A major experimental drought research project entitled “Mechanisms and Early Warning of Drought Disasters over Northern China” (DroughtEX_China) was launched by the Ministry of Science and Technology of China in 2015. The objective of DroughtEX_China is to investigate drought disaster mechanisms and provide early-warning information via multisource observations and multiscale modeling. Since the implementation of DroughtEX_China, a comprehensive V-shape in situ observation network has been established to integrate different observational experiment systems for different landscapes, including crops in northern China. In this article, we introduce the experimental area, observational network configuration, ground- and air-based observing/testing facilities, implementation scheme, and data management procedures and sharing policy. The preliminary observational and numerical experimental results show that the following are important processes for understanding and modeling drought disasters over arid and semiarid regions: 1) the soil water vapor–heat interactions that affect surface soil moisture variability, 2) the effect of intermittent turbulence on boundary layer energy exchange, 3) the drought–albedo feedback, and 4) the transition from stomatal to nonstomatal control of plant photosynthesis with increasing drought severity. A prototype of a drought monitoring and forecasting system developed from coupled hydroclimate prediction models and an integrated multisource drought information platform is also briefly introduced. DroughtEX_China lasted for four years (i.e., 2015–18) and its implementation now provides regional drought monitoring and forecasting, risk assessment information, and a multisource data-sharing platform for drought adaptation over northern China, contributing to the global drought information system (GDIS).

With the rapid development of the general aviation industry in China, the influence of high-impact aeronautical weather events, such as aircraft icing, on flight safety has become more and more prominent. On 1 March 2021, an aircraft conducting weather modification operations crashed over Ji’an City, due to severe icing. Using multi-source meteorological observations and atmospheric numerical simulations, we analyzed the meteorological causes of this icing accident. The results indicate that a cold front formed in northwestern China and then moved southward, which is the main weather system in the icing area. Based on the icing index, we conducted an analysis of the temperature, relative humidity, cloud liquid water path, effective particle radius, and vertical flow field, it was found that aircraft icing occurred behind the ground front, where warm-moist airflows rose along the front to result in a rapid increase of water vapor in 600–500 hPa. The increase of water vapor, in conjunction with low temperature, led to the formation of a cold stratiform cloud system. In this cloud system, there were a large number of large cloud droplets. In addition, the frontal inversion increased the atmospheric stability, allowing cloud droplets to accumulate in the low-temperature region and forming meteorological conditions conducive to icing. The Weather Research and Forecasting model was employed to provide a detailed description of the formation process of the atmospheric conditions conducive to icing, such as the uplifting motion along the front and supercooled water. Based on a real case, we investigated the formation process of icing-inducing meteorological conditions under the influence of a front in detail in this study and verified the capability of a numerical model to simulate the meteorological environment of frontal icing, in order to provide a valuable reference for meteorological early warnings and forecasts for general aviation.

Based on the U.S. Weather Research and Forecasting (WRF) numerical model, this study has developed the Northwest Mesoscale Numerical Prediction Service and Experimental System (NW-MNPS). Surface and sounding data assimilation has been introduced for this system. Effects of model vertical layers and land-use data replacement have been assessed. A year-long forecast validation and analysis have been performed. The following results have been obtained: (1) Data assimilation can improve the performance of regional numerical forecasting. (2) Compared to simulations with 40 vertical layers, simulations with 55 vertical layers are more accurate. The average absolute error and root-mean-square error of the 48 h surface element forecast decrease. The analysis of threat score (TS) and equitable threat score (ETS) shows that there are higher TS and ETS values for various precipitation intense levels, in particular for heavy rainfall when comparing a 55-vertical-layer test with a 40-vertical-layer test. (3) Updating the database to include vegetation coverage can more accurately reflect actual surface conditions. The updated land-use data reduce prediction errors in all domains of the NW-MNPS.

The complex terrain of the Qinghai–Tibetan Plateau (QTP) makes low-level wind shear (LLWS) detection challenging. Using May–September 2023 high-resolution Doppler Wind Lidar (DWL) observations, this study analyzed the spatiotemporal characteristics of LLWS and proposed an optimized detection algorithm. A key novelty of this work lies in the development of a hybrid physical–statistical detection scheme that combines horizontal divergence with logistic regression to dynamically modulate the shear field. This approach effectively reduces noise-induced false alarms in complex plateau terrain. The results show that LLWS occurred mainly near the surface at night in June, while in September it appeared more frequently during daytime throughout the boundary layer. Horizontally, the dominant directions of LLWS shifted seasonally from northwest and west in June to south and east in September. The proposed optimization method effectively suppressed false alarms, reducing moderate and strong LLWS frequencies by 30–40%. In June, optimization significantly reduced spurious detections of LLWS in the northeast and southwest. The frequency of LLWS in the northeast direction was reduced by up to 0.03. In September, scattered shear was removed and strong shear became more organized in the southeast, while southwest shear frequency decreased by up to 0.04, confirming LLWS patterns and method effectiveness.

Changes in atmospheric circulation can be influenced by the collapse characteristics of the polar vortex, a significant system in the Northern Hemisphere. This study reveals the spatiotemporal evolution and causative mechanisms of the collapse of the Northern Hemisphere polar vortex, as well as the polar vortex collapse criteria, Mann–Kendall test, mutation year extraction, and physical mechanism analyses, based on the fifth-generation European Centre for Medium-Range Weather Forecasts (ECMWF) atmospheric reanalysis of the global climate (ERA5) data for 1980–2024. The main conclusions are as follows: (1) The collapse events, which primarily occurred in spring, and the collapse time exhibited a U-shaped trend. (2) The collapse period exhibited significant spatiotemporal nonuniformity, with shorter periods in 10–100 hPa, larger variations in 100–300 hPa, and longer periods in 300–500 hPa. (3) The collapse mutation propagated downward to lower layers, beginning in 10–30 hPa and concentrating between 1995 and 2005. (4) The momentum flux and heat flux exhibit meridionally concentrated structures in the middle–lower stratosphere. The transition layer forms a region of momentum and energy accumulation. In the lower levels, the heat flux weakens. (5) The polar vortex collapse results from enhanced lower-stratospheric instability, weakened transition-layer disturbances, and upward energy transfer from low-level convergence, together forming a characteristic U-shaped collapse structure.

This study compares the environmental conditions and hydrometeor characteristics of successive light hail and moderate rain showers produced by two independent convective cells at Guiyang Airport on 11 April 2025. Automatic weather observations, microwave-radiometer retrievals, wind-profiler measurements, C-band dual-polarization radar data, and ERA5 reanalysis were examined. Before the light hail, the positive-buoyancy layer extended through the 0 to −20 °C hail-growth zone, the equilibrium level was above the −20 °C level, and deep-layer shear and storm-relative helicity were stronger. Its intense echo core extended from 2.5 to 5.0 km, and polarimetric and surface observations indicated mixed rain and hail. Before the moderate rain shower, positive buoyancy was shallower, the equilibrium level was below the −20 °C level, and deep-layer dynamical support was weaker. Its intense echo core was concentrated at 1.6–2.5 km, with signatures dominated by liquid raindrops. For this case, precipitation type differed with the vertical alignment of the buoyancy and hail-growth layers and with the persistence of deep-layer dynamical support. Additional cases are needed to test this interpretation.