Relationship between Regional Rainstorm Index and Flood Disaster Ratio of Crop

According to the daily precipitation data in Beijing area from 1985 to 2008,rainstorm weather index （10.4-38.8 mm） and climate index （daily precipitation ≥27.5 mm） in Beijing area were obtained by using the determination method of extreme climate event index recommended by IPCC. Based on rainstorm weather index,rainstorm climate index and national rainstorm standard,the number of rainstorm days and rainfall amount in past years were calculated,and the correlation of annual number of rainy days,rainstorm days,precipitation and rainstorm amount with the flood disaster ratio of crop was analyzed,and the results showed that annual number of rainy days and rainstorm days couldn＇t reflect flood disaster ratio of crop truly,while annual precipitation and rainstorm amount had obvious linear positive correlation with the flood disaster ratio of crop. In addition,the correlation degree between rainstorm amount calculated by regional climate index and flood disaster ratio of crop was the highest,so it was suggested that rainstorm amount calculated by regional rainstorm climate index could be used to predict and evaluate flood disaster.

Forecast Error and Predictability for the Warm-sector and the Frontal Rainstorm in South China

In south China, warm-sector rainstorms are significantly different from the traditional frontal rainstorms due to complex mechanism, which brings great challenges to their forecast. In this study, based on ensemble forecasting, the high-resolution mesoscale numerical forecast model WRF was used to investigate the effect of initial errors on a warmsector rainstorm and a frontal rainstorm under the same circulation in south China, respectively. We analyzed the sensitivity of forecast errors to the initial errors and their evolution characteristics for the warm-sector and the frontal rainstorm. Additionally, the difference of the predictability was compared via adjusting the initial values of the GOOD member and the BAD member. Compared with the frontal rainstorm, the warm-sector rainstorm was more sensitive to initial error, which increased faster in the warm-sector. Furthermore, the magnitude of error in the warm-sector rainstorm was obviously larger than that of the frontal rainstorm, while the spatial scale of the error was smaller. Similarly, both types of the rainstorm were limited by practical predictability and inherent predictability, while the nonlinear increase characteristics occurred to be more distinct in the warm-sector rainstorm, resulting in the lower inherent predictability.The comparison between the warm-sector rainstorm and the frontal rainstorm revealed that the forecast field was closer to the real situation derived from more accurate initial errors, but only the increase rate in the frontal rainstorm was restrained evidently.

Synergistic Effect of the Planetary-scale Disturbance, Typhoon and Meso-β-scale Convective Vortex on the Extremely Intense Rainstorm on 20 July 2021 in Zhengzhou

On 20 July 2021,northern Henan Province in China experienced catastrophic flooding as a result of an extremely intense rainstorm,with a record-breaking hourly rainfall of 201.9 mm during 0800–0900 UTC and daily accumulated rainfall in Zhengzhou City exceeding 600 mm(“Zhengzhou 7.20 rainstorm”for short).The multi-scale dynamical and thermodynamical mechanisms for this rainstorm are investigated based on station-observed and ERA-5 reanalysis datasets.The backward trajectory tracking shows that the warm,moist air from the northwestern Pacific was mainly transported toward Henan Province by confluent southeasterlies on the northern side of a strong typhoon In-Fa(2021),with the convergent southerlies associated with a weaker typhoon Cempaka(2021)concurrently transporting moisture northward from South China Sea,supporting the rainstorm.In the upper troposphere,two equatorward-intruding potential vorticity(PV)streamers within the planetary-scale wave train were located over northern Henan Province,forming significant divergent flow aloft to induce stronger ascending motion locally.Moreover,the converged moist air was also blocked by the mountains in western Henan Province and forced to rise so that a deep meso-β-scale convective vortex(MβCV)was induced over the west of Zhengzhou City.The PV budget analyses demonstrate that the MβCV development was attributed to the positive feedback between the rainfall-related diabatic heating and high-PV under the strong upward PV advection during the Zhengzhou 7.20 rainstorm.Importantly,the MβCV was forced by upper-level larger-scale westerlies becoming eastward-sloping,which allowed the mixtures of abundant raindrops and hydrometeors to ascend slantwise and accumulate just over Zhengzhou City,resulting in the record-breaking hourly rainfall locally.

Pore Characteristic Design Method of High-strength Pervious Concrete Based on the Mechanical Properties and Rainstorm Waterlogging Resistance

High-strength pervious concrete(HSPC) with porosity ranging from 0.08% to 2.011% was prepared. The mechanical properties and rainstorm waterlogging resistance of HSPC were evaluated,and a design method of HSPC pore characteristics(porosity and pore diameter) based on the mechanical properties and rainstorm waterlogging resistance was proposed. The results showed that the reduction of effective cross-sectional area caused by artificial channels was the main factor affecting flexural strength but had limited influence on compressive strength. Compared with the concrete matrix without artificial channels,the compressive strength of HSPC with porosity of 2.011% decreased by 7.4%, while the flexural strength decreased by 48.3%. The permeability coefficient of HSPC can reach 16.35 mm/s even at low porosity(2.011%).HSPC can meet the requirements of no rainstorm waterlogging, even if exposed to 100-year rainstorms. When the mechanical properties and rainstorm waterlogging resistance are compromised, the recommended porosity ranges from 1.1% to 3.5%, and the recommended pore diameter ranges from 0.8 to 2.7 mm.

Effect of Fatigue Loading on the Mechanical Properties and Resistance of High-strength Straight-hole Recycled Pervious Concrete to Rainstorm-based Waterlogging

A novel high-strength straight-hole recycled pervious concrete(HSRPC)for the secondary highway pavement was prepared in this paper.This study aimed to investigate the effect of porosity(0.126%,0.502%,and 1.13%),vehicle loading stress level(0.5 and 0.8)and service life on the resistance to rainstormbased waterlogging of HSRPC under fatigue loading.The mechanical properties of HSRPC in terms of flexural strength and dynamic elastic modulus were studied.The waterlogging resistance of HSRPC was described by surface water depth and drainage time.The microstructure of HSRPC were observed with scanning electron microscopy(SEM).Results showed that although the dynamic elastic modulus and flexural strength of HSRPC decreased with the increasing number of fatigue loading,the flexural strength of HSRPC was still greater than5 MPa after design service life of 20 years.After 2.5×10^(5)times of fatigue loading,the permeability coefficient of HSRPC with a porosity of 0.502%and 1.13%increased by 18.4%and 22.9%,respectively;while the permeability coefficient of HSRPC with 0.126%porosity dropped to 0.35 mm/s.The maximum surface water depth of HSRPC with a porosity of 0.126%,0.502%,and 1.13%were 8,5 and 4 mm,respectively.SEM results showed that fatigue loading expanded the number and width of cracks around the tiny pores in HSRPC.

Reflection on China's Disaster Prevention and Mitigation Construction after Rainstorm and Snowstorm

On July 10,2004,Beijing was hit by the rainstorm that has not been seen for many years,which caused water accumulation in many places of the urban area,power supply interruption in many places,and traffic paralysis for nearly 5 h. On July 12,2004,the rainstorm in Shanghai lasted less than 1 h,but it caused 7 deaths,more than 20 injuries,extensive power outages and traffic paralysis. At the end of 2005,the continuous snowfall in Weihai City of Shandong Province for half a month caused direct economic losses of over 200 million yuan,and the continuous heavy snowfall had a serious impact on people’s lives. From July 17 to 23,2021,Henan Province suffered a rare extremely heavy rainstorm in history,with a direct economic loss of 120.6 billion yuan. Faced with such urban meteorological disasters and other types of urban disasters,combined with the current situation of disaster prevention and reduction in China,what will managers,decision-makers,and experts and scholars think about from them.

Analysis of a Local Rainstorm in Central Inner Mongolia

Based on conventional observation data,satellite cloud image data and new generation Doppler radar data,the local rainstorm weather situation and physical quantities in Ulanqab City from 08:00 to 20:00 on June 24,2019 were analyzed by means of synoptic methods.The results show that the local rainstorm was caused by the forward trough system and the convergence of warm and cold air,and triggered by the low-level jet and the surface convergence line.The splitting and merging of cloud clusters in satellite cloud images and strong radar echoes had a good guiding effect on short-term heavy precipitation.

Analysis on the Cause and Forecast Deviation of an Extreme Rainstorm in Changsha Urban Area

Using NCEP reanalysis data,high-altitude and ground observation data,numerical model data,satellite and radar data,formation cause and forecast deviation of an extreme rainstorm process in Changsha urban area at night on June 9,2020 were analyzed.The results showed that(1)the extreme rainstorm process developed near the surface convergence line,with strong localization,short duration and large hourly rainfall intensity.(2)Under the high temperature and high humidity environment,the low-level cold advection and the hot low-pressure system interacted,and the potential con-vective unstable energy was released,and a strong convective weather was formed.(3)The convergence of water vapor in the lower layer and the strong upward movement provided sufficient water vapor for the rainstorm.The low-centroid thunderstorm was the main reason for the extreme rainstorm.(4)The forecast deviation of the numerical model to the low-level shear line and the mesoscale convergence line was an important reason for the forecast deviation of the heavy rainfall area.

Analysis of Rainstorm Process over Henan Province of China in July 2021

Based on the data from the China National Meteorological Station and the fifth-generation reanalysis data of the European Center for Medium-Range Weather Forecasts, we investigated and examined the precipitation, circulation, and dynamic conditions of the rainstorm in Henan in July 2021. The results show that: 1) This precipitation is of very heavy rainfall level, beginning on the 19th and lasting until the 21st, with a 3-hour cumulative precipitation of more than 200 mm at Zhengzhou station at 19:00 on the 20th. The major focus of this precipitation is in Zhengzhou, Henan Province, and it also radiates to Jiaozuo, Xinxiang, Kaifeng, Xuchang, Pingdingshan, Luoyang, Luohe, and other places. 2) The Western Pacific Subtropical High (WPSH), typhoons “In-Fa” and “Cempaka”, as well as the less dynamic strengthening of the Eurasian trough ridge structure, all contributed to the short-term maintenance of the favorable large-scale circulation background and water vapor conditions for this rainstorm in Henan. 3) The vertical structure of low-level convergence and high-level dispersion near Zhengzhou, together with the topographic blocking and lifting impact, produced favorable dynamic lifting conditions for this rainstorm.

Temporal and Spatial Characteristics of Rainstorm during the Crops Growth Period in North China Region

By using the daily precipitation data from 1961 to 2005 in North China region,the temporal and spatial distribution characteristics of rainstorm process occurrence and the rainstorm intensity during the crops growth period were studied.The results showed that the rainstorm intensity and the rainstorm process during the crops growth period in North China region both had the obvious annual fluctuations and era variation characteristics.Although the rainstorm and heavy rainstorm occurred in North China region every year,the annual variations were great,and the variation coefficients respectively reached 36.9% and 53.1%.The torrential rain occurred once in every 4-5 years,and the rainstorm process occurred once in every 11 years.Although the torrential rain and rainstorm process occurred in fewer years,their annual fluctuations were more obvious.The peak value zones of rainstorm intensity which was greater and the rainstorm process which occurred frequently were in the 1960s.After 1999,the rainstorm intensity and the rainstorm process were in low value zone of historical stage from 1961 to 2005.Moreover,the 1970s-1990s was between high value and low value,and the rainstorms in different intensities which weren't synchronous happened in the period.In addition,the spatial distribution of annual average rainstorm days presented the tendency which increased obviously from northwest to southeast in Northern China,and the variation coefficient of rainstorm days presented the tendency which increased gradually from southeast to northwest.Generally,the more the annual average rainstorm days are,the smaller the variation coefficient is,and vice versa.The statistics results also showed that precipitation in North China had obvious positive correlation relationship with the rainstorm days.

Occurrence Mechanism of A Local Rainstorm in the Northwest of Hubei Province

A rare local rainstorm weather in the midsummer rainy weather process appeared in the northwest of Hubei Province during July 8-13,2009.The circulation situation,the contributions of dynamic,thermal force and water vapor to this strong precipitation in this process were discussed.The results showed that the cold air which was brought by Lake Balkis cold vortex was the trigger mechanism of local rainstorm,and Lake Baikal low pressure provided the foreign dynamic for the adjustment of East Asia circulation.When the rainstorm occurred,the divergence in the divergence field had the strong 'pumping effect' in the high altitude.The warm wet airflow in the Bay of Bengal and the South China Sea was the water vapor source of rainstorm.The falling zone of rainstorm appeared in the front of energy frontal zone,and the axis line in the top of high-energy tongue deviated to the side of cold air.Q vector divergence and the negative value zone of water vapor helicity had the important indication effect for the short-term forecast of local rainstorm.

Forecast and Analysis of the Rainstorm in Liaoyang on July 15^(th),2008

By using observation data,numerical forecast product and non-conventional observation data,the process of a rainstorm happened on July 15th,2008 was analyzed. The evolution process of situation field and the prediction error by numerical forecast products were mainly analyzed. Some local indices for forecasting rainstorm were obtained,so as to guide rainstorm prediction in the future.

Dry Intrusion Analysis of A Heavy Rainstorm in Southern Shaanxi

[Objective] One regional rainstorm weather in the south area of Shaanxi was expounded.[Method] By employing the NCEP/NCAR 1°×1°reanalysis data,routine observation and automatic precipitation station data,the large scale circulation background field of regional precipitation in the south area of Shaanxi province from July 16-18 in 2010 was expounded.By dint of physical quantity such as the meridional wind,relative humidity and false relative temperature,the characteristics of dry intrusion and its role in rainstorm were expounded.[Result] The mild and high latitude at 500 hPa was stable.The continental high pressure and subtropical high pressure were stable.The 700 and 850 hPa shear lines or low vortexes were the main influence system that resulted into large scale of rainstorm in south Shaanxi.The landing typhoon had distinct influences on the importance of storm.The influence of typhoon and subtropical high was mutual.It not only formed and strengthened the torrent in the low air,also transmitted water vapor and energy incessantly to the south area of Shaanxi,playing an important role in augment of rainstorm.There were two distinct dry intrusions in the rainstorm process,showing a dense dry layer in the high layer of convective layer.The existence of dry layer was conductive to the accumulation of convective unstable energy in the low layer.The release of convective unstable energy could transmit warm and wet airstream in the low level to the higher level,being conductive to the occurrence of precipitation.The analysis of θse in the warp direction vertical profile suggested that there was frontal zone in this rainstorm process and the dry air activity in this rainstorm process was very strong.[Conclusion] The study provided theoretical reference to the forecast in future.

Analysis on the Formation Reason of Regional Rainstorm in Shandong Province during July 8-9,2009

By using the data which included the conventional weather chart,the satellite cloud image,the regional automatic meteorological station and the new generation of weather radar,the regional strong precipitation process which happened in Shandong Province during July 8-9 in 2009 was analyzed comprehensively.The results showed that Shandong Province was in the strong convergence zone of atmospheric vorticity in the low layer and the ascent zone of vertical velocity.The shear line was generated in the eastward process of northwest vortex,and the ground inverted trough extended to Shandong,which provided the dynamic condition for the formation of rainstorm.The coupling of jet stream in the high-low altitude enhanced the development of convection.The low-altitude jet stream was the main water vapor transportation channel,which provided the water vapor condition for the generation of rainstorm.The water vapor was mainly from the South China Sea and the Bay of Bengal.

Analysis on A Rainstorm and Convective Weather Process

By using NCEP reanalysis data and the routine observation data,a rainstorm and convective weather process which occurred in Tianjin was analyzed.The results showed that the rainstorm occurred in the favorable large scale circulation background.The sounding analysis and the physical quantity field analysis could reveal the plentiful water vapor supply condition.The rainstorm had the obvious concomitance relationship with the low level jet.Meanwhile,the existence of warm ridge on the ground was the important condition of convective weather occurrence.

Climatic Characteristics Analysis of Flood-producing Rainstorm in Duhe River Basin

Based on the data from 1998 to 2005,area rainfall,flow of main hydrologic stations in Duhe River and upstream water level of the dam of Huanglongtan Reservoir in the lower reaches of Duhe River were analyzed,and the standard of flood-producing rainstorm in Duhe River was given,while temporal and spatial distribution and circulation flow situation characteristic of flood-producing rainstorm in Duhe River were studied.The results showed that the flood-producing rainstorm in Duhe River was mainly continuous intensive precipitation with the characteristic of long duration.There was most rainfall in Zhuxiquan River,Zhushanguandu River and southwest part of the middle and upper reaches of Duhe River,and next came Zhuxi River.Flood-producing rainstorm occurred in Duhe River with some favorable circulation features.For example,it was more favorable in the west Pacific subtropical high,and the convergence zone at northeast-southwest direction was formed between subtropical high and continental high pressure at 700 hPa,while southwest vortex moved eastward.Low pressure system at 850 hPa in south part of plateau developed and moved eastward to Chongqing region and formed low vortex or shear near Duhe River basin.Moreover,the characteristics of physical quantity field were analyzed,the results showed that temperature in plateau area and the south area of Duhe River basin increased obviously before rainstorm,and east pathway was the main path of cold air which affected flood-producing rainstorm in Duhe River.There was a θse intensive belt with NEE-SWW direction at 30°-40° N at 925-500 hPa,and moisture convergence was beneficial to the occurrence of rainstorm in Duhe River.

ANALYSIS ON INTRA-ANNUAL INHOMOGENEITY OF RAINSTORM EVENTS IN GUANGXI

Based on the daily precipitation data of 83 stations in Guangxi and the NCEP/NCAR monthly reanalysis data from 1979 through 2008, the characteristics of spatial and temporal distribution and variation of the rainstorm concentration degree(RCD) and the rainstorm concentration period(RCP) are analyzed by using the methods of Monte Carlo test etc. The results are shown as follows. The rainstorm events are concentrated in April-September, taking up about 90% of the yearly rainfall total, and the percentages of rainstorms in the annual total precipitation have an increasing tendency. RCD in the east of Guangxi is larger than that in the west. The RCP in the northeast and southwest of Guangxi is later than that in the other regions, and has the earliest onset in the northern mountainous regions of Baise and southeast Guangxi. The RCD exhibits an increasing tendency in the northwest and the coastal region while showing a decreasing tendency in the other regions. On a long-term basis, the RCP in the east and coastal region has a postponing trend but tends to be earlier in the other regions. The proposed mechanism is as follows: If the geopotential height in the south of Qinghai-Tibet Plateau and the West Pacific has a highly negative anomaly in winter, the western Pacific subtropical high will be strong in summer, which increases the RCD in Guangxi. If the geopotential height has a highly positive anomaly in winter, the subtropical high will have a significant periodic oscillation in summer, which decreases the RCD in Guangxi. The value of RCD is high(low) in the area of northern mountainous regions of Guangxi and Beihai in strong(weak) South China Sea summer monsoon years, while in the other areas, the value of RCD is low(high).

Analysis on A Rainstorm Type Landslide Disaster in Wanning

Due to the common influence of tropical depression,the low pressure trough and the cold air,the strong precipitation synoptic process occurred in Hainan Island on October 22,2009.It caused that the landslide geological disaster happened in several spots in the eastern line highway.By analyzing on the generation reason of landslide,it gained that the landslide which happened in several spots in the eastern line highway was caused by the common effect of special topographical condition,strong wind and rainstorm.The strong precipitation and strong wind which were generated by the tropical depression were the direct reasons which induced the rainstorm type landslide in the eastern line highway.

Non-equilibrium Vibration and Diagnosis Analysis of A Rainstorm

The rainstorm weather from July 15,2010 to July 18,2010 is researched by diagnosis analysis method.The results suggest that in the strong and lasting period,the upward air current in the basin is prevail and is above 300 hPa.The convergence layer during strong rainstorm period is not thick.The convergence movement of air current is under 500 hPa.In this rainstorm process,the positive vortex maximum value center of the lower layer of convection layer is perfectly corresponding to rainstorm zone.The air current convergence and divergence intensity is one magnitude larger than the turning intensity.Flux plays a leading role in the system changes process;the non-equilibrium value of the low layer of convection layer during the strong rainstorm period U<0.Strong non-equilibrium is favorable for the movement of convergence.The non-equilibrium value of the high layer of convection layer U>0,and it stimulates the divergence movement of high layer.The divergence of high layer pushes the convergence of the lower layer and thus forms strong upward movement.

ANALYSIS OF MESOSCALE CONVECTIVE SYSTEMS ASSOCIATED WITH A WARM-SECTOR RAINSTORM EVENT OVER SOUTH CHINA

With multiple meteorological data, including precipitation from automatic weather stations, integrated satellite-based precipitation (CMORPH), brightness temperature (TBB), radar echoes and NCEP reanalysis, a rainstorm event, which occurred on May 26, 2007 over South China, is analyzed with the focus on the evolution characteristics of associated mesoscale-β convective systems (Mβcss). Results are shown as follows. (1) The rainstorm presents itself as a typical warm-sector event, for it occurs within a surface inverted trough and on the left side of a southwesterly low-level jet (LLJ), which shows no obvious features of baroclinicity. (2) The heavy rainfall event is directly related to at least three bodies of Mβcss with peak precipitation corresponding well to their mature stages. (3) The Mβcss manifest a backward propagation, which is marked with a new form of downstream convection different from the more usual type of forward propagation over South China, i.e., new convective systems mainly form at the rear part of older Mβcss. (4) Rainstorm-causing Mβcss form near the convergence region on the left side of an 850-hPa southwesterly LLJ, over which there are dominantly divergent air flows at 200 hPa. Different from the typical flow pattern of outward divergence off the east side of South Asia High, which is usually found to be over zones of heavy rains during the annually first rainy season of South China, this warm-sector heavy rain is below the divergence region formed between the easterly and southerly flows west of the South Asian High that is moving out to sea. (5) The LLJ transports abundant amount of warm and moist air to the heavy rainfall area, providing advantageous conditions for highly unstable energy to generate and store at middle and high levels, where corresponding low-level warm advection may be playing a more direct role in the development of Mβcss. As a triggering mechanism for organized convective systems, the effect of low-level warm advection deserves more of our attention. Based on the analysis of surface mesoscale airflow in the article, possible triggering mechanisms for Mβcss are also discussed.