查看更多>>摘要：Arctic marine fog is a severe disastrous weather characterized by drastically reduced visibility, and its occurrence often poses great challenges to navigation and aviation. Accurate measurement of the characteristics of the Arctic marine fog plays a significant role in improving the accuracy of marine fog forecasts in the Arctic region. The Vaisala CL31 ceilometer, with its high sensitivity to liquid water content (LWC), is an effective means of detecting and obtaining the vertical structure of marine fog. In this work, a method to detect fog and retrieve fog thickness based on the ceilometer's backscatter coefficient profile has been proposed. The dataset collected at the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition from September 2019 to September 2020 is analyzed. Results indicate that compared with fog detection results of present weather detector (PWD22), the average deviation of marine fog occurrence probability of the proposed algorithm is within 5 %. Meanwhile, Arctic marine fog has obvious seasonal cycle, with the probability of highconcentration large-particle Arctic marine fog reaching up to 40 % in summer, accompanied by the thickness basically below 300 m. The distribution of marine fog thickness in summer is more concentrated and can last longer, with an average duration of about 6.24 h. In addition, there is an obvious correlation between the marine fog and the atmospheric boundary layer, with the correlation coefficient (CC) between the boundary layer height and the marine fog thickness being 0.7. However, the marine fog is generally shallower than boundary layer height in most cases.
查看更多>>摘要：Aerosols significantly influence high cloud microphysical properties, playing a crucial role in Earth's radiation budget. This study introduces an innovative analytical framework that integrates multi-meteorological constraints through Principal Component Analysis (PCA) with derivative expansion to disentangle aerosol and ice water content (IWP) effects on high cloud properties. Analyzing satellite and reanalysis datasets (2014-2020), we investigate aerosol-cloud interactions at two mid-latitude continental sites with distinct aerosol compositions: the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL) and the US Southern Great Plains (SGP) atmospheric observatory. By combining multiple meteorological factors into a single indicator, our approach enables an effective quantification of aerosol impacts. We find that aerosols enhance IWP at both sites, with SGP showing markedly higher susceptibility (1.22) than SACOL (0.89). Initial unconstrained analysis of ice particle radius (IPR) revealed opposing trends: decreasing with aerosols at SACOL but increasing at SGP. Through partial correlation analysis, we identified IWP as a key modulator of the IPR-aerosol relationship. After constraining both meteorological and IWP conditions, the increased aerosol concentrations consistently reduce IPR at both sites, resolving the apparent contradiction. Further investigation revealed distinct nucleation mechanisms: sulfate aerosols may dominate homogeneous nucleation, producing numerous smaller ice particles, while dust aerosols facilitate heterogeneous nucleation, forming fewer but larger ice particles when sufficient water vapor is present. These findings advance our understanding of regional variations in aerosol-cloud interactions and provide essential insights for improving cloud microphysics parameterization in climate models.
Tsiros, Ioannis X.Proutsos, Nikolaos D.Stefanidis, Stefanos P.
1.1-1.8页
查看更多>>摘要：During the last decades several gridded climatic datasets have been developed offering thus long-term, continuous, and spatially uniform records of key hydrometeorological parameters. Few studies, however, have rigorously evaluated the accuracy and reliability of these datasets, especially in regions characterized by complex topography and sparse observational data, such as the Mediterranean. Moreover, even fewer have explored how uncertainties inherent in these datasets affect derived climatic indices. To address this gap, the present study deals with the application of ground station measurements and a gridded dataset (CRU_TS 4.04) to estimate the aridity index (AI) and Thornthwaite's Moisture index (Im) over the Greek peninsula for three different consecutive climatic periods. Ground station data estimations are compared against the outcomes of the respective gridded datasets. Results show that the application of gridded data led to AI values increase in many areas, altering the aridity classification from semi-arid (SA) to sub-humid (SH) or humid (H) categories. Further, the application of gridded data led to both underestimations and overestimations of the Im, depending on the site: more dry conditions along the western coast (in most cases) and the eastern Aegean islands (with significant differences in some of the islands) and more humid conditions over the northwestern mainland and the southern part along with the Aegean islands. These results suggest that while gridded datasets always offer an alternative, careful consideration is required when they are used in regions characterized by complex topography (heterogenous terrain, site continentality and extensive land-sea contrast) and also temporal climatic variability.
查看更多>>摘要：Using airborne Ka-band probe radar (KPR) and cloud probe data obtained on 16 June 2021, the microphysical structures and particle characteristics in a stratiform cloud case with embedded convection were studied. At the mature stage, ice particles with sizes between 200 and 600 mu m, including plates and linears, were predominant in the stratiform cloud regions, and the maximum particle concentration was greater than 80 L- 1; however, particles larger than 600 mu m, such as plates, irregulars, and aggregates, were predominant at the edge of the stratiform cloud system, and the maximum particle concentration was less than 3.5 L- 1. The irregulars at the edge of the mature stratiform cloud region exhibited larger sizes compared to those in the inner region, while their occurrence frequency was significantly higher than that within the inner region of the mature stratiform cloud. In the embedded convection cloud region during the stratiform dissipation stage, particles ranging from 125 to 625 mu m were predominantly composed of plates, irregulars, and spheres (droplets). The particle concentration in this region was significantly higher compared to that observed in the stratiform cloud regions. We found that the average area of linear, spherical, plate, and dendritic particles in the stratiform cloud region was larger than that in the convective cloud region. The average area of graupel and aggregates in the embedded convection cloud region was larger than that in the stratiform cloud region. Moreover, we found that the larger the average area of graupel was, the lower the proportion of particles in the inner region of the mature stratiform cloud was.
查看更多>>摘要：Severe thunderstorm gales are the predominant meteorological phenomena associated with convective storms. Accurately estimating the extreme wind speed of thunderstorm gales (ESTG) is crucial for both forecasting services and disaster investigations related to severe convective weather. This paper proposes a method for estimating the ESTG based on dual-polarization weather radar hydrometeors classification products (EESonHC). This method utilizes changes in hydrometeors, combines these changes with the atmospheric vertical momentum equation, and estimates the ESTG by approximating the average vertical acceleration of storm cells. Experimental tests were conducted using cases of thunderstorm gales in both strong and weak wind shear environments, demonstrating that this estimation method achieves an accuracy rate as high as 75 % for extreme thunderstorm gales exceeding 25 m/s, with an average error in estimated wind speed of approximately 0.5 m/s. The primary issues include: 1. When multiple storm cells are in close vicinity, accurately isolating the vertical motion acceleration pairs for each individual cell becomes challenging, thereby complicating wind speed estimation; 2. Overestimating ice-phase hydrometeors in HCL could lead to underestimating wind speed or make it impossible to estimate accurately.
查看更多>>摘要：Utilizing the Asian-Pacific oscillation (APO) index on a daily scale to gain a comprehensive understanding of summer daily rainfall variations and their underlying physical mechanisms is helpful to improve the accuracy of daily rainfall pattern predictions in central-northern China. To address this, we utilized observational 24-h accumulated rainfall data from China and the reanalysis products from the European Center for MediumRange Weather Forecast (ECMWF) and investigated the relationship between daily APO, atmospheric circulation, and rainfall in central-northern China on the daily timescale. It delves into the evolution of the daily APO index (DAI) and its connection to atmospheric circulation and rainfall. Corresponding to instances of daily extremely high and low APO, there is a notable intensification in the sea-land thermal contrast and the associated southerly winds, which leads to abundant water vapor and widespread rainfall anomalies in central-northern China. The daily APO signal emerges as an indicator of rainfall events in this region, detectable up to seven days in advance. These findings are in favor of understanding the mechanism for East Asian monsoon and associated rainfall in central-northern China on the daily timescale.
查看更多>>摘要：Based on the results of numerical simulations, a possible mechanism for the occurrence of a rapid increase in lightning frequency preceding a downburst was investigated according to cloud microphysical processes in mixed-phase areas. To elucidate the mechanism, idealized experiments were conducted targeting multi-cell convective clouds using a meteorological model coupled with a bulk lightning model, which explicitly calculates riming, charge separation via riming electrification, and lightning discharge. The model well reproduced a rapid increase in the lightning flash rate in multi-cell convective clouds approximately 15 min before a downburst. In a convective cell during increasing flash rate, solid hydrometeors were supplied to the convective area and riming electrification occurred actively. In contrast, in a convective cell that caused a downburst, riming occurred actively because of the supply of a large amount of supercooled water from the lower layers. A convective cell suitable for riming electrification or graupel growth by riming occurred when the convection was or was not tilted, respectively. The transition from tilted convection suitable for riming electrification to upright convection suitable for active riming growth is critical for the occurrence of the rapid increase of lightning preceding downbursts.
Coll-Hidalgo, PatriciaNieto, RaquelFernandez-Alvarez, Jose CarlosGimeno, Luis...
1.1-1.10页
查看更多>>摘要：Extratropical cyclones (ECs) are large-scale synoptic weather systems characterised by complex mesoscale precipitation-generating features. Unresolved questions remain regarding how their water budget varies depending on the origin of the rainfall. This study aims to address this gap by examining the variability in moisture uptake patterns across EC precipitation structures. To achieve this, 237 cases were selected during the maximum deep phase over the North Atlantic (NATL). The study utilizes ERA5 downscaled simulations and Lagrangian moisture source diagnostics to identify key moisture parameters. We compare different precipitation-targeting approaches, including the radius, Warm Conveyor Belt (WCB) footprint, and square root spiral contours centred on the EC. The radius approach captures central precipitation and innermost rainbands, while the WCB target better represents the full extent. The NATL region was divided into sectors to facilitate a detailed analysis of geographic influences and dynamic factors, including moisture availability. Using the radius approach, moisture sources in the western/W and northern/N NATL are predominantly aligned along the Gulf Stream. When considering WCB and spiral targets, the 95th percentile moisture uptake pattern expands into the subtropics. Moisture patterns shift southward and intensify for broader targets. In NNATL ECs, the spiral region's moisture source shows peak uptake at similar to 3000 km, exceeding the radial target's 1500 km. WNATL ECs exhibit intense moisture uptake, with a southwest (southeast) source extending up to 4500 (4000) km. In eastern/E NATL, EC-relative composites indicate evenly distributed moisture uptake, constrained within a 2000 km radius.
查看更多>>摘要：Due to the scarcity of measured precipitation data in arid zones and the numerous factors affecting the uncertainty of precipitation data from multiple sources, understanding precipitation patterns is limited, and drought monitoring is constrained. Whereas water vapor content is closely related to precipitation, changes in water vapor can be an important indicator of drought development. Therefore, this paper takes Xinjiang as the study area, introduces precipitable water vapor, and constructs two new drought indices, the standardized and nonparametric standardized precipitable water indices (SPWI and NSPWI), using parametric and nonparametric kernel density estimation methods. Aiming at the drought characteristics of long duration and intensity in the study area, an identification method for long-duration and high-severity drought (LHD) events was proposed using the three-dimensional clustering method and the Copula function. The three-dimensional evolution characteristics and centroid migration patterns of LHD events were then analyzed.The results indicate that: (1) The newly constructed drought index can be used for drought monitoring in Xinjiang, and the performance of SPWI is better than that of NSPWI. (2) Based on the three-dimensional clustering method, which can better identify the drought events in the study region, it was found that the droughts were mostly concentrated in 1960-1987, and there was a trend from dry to wet. (3) The LHD events were identified based on the joint distribution probability of drought duration and severity greater than 75 %, and it was found that droughts originated in the southern and died out in the western part of the study region, that droughts were likely to be more frequent the deeper inland and farther away from the ocean, and that droughts lasted for longer periods and had a wider impact area; mountainous areas are more profoundly affected by the LHD events than plains and deserts areas. (4) LHD events have a wider centroid migration distance, and their drought development process is more complex, with spatial and temporal distributions. The drought index that introduces precipitable water vapor and the LHD event identification method proposed in this study can provide some guidance for the enhancement of drought prevention and mitigation capabilities in arid regions.
查看更多>>摘要：The intensification of global change and the escalation of anthropogenic activities have significantly exacerbated drought severity in Central Asia (CA), thereby posing critical challenges to the sustainability of local ecosystems and socioeconomic development. Although current research primarily focuses on changes in drought trends, a comprehensive analysis of the spatiotemporal correlations between regional climatic droughts and their underlying driving factors remains notably absent. Therefore, this study systematically examined the spatiotemporal correlations and driving factors of climatic droughts in CA from 1948 to 2022. The results indicated that: (1) over the past approximately 80 years, significant increases in both the intensity (i.e., rising by 174 %) and spatial extent (i.e., expanding by 138.4 %) of drought events were observed in CA, highlighting the escalating severity and widespread impact of this climatic phenomenon, (2) in 74.5 % of CA, meteorological drought exhibited a significant Granger causal relationship with hydrological drought, marked by a substantial influence (F > 1), while hydrological drought significantly impacted agricultural drought across nearly the entire region, and (3) soil moisture (SM) predominantly influences hydrological drought, with regions exhibiting a relative importance degree (RID) above 0.3 covering 71.4 % of CA. Conversely, snow water equivalent and evapotranspiration significantly impact meteorological drought across 50.4 % of CA. The significance of this study lies in its provision of a scientific basis for drought risk assessment and the formulation of climate adaptation policies in CA.
NETL
NSTL
Elsevier