Jiangsu Institute of Meteorological Sciences

Abstract. Cloud vertical structure plays a central role in regulating Earth’s radiation balance and hydrological cycle, yet it remains poorly represented in weather and climate models due to limited high-resolution observations. Using a newly established national network of 80 Ka-band cloud radars, we provide the first high-spatiotemporal-resolution characterization of cloud vertical structure across China for 2024 and quantify its thermodynamic, dynamical, and land-surface controls. An improved retrieval algorithm accounting for height-dependent radar sensitivity and clutter suppression is applied to derive cloud boundaries. The national annual mean cloud occurrence frequency is 56.7 %, dominated by single-layer clouds (34.7 %), followed by two-layer (14.7 %) and multi-layer clouds (7.1 %). Single-layer clouds prevail over arid northwestern China, whereas multi-layer clouds are more frequent in humid southeastern regions. Cloud base height exhibits strong seasonality, with higher values in summer and lower values in winter, and distinctly lower bases over the Tibetan Plateau. Diurnally, summer clouds show a pronounced afternoon peak between 3 and 9 km, while winter clouds are mainly confined below 3 km with a near-sunrise maximum. Thermodynamic conditions exert primary control on cloud vertical development. Higher low-level humidity favors deeper clouds and higher tops, whereas stronger lower-tropospheric stability suppresses vertical growth. Wind shear generally limits cloud depth, though moderate shear may enhance organization under unstable conditions. Land-surface characteristics further modulate cloud base height, with higher bases over barren land and lower bases over forests. These results provide national-scale observational benchmarks for improving cloud parameterizations in numerical models.

The seasonal dynamics, sources, and ecological risks of polycyclic aromatic hydrocarbons (PAHs) in inland freshwater ports remain largely limited, despite extensive research on coastal port PAH pollution. Here, we investigated sixteen U.S. EPA priority PAHs in surface waters of Jiujiang Port, a major inland hub along the Yangtze River, China. Total PAH concentrations ranged from 21.8 to 121.0 ng·L−1 (mean: 65.0 ng L−1), which represents relatively low levels compared with coastal ports worldwide. In this study, significant seasonal variations were also observed, with higher concentrations during the dry season than the wet season. Diagnostic ratios and multivariate analyses indicated petroleum combustion as the dominant source, while PAH levels showed positive correlations with turbidity and CODMn, underscoring the role of suspended particulates and organic load. Ecological risk assessment revealed low to moderate risks, with elevated risks in the dry season. These findings provide novel insights into PAH pollution in inland port systems and offer a scientific basis for pollution control and ecological management under the Yangtze River Protection framework.

<strong class="journal-contentHeaderColor">Abstract.</strong> To address the challenges in evaluation of aircraft cloud seeding effect, this study proposes a physical evaluation method that integrates multiple key techniques to achieve an integrated quantitative evaluation based on multiple indicators. This evaluation approach was applied to six aircraft cloud seeding operations conducted in Henan Province of China during 2023&ndash;2024. Results show that the six operations exhibited nonlinear growth patterns for dispersion in both the target and control areas, with rapid expansion at the initial stage followed by a slower rate. The dispersion rate, distance, extent and concentration of the seeding agent vary significantly depending on the meteorological conditions, such as atmospheric turbulence, wind speed, stability and humidity. For the six operations, the vertically integrated liquid water content (VIL) showed notably high entropy weights (0.06&ndash;0.43) in multiple operations (No. 2, 3 and 6), making it a relatively stable indicator for evaluating the cloud seeding effects. Due to complex cloud microphysical processes such as latent heat release from deposition, downdrafts, cloud dissipation and cloud development, the responses of cloud-top temperature to seeding varied considerably (&minus;44.56 &deg;C ~ &minus;6 &deg;C). The effects of cloud seeding on cloud effective radius and optical thickness are complex and vary substantially depending on specific seeding conditions. The responses of liquid water path were time-dependent, the seeding-induced responses of radar reflectivity exhibited distinct patterns, including delayed manifestation, strong enhancement, and ineffectiveness or being masked. The strong-echo area and the VIL in the target areas fluctuated and generally decreased over time, respectively. The integrated physical inspection dimensionless index (PIDI) values for the seven indicators ranged from 15.0 % to 69.7 %, showing a smaller variation magnitude compared with the change rates of individual indicators, which reflects the synergistic effects of multiple indicators. This study provides a quantifiable and robust framework that mitigates the interference of natural variability, thereby advancing cloud seeding techniques and improving effect evaluation capabilities for artificial precipitation enhancement.

On September 19, 2023, a rare autumn tornado outbreak, consisting of three successive tornadoes (including one EF3), occurred in northern Jiangsu, China, causing significant damage. This study presents a comprehensive analysis of this event using multisource data, including Doppler radar, ERA5 reanalysis, and surface observations. We find that pretornadic mesoscale vortices were triggered and intensified during the eastward movement of the Jianghuai cyclone, along low‐level shear lines on the warm side of a quasi‐stationary mesoscale front. The synoptic environment was characterized by an anomalously strong and persistent subtropical high, which provided record‐breaking moisture (precipitable water &gt;66 mm) and instability (CAPE &gt;2200 J kg −1 ), coupled with extreme low‐level wind shear (&gt;18 m s −1 in 0–1 km). These conditions created a classic yet extreme setting for tornadic supercells. At the storm scale, the tornadoes formed during the merging and intensification of multicell thunderstorms. Radar analysis revealed that the two strongest tornadoes (EF2 in Nancai and EF3 in Funing) exhibited clear supercell characteristics, including hook echoes and tornado vortex signatures (TVSs). Tornadogenesis in both cases coincided with the peak values of low‐level differential velocity (LLDV exceeding 40 m s −1 ). The Funing EF3 tornado was further confirmed by a prominent tornado debris signature (TDS) in dual‐polarization radar data. A key advance presented here is the identification of a hybrid tornadogenesis mechanism. While the storms displayed classic supercell dynamics (tilting and stretching of vertical vorticity), the process was significantly enhanced by the amplification of pre‐existing horizontal vorticity along successive, evolving meso‐β‐scale convergence centers. This mechanism, which shares characteristics with both supercellular and landspout processes, explains the sequential development of this “tornado cluster.” Our results underscore that in high‐shear, high‐instability environments, detailed analysis of mesoscale boundaries are crucial for anticipating tornadogenesis. This study enhances the understanding of autumn tornado outbreaks in eastern China and provides insights for improving monitoring and warning strategies for such rare but high‐impact events.