specifically, the easterly anomalies at the southern flank of the anticyclone caused air isentropic sliding and transported low moist enthalpy (cold and dry) air to the YR basin, contributing to anomalous sinking motions and extreme heatwaves. In comparison, heatwaves were more serious in August than in July due to stronger upper-level anomalous anticyclone and associated easterlies. Importantly, different mechanisms were responsible for the heatwaves in the two months. In July, the relatively weaker anticyclonic anomaly over northern CEC was dominated by the forcing of diabatic heating over northwestern South Asia (NWSA), corresponding with the record-breaking rainfall in and around Pakistan. In August, a powerful anticyclonic condition for the CEC heatwaves originated from an extreme silk road pattern (SRP), superposing the effect of NWSA diabatic heating due to persistent downpour. We notice that another upstream anticyclonic node in the SRP also created heatwaves in Europe. Therefore, the CEC extreme heat was actually associated with other concurrent extremes over the Eurasian continent through large-scale atmospheric teleconnections in 2022.
We have investigated changes of western North Pacific land-falling tropical cyclone (TC) characteristics due to warmer climate conditions, using the pseudo-global-warming (PGW) technique. Historical simulations of three intense TCs making landfall in Pearl River Delta (PRD) were first conducted using the Weather Research and Forecasting (WRF) model. The same cases were then re-simulated by superimposing near- (2015–2039) and far- (2075–2099) future temperature and humidity changes onto the background climate; these changes were derived from the Coupled Model Intercomparison Project phase 5 (CMIP5) multi-model projections according to the Representative Concentration Pathway (RCP) 8.5 scenario. Peak intensities of TCs (maximum surface wind in their lifetimes) are expected to increase by ~ (3) 10% in the (near) far future. Further experiments indicate that surface warming alone acts to intensify TCs by enhancing sea surface heat flux, while warmer atmosphere acts in the opposite way by increasing the stability. In the far future, associated storm surges are also estimated to increase by about 8.5%, computed by the Sea, Lake, and Overland Surges from Hurricanes (SLOSH) model. Combined with sea level rise and estimated land vertical displacement, TC-induced storm tide affecting PRD will increase by ~1 m in the future 2075–2099 period.
This study investigates the leading pattern of Eurasian summer heat waves (HWs) using observed and simulated data sets and reveals an intensified mode of variability that bridges the HWs in eastern Europe (EE) and northern China (NC). The concurrent variability of the HWs in EE and NC is primarily driven by an atmospheric circum‐global teleconnection that induces anomalous anticyclones over the two regions. The observed upward trends in EE and NC HW days could be related to the warm sea surface temperatures around Greenland Island, which may weaken the Atlantic westerly jet stream and lead to amplified wave trains at the exit of the jet, resulting in strengthened anticyclones over EE and NC that favor the occurrences of HWs. The Geophysical Fluid Dynamics Laboratory high‐resolution atmospheric model fails to simulate the EE and NC HWs, due probably to the model's poor representation of the South Asian summer rainfall.
Pakistan summer monsoon rainfall consists of a large portion of the local annual total rainfall, and in the recent monsoon seasons, prolonged periods of anomalous rainfall and excessive flooding have appeared in Pakistan. A full understanding of the monsoon rainfall variability is important for the sustainable development of the country. Based on multiple data analyses and the weather research and forecasting model, the potential impact of Tibetan Plateau (TP) heating on the interannual variability of Pakistan monsoon rainfall is investigated. It is observed that a significant negative relationship exists between the thermal forcing over the southeastern TP and Pakistan monsoon rainfall in July–August. Both the data analyses and model sensitivity experiments identify that the TP heating drives a Rossby wave response in the upper atmosphere characterized with an anticyclonic anomaly over the southern TP but a cyclonic anomaly to the north. This dipole pattern of anomalous circulation induces an evident upper-level convergence over Pakistan, corresponding with remarkable vertical sinking motion. Meanwhile, in the lower troposphere, the TP heating causes anomalous westerly wind along the Himalayas over the northern India continent. Such westerly anomaly further induces less water vapor transport into Pakistan from the Bay of Bengal. Therefore, both the dynamic and thermodynamic processes regulated by positive TP heating are not beneficial for the occurrence of monsoon rainfall in Pakistan. This study proposes a new potential mechanism in which TP heating acts as a driver of Pakistan monsoon rainfall variability on interannual time scales.