Analysis of Heavy Precipitation Event in Northeast China from August 1 to 5, 2023

This study delves into the multiple weather systems and their interaction mechanisms that caused the severe rainfall event in Northeast China in early August 2023. The analysis reveals that the atmospheric circulation in the mid-to-high latitudes of the Eurasian continent exhibited a significant “two troughs and two ridges” structure, with Northeast China located precisely in the peripheral region of the subtropical high, significantly influenced by its marginal airflows. Additionally, the residual circulation of Typhoon “Doksuri” interacting with the subtropical high and upper-level troughs significantly increased the rainfall intensity and duration in the region. In particular, the continuous and powerful transport of the southwest jet provided the necessary moisture and unstable conditions for the generation and development of convective systems. The rainfall event resulted in nearly 40,000 people affected and crop damage covering an area of approximately 4000 hectares, demonstrating the severity of extreme weather. The study emphasizes that strengthening meteorological monitoring and early warning systems, as well as formulating and improving emergency response mechanisms, are crucial for reducing potential disaster losses caused by heavy rainfall. Future research can further explore the interaction mechanisms among weather systems, limitations of data sources, and the connection between long-term trends of heavy rainfall events and global climate change.

TERRAIN IMPACT ON THE PRECIPITATION OF LANDFALLING TYPHOON TALIM

The impact of terrains on the precipitation of landfalling typhoon Talim (2005) over China's Mainland is investigated using the fifth-generation Pennsylvania State University-National Center for Atmospheric Research Mesoscale Model. The simulated precipitation of simulated typhoon (the control) matches the observations closely. To compare with the control simulation, four sensitivity simulations were carried out in which terrains of Wuyi Mountain, Lushan, Dabieshan, and both Lushan and Dabieshan are completely removed respectively, but other surface properties were retained. It is found that the complex terrains of Wuyi Mountain, Lushan and Dabieshan have a significant impact on the rainfall intensity and distribution of Talim. As the terrains are removed, the rainfall is decreased very greatly and the rainfall in inland area is decreased much more than that in the coastal area. Besides, the rainfall distribution near the Lushan and Dabieshan is spread much more westward compared with the control simulation. Further analysis shows that the Wuyi Mountain would increase both the lower level air convergence and the upper level air divergence for Talim that just made landfall and thus it would contribute to the convection and increase rainfall intensity. It can be concluded that the terrains of Wuyi Mountain, Lushan and Dabieshan have obvious impacts on the Talim rainfall, and their impacts are different in various landfalling periods. The present study is a useful attempt to explore the influence of orography on the TCs in China's Mainland.

CLIMATOLOGICAL VARIATION FEATURES OF TYPHOON PRECIPITATION INFLUENCING FUJIAN FOR THE PAST 46 YEARS

The results of an analysis of the temporal and spatial distribution of typhoon precipitation influencing Fujian from 1960 to 2005 show that typhoon precipitation in Fujian province occurs from May to November, with the most in August. There has been a decreasing trend since 1960. Typhoon precipitation gradually decreases from the coastal region to the northwestern mainland of Fujian and the maximum typhoon precipitation occurs in the northeast and the south of Fujian. Typhoon torrential rain is one of the extreme rainfall events in Fujian. High frequencies of typhoon torrential rain occur in the coastal and southwest regions of the province. With the impact of Fujian＇s terrain, typhoon precipitation occurs more easily to the east of the mountains than to the west. Atmospheric circulation at 500 hPa over Asia and sea surface temperature anomalies of the equatorial eastern Pacific are analyzed, with the finding that they are closely connected with the anomaly of typhoon precipitation influencing Fujian, possibly mainly by modulating the northbound track of typhoons via changing the atmosphere circulation to lead to the anomaly of typhoon precipitation over the province

THE DIAGNOSTIC ANALYSIS OF THE TRACK AND PRECIPITATION OF TYPHOON “RANANIM” AFTER LANDFALL

Over the past few years, landfall and track,intensity, sustaining mechanisms of tropical cyclones （hereafter TCs） and associated weather changes have become heated topics of research, From the viewpoints of energy transformation, moisture transfer, midlatitude baroclinic frontal zones and ambient wind fields, Chen et al.Le et al.and Zeng et al.studied the sustaining mechanism of TCs that have made landfall. Li et al.also pointed out that the intensification of TCs during transition was associated with the disturbance and downward transportation of high-level potential vortexes, low-level frontal zones and low-pressure circulation around TCs, after explaining the difference in TCs transition following the theory of wet potential vortexes. With large-scale diagnostic study of two types of TCs that unexpectedly weaken or enhance just before landfall in southern China, Hu et al.noted that enhancing TCs were usually to the southwest or south of the subtropical high with low levels featured by well-defined southwesterly inflow inside TCs and sufficient supply of water vapor. Liang et al.not only analyzed the changes in convective cloud bands, precipitation, track and temperature and humidity structure in the course of TC Vongfang landfall, but the effect of cold air and Southwest Monsoon on its intensity in particular. As also shown in numerical experiments conducted both at home and abroad and relevant studies,saturated humidity and large-sized bodies of water are favorable for the maintenance and enhancement of landfall TCs circulation. All of the above research achievements not only help broaden the understanding of the patterns by which TCs behave but are positive in improving the forecast of the track, winds and rains after landfall. It is.however, not much addressed in the field or evounon of landfall TCs when they are with special underlying surface and circulation background. TC Rananim （0414） was the most serious typhoon that ever affected Zhejiang province after landfall in the 48 years from 1956 to 2004, which was also the storm that caused heavy rains in the most widespread area in Jiangxi province in the past 20 years. There are two points about Rananim that stand out from the other storms. The first was the sudden westward turning of its track and the second the significant enhancement of precipitation after moving above the Boyang Lake.What kind of mechanism caused such remarkable change in the storm？ With 6-hourly 1×1°NECP global reanalysis data, real-time upper-level observations and TCs location reports by the Central Observatory, the above two points and possible causes are studied in terms large-scale circulation background, underlying surface, cold air and diagnosis of physical quantity fields. New understanding has been made about the behavioral pattern of landfall TCs and related results will offer effective help in operational forecast.

AN ANALYSIS OF THE ASYMMETRICAL STRUCTURE OF TYPHOON AERE'S PRECIPITATION

The structural characteristics of 2004 typhoon Aere's precipitation are analyzed using the high-resolution data from the Tropical Rainfall Measuring Mission(TRMM) of the National Aeronautics Space Administration(NASA).It is found that the typhoon's characteristics vary at different stages of its development.To analyze the asymmetric causation of precipitation distribution,data from the National Center for Environmental Prediction(NCEP) reanalysis are used to calculate the vertical integral of the water vapor flux vector.The results show that because of this process,along with the unique phenomenon of twin-typhoon circulation,the easterly air current of the typhoon's northern side and the southwesterly air current of its southern side play a joint role in transporting water vapor.Furthermore,its transport effects vary greatly at the different stages of development,showing the peculiarity of the water source for this typhoon process.The distributions of the typhoon convection area—characterized by heavy precipitation and a maximum-value area of the water vapor flux,as well as a strong ascending-motion area—differ at different stages of the typhoon's development.The non-uniform distribution of water vapor flux and the vertical motion bring about asymmetrical distribution of the typhoon precipitation.

Effect of typhoon with extreme precipitation on mountain reservoir drinking water treatment: a case study in Ningbo, China

Due to frequent drinking water pollution accidents in the past decade, it is common that mountain reservoirs were used as the source of drinking water in China. However, some coastal areas frequently suffer from typhoon with extreme precipitation, which results in the water quality deterioration of the reservoirs. The influence of typhoons with extreme precipitation on Jiaokou reservoir and the emergency treatment process of Maojiaping water treatment plant in the past three typical typhoons with extreme precipitation from the year of 2012-2015 were studied. It was found that the degradation of water quality, such as the increase of turbidity and bacteria index, may not merely appear during the events, but last for several days. Changing the dosage of water purification agent, such as coagulant and disinfectant at right time and place may be an efficient emergency water treatment process. Based on the analysis of water quality variation rule during and after the events, it was also found that emergency treatment can be fully prepared before the arrival of a typhoon with extreme precipitation. And in order to better respond to the typhoon with extreme precipitation, several suggestions are also proposed in this paper as follows: establishing vegetated buffers at right place, such as macrophanerophytes,shrub or herbage, increasing investments in infrastructure management, merging or cancelling the small-scale water treatment plants, preparing adequate water purification agent before the typhoon comes, etc.

CLIMATIC CHARACTERISTICS OF TYPHOON PRECIPITATION OVER CHINA

The spatio-temporal characteristics of typhoon precipitation over China are analyzed in this study. The results show that typhoon precipitation covers most of central-eastern China. Typhoon precipitation gradually decreases from the southeastern coastal regions to the northwestern mainland. The maximum annual typhoon precipitation exceeds 700 mm in central-eastern Taiwan and part of Hainan, while the minimum annual typhoon precipitation occurs in parts of Inner Mongolia, Shanxi, Shaanxi and Sichuan, with values less than 10 mm. Generally, typhoons produce precipitation over China during April - December with a peak in August. The annual typhoon precipitation time series for observation stations are examined for long-term trends. The results show that decreasing trends exist in most of the stations from 1957 to 2004 and are statistically significant in parts of Taiwan, Hainan, coastal Southeast China and southern Northeast China. The anomaly of typhoon precipitation mainly results from that of the general circulation over Asia and the Walker Cell circulation over the equatorial central and eastern Pacific. Typhoon torrential rain is one of the extreme rainfall events in the southeastern coastal regions and parts of central mainland. In these regions, torrential rains are mostly caused by typhoons.

Roles of Mesoscale Terrain and Latent Heat Release in Typhoon Precipitation: A Numerical Case Study

The mesoscale orographic effects on typhoon Aere＇s precipitation are simulated using an Advanced Regional Eta-coordinate Model （AREM） version 3.0. In particular, the effects of the latent heat release are studied by two comparable experiments： with and without condensational heating. The results show that the typhoon rainfall is tripled by the southeastern China mesoscale terrain, and the condensational heating is responsible for at least half of the increase. One role of the latent heat release is to warm the atmosphere, leading to a depression of the surface pressure, which then causes a larger pressure difference in the zonal direction. This pressure gradient guides the water vapour to flow into the foothills, which in turn amplifies the water vapour flux divergence amplified, causing the typhoon rainfall to increase eventually. The other role of the latent heat release is to make the convection more organized, resulting in a relatively smaller rain area and stronger precipitation.

COMPARATIVE ANALYSIS OF THE INTENSITY AND DISTRIBUTION OF HEAVY RAINS IN ZHEJIANG PROVINCE CAUSED BY TYPHOONS HAITANG AND MATSA

Study was carried out on two landfall typhoons Haitang and Matsa, which affected Zhejiang province seriously in 2005. Firstly, the similarity and difference between the two typhoon-induced heavy rains were compared and it was pointed out that both of them brought strong large-scale precipitation and the maximum centers of rainfall were located on the north side of the landfall site. Making landfall on Fujian, Haitang was weaker than Matsa in intensity but surpassed it in rainfall. Then with focus on intensity, moving speed, structure of typhoon, circulation and terrain, the two typhoon-related heavy rains were compared and analyzed. Results show that the asymmetrical distribution of rainfall was closely related to the structure of typhoons themselves, moisture transportation and mesoscale terrain. In contrast to the south side, the north side was hotter and wetter and water vapor was also more abundant. The phenomenon of more rainfall induced by Haitang was in connection with the following reasons. Invading cold air led to rainfall increases, weakened dynamic field and slower movement both benefited precipitation. For the last part, the cold characteristic of air mass over Zhejiang was also a favorable factor for the rain.

Distribution and Oceanic Dynamic Mechism of Precipitation Induced by Typhoon Lekima

Air-sea interaction usually affects the distribution of precipitation during typhoon period, but whether typhoon precipitation distribution is affected by ocean eddies is still unclear. In this study, based on a multi-source satellite database, reanalysis data and in-situ data were used to study the precipitation characteristics of Typhoon Lekima (2019) as well as its physical causes. The results showed that the precipitation of Lekima presents an asymmetric structure, exhibiting heavier precipitation on the left side of the typhoon path before 7 August, and with the typhoon strengthened, precipitation was evenly distributed around the typhoon center. The typhoon cloud system, characteristics of the typhoon, and ocean factors could be responsible for the asymmetric structure of precipitation during the typhoon period. The change in the typhoon cloud system during the typhoon influenced the distribution of precipitation. And there have been some oceanic processes that influenced the distribution of precipitation. Anticyclonic eddies and thick mixing level depths (MLDs) play important roles in typhoon precipitation. The anticyclonic eddies with thick MLD exist to reduce the mixing of the upper ocean to maintain the SST. Therefore, the SST and air-sea exchange can be sustained to influence typhoon precipitation. This study provides a new understanding of the impact of ocean processes on typhoon precipitation distribution.

Analysis of Extreme Precipitation Weather Process in Henan during July 17-22, 2021

To learn more about the unusually heavy rainfall in central China, this research uses the monthly climatic data, weather map information and US NCEP re-analysis data to analyze the atmospheric circulation, precipitation and weather situation of this extreme precipitation weather process in Henan during July 17-22, 2021. The results show that the precipitation process is affected by the joint action of the subtropical high, the continental high, the low vortex, the low-level jet, the typhoon “In-fa” and other multi-scale systems in the middle and low latitudes. This precipitation process was also affected by the topographic uplift and blocking of Taihang Mountain and Funiu Mountain.

Climate Prediction and Diagnostic Analysis of Typhoon Precipitation in Midsummer of Yongzhou

By consulting the typhoon yearbook and restoring the historical weather chart,technical separation of typhoon precipitation in Yongzhou from July to September of 1981-2015 was conducted.On this basis,climatic characteristics of typhoon precipitation in midsummer of Yongzhou were analyzed,and climate prediction and diagnostic analysis were carried out.The research results showed that typhoon precipitation was an important component of midsummer precipitation in Yongzhou,but its contribution to total precipitation was not as much as precipitation of the westerly belt system.When the ridge line of the western Pacific subtropical high was northward,typhoon precipitation was more than westerly precipitation in midsummer of Yongzhou;when the subtropical high was southward,there were more patterns of westerly precipitation year;when the subtropical high was normally northward,typhoon precipitation and westerly precipitation were less,with more dry years.In summer,abnormal cold sea surface temperature(SST)in tidal zone and warm pool zone of western Pacific and abnormal warm SST in NinoZ zone(strong El Nino event)were favorable for that the ridge line of the western Pacific subtropical high was southward,and there were more patterns of westerly precipitation year in midsummer of Yongzhou.On the contrary,when subtropical high was northward or normally northerly,there was less westerly precipitation.In non La Nina years when the subtropical high was northward,most of them were typhoon precipitation years.In La Nina years when the subtropical high was northward,most of them were dry years.

Typhoon Impacts on China's Precipitation during 1957-1996

Tropical Cyclone (TC) activity is an important feature of China's climate that can have important impacts on precipitation and can cause extensive property damage. In particular, precipitation from TCs contributes a significant portion of overall precipitation. This study deals with typhoons that influence China and focuses on their impact on China's precipitation. Four aspects are examined in this research. Firstly, the study of influencing typhoon frequency reveals that the main season that typhoons affect China is from May to November, especially between July and September. The frequency of influencing typhoons was steady during the past 40 years. Secondly, inspection of the climatology of station typhoon precipitation shows that Hainan and the southeastern coastalmost regions are most frequently affected by typhoons, and most of the regions south of the Yangtze River are affected by typhoons each year. Meanwhile, during 1957-1996, most of the typhoon-influenced regions show decreasing trends in typhoon precipitation but only the trends in southern Northeast China are significant. Thirdly, examination of the typhoon cases shows that there exists it significant linear relationship between the precipitation volume and impacted area. Finally, study of variations of typhoon impacts on China's precipitation suggests that there exists a decreasing trend in the contribution of typhoon precipitation to overall precipitation, while total annual volume of typhoon precipitation decreases significantly during the period.

Changes in Typhoon Regional Heavy Precipitation Events over China from 1960 to 2018

In earlier studies,objective techniques have been used to determine the contribution of tropical cyclones to precipitation(TCP)in a region,where the Tropical cyclone Precipitation Event(TPE)and the Regional Heavy Precipitation Events(RHPEs)are defined and investigated.In this study,TPE and RHPEs are combined to determine the Typhoon Regional Heavy Precipitation Events(TRHPEs),which is employed to evaluate the contribution of tropical cyclones to regional extreme precipitation events.Based on the Objective Identification Technique for Regional Extreme Events(OITREE)and the Objective Synoptic Analysis Technique(OSAT)to define TPE,temporal and spatial overlap indices are developed to identify the combined events as TRHPE.With daily precipitation data and TC best-track data over the western North Pacific from 1960 to 2018,86 TRHPEs have been identified.TRHPEs contribute as much as 20%of the RHPEs,but100%of events with extreme individual precipitation intensities.The major TRHPEs continued for approximately a week after tropical cyclone landfall,indicating a role of post landfall precipitation.The frequency and extreme intensity of TRHPEs display increasing trends,consistent with an observed positive trend in the mean intensity of TPEs as measured by the number of daily station precipitation observations exceeding 100 mm and 250 mm.More frequent landfalling Southeast and South China TCs induced more serious impacts in coastal areas in the Southeast and the South during 1990-2018 than1960-89.The roles of cyclone translation speed and"shifts"in cyclone tracks are examined as possible explanations for the temporal trends.

A SIMILARITY SCHEME FOR QUANTITATIVE FORECAST OF PRECIPITATION OF TYPHOONS

A quantitative scheme is put forward in our work of forecasting the storm rainfall of typhoons for specific sites.Using the initial parameters,weather situations and physical quantities as well as numerical weather prediction products,the scheme constructs multivariate,objective and similarity criteria for environmental factors for the time between the current and forthcoming moment within the domain of forecast.Through defining a non-linear similarity index,this work presents a comprehensive assessment of the similarity between historical samples of typhoons and those being forecast in terms of continuous dynamic states under the multivariate criteria in order to identify similar samples.The historical rainfall records of the similar samples are used to run weighted summarization of the similarity index to determine site-specific and quantitative forecasts of future typhoon rainfall.Samples resembling the typhoon being forecast are selected by defining a non-linear similarity index composed of multiple criteria.Trial tests have demonstrated that this scheme has positive prediction skill.

ANALYSIS OF CAUSATION OF ASYMMETRIC PRECIPITATION ASSOCIATED WITH SEVERE TYPHOON DAMREY

Severe typhoon Damrey moved across Hainan Island from 00:00 UTC 25 September to 00:00 UTC 27 September in 2005 and gave rise to a significant rain process during its 48-h passage.The precipitation intensity on the southern part of the island is stronger than that on the northern,showing obvious asymmetric distribution.Using Tropical Rainfall Measuring Mission(TRMM) data,the associated mesoscale characteristics of the precipitation were analyzed and the formation of asymmetric rainfall distribution was investigated in the context of a subsynoptic scale disturbance,vertical wind shear and orographic factors.The results are shown as follows.(1) The subsynoptic scale system provided favorable dynamic conditions to the genesis of mesoscale rain clusters and rainbands.(2) The southern Hainan Island was located to the left of the leeward direction of downshear all the time,being favorable to the development of convection and leading to the asymmetric rainfall distribution.(3) Mountain terrain in the southern Hainan Island stimulated the genesis,combination and development of convective cells,promoting the formation of mesoscale precipitation systems and ultimately resulting in rainfall increase in the southern island.

A Precipitation Detection Method for MWTS-Ⅱ Radiance Assimilation in Typhoon Simulation

FY-3C Microwave Temperature SounderⅡ(MWTS-Ⅱ)lacks observations at 23.8 GHz,31 GHz and 89 GHz,making it difficult to remove the data contaminated by precipitation in assimilation.In this paper,a fast forward operator based on the Community Radiative Transfer Model(CRTM)was used to analyze the relationship between the observation minus background simulation(O-B)and the cloud fractions in different MWTS-Ⅱchannels.In addition,based on the community Gridpoint Statistical Interpolation(GSI)system,the radiation brightness temperature of the MWTS-Ⅱwas assimilated in the regional Numerical Weather Prediction(NWP)model.In the process of assimilation,Visible and Infrared Radiometer(VIRR)cloud detection products were matched to MWTS-Ⅱpixels for precipitation detection.For typhoon No.18 in 2014,impact tests of MWTS-Ⅱdata assimilation was carried out.The results show that,though the bias observation minus analysis(O-A)of assimilated data can be reduced by quality control only with|O-B|<3 K;however,the O-A becomes much smaller while the precipitation detection is performed with Fvirr<0.9(VIRR cloud fraction threshold of 0.9).Besides,the change of the environmental field around the typhoon is more conducive to make the simulated track closer to the observation.The 72-hour typhoon track simulation error also shows that,after the precipitation detection,the error of simulated typhoon track is significantly reduced,which reflects the validity of a precipitation detection method based on a double criterion of|O-B|<3 K and Fvirr<0.9.

Analysis of Heavy Precipitation Process in North China from August 23 to 24, 2020

In order to better understand the formation mechanism of rainstorm in China and promote disaster prevention and reduction, based on the meteorological data of National Meteorological Information Center and Japan Meteorological Agency, this paper draws the isobaric surface map of 850 hPa and 500 hPa, relative humidity and precipitation distribution map. In this study, synoptic methods were used to analyze the heavy precipitation process in North China from August 23th to 24th, 2020. The results show that 1) The formation of short-term heavy precipitation requires sufficient water vapor and very strong upward movement;2) the heavy precipitation in August 23th to 24th 2020 in North China was influenced by the upper-level trough line, cold vortex and cold front, which made the warm and cold air strongly converge over North China, resulting in strong convective weather;3) the heavy rainfall over North China was also influenced by Typhoon Bawei, which caused maximum precipitation and air humidity.

ASYMMETRIC RAINBAND BREAKING IN TYPHOON HAITANG(2005) BEFORE AND AFTER ITS LANDFALL

Using the WRF(Weather Research Forecast)model,this work performed analysis and simulation on the rainband change during the landfall of Typhoon Haitang(2005)and found that breaking may occur over land and oceans leads to distinct asymmetric precipitation.The breaking is related to the topographic effect as well as interactions between the typhoon and midlatitude systems at upper levels.During the landfall,divergent flows at the 200-hPa level of the South-Asian high combined with divergent flows at the periphery of the typhoon to form a weak,inverted trough in the northwest part of the storm,with the mid- and low-level divergence fields on the west and northwest side of the typhoon center maintaining steadily.It intensifies the upper-level cyclonic flows,in association with positive vorticity rotating counterclockwise together with air currents that travel stepwise into a vorticity zone in the vicinity of the typhoon core, thereby forming a vorticity transfer belt in 22–25°N that extends to the eastern part of the storm.It is right here that the high-level vorticity band is subsiding so that rainfall is prevented from developing,resulting in the rainbelt breaking,which is the principal cause of asymmetric precipitation occurrence.Migrating into its outer region,the banded vorticity of Haitang at high levels causes further amplification of the cyclonic circulation in the western part and transfer of positive vorticity into the typhoon such that the rainband breaking is more distinct.

CONTRAST ANALYSIS OF APRIL TYPHOONS LEO AND NEOGURI

The conventional observations data,NCAR/NCEP-2 reanalysis data,and NOAA outgoing longwave radiation data are used to investigate different characteristics of Leo and Neoguri,two April typhoons that ever made landfall on the continent of China over the past 60 years.The results showed that both Leo and Neoguri occurred during the La Nina events.Strong convective activity,weak vertical wind shear and upper-level divergence were in favor of the formation of these April typhoons.Leo originated from a monsoon depression and Neoguri evolved from an easterly wave.The meandering moving track of Leo attributed to strong northeast monsoon and a weak and changeable subtropical high;the steady moving track of Neoguri was governed by a strong and stable subtropical high.Leo and Neoguri had similar terrain conditions and intensities during landfall but were different in precipitation as water vapor transport and duration of kinetic uplifting resulted in apparent discrepancies between them.