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Precipitation data in urban hydrological models are derived from an ideal stormwater model, which has some uncertainties and limited prediction times. Therefore, to reliably forecast urban flooding, prolong prediction time periods, and better support associated research in urban flood forecasting, a combination of weather forecasts and urban hydrology is necessary. By applying comprehensive cloud microphysical schemes in the Weather Research and Forecasting (WRF) model to the predecessor torrential rainfall associated with Typhoon Khanun (2017), this study evaluated different configurations of atmospheric-hydrological simulations based on the WRF model and InfoWorks ICM. Results showed that the microphysics scheme could significantly affect spatial and temporal distributions of the simulated torrential rainfall. Generally, the combination of WRF and NSSL schemes produced better performance. Applying the NSSL scheme to the WRF model and combining it with the InfoWorks ICM system can reproduce torrential rainfall and urban flood formations. [ABSTRACT FROM AUTHOR]

An extreme rainfall event occurred over Hangzhou, China, during the afternoon hours on 24 June 2013. This event occurred under suitable synoptic conditions and the maximum 4-h cumulative rainfall amount was over 150 mm. This rainfall event had two major rainbands. One was caused by a quasi-stationary convective line, and the other by a back-building convective line related to the interaction of the outflow boundary from the first rainband and an existing low-level mesoscale convergence line associated with a mei-yu frontal system. The rainfall event lasted 4 h, while the back-building process occurred in 2 h when the extreme rainfall center formed. So far, few studies have examined the back-building processes in the mei-yu season that are caused by the interaction of a mesoscale convergence line and a convective cold pool. The two rainbands are successfully reproduced by the Weather Research and Forecasting (WRF) model with four-level, two-way interactive nesting. In the model, new cells repeatedly occur at the west side of older cells, and the back-building process occurs in an environment with large CAPE, a low LFC, and plenty of water vapor. Outflows from older cells enhance the low-level convergence that forces new cells. High precipitation efficiency of the back-building training cells leads to accumulated precipitation of over 150 mm. Sensitivity experiments without evaporation of rainwater show that the convective cold pool plays an important role in the organization of the back-building process in the current extreme precipitation case. [ABSTRACT FROM AUTHOR]

The southwest vortices (SWVs) are a unique type of mesoscale vortex that frequently induce torrential rainfall in China. In this study, we focused a long‐lived quasi‐stationary SWV, which was the primary system for producing an extremely heavy rainstorm within/around Sichuan (the maximum hourly precipitation was ~103.8 mm) in Mid July 2021. After reproduced the SWV's formation by using Weather Research and Forecasting model, we conducted trajectory analyses and topography sensitivity simulations to understand the effects of complicated topography on the vortex's formation. It is found that, the regions south and southwest of the SWV acted as the most important source regions for the air clusters that formed the SWV (proportion ≥ 65%), and the air clusters originated from the upper layer contributed the most (≥60%). Of these, the air clusters sourced from the upper layer southwest and south of the SWV played the most important role in the SWV's formation, as their increase in cyclonic vorticity and their contributions to trajectory number and vorticity were all much larger than those of the others. Sensitivity simulations indicated that, detailed topography features around the Sichuan Basin were crucial in determining the structure, intensity and precipitation of the SWV, whereas, the topography features were not a decisive factor for the SWV's formation. In summary, our findings are useful to enrich the current understanding of the SWVs' formation, which would be helpful to improve the related forecasts. [ABSTRACT FROM AUTHOR]

Coastal urban areas in tropical regions, such as Greater Jakarta (GJ) in Indonesia, are susceptible to flood hazards from torrential rainfall. Efforts to understand the convective mechanisms leading to this type of rainfall have been carried out extensively, especially for events occurring in the wet season. However, hydrometeorological risks persist even in the dry season, when the rainfall is more closely correlated with the diurnal wind circulation. Among the aspects of convective activities and this diurnal circulation, the details of the updraft remain the least studied and open for discussion. We investigate the role of the updraft in urban torrential rainfall over GJ, using data from a C‐band Doppler radar and reanalysis dataset during the dry season of 2018–2019. Employing back‐trajectory calculations, we locate updraft origins corresponding to the peak of daytime inland rainfall. Most updraft origins are localized at an NW–SE‐oriented front nearly parallel to the coastline on the low‐lying plain, suggesting a region of atmospheric destabilization favorable for convective activity. The dry‐season torrential rainfall over GJ may involve convective activity from this front, that from earlier updrafts originating above the densely populated area, and further enhancement coming from orographic contributions. Our findings suggest the important role of updrafts in the rainfall generation, providing insights into the convective mechanism over GJ. [ABSTRACT FROM AUTHOR]

Abstract The southwest vortices (SWVs) are a unique type of mesoscale vortex that frequently induce torrential rainfall in China. In this study, we focused a long‐lived quasi‐stationary SWV, which was the primary system for producing an extremely heavy rainstorm within/around Sichuan (the maximum hourly precipitation was ~103.8 mm) in Mid July 2021. After reproduced the SWV's formation by using Weather Research and Forecasting model, we conducted trajectory analyses and topography sensitivity simulations to understand the effects of complicated topography on the vortex's formation. It is found that, the regions south and southwest of the SWV acted as the most important source regions for the air clusters that formed the SWV (proportion ≥ 65%), and the air clusters originated from the upper layer contributed the most (≥60%). Of these, the air clusters sourced from the upper layer southwest and south of the SWV played the most important role in the SWV's formation, as their increase in cyclonic vorticity and their contributions to trajectory number and vorticity were all much larger than those of the others. Sensitivity simulations indicated that, detailed topography features around the Sichuan Basin were crucial in determining the structure, intensity and precipitation of the SWV, whereas, the topography features were not a decisive factor for the SWV's formation. In summary, our findings are useful to enrich the current understanding of the SWVs' formation, which would be helpful to improve the related forecasts.

Precipitation data in urban hydrological models are derived from an ideal stormwater model, which has some uncertainties and limited prediction times. Therefore, to reliably forecast urban flooding, prolong prediction time periods, and better support associated research in urban flood forecasting, a combination of weather forecasts and urban hydrology is necessary. By applying comprehensive cloud microphysical schemes in the Weather Research and Forecasting (WRF) model to the predecessor torrential rainfall associated with Typhoon Khanun (2017), this study evaluated different configurations of atmospheric-hydrological simulations based on the WRF model and InfoWorks ICM. Results showed that the microphysics scheme could significantly affect spatial and temporal distributions of the simulated torrential rainfall. Generally, the combination of WRF and NSSL schemes produced better performance. Applying the NSSL scheme to the WRF model and combining it with the InfoWorks ICM system can reproduce torrential rainfall and urban flood formations.

Abstract Coastal urban areas in tropical regions, such as Greater Jakarta (GJ) in Indonesia, are susceptible to flood hazards from torrential rainfall. Efforts to understand the convective mechanisms leading to this type of rainfall have been carried out extensively, especially for events occurring in the wet season. However, hydrometeorological risks persist even in the dry season, when the rainfall is more closely correlated with the diurnal wind circulation. Among the aspects of convective activities and this diurnal circulation, the details of the updraft remain the least studied and open for discussion. We investigate the role of the updraft in urban torrential rainfall over GJ, using data from a C‐band Doppler radar and reanalysis dataset during the dry season of 2018–2019. Employing back‐trajectory calculations, we locate updraft origins corresponding to the peak of daytime inland rainfall. Most updraft origins are localized at an NW–SE‐oriented front nearly parallel to the coastline on the low‐lying plain, suggesting a region of atmospheric destabilization favorable for convective activity. The dry‐season torrential rainfall over GJ may involve convective activity from this front, that from earlier updrafts originating above the densely populated area, and further enhancement coming from orographic contributions. Our findings suggest the important role of updrafts in the rainfall generation, providing insights into the convective mechanism over GJ.

Using the ERA5 reanalysis data, observational data from automated weather stations, and local radar data, this paper presents a comparative study to analyze the rainfall, weather patterns, physical parameters, and radar echo characteristics during two extreme torrential rainfall events on May 20--22, 2020 (Process 1) and on June 6--8, 2020 (Process 2) in the Shenzhen-Shanwei Special Cooperation Zone (SSCZ). The results show that both of the two events occurred under the background of favorable largescale circulation, and low-level jet (LLJ) streams provided sufficient water vapor. Meanwhile, the transport of low-level warm and humid airflow kept the low level of the rainstorm area under the control of high energy and high humidity for a long time, and the strong convergent upward motion provided favorable dynamic conditions. A surface convergence line was formed under the influence of a warm and moist airflow from the ocean and a southward cold airflow along the Lianhua Mountain. The difference was that the low-level wind speed in the rainfall area was stronger and the strengthening was more obvious, and the intensity of the mesoscale kinetic energy front was stronger in Process 1. In Process 2, the large value of water vapor flux was more northerly, and the unstable atmospheric stratification in the rainfall area was maintained for a longer period of time. The height range of the large value area of vertical motion was wider. The radar echo of Process 1 was a strong mono echo moving northward to the surface convergence line of the SSCZ. Subsequently, it developed rapidly and moved less, and was accompanied by a meso-γ-scale vortex. In Process 2, the radar echo was a linear strong echo that was triggered continuously near the long-maintained surface convergence line and thus the "train effect" was developed. [ABSTRACT FROM AUTHOR]

The composite characteristics of northwest vortex that causes torrential rain in northern Shaanxi were analyzed statistically based on the in-situ observations from the automatic meteorological stations， ground-based sounding observations and reanalysis data from NECP.The main conclusions are as follows： one third of the torrential rains in northern Shaanxi can be attributed to the northwest vortex， which mainly occurred in July or August； the northwest vortex， mainly originated in the western Qinghai province， will probably trigger torrential rains in northern Shannxi 36 to 48 hours later； the torrential rains in the northern Shaanxi were closely related to the upper-level jet， the upper trough， the western Pacific subtropical high and 700 hPa northwest vortex.In-depth analysis of northwest vortex showed that the torrential rain area was just corresponding to the southeast of 700 hPa positive vorticity center， which was featured by the significant upward movement induced by high-level divergence and low-level convergence； the torrential rain in northern Shannxi was also beneficial from the favorably unstable and high humidity conditions， which were closely linked with the southern and eastern water vapor transportation.

In March 2018, a large fissure closely parallel to the eastern rift belt of the East African Rift (EAR) system in Kenya emerged across the highway near Mai Mahiu town. It raises the possibility of rift tectonics aided by subsurface erosion. A thorough investigation was made based on remote sensing-based lineament analysis, land surface deformation by spaceborne geodetic techniques, and rainfall pattern vs denudational processes in the affected area in relation to local geology to adjudge the cause of the aseismic fissure. By conventional and advanced differential interferometric SAR (DInSAR and ADInSAR) and GNSS data analyses aided by the knowledge of generalised rift direction obtained from remote-sensing based lineament analysis, we inferred miniature dike intrusion and reactivation of pre-existing fault in a transiently elevated extensional regime. Episodic magmatic inflation in the Mt Longonot volcano and sudden increase in hydrological loading due to prolonged torrential rainfall led to the elevated extension and fracturing of the magma chamber, which prompted to miniature dyke intrusion along the pre-existing NNW-SSE fault, reactivation of faults and fractures and subtle rifting on SW dipping normal fault. Further, internal erosion in porous and permeable sandy soil and volcaniclastic deposits led to cavity formation along the reactivated weak plane, which finally led to the emergence of the ground fissure. In this paper, we presented our observations on volcano movements (due to magmatic inflation), reactivation of the pre-existing fault(s)/fracture(s) and, finally, their linkage with the formation of the surface fissure in an area with favourable geomorphology, rock and soil properties for internal erosion during heavy torrential rainfall. [ABSTRACT FROM AUTHOR]

Predicting warm-sector torrential rainfall over South China, which is famous for its destructive power, is one of the most challenging issues of the current numerical forecast field. Insufficient understanding of the key mechanisms underlying this type of event is the root cause. Since understanding the energetics is crucial to understanding the evolutions of various types of weather systems, a general methodology for investigating energetics of torrential rainfall is provided in this study. By applying this methodology to a persistent torrential rainfall event which had concurrent frontal and warm-sector precipitation, the first physical image on the energetics of the warm-sector torrential rainfall is established. This clarifies the energy sources for producing the warm-sector rainfall during this event. For the first time, fundamental similarities and differences between the warm-sector and frontal torrential rainfall are shown in terms of energetics. It is found that these two types of rainfall mainly differed from each other in the lower-tropospheric dynamical features, and their key differences lay in energy sources. Scale interactions (mainly through downscale energy cascade and transport) were a dominant factor for the warm-sector torrential rainfall during this event, whereas, for the frontal torrential rainfall, they were only of secondary importance. Three typical signals in the background environment are found to have supplied energy to the warm-sector torrential rainfall, with the quasi-biweekly oscillation having contributed the most. [ABSTRACT FROM AUTHOR]

From 17–22 July 2021, Henan Province experienced the most severe torrential rainfall event since 1975 with a maximum hourly precipitation of 201.9 mm appeared in Zhengzhou, which was the largest hourly rainfall thus far observed by meteorological observation stations over the Chinese Mainland. The appearance of a long‐lived (21‐hr) northwestward‐moving mesoscale convective vortex (MCV) and its interaction with its parent mesoscale convective system (MCS) was crucial to produce the extremely strong heavy rainfall in Zhengzhou. The backward trajectory analysis indicates that air particles in the lower troposphere beneath the MCS over Henan contributed mostly to the MCV's formation. These air particles experienced notable ascending motions and condensation with their strong cyclonic vorticity mostly produced 1‐hr before the MCV's formation. Vorticity budget denotes that strong upward transport of cyclonic vorticity and convergence‐related vertical stretching, both of which were mainly due to convection associated with the parent MCS, acted as dominant factors for the MCV's formation. After formation, the MCV first coupled with its parent MCS, during which its intensity, thickness, and precipitation were all maximized; then, it moved northwestward and decoupled from the MCS, during which it weakened rapidly and finally dissipated. Convection‐related upward cyclonic vorticity transport and inward horizontal advection of cyclonic vorticity associated with an inverted trough over the Henan Province dominated the vortex's development/maintenance in the coupling stage; whereas outward horizontal advection of cyclonic vorticity dominated the MCV's dissipation after it completely decoupled from its parent MCS. These differ notably from the findings documented in previous MCV‐related literature. Key Points: A long‐lived mesoscale vortex was crucial to produce the hourly precipitation of 201.9 mm that appeared in Zhengzhou on 20 July 2021The extremely strong hourly precipitation appeared in the stage when the vortex interacted with its parent mesoscale convective systemConvection‐related upward and net‐import horizontal transport of cyclonic vorticity dominated the vortex's development [ABSTRACT FROM AUTHOR]

Copyright of Plateau Meteorology is the property of Plateau Meteorology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

From 17 to 22 July 2021, a series of disastrous rainstorms appeared within Henan Province and its surroundings, which rendered 398 dead/missing and a direct economic loss of up to ∼114 billion Yuan. This event was named as the “21.7” Henan torrential rainfall event (TRE), and it could be divided roughly into three stages according to the precipitation features and dominant weather systems. This study mainly focused on the development and maintenance mechanisms of a long-lived (72 h) quasi-stationary mesoscale vortex that governed the earlier stage of the “21.7” TRE. Main results are as follows: 1) the mesoscale vortex formed/maintained in a favorable environment which was characterized by the South-Asia-high associated divergence in the upper troposphere, and the relay transport of relatively cold air by the trough and high-pressure system in the middle troposphere. 2) the vertical stretching due to lower-level convergence and the upward transport of cyclonic vorticity by ascending motions served as the first and second dominant factors for the mesoscale vortex’s rapid development and long-time maintenance, whereas, the import/export transport of anticyclonic/cyclonic vorticity into/from the vortex’s central region and the tilting effects were mainly detrimental for the vortex’s development/maintenance. 3) the air particles that formed the mesoscale vortex mainly came from the levels below 1,500 m, within the regions in lower latitudes. The air particles experienced notable precipitation before the formation of the mesoscale vortex, which contributed to the vortex’s formation through latent heat release.

Jianghuai region was hit by a torrential rainfall event on 18th-19th July, 2020. Numerical prediction models from ECMWF(hereinafter as EC model), East China Regional Meteorological Center/CMA(hereinafter as Huadong model), National Meteorological Center/CMA (3km resolution, hereinafter as G3 model) all present obvious northerly-offset in heavy rainfall area forecasts, and with weaker rainfall amounts as well. After detailed verification and analysis on models' wind fields and precipitation forecasts, it is founded that the performance of a model's synoptic situation forecasts are closely related to the model's precipitation forecast in most of times, especially for middle and low level wind fields which are easily affected by the model's precipitation latent heating process and thus would present wrong revision instruction to duty forecasters. Comparatively speaking, a model's forecast on high-level wind field is likely not affected by the model's precipitation latent heating process, which could be a reference deserving more attention during synoptic analysis. Furthermore, for a torrential rainfall caused by propagation of meso-or smaller scale weather systems, regional numerical model with higher resolution would be a better reference for forecast decision during similar heavy rainfall events.

The short-range numerical weather prediction model has been developed as a tool to forecast the torrential rainfall since it has the capability to describe the dynamic convergence, fundamental physics and the real topography reasonably when the horizontal resolution is increased to a few tens of kilometers. The nearly fifty years of development in the meso-scale numerical prediction model for heavy rainfall has witnessed great changes in the dynamical core from hydrostatic to non-hydrostatic, the resolution from coarse to fine, the physical processes from simple to comprehensive, cloud and precipitation forecast from implicit to explicit and initialization from simple interpolation to complicated assimilation. In this paper, we mainly focus on dynamical frames, physical packages and initialization techniques of the meso-scale numerical heavy rainfall prediction model to analyze its important advances at home and abroad. Some future directions of the model development are also suggested. The review will be helpful to understand the current status and development trend of meso-scale model as an important tool to study and forecast heavy rainfall.

Continuing urbanization has reduced permeable land areas, causing rainwater runoff volumes to rise, which not only increases the drainage burden placed on rivers and sewerage system, but also increases flood damage risk with the increases in torrential rains brought about by climate change. As physical flood control infrastructure has high costs and requires long planning and construction times, more effective utilization of existing infrastructure is required in addition to new construction. Moreover, as urbanization continues, the use of privately owned land for flood control as well as the limited publicly owned land available is increasingly important. This article reports the results and efficacy of a project to create a rainwater management network by connecting multiple pumping stations with the city's main rainwater pipeline in coordination with river development in a major river drainage basin region, while rebuilding aging pumping stations for continued use, as well as the effectiveness of rainwater storage facilities in underground locations beneath privately owned buildings. [ABSTRACT FROM AUTHOR]

On 28 July 2013, an intense torrential rainfall occurred at the boundary of Yamaguchi and Shimane Prefectures in western Japan, and triggered a debris flow on an ungauged hillslope to bury the entrance of Shirai tunnel and to shutdown railway service in that region for 1 year. To assess this disaster, this study aims at numerically modeling this debris flow event through a methodology incorporating empirical hydrologic analysis and mechanical debris flow model. For hydrologic analysis, the SCS-CN method implemented by HEC-HMS was used to obtain direct runoff hydrograph with high-resolution precipitation data reanalyzed using observations from radars and rain gauges. Then, the obtained runoff-discharge information was applied as an input for numerically simulating the debris flow movement from source to deposition areas. The simulation result is verified by the field evidence from field survey. The study demonstrates the applicability of the proposed empirical–mechanical approach for assessing debris flows in ungauged basins. [ABSTRACT FROM AUTHOR]

On the morning of 14th October 1956, a mass made of boulders and mud fall through the slope of the Rodeno Mountain (Calderona range) and destroyed part of the urban area of Marines (Valencia), causing 6 fatalities and numerous material damages. This research reconstructs this event and develops an interpretation of the mass movement, based on documents from historical archives, post-event pictures, interviews with witnesses and sediment examination. These materials allow mapping the event and identifying this phenomenon as a debris flow most likely connected to initial debris avalanches that took place at the headwaters area. The magnitude of the event and the existence of similar sediment deposits in the surrounding area highlight the significant hazard that still threatens this mountain village. [ABSTRACT FROM AUTHOR]

Copyright of Cuadernos de Investigación Geográfica is the property of Universidad de la Rioja, Servicio de Publicaciones and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

As a consequence of the climate change, localized torrential rainfall has increased in intensity and frequency in Northeast Asia. This work aims at studying the effect of rainfall intensity on benthic macroinvertebrate communities in a mid-sized mountain stream in Korea, where the summer monsoon flood is prevalent. Sampling was conducted along reaches in Gapyeong stream (42 km in length), central Korean Peninsula, from a period of July 2008–October 2009. The sampling collection was carried out within 48 h after every major rain occasion and rainfall intensity was quantified by using the total rainfall amount for three days. Both water velocity and Froude number were found to increase with respect to the increase of rainfall at all study sites. As a consequence, the habitat environment and benthic macroinvertebrate communities were apparently affected by the rainfall intensity along the stream reaches. The species richness and abundance of benthic macroinvertebrates were significantly decreased at a rainfall over 200 mm, while much less decreased at a rainfall below 100 mm. Furthermore, the richness and abundance of species generally decreased with an increase of rainfall and their decrease was more evident at the downstream site, as compared to the upstream and midstream one.

Warm‐sector torrential rainfall (WR) in the South China monsoon region has long been a forecasting challenge because of the limited capability of numerical models in heavy rainfall without strong synoptic forcing. Through convection‐allowing ensemble forecasts, this study explores both the intrinsic and practical predictability of a coastal WR event on 19–20 May 2015 during SCMREX (the Southern China Monsoon Rainfall Experiment). The results show a large variability in forecast performance among different members, indicating the practical limit of predictability. In general, GOOD members tend to have a stronger low‐level southerly wind over the sea (monsoon flow) and a considerable surface cooling over the northern mountains (associated with land/mountain breeze). Further investigation via ensemble‐based sensitivity analysis shows that the occurrence of WR is closely related to the nighttime strengthened (cooling) southerly wind (temperatures) over the sea (mountains), 1–3 hr prior to the convection initiation. In contrast, spatial scaling of the initial perturbations has little impact on the forecast after 3 hr and the meso‐γ‐scale rainfall is fully decorrelated after 12 hr, suggesting an intrinsic predictability limit for lead times as short as 6–12 hr. Sensitivity experiments are conducted with the initial‐condition differences reduced by almost an order of magnitude smaller than typical ensemble perturbations, with the results demonstrating that the rainstorm might be near the point of bifurcation, where predictability is intrinsically limited. The limits of both intrinsic and practical predictability highlight the need for rapidly updated and probabilistic convection‐allowing ensemble forecasts for events of this type. Key Points: Both the practical and intrinsic predictability of a coastal warm sector torrential rainfall event during the Southern China Monsoon Rainfall Experiment (SCMREX) are investegatedThe occurrence of warm‐sector rainfall is closely related to the nighttime strengthened (cooling) monsoon flow (temperature) over the sea (mountain)The warm‐sector rainstorm could be near the point of bifurcation, where predictability is intrinsically limited [ABSTRACT FROM AUTHOR]

The abnormal 2020 Meiyu season caused the worst disasters over the Yangtze River Valley in recent decades. Of these, the Sichuan Basin (SCB) and its surrounding regions were one of the most severely affected areas. Disastrous weather frequently occurs in these regions, with a large proportion of it closely related to the southwest vortices (SWVs). In order to further the understanding of SWV generation, this study investigated the formation mechanisms of a quasi-stationary SWV (by using two sets of vorticity budgets), which caused torrential rainfall (resulting in flash floods in Sichuan and Chongqing), lightning activities (causing tripping incidents of transmission lines in Sichuan) and strong winds (leading to shutting down of wind turbines in Hubei). Results showed that the SWV was generated in a favorable background environment, during which an upper-tropospheric divergence and a middle-tropospheric warm advection appeared over the SCB. Trajectory analyses and vorticity budget showed that the air particles that came from the lower troposphere of the regions south of the Tibetan Plateau dominated the SWV formation. These air particles experienced notable ascending during which an increase in their cyclonic vorticity occurred mainly due to convergence-related stretching, whereas, tilting mainly decelerated this increase. The air particles sourced from the areas within the key region of the SWV and areas northeast of the key region were the second dominant factor for the vortex formation. Overall, for the air particles that formed the SWV, their most rapid changes of vorticity and divergence appeared in the period 24 h before SWV formation, implying that this was the critical period for the SWV generation.

The increase in the frequency of heavy rainfall events in Mediterranean areas is a matter of concern and not only from the hydro-geomorphological point of view, but also from the human, socioeconomic and infrastructural point of view. The definition of the heavy rainfall threshold is key to determine the dangerousness of a territory. In this study we adjusted different classifications of this, with the problems and impacts identified in two contrasted Mediterranean areas of the province of Malaga, one of them characterized by a subhumid Mediterranean climate (Guadalhorce), and another by a dry-semi-arid Mediterranean climate (Axarquía). From the analysis of the rainfall data of 18 observatories (SAIH Network), the results determine a low recurrence of the predefined heavy rainfall events (> 100 mm 24 h-1;> 60 mm h-1), proposing the use of a new threshold of shorter duration, but much higher intensity (> 10 mm 10 min-1), because there are many episodes produced below the previous thresholds, but with territorial consequences, as we noted after the media analysis. Precipitation that fits this criterion has been defined as "geomorphological rainfall" due to its high capacity to modify surface formations. This type of precipitation presents in both environments a high recurrence, a practically annual return period and high erosivity. [ABSTRACT FROM AUTHOR]

The July 2018 torrential rainfall caused tremendous damage to western Japan, claiming the lives of 237 people. This research analyzed the mortality due to the disaster by age group and municipality and compared it with historical records of past wind and flood disasters. The analysis confirmed that the total death toll of 237 including 115 deaths in Hiroshima Prefecture alone was the second highest in 41 years since 1978, following 427 deaths including 294 in Nagasaki Prefecture in the NagasakiGreat Flood in 1982. The analysis also found that the mortality rate in the age group 70 years and more was extremely high in Mabi Town of Kurashiki City, Okayama Prefecture and Saka Town, Hiroshima Prefecture, compared with that recorded in past disasters. Moreover, the paper discusses practical target setting for future mortality reduction by comparing the mortality rates in past disasters. [ABSTRACT FROM AUTHOR]

This study investigated the characteristics of rainfall-triggered landslides during the Typhoon Bilis in the Dongjiang Reservoir Watershed, China. The comparative shallow landslide susceptibility mappings (LSMs) were produced by the ensemble data-driven statistical models in a GIS environment. At first, the landslide inventory for the study area was prepared from the high-resolution QuickBird images, and China–Brazil Earth Resources Satellite images, and field survey. Other necessary data for landslide susceptibility analysis such as the amount of rainfall, geology, and topography were also collected from the respective agencies. Twelve predisposing factors were then prepared using this available dataset. To reduce the subjectivity of models and caution in the selection of predisposing factors, and to avoid the spatial autocorrelation redundancy, certainty factor approach was attempted to optimize these twelve set of parameters. For validating the accuracy of the model, the original landslide data were randomly divided into two parts: 70% (1545 landslides) for training the model and the remaining 30% (662 landslides) for validation. The verified results showed that using the optimized predisposing factors has a higher performance than using all the original twelve factors. The results of ensemble models also showed that LSM maps prepared using binary logistic regression (accuracy is 0.848) model are more accurate than those prepared using bivariate statistical analysis (accuracy is 0.837) model. Additionally, our analysis concludes that the short duration and high-intensity rainfall, drainage density, lithology, and curvature are the major influencing factors for landslide occurrences in this case study area. This research provides an improved understanding of the mechanism of landslides caused by the typhoons for the adjoining watersheds nearby the reservoir. The preliminary understandings and approach could also be applied in similar geological and rainfall-triggered case study sites in the other parts of the world for risk mitigation. [ABSTRACT FROM AUTHOR]

As a consequence of the climate change, localized torrential rainfall has increased in intensity and frequency in Northeast Asia. This work aims at studying the effect of rainfall intensity on benthic macroinvertebrate communities in a mid-sized mountain stream in Korea, where the summer monsoon flood is prevalent. Sampling was conducted along reaches in Gapyeong stream (42 km in length), central Korean Peninsula, from a period of July 2008-October 2009. The sampling collection was carried out within 48 h after every major rain occasion and rainfall intensity was quantified by using the total rainfall amount for three days. Both water velocity and Froude number were found to increase with respect to the increase of rainfall at all study sites. As a consequence, the habitat environment and benthic macroinvertebrate communities were apparently affected by the rainfall intensity along the stream reaches. The species richness and abundance of benthic macroinvertebrates were significantly decreased at a rainfall over 200 mm, while much less decreased at a rainfall below 100 mm. Furthermore, the richness and abundance of species generally decreased with an increase of rainfall and their decrease was more evident at the downstream site, as compared to the upstream and midstream one. [ABSTRACT FROM AUTHOR]

The prediction of landslides and other events associated with slope movement is a very serious issue in many national parks around the world. This article deals with the territory of the Malá Studená Dolina (Little Cold Valley, High Tatras National Park—Slovakia), where there are extensive talus cones, through which seasonally heavy hiking trails lead. In the last few years particularly, there have been frequent falls and landslides in the mountainous environment, which also caused several fatal injuries in 2018. For the above reasons, efforts are being made to develop a methodology for monitoring the changes of the talus cones in this specific alpine area, to determine the size, speed, and character of the morphological changes of the soil. Non-contact methods of mass data collection (laser scanning with Leica P40 and aerial photogrammetry with unmanned aerial system (UAS) DJI Phantom 4 Pro) have been used. The results of these measurements were compared and the overall suitability of both methods for measurement in such terrain evaluated. The standard deviation of the difference of surface determination (represented by the point cloud) is about 0.03 m. As such accuracy is sufficient for the purpose of monitoring talus cones and the use of UAS is easier and associated with lower risk of damage of expensive equipment, we conclude that this method is more suitable for mapping and for repeated monitoring of such terrain. The properties of the outputs of the individual measurement methods, the degree of measurement difficulty and specific measurement conditions in the mountainous terrain, as well as the economy of the individual methods, are discussed in detail.

Several natural disasters occur because of torrential rainfalls. The change in global climate most likely increases the occurrences of such downpours. Hence, it is necessary to investigate the characteristics of the torrential rainfall events in order to introduce effective measures for mitigating disasters such as urban floods and landslides. However, one of the major problems is evaluating the number of torrential rainfall events from a statistical viewpoint. If the number of torrential rainfall occurrences during a month is considered as count data, their frequency distribution could be identified using a probability distribution. Generally, the number of torrential rainfall occurrences has been analyzed using the Poisson distribution (POI) or the Generalized Poisson Distribution (GPD). However, it was reported that POI and GPD often overestimated or underestimated the observed count data when additional or fewer zeros were included. Hence, in this study, a zero-inflated model concept was applied to solve this problem existing in the conventional models. Zero-Inflated Poisson (ZIP) model, Zero-Inflated Generalized Poisson (ZIGP) model, and the Bayesian ZIGP model have often been applied to fit the count data having additional or fewer zeros. However, the applications of these models in water resource management have been very limited despite their efficiency and accuracy. The five models, namely, POI, GPD, ZIP, ZIGP, and Bayesian ZIGP, were applied to the torrential rainfall data having additional zeros obtained from two rain gauges in South Korea, and their applicability was examined in this study. In particular, the informative prior distributions evaluated via the empirical Bayes method using ten rain gauges were developed in the Bayesian ZIGP model. Finally, it was suggested to avoid using the POI and GPD models to fit the frequency of torrential rainfall data. In addition, it was concluded that the Bayesian ZIGP model used in this study provided the most accurate results for the count data having additional zeros. Moreover, it was recommended that the ZIP model could be an alternative from a practical viewpoint, as the Bayesian approach used in this study was considerably complex. [ABSTRACT FROM AUTHOR]

Based on the governing equations for water species in the Weather Research and Forecasting (WRF) model, a three-dimensional WRF-based surface precipitation equation was obtained and applied to investigate the surface rainfall processes of a torrential rain event. Sensitivity experiments were performed to further explore roles of surface evaporation in the heavy rainfall event. The results show that the contributions of moisture-related processes to precipitation ( Q WV , including water vapor local change ( Q WVL ), surface evaporation ( Q WVE ), moisture advection ( Q WVA ), and so on) dominate the torrential rain event, while the contributions of cloud-related processes ( Q CM ) also play indispensable roles whose maximum net contributions could exceed 20%. Q WVA dominates the budget of water vapor, while Q WVL and Q WVE play smaller but by no means negligible roles in the event. Sensitivity experiments show that the changes of surface evaporation affect both moisture-related processes and cloud-related processes, and then influence the intensity and regional redistribution of precipitation. Surface evaporation favors the accumulation of convective available potential energy and enhances the instability of atmosphere, being prone to the development of convective systems. Meanwhile, it also affects the development of vertical motions and cloud systems. Thus accurate estimation of surface evaporation is necessary for accurate simulation and forecast of surface precipitation. [ABSTRACT FROM AUTHOR]

Every few years torrential rains occur in Lublin Upland region, causing local floods. According to many previous researches, such downpours especially often occur in the area of Krasnystaw (Ziemnicki 1956, Dębski 1958, Maruszczak, Trembaczowski 1958, Ciepielowski, Dąbkowski 1967, Ciepielowski, Dąbkowski 1968, Górniak 1982, Kaszewski, Siwek 2005, Siwek 2010). The main aim of this research is to characterize conditions of forming and course of the flood in May 2014. Study area was defined as the upper Wieprz river catchment, including its tributary rivers, closed by gauging station in Krasnystaw. It is located in Eastern Poland, in borderland zone of Lublin Upland and Roztocze. Main material of this research was data from 8 gauging and 17 meteorological stations acquired from Institute of Meteorology and Water Management. In the middle of May 2014, a torrential rainfall occurred in a study area and caused, according to historical data, one of the biggest floods in the upper Wieprz river basin. Maximum intensity of rain during this episode reached 60 mm·h-1. Maximum flow rate reached from 73,2 m³·s-1 in Nielisz to 138 m³·s-1 in Wirkowice and 109 m³·s-1 in Krasnystaw. It was clear evidence of transformation of flood wave between particular gauging stations located on the upper Wieprz. To estimate total volume of precipitation and calculate hydrological statistics of runoff during the flood there were prepared isohyets maps and conducted zonal statistics, using GIS tools. [ABSTRACT FROM AUTHOR]

A mesoscale torrential rainfall event that occurred over eastern China in June 2013 is analyzed by using observational data. The results show that a mesoscale convergence line and a weak convective cloud line formed over the northern part of the Hangzhou Bay during the onset of the torrential rainfall event. A meso-vortex appeared over the confluence point of northeasterly flow associated with the Yellow-Sea high, easterly flow from rainfall area, and southeasterly flow from the Hangzhou Bay. The meso-vortex with a horizontal scale of 10-20 km lasted for about 1 h for stable surface circulations. The analysis of radar retrieval reveals that the meso-vortex in the boundary layer occurred at the south of strong radar echo. The formation of the meso-vortex turned to enhance convergence and cyclonic vorticity in the lower troposphere, which strengthened updrafts that are tilted into convective clouds and caused torrential rainfall. Thus, the occurrence of the meso-vortex in boundary layer is one of the mechanisms that are responsible for the enhancement of convective development. [ABSTRACT FROM AUTHOR]

High-resolution numerical simulation data of a rainstorm triggering debris flow in Sichuan Province of China simulated by the Weather Research and Forecasting (WRF) Model were used to study the dominant cloud microphysical processes of the torrential rainfall. The results showed that: (1) In the strong precipitation period, particle sizes of all hydrometeors increased, and mean-mass diameters of graupel increased the most significantly, as compared with those in the weak precipitation period; (2) The terminal velocity of raindrops was the strongest among all hydrometeors, followed by graupel's, which was much smaller than that of raindrops. Differences between various hydrometeors' terminal velocities in the strong precipitation period were larger than those in the weak precipitation period, which favored relative motion, collection interaction and transformation between the particles. Absolute terminal velocity values of raindrops and graupel were significantly greater than those of air upward velocity, and the stronger the precipitation was, the greater the differences between them were; (3) The orders of magnitudes of the various hydrometeors' sources and sinks in the strong precipitation period were larger than those in the weak precipitation period, causing a difference in the intensity of precipitation. Water vapor, cloud water, raindrops, graupel and their exchange processes played a major role in the production of the torrential rainfall, and there were two main processes via which raindrops were generated: abundant water vapor condensed into cloud water and, on the one hand, accretion of cloud water by rain water formed rain water, while on the other hand, accretion of cloud water by graupel formed graupel, and then the melting of graupel formed rain water. [ABSTRACT FROM AUTHOR]

Progress over the past decade in understanding moisture-driven dynamics and torrential rain storms in China is reviewed in this paper. First, advances in incorporating moisture effects more realistically into theory are described, including the development of a new parameter, generalized moist potential vorticity (GMPV) and an improved moist ageostrophic Q vector ( Q). Advances in vorticity dynamics are also described, including the adoption of a 'parcel dynamic' approach to investigate the development of the vertical vorticity of an air parcel; a novel theory of slantwise vorticity development, proposed because vorticity develops easily near steep isentropic surfaces; and the development of the convective vorticity vector (CVV) as an effective new tool. The significant progress in both frontal dynamics and wave dynamics is also summarized, including the geostrophic adjustment of initial unbalanced flow and the dual role of boundary layer friction in frontogenesis, as well as the interaction between topography and fronts, which indicate that topographic perturbations alter both frontogenesis and frontal structure. For atmospheric vortices, mixed wave/vortex dynamics has been extended to explain the propagation of spiral rainbands and the development of dynamical instability in tropical cyclones. Finally, we review wave and basic flow interaction in torrential rainfall, for which it was necessary to extend existing theory from large-scale flows to mesoscale fields, enriching our knowledge of mesoscale atmospheric dynamics. [ABSTRACT FROM AUTHOR]

Effects of vertical wind shear, radiation, and ice clouds on cloud microphysical budget associated with torrential rainfall during landfall of severe tropical storm Bilis (2006) are investigated by using a series of analysis of two-day grid-scale sensitivity experiment data. When upper-tropospheric upward motions and lower-tropospheric downward motions occur on 15 July 2006, the removal of vertical wind shear and ice clouds increases rainfall contributions from the rainfall type (CM) associated with positive net condensation and hydrometeor loss/convergence, whereas the exclusion of cloud radiative effects and cloud-radiation interaction reduces rainfall contribution from CM. The elimination of vertical wind shear and cloud-radiation interaction increases rainfall contribution from the rainfall type (Cm) associated with positive net condensation and hydrometeor gain/divergence, but the removal of cloud radiative effects and ice clouds decreases rainfall contribution from Cm. The enhancements in rainfall contribution from the rainfall type (cM) associated with negative net condensation and hydrometeor loss/convergence are caused by the exclusion of cloud radiative effects, cloud-radiation interaction and ice clouds, whereas the reduction in rainfall contribution from cM results from the removal of vertical wind shear. When upward motions appear throughout the troposphere on 16 July, the exclusion of all these effects increases rainfall contribution from CM, but generally decreases rainfall contributions from Cm and cM. [ABSTRACT FROM AUTHOR]

Abstract: Results of recent investigations suggest that climate change tends to exacerbate geo-disasters. Therefore, it is understood clearly that adaptation to climate change has rapidly become the most important and urgent issue for the future existence of human beings on Earth. These inferences form the background of this research. In comparison to those examining water disasters, few studies have examined climate-change-induced geo-disasters. This study aims at upgrading the methodology for estimating effects on geo-disasters of combined events, e.g., global warming with increased typhoon and rainfall severity or occurrence of great earthquakes. Such a methodology is expected to contribute to progress in the fields of natural disaster mitigation and land preservation, particularly near seacoasts and rivers. [Copyright &y& Elsevier]

The surface rainfall processes associated with the torrential rainfall event over Hubei, China, during July 2007 were investigated using a two-dimensional cloud-resolving model. The model integrated the large-scale vertical velocity and zonal wind data from National Centers for Environmental Prediction (NCEP)/Global Data Assimilation System (GDAS) for 5 days. The time and model domain mean surface rain rate was used to identify the onset, mature, and decay periods of rainfall. During the onset period, the descending motion data imposed in the lower troposphere led to a large contribution of stratiform rainfall to the model domain mean surface rainfall. The local atmospheric drying and transport of rain from convective regions mainly contributes to the stratiform rainfall. During the mature periods, the ascending motion data integrated into the model was so strong that water vapor convergence was the dominant process for both convective and stratiform rainfall. Both convective and stratiform rainfalls made important contributions to the model domain mean surface rainfall. During the decay period, descending motion data input into the model prevailed, making stratiform rainfall dominant. Stratiform rainfall was mainly caused by the water vapor convergence over raining stratiform regions. [ABSTRACT FROM AUTHOR]

A series of numerical simulations are conducted using the Weather Research and Forecasting (WRF-ARW) model with a 9-km mesh to examine the physical processes responsible for the torrential rainfall associated with a mesoscale convective system (MCS) along the Mei-Yu front that caused severe damage over southwestern Taiwan on 12 June 2005. In the control experiment (with full Taiwan terrain), the MCS tends to propagate northward along the windward (western) slope, rather than being advected downstream, as it encounters the southern Central Mountain Range (CMR). The low-level convergence between the dynamically-driven return flow and the incoming southwesterly flow is an important factor for the northward propagation of the MCS. The values of the unsaturated moist Froude number (Fw) and the convective available potential energy (CAPE) are about 0.333 and 2858 J kg-1 for the convectively unstable basic flow. This airflow belongs to the flow-around regime as suggested by previous studies. In this flow regime, the torrential rainfall associated with the simulated MCS occurs on both the upslope side and adjacent plains over southwestern Taiwan, which agrees well with the observed rainfall distribution. A sensitivity study of lowering the Taiwan terrain elevations to 80% (Fw~0.416) or 60% (F~-0.555) of that in the control experiment reveals that the airflow is characterized by a long-lasting orographic convective system near the mountain peaks. The simulated torrential rainfall mainly occurs along the mountain peaks of the southern CMR. The experiment with a reduced elevation to 40% (Fw~0.833) or 20% (Fw ~1.666) in the control experiment shows a downstream-propagating MCS, which falls into the flow-over regime. This study demonstrates that the northward propagating MCS, which is mainly caused by the flow deflection by southern CMR, played a key role in producing torrential rainfall over southwestern Taiwan during 0000 - 1200 UTC 12 June 2005. [ABSTRACT FROM AUTHOR]

Abstract: A quantitative analysis of torrential rainfall associated with typhoon Haitang (2005) is carried out using a modified moist ageostrophic Q vector and data from Weather Research and Forecasting (WRF) model simulation. Four major factors determining the ascending motion associated with torrential rainfall have been studied: large-scale and convective condensational heating, topographic lifting and friction. The results show that the convective condensational heating plays a major role in the torrential rainfall process, and the large-scale condensational heating is secondary before the landfall of typhoon Haitang, and vice versa after the landfall. The topographic lifting affects the formation of rainfall, whereas the topographic friction has important impacts on torrential rainfall after the landfall. The rainfall amounts forced by the topographic friction and lifting have similar horizontal distributions, but the magnitudes of the former are 2–3 times larger than those of the latter. The rainfall amounts forced by topography (lifting and friction) and modified moist ageostrophic Q vector have different horizontal distributions, and the magnitudes of the former are 2–5 times larger than those of the latter. Synthetic analysis shows that the typhoon rainfall may be motivated by modified moist ageostrophic Q vector and enhanced further by the topographic effects. [Copyright &y& Elsevier]