The drivers and mechanisms of the decadal change in summer precipitation over eastern China have been widely investigated. In this context, the potential impact of vegetation changes on the Qinghai–Xizang Plateau (QXP) and its associated processes remain unclear. Using the GIMMS (Global Inventory Modeling and Mapping Studies) Leaf Area Index (LAI) dataset and gridded precipitation data over China, this study investigated the relationship between the decadal increase in spring vegetation cover in the QXP and the decadal change in summer precipitation over eastern China, and the associated mechanism. The results revealed that the late-spring (May) vegetation in the QXP has undergone notable decadal changes around 2010, with LAI anomalies turning from negative to positive. Concurrently, there has been a noticeable decadal change in the summer precipitation over eastern China after 2010, with a shift from wet to dry situations over the Huaihe River basin and South China, and precipitation anomalies turning from negative to positive over Northeast China, North China, and the middle and lower reaches of the Yangtze River basin. A composite analysis of the changes in the surface energy budget over the QXP and the East Asian summer monsoon circulation showed that, as the vegetation cover in the QXP increased in the late spring after 2010, the net surface shortwave radiation increased in response to the low-albedo characteristics of vegetation, leading to an increase in the surface temperature over the QXP and consequently enhancing the upward surface sensible heat flux. The stronger spring sensible heat flux provides a stronger atmospheric heating source in the subsequent summer, intensifying and extending the South Asian High eastward. This effect is accompanied by the strengthening and westward movement of the Western Pacific Subtropical High, thereby changing the decadal summer precipitation over eastern China around 2010. Thus, this study has elucidated the important modulating role of vegetation change in the QXP on the decadal change in summer precipitation over eastern China.

Using ground station observation data, ERA5 reanalysis data, and GPCP global precipitation data, this paper takes the regional heavy rainstorm caused by the coupling of the Qinghai–Xizang Plateau vortex and the Southwest China vortex on June 4–7, 2019, as an example to diagnose and analyze the coupling characteristics and formation mechanism of precipitation. The results show that (1) the weather process was caused by the combined action of the Qinghai–Xizang Plateau vortex and the Southwest China vortex, and the precipitation developed explosively from night to early morning. On June 4, the two vortices produced precipitation centers in the northwest and southwest, respectively, and the precipitation was located in the rear of the Qinghai–Xizang Plateau vortex and the center of the Southwest China vortex. The two vortices were coupled in the early morning of June 5–6, and the precipitation shifted to the front of the vortex, strengthening to its peak. The center of the heavy rainstorm was north of Hubei Province. On the night of 6, the two vortices moved eastward toward the sea, and the precipitation area disappeared on land. (2) During the evolution of the two vortices, when the plateau vortex moved eastward from the plateau, the divergence term and the vertical transport term enhanced the positive vorticity of the basin. At the same time, as the low-level convergence configuration strengthened, the southwest vortex was further induced to develop in the basin, and precipitation occurred in both vortex regions, providing a key dynamic condition for the subsequent coupling of heavy rain. (3) During the coupling development, the centers of the two cyclones at different heights merged to form a deep convective system, which generated strong positive vorticity columns and strong convective instability, accompanied by vertical upward motion and secondary circulation development. The southwest monsoon and the southerly airflow outside the subtropical high transported abundant water vapor to the front of the vortex, and under the synergistic effect of deep shear convergence and strong dynamic uplift, this process eventually led to heavy rain.

This study utilizes daily minimum temperature and relative humidity data from China’s CN05.1 dataset (1982–2022), along with ERA5 reanalysis data, to examine the spatiotemporal distribution characteristics and potential causes of two types of compound extreme low-temperature events in southern China during winter. The results indicate that cold–dry events are distributed across most of southern China, with high-frequency centers in the eastern and Jianghuai regions, whereas cold–wet events exhibit a south-to-north decreasing trend, occurring primarily in the southwestern and western South China regions. Over the past 41 years (1982–2022), cold–dry events have shown an increasing trend in most southern regions of China, whereas cold–wet events have significantly decreased, with notable interannual variability in both event types. Cold–dry events typically occur in early winter, while cold–wet events are more likely to occur in late winter. Further analysis of the different causes of these two event types reveals that early and late winter are associated with distinct atmospheric circulation systems and moisture conditions. The mid-to-high-latitude oblique ridge over Asia and the East Asian trough are key circulation features for cold–dry events, providing favorable conditions for the southward intrusion of cold air. During this period, pronounced moisture divergence over southern China promotes the occurrence of cold–dry events. In contrast, during cold–wet events, the northern branch of the wave pattern maintains a two-trough, one-ridge circulation over the middle and high latitudes of the Eastern Hemisphere. The southern branch of the wave pattern, propagating through West Asia and the Middle East, deepens the southern trough and interacts with the anomalous anticyclone over the western Pacific, transporting warm, moist air to southern China. This leads to moisture convergence in the region, providing abundant moisture for cold–wet events.

The characteristics of convective-scale updrafts in the outer core of tropical cyclones (TCs) simulated under lower- and upper-layer vertical wind shear are compared in this study. The results reveal notable differences between the two experiments. (1) The lower-layer shear experiment features a larger proportion of deep updrafts with top heights above 12 km; vertical mass transport and the maximum vertical velocity associated with outer core updrafts are statistically significantly larger in the lower-layer sheared TC than in the upper-layer sheared TC; this difference is related to the larger convective effective potential energy, equivalent temperature, and water vapor mixing ratio in the boundary layer. Furthermore, interactions among the lower-layer vertical wind shear, local wind shear induced by the circulation of the TC, and surface cold pools are conducive to the initiation and development of updrafts. (2) The radial tilts of updrafts are associated with the updraft top height and asymmetric radial flows. Deep-penetrating updrafts are prevalent in the lower-layer shear experiment, tilting radially outward with height in the downshear quadrants under upper-level radial outflow and inward in the upshear quadrants under upper-level radial inflow. However, in the upper-layer shear experiment, most updrafts tend to tilt radially inward with height, primarily driven by asymmetric radial inflow at upper levels in the downshear-right and upshear quadrants and at lower-to-middle levels in the downshear-left quadrant. (3) In the lower-layer shear experiment, relatively symmetric low-level radial inflow prevails, driving most updrafts to migrate inward toward the TC eye across all quadrants. However, in the upper-layer shear experiment, updrafts in the upshear quadrants tend to move radially outward under the influence of radial outflow in the lower levels, whereas those in the downshear quadrants tend to move radially inward under the radial inflow in the lower levels. (4) In the lower-layer sheared TC, most updrafts exhibit large positive thermal buoyancy, large negative water loading, and large negative dynamic buoyancy; hence, the total buoyancy ranges from negative to positive. In comparison, in the upper-layer sheared TC, most updrafts exhibit smaller positive thermal buoyancy, smaller positive dynamic buoyancy, and smaller negative water loading, resulting in smaller positive total buoyancy.

This study employs ERA5 reanalysis data, station precipitation data from the China Meteorological Administration, NOAA monthly average SST (sea surface temperature), and outgoing longwave radiation flux data from 1980 to 2020 to analyze the impact of zonal position of EASJ (East Asian subtropical jet) on summer precipitation in China, as well as its response to SST in the tropical central-eastern Pacific. The results indicate that in westward-shift years of the EASJ, upper-level convergence and lower-level divergence play an important role in YRV (Yangtze River valley). The eastward displacement and weakening of WPSH (western Pacific subtropical high) at 500 hPa suppress moisture transport to the YRV, leading to reduced precipitation. Meanwhile, upper-level divergence over the Hetao area promotes rising motion, accompanied by lower-level moisture convergence, increasing precipitation in the Hetao area. Meanwhile, in eastward-shift years of the EASJ, the WPSH strengthens and shifts westward. The convergence and divergence patterns in the upper and lower troposphere, along with moisture conditions and vertical motion in these two regions, exhibit reversed characteristics compared with those in westward-shift years of the EASJ. As a result, the precipitation anomalies of eastward-shift years of the EASJ display an opposite phase distribution compared with in westward-shift years of the EASJ. The EASJ’s zonal position is closely related to the summer SST in the tropical central-eastern Pacific. In this region, negative (positive) SST anomalies directly cool (warm) the atmosphere, suppressing (enhancing) local convective activity. These alterations modulate Walker circulation and lead to anomalous ascending (descending) motion in the tropical western Pacific. The vertical motion anomalies further affect East Asia’s mid-latitude region through meridional circulation, reducing (intensifying) convective activity near 30°N. Consequently, the meridional temperature gradient in the eastern part of the climatological jet region decreases (increases) due to diabatic heating, weakening (strengthening) the tropospheric westerlies and resulting in an anomalous westward (eastward) EASJ.

Millimeter-wavelength cloud radar serves as a pivotal instrument for cloud microphysical characterization but is susceptible to clear-air echoes induced by insects, birds, and aerosols, leading to considerable retrieval biases. To enhance detection accuracy and generalizability, this study presents ATNN (Multi-Head Attention Neural Networks), a universal deep learning framework that exclusively employs the reflectivity factor, radial velocity, and relative height for adaptive learning of vertical structural features. Evaluated on observations from Baise, Guangxi, ATNN demonstrates robust performance during the rainy season, achieving a clear-air echo detection rate of 91.98% and a meteorological echo preservation rate of 94.28%; during the non-flood season transition, these metrics are 87.56% and 86.38%, respectively. In contrast, conventional neural networks (NN) achieve marginally higher detection rates but misclassify numerous low-altitude, weak meteorological echoes as clear-air signals, yielding a preservation rate of only 54.96% in non-flood periods. Nationwide validation across 15 operational radar sites further confirms that ATNN attains an average clear-air echo removal rate of 81.17% while preserving 93.89% of meteorological echoes, thereby demonstrating strong regional adaptability.

Based on subseasonal-to-seasonal (S2S) datasets obtained from four models (ECMWF, CMA, UKMO, and NCEP) and ground-observed precipitation data for April–September 1997–2022, an improved deep residual network (ResNet) model was developed for the extended-range probabilistic forecasting of persistent extreme precipitation (PEP). The deterministic and probabilistic forecasts of the improved ResNet model were compared with those of five other methods (single-model ensemble, multi-model ensemble, principal component regression, and Bayesian model averaging). Results demonstrated that the improved ResNet model outperformed other methods in probabilistic forecasting. The enhanced performance of the ResNet model is attributed to the improvement in spatial correlation coefficients, which stems from its ability to deeply extract PEP features from the ECMWF S2S data and the optimization of the ResNet structure. As a result, the improved ResNet model achieves a positive Brier skill score for forecast lead times up to 30 d, highlighting its considerable potential for extended-range probabilistic forecasting of PEP in eastern China.

Southwestern China experienced a typical compound heat–drought event between mid-August and mid-September 2024, which significantly impacted the local economy and livelihoods. In this region, such compound events are related to intraseasonal oscillations (ISOs) originating from different areas. However, conventional statistical methods fail to distinguish the specific contributions of various ISOs to these extreme conditions. Using atmospheric-circulation diagnostics and numerical simulations using the Weather Research and Forecasting model with varying-ISO-signal-driven boundary forcings, this study reveals the following: the ISO signal induced by a mid-latitude westerly wave train in the upper troposphere increased the regional average temperature by 1.331°C in Southwestern China, primarily affecting the northern part of the region. This ISO signal accounted for 62.8% of the overall compound heat–drought event. The ISO signal associated with a middle-tropospheric teleconnection wave train increased regional average temperatures by 0.768°C. This impact is mainly concentrated in the eastern Sichuan Basin and most of Chongqing, accounting for 37.2% of the event. The development of this compound event was predominantly influenced by a mid-latitude westerly wave train from the northwestern boundary. This promoted the significant expansion of the South Asian High over Southwestern China, resulting in strong positive geopotential height anomalies. Simultaneously, warm advection due to the westward extension and northward shift of the Western North Pacific Subtropical High, coupled with positive tropospheric geopotential height anomalies, contributed to regional temperature increases and decreased soil moisture. Overall, this study enhances the understanding of the mechanisms driving compound heat–drought events in Southwestern China, providing a foundation for improving subseasonal-prediction capabilities.

Uncertainties in cloud simulations can affect key physical processes in climate modelling. Using satellite data from CloudSat/CALIPSO and CERES, together with ERA5 reanalysis data, this study analyzes the distribution characteristics of global climatological cloud fraction and cloud radiative effects (CREs) simulated by the atmospheric component FAMIL in the climate system model FGOALS-f3 at resolutions of 100, 25, and 12.5 km. Moreover, the study investigates the potential sources of simulation errors based on the Xu–Randall cloud diagnostic scheme. The results show that at different resolutions, cloud fraction is underestimated in low-latitude areas and overestimated in high-latitude areas and that the simulation performance changes nonlinearly with increasing resolution. On the global scale, the deviation in the 25 km model increases compared with the 100 km model, and the cloud fraction deviation of the 12.5 km model is approximately 4% higher than that of the 25 km model in regions such as the Western Pacific Warm Pool. As model resolution increases, the simulated CRE decreases in association with a reduction in cloud fraction. In the Xu–Randall scheme, relative humidity (RH) is the dominant factor controlling climatological cloud fraction. Resolution enhancement further changes RH by affecting variables such as temperature and vertical velocity, thereby indirectly affecting cloud fraction bias. The weak vertical velocity in the 100 km model indirectly leads to underestimation of middle- and high-level cloud fractions in low-latitude areas. The higher temperature in the 25 km model compared with the 100 km model increases the cloud fraction bias. Furthermore, the lower temperature in the 12.5 km model compared with the 25 km model decreases the cloud fraction bias.

The El Niño–Southern Oscillation (ENSO) represents the most prominent interannual signal within the global ocean–atmosphere system and stands as one of the crucial factors influencing the interannual variability of summer precipitation in the Beijing–Tianjin–Hebei (BTH) region. Based on data such as spring SST (Sea Surface Temperature), summer precipitation in the BTH region, and atmospheric circulation from 1961 to 2023, this study analyzes the interdecadal variation in the relationship between spring ENSO and summer precipitation in the BTH region as well as its possible causes. Results show that the key spring ENSO region significantly impacting the interannual summer-precipitation anomalies in the BTH region underwent an interdecadal shift in the late 1990s, migrating from the eastern Pacific in the earlier period to the central Pacific in the later period. Although SST anomalies (SSTAs) in the key spring ENSO region exhibit a strong negative correlation with the summer precipitation anomalies in the BTH region before and after the shift, the underlying mechanisms differ significantly. When SSTAs exist in the key spring ENSO region, the summer SSTAs in the North Pacific, Indian Ocean, and Atlantic Ocean show different characteristics, which in turn cause circulation anomalies in the tropics and mid-high latitudes through the synergistic effect of SSTAs in different regions. When the key spring ENSO region exhibits warm SSTAs, a distinct anticyclonic circulation is observed in the subtropical northwestern Pacific. After the interdecadal shift, this anticyclonic circulation strengthens, but it still fails to transport water vapor to the BTH region. The BTH region is controlled by a cyclonic circulation. In the earlier period, this cyclonic circulation is associated with SSTAs in the North Pacific, and in the later period, it is caused by the zonal wave train over the Eurasian continent, excited by SSTAs in the North Atlantic. The control of anomalous northerly winds over the BTH region reduces precipitation.