Supercells are the most severe and long-lasting type of highly organized convective storms, with the greatest potential for producing extreme weather events and causing significant disasters. This article provides a comprehensive overview and recent highlights of supercell research, including the unique structure, environmental characteristics, and the formation and maintenance mechanisms of the mesocyclone. Buoyancy instability is a necessary ingredient in the supercell's environment, whereas dynamic factors such as vertical wind shear and low-level storm relative helicity are more sensitive parameters for distinguishing supercells from non-supercells. The near-storm environmental parameters derived from multi-sensor observations are expected to enhance high-resolution nowcasting of supercell storms. Different types of supercells, including those producing distinct hazardous weather, exhibit unique reflectivity morphology and dynamical/microphysical structures, e.g., tornadic supercells have a strong low-level meso-cyclone while severe hail supercells feature a strong and deep mesocyclone. Mesocyclones associated with damaging winds are accompanied by significant mid-level radial convergence, while those responsible for heavy precipitation are typically located at low levels. The vertical vorticity of the mesocyclone is generated through the tilting of environmental horizontal vorticity by storm-related intense updrafts. The horizontal vorticity that tilts into the mid-level mesocyclone originates from the environmental vertical wind shear, which produces the horizontal vorticity along the inflow to the storms. In contrast, the horizontal vorticity contributing to the low-level mesocyclone derives from two distinct mechanisms, i.e., environmental vertical shear in the boundary layer and gust front-induced baroclinicity. It remains unclear which mechanism is more dominant. Moreover, the maintenance and enhancement mechanisms of mesocyclones are complex and vary across different scenarios, particularly when embedded within heavy precipitation, during storm mergers, or in proximity to surface mesoscale boundaries (e.g., fronts, drylines, gust fronts, and their associated convergence lines). In recent years, based on super high-resolution numerical experiment results, the physical conceptual models of the supercell tornadogenesis have been updated. The newly revealed micro-physical and dynamic characteristics from polarimetric Doppler radar observations enable more accurate hail size detection. However, the refined physical conceptual model of severe hail growth still requires improvement, and our understanding of the formation mechanisms behind extreme wind gusts and flash floods associated with supercells remains limited.

To study the organization mode and evolution characteristics of mesoscale convective systems (MCS) that cause heavy rain during rainstorm days in Tai mountain area as well as possible influence of terrain, the modes and evolution characteristics of MCS are analyzed using the new generation composite radar reflectivity data, satellite data and operational observation data from May to October during 2020—2022. The results show that MCSs in Tai mountain area can be divided into six classes: Nonline-MCS (NL), Embedded line MCS (EL₁), Embedded lines MCS (EL₂), Trailing stratiform MCS (TS), Training line MCS (TL) and Parallel stratiform MCS (PS). Four of them are the same as previously classified archetypes, and the EL₂ and TL are two new statistical classes in Tai mountain area. On satellite cloud charts, the six classes often appear as irregular ovals or long stripes with the highest black body temperature (TBB) below −50°C, making it difficult to distinguish detailed mode of MCS. However, the new generation of weather radar data can make up for this defect. According to the analysis, NL, EL₁ and EL₂ are the main classes affecting the Tai mountain area, accounting for 86% of the total samples, and EL₁ is the most common. EL₁ class, including the embedded line (EL) in existing research results and the convective line without stratiform rainfall (NS) , originates in the area from Xingtai to Dezhou and Liaocheng, and mostly moves along the southeastern direction. The second most common class is the NL, which generates in the Tai mountain area with strong echoes dispersed and little movement; the third is the EL₂ class, which generates in the area between Kaifeng and Heze, and mostly moves along the northeastern direction after formation. Except for the EL₂ and PS, the other classes appear with a distinct diurnal variation, showing two peaks in the afternoon and at night respectively. Tai mountain has impacts on the intensity, shape, moving speed and direction of most rainfall echoes, especially on the formation of TS and the transformation of NL into EL₁ and EL₁ into EL₂ or NL. According to statistics, only 12% of MCS modes do not change significantly, and the rest of the samples change every 1.5—3 h. In contrast, NL is not only one of the main classes that cause heavy rain in Tai mountain area, but also an intermediate mode in the evolution of other MCS in many cases.

Supercells are the most severe and long-lasting type of highly organized convective storms, with the greatest potential for producing extreme weather events and causing significant disasters. This article provides a comprehensive overview and recent highlights of supercell research, including the unique structure, environmental characteristics, and the formation and maintenance mechanisms of the mesocyclone. Buoyancy instability is a necessary ingredient in the supercell’s environment, whereas dynamic factors such as vertical wind shear and low-level storm relative helicity are more sensitive parameters for distinguishing supercells from non-supercells. The near-storm environmental parameters derived from multi-sensor observations are expected to enhance high-resolution nowcasting of supercell storms. Different types of supercells, including those producing distinct hazardous weather, exhibit unique reflec-tivity morphology and dynamical/microphysical structures, e.g., tornadic supercells have a strong low-level meso-cyclone while severe hail supercells feature a strong and deep mesocyclone. Mesocyclones associated with damaging winds are accompanied by significant mid-level radial convergence, while those responsible for heavy precipitation are typically located at low levels. The vertical vorticity of the mesocyclone is generated through the tilting of environmental horizontal vorticity by storm-related intense updrafts. The horizontal vorticity that tilts into the mid-level mesocyclone originates from the environmental vertical wind shear, which produces the horizontal vorticity along the inflow to the storms. In contrast, the horizontal vorticity contributing to the low-level mesocyclone derives from two distinct mechanisms, i.e., environmental vertical shear in the boundary layer and gust front-induced baroclinicity. It remains unclear which mechanism is more dominant. Moreover, the maintenance and enhancement mechanisms of mesocyclones are complex and vary across different scenarios, particularly when embedded within heavy preci-pitation, during storm mergers, or in proximity to surface mesoscale boundaries (e.g., fronts, drylines, gust fronts, and their associated convergence lines). In recent years, based on super high-resolution numerical experiment results, the physical conceptual models of the supercell tornadogenesis have been updated. The newly revealed micro-physical and dynamic characteristics from polarimetric Doppler radar observations enable more accurate hail size detection. However, the refined physical conceptual model of severe hail growth still requires improvement, and our understanding of the formation mechanisms behind extreme wind gusts and flash floods associated with supercells remains limited.

Not many researches have been conducted on typical cases of convection triggered by dry lines in the Hetao region of China. The formation of three typical dry lines and their roles in triggering convection in the Hetao region of Yellow River are analyzed in detail based on upper air soundings, intensive surface observations, EC-ERA5 (0.25º×0.25º) reanalysis data and FY-2 meteorological satellite images (the resolution of subsatellite point in the visible images is 1.25 km while that in the infrared images is 5 km). The results are as follows. (1) The three cases occurred under the background of the development of the Mongolia cyclone, which was induced by the eastward movement of the upper trough in the middle and upper troposphere. The structure of the forward-tilting trough indicates that the upper-level northwesterly flows and cold advection were superimposed on the lower-level warm zone, providing a favorable environmental condition for the occurrence of severe convection over large areas. (2) All the three cases occurred along the gentle slope of the Loess Plateau, which is high in the west and low in the east, and under the condition of the Mongolia cyclone development, presenting significant regional characteristics. Besides, the dry lines with a length of about 600—800 km and a width of about 80—100 km were oriented along north-northeast to south-southwest direction and coincided with the orientation of the 1300 m contour line in the Hetao region. Furthermore, the main cause for dry lines generation is the effect of the dry-warm air produced by the near adiabatic descending warming and the rapid diabatic warming and dehumidification in the western Hetao area. (3) The dry lines show obvious diurnal characteristics. The western part of the dry line warmed up rapidly in the daytime and the dry line moved eastward, while it cooled off faster than the eastern part from the nighttime to early morning and the dry line retreated westward. The dry lines present their most marked features around 14:00 BT with the dew point temperature difference between wet and dry sides reaching 10℃/(100 km) or more with an obvious convergent flow field of the westerly and the southerly wind. (4) Due to impact of the dry line and its associated convergent flow field, the initial convection was generated near the dry line from 13:00 to 14:00 BT in the afternoon, which were then reinforced on both sides of the dry line and the linear convective band formed. The convective band moved eastward and gradually stayed away from the dry lines under the steering of upper-level westerly airflows and continued to move eastward, expanding to a range of about 500 km to the east of the ground drylines under favorable environmental conditions in the eastern Hetao region. Severe convections such as large-scale thunderstorms, strong winds, local hails and even tornadoes subsequently developed over central and northern Shannxi province and some areas in North China. Finally, the synoptic conceptual model of the generation of typical dry lines in Hetao and the areas prone to severe convection are summarized according to the common characteristics of the three typical dry lines in Hetao area. This study provides a reference for analysis and forecast of dry lines that could trigger convections in the similar situation.

Based on the 36 Derechos that occurred in China during 18 years from 2002 to 2019, a study on the spatiotemporal distribution and environmental characteristics of Derechos as well as the morphology of Derechos producing convective systems have been conducted using proximity soundings, surface observations, satellite images, single Doppler weather radar data, and weather radar mosaics data. The results are as follows. (1) Derechos mainly occur in the eastern half of China, including North China, East China, South China, and regions to the south of the Yangtze River. The regions of high occurrence frequency show remarkable seasonal variation, which is manifested as the northward movement during the first phase and the southward movement during the second phase from spring to summer. Derechos activity has significant seasonal changes. They mainly occur from March to August with the highest frequency in June and the lowest in August. The convective systems producing the Derechos tend to initiate around noon, while the Derechos themselves tend to occur between mid-afternoon and early midnight. (2) The main characteristics of environmental parameters of Derechos in China are as follows: The 50th percentile of CAPE is 1420 J/kg, the 50th percentile of the 0—6 km vertical shear is 18.0 m/s, the 50th percentile of DCAPE is 1090 J/kg. (3) The weather pattern of Derechos can be divided into the following four types: The subtropical high periphery type, the weak trough type, the high level dry-cold advection forced type and the strong trough type, among which the strong trough type has the highest frequency and the high level dry-cold advection forced type has the lowest frequency. (4) During the period when the maximum wind gust occurs, the most frequent convective storm type is squall line, the second frequent storm type is multi-cell cluster storm and the third frequent storm type is supercell storm.