Guolu Gao

In August 2022, the South Asian High (SAH) deviated from its typical northwest–southeast displacement pattern and exhibited a record‐breaking northeastward shift over the period 1980–2024. Accompanying this displacement, a deep and persistent high‐pressure centre developed over mid‐latitude East Asia, directly leading to extreme heat over the Yangtze River Valley (YRV) in August 2022. Our results indicate that the northeastward shift of the SAH is significantly associated with the negative phase of the Silk Road Pattern (SRP) wave train that is a major atmospheric dynamical process over summer Eurasia. Compared with the weak cold sea surface temperature anomalies (SSTA) over the tropical Indian Ocean and Pacific, the unprecedented negative‐phase SRP played a more critical role in driving the shift of the SAH in August 2022. Furthermore, the strongest warming over the mid‐latitude North Atlantic contributed to triggering and maintaining the unprecedented negative‐phase SRP since 1980, ultimately facilitating the occurrence of the record‐breaking northeastward shift of the SAH in August 2022. The extreme warming in the mid‐latitude North Atlantic is attributed to the northward shift and strengthening of the Gulf Stream. This study provides a novel explanation of the linkage between the Gulf Stream and the northeastward shift of the SAH in August 2022 via the warming North Atlantic, which carries a potential source of predictability of the SAH location and climate change in East Asia.

Due to the effects of large‐scale topography of the Tibetan Plateau (TP), Yunnan‐Guizhou Plateau and Sichuan Basin (SCB), Southwest China (SWC) is characterised by complex synoptic patterns and variable precipitation features. However, the impacts of different synoptic patterns on fine‐scale daily and sub‐daily precipitation in SWC remain poorly understood. To address this issue, this study employs the Self‐Organising Map method to classify summertime synoptic patterns based on rainy‐day circulation fields over SWC into three distinct types. These types are primarily distinguished by the position of the western Pacific subtropical high (WPSH). In the northward‐shifted and inland‐extended pattern (Type 2, 31%), strong afternoon radiative forcing over SWC enhances nocturnal southerly advection, which transports moisture from the South China Sea northward into the SCB, enhancing CAPE and facilitating rapid convective development along the eastern slope of the TP. Under the eastward‐displaced pattern (Type 3, 30%), both radiative forcing and southerly advection weaken. South‐westerly moisture transport from the Bay of Bengal converges with cold air over southern Guizhou (GZ) and South China, creating a high‐CAPE zone conducive to precipitation initiation and subsequent eastward propagation. When the WPSH is located near its climatological position (Type 1, 39%), the lower troposphere over SWC is simultaneously influenced by warm‐moist flows from both the Bay of Bengal and the South China Sea. This configuration leads to pronounced and long‐lasting nocturnal precipitation peaks in both the SCB and GZ, with SCB precipitation primarily associated with a low‐level vortex. The findings of this study provide a new perspective for understanding fine‐scale precipitation characteristics over SWC.

The eastern Tibetan Plateau has a high elevation, with a cold and dry atmospheric background. The features of the raindrop size distributions (DSD) in this region have notable differences from those in the plains. The general empirical relationships for retrieving parameters of precipitation from radar observations are not applicable in the eastern Tibetan Plateau. In this study, we developed a new method based on optimal estimation theory to retrieve the vertical profiles of N₀ and D_m from a Ka-band zenith-pointing Doppler radar. Validation by a field campaign during the summer of 2024 indicates that the mean bias in the log ₁₀(N₀) and D_m derived from the PARSIVEL² disdrometer and the retrieved values are 0.12 and −0.1 mm respectively, demonstrating the effectiveness of the retrieved DSD parameters in this region. Based on the retrieved vertical profiles of DSD parameters, some unique characteristics are found. The heavy precipitation (the maximum value in the reflectivity profile exceeding 30 dBZ) exhibits a higher particle number concentration above 2 km and larger raindrop size in the bottom of the rainfall on average. The mean values of D_m above 2 km are approximately 0.5 mm, for heavy precipitation, the value increase as the raindrops fall, reaching a peak at around 0.5 km. Precipitation that occurs after the nighttime cooling usually has higher particle concentrations and smaller particle sizes. Based on the above research, empirical relationships for the quantitative precipitation estimates (QPE) and attenuation correction using Ka-band radar in the eastern Tibetan Plateau are established.

The eastern Tibetan Plateau has a high elevation, with a cold and dry atmospheric background. The features of the raindrop size distributions (DSD) in this region have notable differences from those in the plains. The general empirical relationships for retrieving parameters of precipitation from radar observations are not applicable in the eastern Tibetan Plateau. In this study, we developed a new method based on optimal estimation theory to retrieve the vertical profiles of N₀ and D_m from a Ka-band zenith-pointing Doppler radar. Validation by a field campaign during the summer of 2024 indicate that the average bias in the log₁₀(N₀) and D_m derived from the PARSIVEL² disdrometer and the retrieved values is 0.12 and -0.1 mm, demonstrating the effectiveness of the retrieved DSD parameters in this region. Based on the retrieved vertical profiles of DSD parameters, some unique characteristics are found. The heavy precipitation (the maximum value in the reflectivity profile exceeding 30 dBZ) exhibits a higher particle number concentration above 2 km and larger raindrop size in the bottom of the rainfall on average. The mean values of D_m above 2 km are approximately 0.5 mm, for heavy precipitation, the value increase as the raindrops fall, reaching a peak at around 0.5 km. Precipitation that occurs after the nighttime cooling usually has higher particle concentrations and smaller particle sizes. Based on the above research, empirical relationships for the quantitative precipitation estimates (QPE) and attenuation correction using Ka-band radar in the eastern Tibetan Plateau are established.

The eastern Tibetan Plateau has a high elevation, with a cold and dry atmospheric background. The features of the raindrop size distributions (DSD) in this region have notable differences from those in the plains. The general empirical relationships for retrieving parameters of precipitation from radar observations are not applicable in the eastern Tibetan Plateau. In this study, we developed a new method based on optimal estimation theory to retrieve the vertical profiles of N₀ and D_m from a Ka-band zenith-pointing Doppler radar. Validation by a field campaign during the summer of 2024 indicate that the average bias in the log₁₀(N₀) and D_m derived from the PARSIVEL² disdrometer and the retrieved values is 0.12 and -0.1 mm, demonstrating the effectiveness of the retrieved DSD parameters in this region. Based on the retrieved vertical profiles of DSD parameters, some unique characteristics are found. The heavy precipitation (the maximum value in the reflectivity profile exceeding 30 dBZ) exhibits a higher particle number concentration above 2 km and larger raindrop size in the bottom of the rainfall on average. The mean values of D_m above 2 km are approximately 0.5 mm, for heavy precipitation, the value increase as the raindrops fall, reaching a peak at around 0.5 km. Precipitation that occurs after the nighttime cooling usually has higher particle concentrations and smaller particle sizes. Based on the above research, empirical relationships for the quantitative precipitation estimates (QPE) and attenuation correction using Ka-band radar in the eastern Tibetan Plateau are established.

The eastern Tibetan Plateau has a high elevation, with a cold and dry atmospheric background. The features of the raindrop size distributions (DSD) in this region have notable differences from those in the plains. The general empirical relationships for retrieving parameters of precipitation from radar observations are not applicable in the eastern Tibetan Plateau. In this study, we developed a new method based on optimal estimation theory to retrieve the vertical profiles of N₀ and D_m from a Ka-band zenith-pointing Doppler radar. Validation by a field campaign during the summer of 2024 indicate that the average bias in the log₁₀(N₀) and D_m derived from the PARSIVEL² disdrometer and the retrieved values is 0.12 and -0.1 mm, demonstrating the effectiveness of the retrieved DSD parameters in this region. Based on the retrieved vertical profiles of DSD parameters, some unique characteristics are found. The heavy precipitation (the maximum value in the reflectivity profile exceeding 30 dBZ) exhibits a higher particle number concentration above 2 km and larger raindrop size in the bottom of the rainfall on average. The mean values of D_m above 2 km are approximately 0.5 mm, for heavy precipitation, the value increase as the raindrops fall, reaching a peak at around 0.5 km. Precipitation that occurs after the nighttime cooling usually has higher particle concentrations and smaller particle sizes. Based on the above research, empirical relationships for the quantitative precipitation estimates (QPE) and attenuation correction using Ka-band radar in the eastern Tibetan Plateau are established.

The eastern Tibetan Plateau has a high elevation, with a cold and dry atmospheric background. The features of the raindrop size distributions (DSD) in this region have notable differences from those in the plains. The general empirical relationships for retrieving parameters of precipitation from radar observations are not applicable in the eastern Tibetan Plateau. In this study, we developed a new method based on optimal estimation theory to retrieve the vertical profiles of N₀ and D_m from a Ka-band zenith-pointing Doppler radar. Validation by a field campaign during the summer of 2024 indicate that the average bias in the log₁₀(N₀) and D_m derived from the PARSIVEL² disdrometer and the retrieved values is 0.12 and -0.1 mm, demonstrating the effectiveness of the retrieved DSD parameters in this region. Based on the retrieved vertical profiles of DSD parameters, some unique characteristics are found. The heavy precipitation (the maximum value in the reflectivity profile exceeding 30 dBZ) exhibits a higher particle number concentration above 2 km and larger raindrop size in the bottom of the rainfall on average. The mean values of D_m above 2 km are approximately 0.5 mm, for heavy precipitation, the value increase as the raindrops fall, reaching a peak at around 0.5 km. Precipitation that occurs after the nighttime cooling usually has higher particle concentrations and smaller particle sizes. Based on the above research, empirical relationships for the quantitative precipitation estimates (QPE) and attenuation correction using Ka-band radar in the eastern Tibetan Plateau are established.

A record‐breaking rainfall event (RBRE) with a maximum daily rainfall amount of 428.2 mm occurred in the eastern periphery of the Tibetan plateau (EPTP) on 10 August 2020. However, the mesoscale and cloud microphysical processes underlying such RBREs in regions with complex terrain remain unclear. Based on multisource observations and a convective‐permitting model, the dominant synoptic systems and key cloud microphysical processes associated with this RBRE are examined. The results reveal that the RBRE was primarily driven by the synergistic interaction between the Tibetan Plateau vortex (TPV) to the northwest of the EPTP region and the low‐level jet (LLJ) to the southeast. This interaction promoted local vorticity growth, leading to the formation of a meso‐β‐scale convective vortex accompanied by enhanced vertical motion, which drove the rapid development of the rainstorm. Further analysis demonstrated the vertically distinct mechanisms in vorticity enhancement: positive vorticity advected by the eastward‐moving TPV dominantly contributed to the vorticity above 500 hPa, and LLJ‐induced inhomogeneous diabatic heating prompted vorticity enhancement below 700 hPa. Latent heat budget analysis showed that diabatic heating in the upper levels was primarily driven by the deposition of water vapor into snow, while in the mid‐to‐lower atmosphere, it was mainly due to the condensation of water vapor into cloud water. The growth of rainwater particles primarily resulted from cloud water collection and snow melting, demonstrating the active roles of both collision–coalescence and ice‐phase microphysical processes. The results provide new insights into the physical mechanisms of heavy rainfall events in the EPTP region.

The Southwest Vortex (SWV) is a crucial rainstorm‐causing mesoscale system in China. However, despite its significance, its early formation process remains unclear due to complex dynamics and sparse observations. Using data from a spatiotemporally intensive sounding experiment for the first time we found a very interesting dual‐SWVs event in the western and eastern Sichuan Basin (SCB). Combined with ground radars and a convection‐permitting model, we have investigated the early formation processes of the dual‐SWV event and found their primary formation drivers differed. The first SWV (SWV1) was mainly driven by spatially non‐uniform diabatic heating from severe convective activities. The convections were triggered when the downslope wind from the Tibetan Plateau (TP) encountered the warm‐moist airflow within the SCB. A shear line on the eastern slope of TP created an upper‐level divergence environment conducive to convection development, thereby reinforcing the local secondary circulation and low‐level vortex. The second SWV (SWV2), however, was mainly driven by the 850‐hPa low‐level jet (LLJ). As airflow poured from the Yunnan‐Guizhou Plateau into the SCB, the LLJ's terminal convergence contributed to the growth in low‐level vorticity. In contrast, thermodynamically driven SWV1 was smaller (100–200 km) and higher (700 hPa) than the dynamically driven SWV2 (300–500 km, 850 hPa). This difference of vortex structure could be attributed to the potential vorticity (PV) redistribution induced by vertical PV advection. The strong vertical PV advection caused by convections lifted the PV to higher isobaric surfaces but also constrained the horizontal scale of SWV1. Moreover, since the positive PV forcing is concentrated below the altitude of diabatic heating peak, the relatively lower peak altitude caused by LLJ also renders SWV2 a shallower vortex than SWV1.

The eastern Tibetan Plateau has a high elevation, with a cold and dry atmospheric background. The features of the raindrop size distributions (DSD) in this region have notable differences from those in the plains. The general empirical relationships for retrieving parameters of precipitation from radar observations are not applicable in the eastern Tibetan Plateau. In this study, we developed a new method based on optimal estimation theory to retrieve the vertical profiles of N₀ and D_m from a Ka-band zenith-pointing Doppler radar. Validation by a field campaign during the summer of 2024 indicate that the average bias in the log₁₀(N₀) and D_m derived from the PARSIVEL² disdrometer and the retrieved values is 0.12 and -0.1 mm, demonstrating the effectiveness of the retrieved DSD parameters in this region. Based on the retrieved vertical profiles of DSD parameters, some unique characteristics are found. The heavy precipitation (the maximum value in the reflectivity profile exceeding 30 dBZ) exhibits a higher particle number concentration above 2 km and larger raindrop size in the bottom of the rainfall on average. The mean values of D_m above 2 km are approximately 0.5 mm, for heavy precipitation, the value increase as the raindrops fall, reaching a peak at around 0.5 km. Precipitation that occurs after the nighttime cooling usually has higher particle concentrations and smaller particle sizes. Based on the above research, empirical relationships for the quantitative precipitation estimates (QPE) and attenuation correction using Ka-band radar in the eastern Tibetan Plateau are established.