CAMS Rainstorm Proj

2026project list

Number	Name	category	station	PDF
2026001	On the Extreme Rainfall Event of 7 May 2017 over the Coastal City of Guangzhou. Part I: Impacts of Urbanization and Orography	Aaa	Guangzhou	PDF
	In this study, a nocturnal extreme rainfall event induced by the urban heat island (UHI) effects of the coastal city of Guangzhou in South China on 7 May 2017 is examined using observational analyses and 18-h cloud-permitting simulations with the finest grid size of 1.33 km and the bottom boundary conditions nudged. Results show that the model reproduces convective initiation on Guangzhou’s downstream side (i.e.,Huashan), where a shallow thermal mesolow is located, the subsequent back-building of convective cells as a larger-scale warm-moist southerly flow interacts with convectively generated cold outflows, and their eastward drifting and reorganization into a localized extreme-rain-producing storm near Jiulong under the influences of local orography. In particular, the model produces the maximum hourly, 3- and 12-hourly rainfall amounts of 146, 315, and 551 mm, respectively, at nearly the right location compared to their cor responding observed extreme amounts of 184, 382, and 542 mm. In addition, the model reproduces an intense meso-g-scale vortex associated with the extreme-rain-producing Jiulong storm, as also captured by Doppler radar, with organized updrafts along cold outflow boundaries over a semicircle. A comparison of sensitivity and control simulations indicates that despite the occurrence of heavier rainfall amounts without the UHI effects than those without orography, the UHI effects appear to account directly for the convective initiation and heavy rainfall near Huashan, and indirectly for the subsequent formation of the Jiulong storm,while orography plays an important role in blocking cold outflows and enhancing cool pool strength for the sustained back-building of convective cells over the semicircle, thereby magnifying rainfall production near Jiulong.
2026002	A Possible Dynamic Mechanism for Rapid Production of the Extreme Hourly Rainfall in Zhengzhou City on 20 July 2021	Bbb	Zhengzhou	PDF
	In this study, the unprecedented extreme rainfall event during 19–20 July 2021, which caused devastating flooding in Zhengzhou City and its nearby areas, is examined based on observational data analysis and WRF model 40-h simulations on 1-km horizontal resolution. The results show that the model successfully reproduces (i) major synopticscale weather systems (i.e., the western Pacific subtropical high, the Tibetan high, two typhoons, and the Huang–Huaicyclone), (ii) convective initiation along the east to north edge of the Songshan Mountain, where orographic lifting is obvious, and (iii) subsequent formation of the convective storm producing the extreme rainfall in Zhengzhou. In particular, the model generates the maximum rainfall rate of 233 mm h−1 and 40-h accumulated rainfall of 704 mm, corresponding well to the observed extreme values of 201.9 mm h−1 and 818 mm, at nearly observed timing and location. Importantly, the model reproduces an intense quasi-stationary, well-organized meso-γ-scale convective system,surrounded by an arc-shaped convergence zone, allowing the development of convective updrafts in a three-quarter circle around the convective system, in a way similar to multidirectional pumping, attracting all associated precipitation overlaid and concentrated into the same trailing region to generate the extreme hourly rainfall over Zhengzhou.Our study emphasizes the significant contribution of the unique dynamic structure of the well-organized meso-γ-scaleconvective system to the record-high hourly rainfall. A possible dynamic mechanism for short-time extreme rainfallproduction is proposed. That is, the arc-shaped convergence zone of the mesoscale convective system, acting like multidirectional lifting pumps, transports precipitation from different directions into the same region, and thus prosixduces the extreme rainfall. The results gained herein may shed new light on better understanding and forecasting of short-time extreme rainfall.
2026003	The extreme short‐term rainfall rate as caused by a convective storm under a beneficial dynamic pattern
	Within a meso‐γ‐scale convective storm, dynamic processes play a pivotal role in extreme rainfall production. However, there are still large unexplained gaps in understanding the effects of dynamic processes on the generation of extreme short‐term rainfalls. In this study, a nocturnal rainfall event with an extreme hourly rainfall (EHR) of 184 mm on 7 May 2017 over the coastal city of Guangzhou is examined based on cloud‐permitting simulations, focusing on the generation of the EHR. Results reveal that the EHR is featured by obvious horizontally delivered rainwater (qr) from the front to the rear within a meso‐γ‐scale convective storm. The horizontally delivered qr from the front of the storm overlayed on the qr produced by cloud microphysical processes locally overhead in the rear of the storm, leading to a deep qr layer with values over 4 g·kg⁻¹ at the lowest 0–4 km levels above the ground. Thus, huge qr poured down in a short time, resulting in the EHR. According to statistical results, at least 80 mm qr was provided by horizontal delivery for the majority of grid points with hourly rainfall over 120 mm. This dynamic delivery mechanism is further confirmed by a trajectory analysis of raindrops. We argue that this mechanism may play a decisive role in EHR formation in particular scenarios while admitting that EHR can also be produced sometimes mainly via cloud microphysical processes. The formation mechanism of EHR proposed herein may help further understand and forecast localized extreme short‐term rainfall.
2026004	An investigation into the dominant cloud microphysical processes in extreme-rain-producing storms occurred on 7 May 2017 over Southern China
	This paper presents an analysis of the dominant cloud microphysical processes of the extreme rainfall event on 7 May 2017, using a series of convective-permitting simulations. Special emphasis is placed on the microphysical processes of two extreme-rain-producing storms, yielding hourly rainfalls exceeding 120 mm. For the Huashan (HS) storm, a large amount of cloud water is produced through condensation (PRW_VCD) within the storm, and significant rainwater is generated by the collection of cloud water by raindrops (PRR_RCW). As for the Jiulong (JL) storm, warm rain microphysical processes are as same as the HS storm. Additionally, considerable rainwater is produced via the collection of graupel by raindrops (PRR_RCG), with contributions also coming from the melting of graupel (PRR_GML). It is noteworthy that there is slight evaporation of raindrops (PRV_REV) in both storms. To verify the dominant cloud microphysical processes of the extreme rainfalls, an experiment has been conducted using a simple ice microphysics scheme that covers the aforementioned dominant microphysical processes. The results indicate that extreme rainfalls are well replicated with the simple microphysics scheme, showing good agreement in spatial distribution and temporal evolution with observations and the control run. The experiment confirms largely the dominant cloud microphysical processes responsible for the extreme rainfall. Based on the results, we propose that placing special emphasis on the treatment of snow terminal velocity in the Thompson scheme would improve the performance of the scheme for heavy rainfall simulation. The findings gained here may help further understand cloud microphysical processes for localized extreme rainfall over southern China, and provide guidance for the improvement of cloud microphysics schemes.
2026005	ZDR BACKWARDS ARC: RADAR EVIDENCE OF MULTI-DIRECTIONAL SIZE SORTING IN THE STORM PRODUCING 201.9 MM HOURLY RAINFALL ON 20 JULY 2021 IN ZHENGZHOU, CHINA		ZHENGZHOU
	In this study, we present radar polarimetric characterizations of the storm producing 201.9 mm hourly rainfall on 20 July 2021 in Zhengzhou, China. We employed the separation signatures of enhanced polarimetric observations to investigate hydrometeor size sorting processes, and developed an algorithm to quantify the size sorting directions. Analysis of coupled polarimetric observations unraveled multi-directional size sorting (MSS) occurred as a low-level differential reflectivity ZDR backwards arc signature encompassing the rainfall center during the most intensive rainfall period. The rainfall intensification is in step with the increase of size sorting directions. Model simulations with two-moment microphysics scheme suggest that the presence of arc-shaped updrafts is conducive to MSS and increased rain rates around the rainfall center. This work sheds novel insights into the kinematics-driven microphysics in extreme rainfall storms, warranting the potential of using coupled polarimetric signatures for warning catastrophic extreme rainfall events.
2026006	Microphysics affect the sensitivities of rainfall to different horizontal-resolution simulations: Evidence from a case study of the Weather Research and Forecasting model runs
	The Weather Research and Forecasting (WRF) model was used to examine the sensitivities of Typhoon Fitow (2013) to the variations in horizontal mesh spacing ranging from 9 km to 1 km and to different microphysics schemes. The minimum sea level pressure decreased by 5 hPa and the maximum wind speeds increased by 20 m s− 1 near the typhoon center as the horizontal grid spacing decreased from 9 km, 3 km, and 1 km in both Purdue-Lin and National Severe Storms Laboratory (NSSL) microphysics. The strengthening of the tropical cyclone may have been due to similar physical processes in the Purdue-Lin and NSSL simulations. Fine-resolution simulations produced localized and intense rainfall, in correspondence to localized and intense upward motions. Moreover, as the horizontal mesh spacing reduced from 9 km to 1 km, the distributions of the upward and downward motions broadened and the radar reflectivity bins with contour frequencies >10% increased. The simulated rainfall in the NSSL with a horizontal grid spacing below 3 km and in Purdue-Lin with a 1 km grid spacing reproduced spatial and temporal distributions similar to the actual observations. This suggested that the elaborate microphysics may compensate for the lack of horizontal resolution, to some extent. The precipitation budget analysis further suggested that the diminishment of rainfall was attributed to the reduced net condensation and hydrometeor convergence respectively in the Purdue-Lin and NSSL scheme as the mesh spacing reduced, which was further attributable to the decreased condensation or deposition.
2026007	Indirect Effects of Binary Typhoons on an Extreme Rainfall Event in Henan Province, China From 19 to 21 July 2021. 3. Sensitivities to Microphysics Schemes		Henan
	Previous numerical studies have focused on the direct impact of microphysics schemes on multiscale atmospheric systems that produce rainfall. However, the indirect impact of microphysics schemes on the key large‐scale circulation around areas of extreme rainfall has not yet been examined systematically. We used the ARW‐WRF (Advanced Research WRF (Weather Research and Forecasting) Model) to simulate the extreme rainfall event in Henan province, China from 19 to 21 July 2021. Experiments were conducted to investigate the sensitivity of the simulation to the three popular double‐moment microphysics parameterizations: the Thompson, Morrison and WDM6 (WRF Double‐Moment 6‐Class Microphysics Schemes). We found significant sensitivity to the microphysics parameterization, with the maximum precipitation varying by up to 400 mm and the area‐averaged precipitation by 33 mm. The Thompson and Morrison microphysics schemes produced the largest amount of precipitation, whereas the WDM6 scheme produced the smallest amount of precipitation. The simulated southerly flow varied substantially between the different microphysics schemes. This is due to the ability of the microphysics schemes to produce latent heat, which enhances the southerly flow, leading to more intense precipitation. The higher the parameterized latent heat, the stronger and more obvious the southerly flow over southern Henan province, with the WDM6 scheme simulating a much weaker southerly flow and the Thompson scheme producing the strongest southerly flow. These results indicate that the indirect effects on the key circulation patterns can be just as sensitive to the formulation of the microphysics scheme as the direct effects on extreme rainfall. These results may help to improve the prediction of extreme rainfall events.
2026008	Synergetic roles of dynamic and cloud microphysical processes in extreme short‐term rainfall: A case‐study
	Both dynamic and cloud microphysical processes play significant roles in the intensity of severe rainfall within a convective storm. In this study, a quantitative analysis has been performed to investigate dynamic and cloud microphysical contributions to extreme hourly rainfall (EHR) with the peak value of 201.9 mm in Zhengzhou City, China, on 20 July 2021. It is found that the EHR is generated by the overlay of rainwater provided by both dynamic delivery and cloud microphysical production within a meso‐γ‐scale convective storm over Zhengzhou. Specifically, part of the rainwater is directly produced by cloud microphysical processes over the EHR region. More importantly, considerable rainwater, which is produced in the front of the storm associated with strong updraughts, is delivered into the EHR region. The dynamically delivered rainwater overlays the rainwater produced by cloud microphysical processes, forming a deep layer with a large amount of rainwater over the EHR region. As the massive rainwater pours down within a short time, EHR is formed. It should be highlighted that the dynamic delivery plays a decisive role in EHR formation, although sometimes EHR can be generated mainly through cloud microphysical production in the case of weak dynamic delivery. Concerning the cloud microphysical processes, the collision of cloud droplets by raindrops produces the largest amount of rainwater, followed by graupel melting. Linking the EHR with dynamic and cloud microphysical processes within a convective storm, a new light on further understanding and forecasting of short‐duration extreme rainfall would be shed.
2026009	Microphysical Structures of an Extreme Rainfall Event Over the Coastal Metropolitan City of Guangzhou, China: Observation Analysis with Polarimetric Radar
	A record-breaking nocturnal rainfall event (543 mm in 16-h) under weak synoptic forcing occurred in the metropolitan city of Guangzhou, China, during 6–7 May 2017. The evolution and microphysical structures of this torrential rainfall event are investigated using S-band polarimetric radar datasets. The torrential rainfall concentrated in two cores: one over Huadu District (HD) in which the storms were initiated between urban areas and mountains at mid-night, and the other over Huangpu and Zengcheng District (ZC) which was characterized by locally triggered storms merging with the storms from HD. The two heavy precipitation regions show some similarities, including strong reflectivity factor for horizontal polarizations (ZH) magnitude, low centroid cumulonimbus structures, and column shape of differential reflectivity (ZDR). But obvious differences can also be viewed between them. Compared to HD, ZC has higher precipitation intensity, longer precipitation duration, and larger accumulated rainfall. Besides, ZC also has a relatively lower ZDR value of ~ 0.2 dB and a higher specific differential phase (KDP) of approximately ~ 0.35° km−1, which indicates the larger population of medium-sized rain droplet and higher water content in ZC. The radar-retrieved drop size distributions (DSDs) (i.e., mass-weighted diameter, logarithmic normalized intercept, and liquid water content) show that small size particles and high particle number concentration are more obvious in the storm over ZC. Combined with the retrieved DSDs, the merger process brings more medium-sized raindrops to ZC, and increases the possibility of raindrop growth via the accretion of cloud water by rain, which leads to enhancement of precipitation. In addition, strong KDP may be a good indicator of intensity for extreme precipitation.
2026010	A Possible Dynamic Mechanism for Rapid Production of the Extreme Hourly Rainfall in Zhengzhou City on 20 July 2021
	In this study, the unprecedented extreme rainfall event during 19–20 July 2021, which caused devastating flooding in Zhengzhou City and its nearby areas, is examined based on observational data analysis and WRF model 40-h simulations on 1-km horizontal resolution. The results show that the model successfully reproduces (i) major synoptic-scale weather systems (i.e., the western Pacific subtropical high, the Tibetan high, two typhoons, and the Huang-Huai cyclone), (ii) convective initiation along the east to north edge of the Songshan Mountain, where orographic lifting is obvious, and (iii) subsequent formation of the convective storm producing the extreme rainfall in Zhengzhou. In particular, the model generates the maximum rainfall rate of 233 mm h−1 and 40-h accumulated rainfall of 704 mm, corresponding well to the observed extreme values of 201.9 mm h−1 and 818 mm, at nearly observed timing and location. Importantly, the model reproduces an intense quasi-stationary, well-organized meso-γ-scale convective system, surrounded by an arc-shaped convergence zone, allowing the development of convective updrafts in a three-quarter circle around the convective system, in a way similar to “multidirectional pumping,” attracting all associated precipitation overlaid and concentrated into the same trailing region to generate the extreme hourly rainfall over Zhengzhou. Our study emphasizes the significant contribution of the unique dynamic structure of the well-organized meso-γ-scale convective system to the record-high hourly rainfall. A possible dynamic mechanism for short-time extreme rainfall production is proposed. That is, the arc-shaped convergence zone of the mesoscale convective system, acting like multidirectional lifting pumps, transports precipitation from different directions into the same region, and thus produces the extreme rainfall. The results gained herein may shed new light on better understanding and forecasting of short-time extreme rainfall.
2026011	Representation of the autoconversion from cloud to rain using a weighted ensemble approach: a case study using WRF v4.1.3
	Cloud and precipitation processes remain among the largest sources of uncertainties in weather and climate modelling, and considerable attention has been paid to improving the representation of the cloud and precipitation processes in numerical models in the last several decades. In this study, we develop a weighted ensemble (named EN) scheme by employing several widely used autoconversion (ATC) schemes to represent the ATC from cloud water to rainwater. One unique feature of the EN approach is that the ATC rate is a weighted mean value based on the calculations from several ATC schemes within a microphysics scheme with a negligible increase in computation cost. The EN scheme is compared with the several commonly used ATC schemes by performing real case simulations. In terms of accumulated rainfall and extreme hourly rainfall rate, the EN scheme provides better simulations than by using the single Berry–Reinhardt scheme, which was originally used in the Thompson scheme. It is worth emphasizing, in the present study, that we only pay attention to the ATC process from cloud water into rainwater with the purpose of improving the modelling of the extreme rainfall events over southern China. Actually, any (source and sink) term in a cloud microphysics scheme can be treated with the same approach. The ensemble method proposed herein appears to have important implications for developing cloud microphysics schemes in numerical models, especially for the models with variable grid resolution, which would be expected to improve the representation of cloud microphysical processes in the weather and climate models.
2026012	Representation of the autoconversion from cloud to rain using a weighted ensemble approach: a case study using WRF v4.1.3
	Cloud and precipitation processes remain among the largest sources of uncertainties in weather and climate modeling, and considerable attention has been paid to improve the representation of the cloud and precipitation processes in numerical models in the last several decades. In this study, we develop a weighted ensemble (named as EN) scheme by employing several widely used autoconversion (ATC) schemes to represent the ATC from cloud water to rainwater. One unique feature of the EN approach is that ATC rate is a weighted mean value based on the calculations from several ATC schemes within a microphysics scheme with a negligible increase of computation cost. The EN scheme is compared with the several commonly used ATC schemes by performing a real case simulations. In terms of accumulated rainfall and extreme hourly rainfall rate, the EN scheme provides better simulations than that by using the single Berry-Reinhardt scheme which was originally used in the Thompson scheme. It is worth emphasizing, in the present study, we only pay our attention to the ATC process from cloud water into rainwater with the purpose to improve the modeling of the extreme rainfall events over southern China. Actually, any (source/sink) term in a cloud microphysics scheme can be dealt with the same approach. The ensemble method proposed herein appears to have important implications for developing cloud microphysics schemes in numerical models, especially for the models with variable grid resolution, which would be expected to improve of the representation of cloud microphysical processes in the weather and climate models.
2026013	Effects of Microphysical Latent Heating on the Rapid Intensification of Typhoon Hato (2017)
	A 72-h cloud-resolving numerical simulation of Typhoon Hato (2017) is performed by using the Weather Research and Forecasting (WRF) model with the Advanced Research WRF (ARW) core (V3.8.1) on a horizontal resolution of 2 km. To enhance the background tropical cyclone structure and intensity, a vortex dynamic initialization scheme with a terrain-filtering algorithm is utilized. The model reproduces reasonably well the track, structure, and intensity change of Typhoon Hato. More specifically, the change trend of simulated maximum wind speed is consistent with that of best-track analysis, and the simulated maximum wind of 49 m s−1 is close to that (52 m s−1) of the best-track analysis, indicating that the model has successfully captured the rapid intensification (RI) of Typhoon Hato (2017). Analyses of the model outputs reveal that the total microphysical latent heating of the inner-core region associated with enhanced vertical upward motion reaches its maximum at 9-km height in the upper troposphere during the RI stage. The dominant microphysical processes with positive latent heat contributions (i.e., heating effect) are water vapor condensation into cloud water (67.6%), depositional growth of ice (12.9%), and generation (nucleation) of ice from vapor (7.9%). Those with negative latent heat contributions (cooling effect) are evaporation of rain (47.6%), melting of snow (27.7%), and melting of graupel (9.8%). Sensitivity experiments further show that the intensification speed and peak intensity of this typhoon are highly correlated to the dominant heating effect. A significant increase in graupel over 5-10-km height and snow at 10–14-km height in the inner-core region of Typhoon Hato corresponds well with its RI stage, and the latent heating from nucleation and depositional growth is crucial to the RI of simulated Hato.
2026014	On the Extreme Rainfall Event of 7 May 2017 Over the Coastal City of Guangzhou. Part I: Impacts of Urbanization and Orography
	In this study, a nocturnal extreme rainfall event induced by the urban heat island (UHI) effects of the coastal city of Guangzhou in South China on 7 May 2017 is examined using observational analyses and 18-h cloud-permitting simulations with the finest grid size of 1.33 km and the bottom boundary conditions nudged. Results show that the model reproduces convective initiation on Guangzhou’s downstream side (i.e., Huashan), where a shallow thermal mesolow is located, the subsequent back-building of convective cells as a larger-scale warm-moist southerly flow interacts with convectively generated cold outflows, and their eastward drifting and reorganization into a localized extreme-rain-producing storm near Jiulong under the influences of local orography. In particular, the model produces the maximum hourly, 3- and 12-hourly rainfall amounts of 146, 315 and 551 mm, respectively, at nearly the right location compared to their corresponding observed extreme amounts of 184, 382 and 542 mm. In addition, the model reproduces an intense meso-γ-scale vortex associated with the extreme-rain-producing Jiulong storm, as also captured by Doppler radar, with organized updrafts along cold outflow boundaries over a semicircle. A comparison of sensitivity and control simulations indicates that despite the occurrence of heavier rainfall amounts without the UHI effects than those without orography, the UHI effects appear to account directly for the convective initiation and heavy rainfall near Huashan, and indirectly for the subsequent formation of the Jiulong storm, while orography plays an important role in blocking cold outflows and enhancing cool pool strength for the sustained back-building of convective cells over the semicircle, thereby magnifying rainfall production near Jiulong.
2026015	A Case Study of the Effects of a Synoptic Situation on the Motion and Development of Warm-Sector Mesoscale Convective Systems over South China
	The effects of a synoptic situation on the motion and development of warm-sector mesoscale convective systems (MCSs) in a heavy rainfall event occurred in South China on 8 May 2014 are investigated using high-resolution observational data and ERA-Interim data. The results show that the blocking of an eastward moving low-level trough over southwestern China by a stable anticyclone over eastern China induced strong southerly winds ahead of the trough and an eastward vertical slant of the wind speed maximum. Consequently, a southeastward low-level wind shear formed in the region under the southerly jet, which caused a southeastward turning of the motion of a large inland MCS. Meanwhile, a northeastward/eastward low-level wind shear formed in the region under the east side of the southerly jet, leading to northeastward/eastward movement of some small MCSs in the coastal region. The continuous merging of the southeastward-moving MCS with the northeastward/eastward-moving MCSs resulted in heavy rainfall along the coastal region. On the other hand, the intensification and expansion of associated low and high mean-sea-level pressure (MSLP) centers caused southeastward migration of strong boundary-layer moisture flux convergence and high convective available potential energy zones, which promoted the persistent development of the large MCS and the later development of the small MCSs. Moreover, the strong boundary-layer southeasterly winds associated with the high MSLP center continuously enhanced the frontal ascent of the large MCS. These southeasterly winds also triggered the small MCSs through the convergence induced by differential surface friction between the land and sea or the convergence of them with the southwesterly winds from the South China Sea.
2026016	Numerical Study of the Role of Microphysical Latent Heating and Surface Heat Fluxes in a Severe Precipitation Event in the Warm Sector over Southern China
	Simulations of the severe precipitation event that occurred in the warm sector over southern China on 08 May 2014 are conducted using the Advanced Weather Research and Forecasting (WRF-ARWv3.5.1) model to investigate the roles of microphysical latent heating and surface heat fluxes during the severe precipitation processes. At first, observations from surface rain gauges and ground-based weather radars are used to evaluate the model outputs. Results show that the spatial distribution of 24-h accumulated precipitation is well reproduced, and the temporal and spatial distributions of the simulated radar reflectivity agree well with the observations. Then, several sensitive simulations are performed with the identical model configurations, except for different options in microphysical latent heating and surface heat fluxes. From the results, one of the significant findings is that the latent heating from warm rain microphysical processes heats the atmosphere in the initial phase of the precipitation and thus convective systems start by self-triggering and self-organizing, despite the fact that the environmental conditions are not favorable to the occurrence of precipitation event at the initial phase. In the case of the severe precipitation event over the warm sector, both warm and ice microphysical processes are active with the ice microphysics processes activated almost two hours later. According to the sensitive results, there is a very weak precipitation without heavy rainfall belt when microphysical latent heating is turned off. In terms of this precipitation event, the warm microphysics processes play significant roles on precipitation intensity, while the ice microphysics processes have effects on the spatial distribution of precipitation. Both surface sensible and latent heating have effects on the precipitation intensity and spatial distribution. By comparison, the surface sensible heating has a strong influence on the spatial distribution of precipitation, and the surface latent heating has only a slight impact on the precipitation intensity. The results indicate that microphysical latent heating might be an important factor for severe precipitation forecast in the warm sector over southern China. Surface sensible heating can have considerable influence on the precipitation spatial distribution and should not be neglected in the case of weak large-scale conditions with abundant water vapor in the warm sector.
2026017	Study on the genesis of a short squall line in mountains of Southern Zhejiang in 2012
	for initiating and developing severe convection in mountainous terrain, the squall line hitting Southern Zhejiang on 5th July 2012 was investigated. Based on the observation from dense automatic weather stations, and the data of Doppler radar and Temperature of brightness blackbody(TBB), mesoscale analysis was performed and the divergence field on the surface was analyzed statistically to reveal the mountains' role in convection. Numerical simulation was also applied. Results indicate that the southeasterly wind from eastern sea is more likely to cause convergence zones at the windward side. These convergence zones are favorable to initiate convection. The convergence zones usually exist before the radar echoes appear. TBB signatures show that convergence lines on the surface contribute to the appearance of low cloud. Mesoscale mountains activate convection cells near the mountains and arrange them along convergence points or convergence lines, producing mesoscale squall line system, which results in severe weather.
2026018	A Case Study of the November 2012 Mixed Rain-Snow Storm over North China
	A mixed rain-snow storm associated with a strong burst of cold air and development of an extratropical cyclone occurred over North China from 3 to 5 November 2012. This early snowfall event was characterized by a dramatic drop in temperature, strong winds, high precipitation intensity, broad spatial extent, and coexistence of multi-phase precipitating hydrometeors. This study investigates the multi-scale interactions between the large-scale circulation background and the synoptic-scale weather systems associated with the storm. The results are as follows. (1) The Arctic Oscillation (AO) had been in its negative phase long before the event, leading to southward advection of cold air into North China in advance of the storm. (2) The large-scale atmospheric circulation experienced a decreased number of long waves upstream of North China prior to the storm, resulting in reduced wave velocity and an almost stagnant low pressure system (extratropical cyclone) over North China. (3) An Ω-shaped blocking high over East Asia and the western Pacific obstructed the eastward movement of an upstream trough, allowing the corresponding surface cyclone to stabilize and persist over Beijing and its neighboring areas. This blocking high was a major factor in making this event a historically most severe precipitation event in autumn in Beijing for the past 60 years. (4) Baroclinic instability at lower levels gave rise to rapid development of the cyclone under the classical “second type” development mechanism for extratropical cyclones. (5) Moisture originated from the Yellow Sea entered the slowly-moving cyclone in a steady stream, creating fairly favorable water vapor supply for the heavy rainfall-snowfall, especially during the later stage of the cyclone development. (6) Moisture transport and frontal lifting triggered low-level instability and updrafts. Intensification of the front enhanced the vertical wind shear, causing conditional symmetric instability (CSI) to expand upward within the unstable lower troposphere, and to eventually gear into the CSI region of the upper troposphere, which facilitated the upward development of low-level updrafts.

Rainstorm Project

2026project list