Atmosphere

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.

This study presents a multi-platform airborne empirical evaluation of an engineered thermodynamic reactive seeding agent, Thai Formula8 (a CaO-based powder), for warm convective cloud modification under the Thai Royal Rainmaking patent framework. Laboratory XRD and laser diffraction confirmed the reactive seeding agent XRD identified CaO as the dominant crystalline phase, accounting for 75.51% of the normalized crystalline-phase composition with a median particle diameter of 17.62 µm and a specific surface area of 4971.77 cm²/g. Calibrating these mineralogical fractions under cloud-base conditions (20 °C, 850 hPa) establishes a theoretical composite reaction enthalpy (ΔH_{Formula8,composite}) of −1115.35 kJ/kg. Coordinated airborne campaigns deploying a Construcciones Aeronauticas S.A. (CASA) seeding aircraft at Cloud Base +2000 feet and a Super King Air profiling aircraft across three vertical layers investigated this thermodynamic mechanism across a 4-day dataset. In situ exothermic slaking at the mid-level core generated localized warming up to +0.92 °C, activating an artificial “thermodynamic pump”. This vertical suction conduit evacuated core liquid water content (ΔMLW down to −0.128 g/m³) and lofted moisture upward, accompanied by cloud-top accumulation (ΔTLW up to +0.145 g/m³) and a 2.4-fold (+140.5%) particle concentration surge. Rapid mass accumulation accelerated collision-coalescence, triggering warm-rain initiation via precipitation mass loading drag. This provides the first physics-based observational evidence for systematic, high-density thermodynamic cloud seeding.

In this study, based on daily soil moisture, air temperature, and radiation data from the ERA5-Land reanalysis dataset spanning 1980–2021, flash-drought events on the Mongolian Plateau were identified. This research reveals the spatiotemporal characteristics and driving factors of flash droughts and hot flash droughts over the last 42 years on the Mongolian Plateau. The main results are as follows: (1) Spatially, flash droughts are concentrated in the southeastern and northern regions, with fewer occurrences in the west, and the intensity increases from southwest to northeast. Temporally, flash-drought events primarily occur in the summer. (2) An exploration of the meteorological driving mechanisms of flash droughts reveals that the occurrence rate of Standardized Precipitation Index (SPI) anomalies is higher than that of Potential Evapotranspiration (PET) anomalies during flash-drought periods. (3) GPP (Gross Primary Productivity) is most sensitive to flash droughts in spring and autumn, with the highest response rates in the southeast and northwest during autumn. The response rate is lower in summer and more evenly distributed. (4) Among vegetation types, croplands exhibited the highest GPP response rate, followed by grasslands, shrublands, broadleaf forests, and coniferous forests, although these differences may partly reflect contrasting climatic, topographic, and management settings. The findings of this study provide important scientific evidence and practical references for drought monitoring, adaptive management, and integrated ecosystem management on the Mongolian Plateau.