Significance: Torrential rains induced by tropical cyclones (TCs) are a major trigger of catastrophic flood hazards. Devastating TCs causing unprecedented floods in recent years were usually characterized with low translation speeds. We find that both observations and numerical simulations show a significant slowdown of TCs over the coast of China. Our analyses of long-term observations exhibit a significant increase in extreme rainfall amounts induced by TCs, and significant inverse relationships between TC translation speeds and local rainfall totals over the study period. Our probability analysis reveals the association of higher local rainfall totals and slow-moving TCs. We provide observational evidence that slowdown of TCs tends to elevate local rainfall totals and thus impose greater flood risks at the regional scale.

The coastal part of China and its surrounding regions are dominated by a highly dense population and highly developed economy. Extreme precipitation events (EPEs) cause a lot of damage and hence changes in these events and their causes have been drawing considerable attention. This study investigated EPEs resulting from western North Pacific (WNP) tropical cyclones (TCs) and their potential link to El Niño–Southern Oscillation (ENSO), using TC track data, daily precipitation data from 2313 stations for 1951–2014, and the NCAR–NCEP reanalysis dataset. Two types of EPEs were considered: EPEs within 500 km from the TC center, and those caused by mesoscale and synoptic systems, referred to as predecessor rain events (PREs), beyond 1000 km from the TC center. Results indicated significant impacts of TCs on EPEs along the coastal areas, and discernable effects in inland areas of China. However, the effect of TCs on EPEs tended to be modulated by ENSO. During neutral years, inland areas of China are more affected by TC-induced extreme precipitation than during El Niño or La Niña years, with the highest density of TC tracks and larger-than-average numbers of tropical storms, typhoons, and landfalling TCs. During the El Niño phase, the central and eastern equatorial Pacific was characterized by higher sea surface temperature (SST), greater low-level vorticity (1000 hPa) and upper-level divergence (250 hPa), and stronger prevailing westerlies, which combined to trigger the movement of mean genesis to the eastern and southeastern WNP, resulting in fewer TCs passing through the Chinese territory.

Urbanization has become a prominent anthropogenic activity globally, resulting in the substantial modification of temperature and rainfall in and around urban areas. Studies also indicate that rainfall exhibits an asymmetrical shift from light to extreme rainfall, causing both floods and droughts over different parts of the globe. However, to what extent urbanization influences the asymmetrical changes in rainfall and urban drought remains understudied. Accordingly, we provided an investigation of the urbanization effects on both rainfall and drought events from both statistical and model‐based perspectives. Results showed that urbanization generally increased heavy rainfall and decreased light rainfall in the rainy season over five urban agglomerations (i.e., Yangtze River Delta [YRD], Middle Region of Yangtze River [MRYR], Chengdu‐Chongqing, Guizhou, and Yunnan) in the Yangtze River Basin during 1981–2020. Specifically, urbanization contributed 42.7% and 30.8% of the increases of heavy rainfall in MRYR and YRD while 30.6% contribution to the decrease of light rainfall. Interestingly, results suggested that the urban regions were more prone to drought due to urbanization. Nevertheless, we also found that the urbanization effects showed some variabilities across different areas due to the interactions with complex terrains and climate patterns. Further model‐based simulations using the Weather Research and Forecasting model confirmed our findings and helped understand the potential underlying mechanism. The current research is expected to provide scientific knowledge for better urban planning and preparedness for urbanization‐induced hazards.

Urbanization and global warming are the two major drivers of the warming environment in cities. The contributions of urbanization and global warming to the past occurrence of human‐perceived heatwaves (HWs) over China are evaluated in this study. Both observations and model simulations show HWs have become more intensive, longer‐lasting, and more frequent in recent decades. Urbanization and greenhouse gases contribute to 21.9% and 72.9% of the intensification of HWs, respectively. The occurrence probability of observed human‐perceived HWs has doubled over 1961–2012 and is projected to be about 4.36/5.92 times under the 1.5/2°C warming relative to the preindustrial level. At the 3.5°C warming, the average duration of HWs is projected to increase to 43.63 days/year, and the occurrence probability is expected to increase by 11.95 times, 91% of which is attributable to human‐induced warming. The highest sensitivity of the increases in HWs due to human‐induced warming is in Southern China.