The Response of Anomalous Vertically Integrated Moisture Flux Patterns Related to Drought and Flood in Southern China to Sea Surface Temperature Anomaly

With the extreme drought(flood)event in southern China from July to August in 2022(1999)as the research object,based on the comprehensive diagnosis and composite analysis on the anomalous drought and flood years from July to August in 1961-2022,it is found that there are significant differences in the characteristics of the vertically integrated moisture flux(VIMF)anomaly circulation pattern and the VIMF convergence(VIMFC)anomaly in southern China in drought and flood years,and the VIMFC,a physical quantity,can be regarded as an indicative physical factor for the"strong signal"of drought and flood in southern China.Specifically,in drought years,the VIMF anomaly in southern China is an anticyclonic circulation pattern and the divergence characteristics of the VIMFC are prominent,while those are opposite in flood years.Based on the SST anomaly in the typical draught year of 2022 in southern China and the SST deviation distribution characteristics of abnormal draught and flood years from 1961 to 2022,five SST high impact areas(i.e.,the North Pacific Ocean,Northwest Pacific Ocean,Southwest Pacific Ocean,Indian Ocean,and East Pacific Ocean)are selected via the correlation analysis of VIMFC and the global SST in the preceding months(May and June)and in the study period(July and August)in 1961-2022,and their contributions to drought and flood in southern China are quantified.Our study reveals not only the persistent anomalous variation of SST in the Pacific and the Indian Ocean but also its impact on the pattern of moisture transport.Furthermore,it can be discovered from the positive and negative phase fitting of SST that the SST composite flow field in high impact areas can exhibit two types of anomalous moisture transport structures that are opposite to each other,namely an anticyclonic(cyclonic)circulation pattern anomaly in southern China and the coastal areas of east China.These two types of opposite anomalous moisture transport structures can not only drive the formation of drought(flood)in southern China but also exert its influence on the persistent development of the extreme weather.

Spatiotemporal Characteristics of Droughts and Floods in Shandong Province,China and Their Relationship with Food Loss

Mastering the pattern of food loss caused by droughts and floods aids in planning the layout of agricultural production,determining the scale of drought and flood control projects,and reducing food loss.The Standardized Precipitation Evapotranspiration Index is calculated using monthly meteorological data from 1984 to 2020 in Shandong Province of China and is used to identify the province’s drought and flood characteristics.Then,food losses due to droughts and floods are estimated separately from disaster loss data.Finally,the relationship between drought/flood-related factors and food losses is quantified using methods such as the Pearson correlation coefficient and linear regression.The results show that:1)there is a trend of aridity in Shandong Province,and the drought characteristic variables are increasing yearly while flood duration and severity are decreasing.2)The food losses caused by droughts in Shandong Province are more than those caused by floods,and the area where droughts and floods occur frequently is located in Linyi City.3)The impact of precipitation on food loss due to drought/flood is significant,followed by potential evapotranspiration and temperature.4)The relationship between drought and flood conditions and food losses can be precisely quantified.The accumulated drought duration of one month led to 1.939×10^(4)t of grain loss,and an increase in cumulative flood duration of one month resulted in1.134×10^(4)t of grain loss.If the cumulative drought severity and average drought peak increased by one unit,food loss due to drought will increase by 1.562×10^(4)t and 1.511×10^(6)t,respectively.If the cumulative flood severity and average flood peak increase by one unit,food loss will increase by 8.470×103t and 1.034×10^(6)t,respectively.

CHARACTERISTICS OF RAINFALL VARIATION OVER EAST CHINA FOR THE LAST 50 YEARS AND THEIR RELATIONSHIP WITH DROUGHTS AND FLOODS

With the precipitation data of 113 stations in East China during the last 50 years,the characteristics of the precipitation,including Precipitation Concentration Degree (PCD) and Precipitation Concentration Period (PCP) and their tendencies,are analyzed.The results show that the PCD in the northern part of the region is markedly higher than that in the southern part,but the PCP in the south is much earlier than that in the north by about one and a half months,which displays significant regional differences in precipitation.With the global warming,precipitation over East China shows an increasing tendency,but PCD displays a trend that is neither increasing nor decreasing.At the same time,the PCP is later than before,which can be mainly found in Jiangxi and southern Henan provinces.As a result,there are strong associations between the precipitation,PCD and PCP,which can be shown in the years with more precipitation,stronger PCD and later-than-usual PCP.In a word,the abnormal distribution of precipitation,PCP,and PCD over East China results in more extreme events of precipitation and more droughts and floods.

CLIMATOLOGICAL CHARACTERISTICS FOR THE ONSET OF ASIAN SUMMER MONSOON AS REVEALED BY HIRS-Tb12 AND DROUGHT AND FLOODS IN EASTERN CHINA

As shown in comparison and study of the HIRS-Tb12 data and conventional data, temperature, humidity and vertical motion are structured differently in the Southern and Northern Hemispheres, which are well depicted with the HIRS-Tb12 data. When high pressures rapidly decrease over the regions of South China Sea and Arabian Sea with the HIRS-Tb12 less than 200 W/m2, monsoons will set off in the South China Sea, Arabian Sea and Bay of Bengal, respectively. From a year of significant drought to one of significant floods, the trend of evolution is significantly different in the downdraft areas of the subtropical highs between the two hemispheres.

Combined Impacts of Warm Central Equatorial Pacific Sea Surface Temperatures and Anthropogenic Warming on the 2019 Severe Drought in East China

A severe drought occurred in East China(EC)from August to October 2019 against a background of long-term significant warming and caused widespread impacts on agriculture and society,emphasizing the urgent need to understand the mechanism responsible for this drought and its linkage to global warming.Our results show that the warm central equatorial Pacific(CEP)sea surface temperature(SST)and anthropogenic warming were possibly responsible for this drought event.The warm CEP SST anomaly resulted in an anomalous cyclone over the western North Pacific,where enhanced northerly winds in the northwestern sector led to decreased water vapor transport from the South China Sea and enhanced descending air motion,preventing local convection and favoring a precipitation deficiency over EC.Model simulations in the Community Earth System Model Large Ensemble Project confirmed the physical connection between the warm CEP SST anomaly and the drought in EC.The extremely warm CEP SST from August to October 2019,which was largely the result of natural internal variability,played a crucial role in the simultaneous severe drought in EC.The model simulations showed that anthropogenic warming has greatly increased the frequency of extreme droughts in EC.They indicated an approximate twofold increase in extremely low rainfall events,high temperature events,and concurrently dry and hot events analogous to the event in 2019.Therefore,the persistent severe drought over EC in 2019 can be attributed to the combined impacts of warm CEP SST and anthropogenic warming.

Numerical Study of Ural Blocking High＇s Effect Upon Asian Summer Monsoon Circulation and East China Flood and Drought

In terms of Kuo-Qian pesigma incorporated coordinate five-level primitive equation spheric band (70°N-30°S)model with the Ural high's effect introduced into it as initial and boundary conditions, study is made of the high's influence on Asian summer monsoon circulation and dryness / wetness of eastern China based on case contrast andcontrol experiments. Rusults show that as an excitation source, the blocking high produces a SE-NW stationarywavetrain with its upper-air atnicyclonic divergent circulation oust over a lower-level trough zone) precisely over themiddle to lower reaches of the Changjiang River, enhancing East Asian westerly jet, a situation that contributes toPerturbation growth, causing an additional secondary meridional circulation at the jet entrance, which intensifies theupdraft in the monsoon area. As such, the high's presence and its excited steady wavetrain represent the large-scalekey factors and acting mechanisms for the rainstorm over the Changjiang-Huaihe River catchment in the easternpart of the land.

RELATIONSHIP BETWEEN THE 30 TO 60 DAY OSCILLATION OF ATMOSPHERIC HEAT SOURCE AND THE DROUGHT AND FLOOD EVENTS IN JUNE IN THE SOUTH OF CHINA

Based on the NCEP/NCAR reanalysis data and the observed precipitation data in the south of China from 1958 to 2000,the impact of 30 to 60 day oscillation of atmospheric heat sources on the drought and flood events in June in the south of China is discussed.During the flood(drought) events,there exists an anomalous low-frequency anticyclone(cyclone) at the low level of the troposphere over the South China Sea and the northwestern Pacific,accompanied with anomalous low-frequency heat sinks(heat sources),while there exists an anomalous low-frequency cyclone(anticyclone) with anomalous heat sources(sinks) over the area from the south of China to the south of Japan.On average,the phase evolution of the low-frequency in drought events is 7 to 11 days ahead of that in flood events in May to June in the south of China.In flood events,low-frequency heat sources and cyclones are propagated northward from the southern South China Sea,northwestward from the warm pool of the western Pacific and westward from the northwestern Pacific around 140°E,which have very important impact on the abundant rainfall in June in the south of China.However,in drought events,the northward propagations of the low-frequency heat sources and cyclones from the South China Sea and its vicinity are rather late compared with those in flood events,and there is no obvious westward propagation of the heat sources from the northwestern Pacific.The timing of the low-frequency heat source propagation has remarkable impact on the June rainfall in the south of China.

Impact of the exceptionally high flood from the Changjiang River on the aquatic chemical distributions on the Huanghai Sea and East China Sea shelves in the summer of 1998

On the basis of the field observation in the Huanghai Sea and East China Sea in the summer of 1998, a rare event of exceptionally high discharge from the Changjiang River was described and how this high discharge altered water masses as well as chemical distributions on the shelves of the Huanghai Sea and East China Sea. The maximal extending ranges of the Changjiang diluted water and the nutrients in the freshwater from the Changjiang River were recorded for the first time. It was also found that there was a closed area with high oxygen and pH values in the offshore area of the southern Huanghai Sea and the northern East China Sea, indicating that the extensive spreading of nutrients due to the high discharge led to photosynthesis of phytoplankton mostly taking place in the offshore area far from the river mouth. The presence of ＂excess nitrogen＂ in almost all the northern East China Sea and the south of the Huanghai Sea suggests that these areas are potentially phosphorus-limited rather than nitrogen-limited, manifesting more like an estuarine ecosystem rather than a common marine ecosystem.

Drought and flood characteristics in the farmingpastoral ecotone of northern China based on the Standardized Precipitation Index

The farming-pastoral ecotone of northern China(FPENC)provides an important ecological barrier which restrains the invasion of desert into Northwest China.Studying drought and flood characteristics in the FPENC can provide scientific support and practical basis for the protection of the FPENC.Based on monthly precipitation data from 115 meteorological stations,we determined the changes in climate and the temporal and spatial variations of drought and flood occurrence in the FPENC during 1960-2020 using the Standardized Precipitation Index(SPI),Morlet wavelet transform,and inverse distance weighted interpolation method.Annual precipitation in the FPENC showed a slightly increasing trend from 1960 to 2020,with an increasing rate of about 1.15 mm/a.The interannual SPI exhibited obvious fluctuations,showing an overall non-significant upward trend(increasing rate of 0.02/a).Therefore,the study area showed a wetting trend in recent years.Drought and flood disasters mainly occurred on an interannual change cycle of 2-6 and 9-17 a,respectively.In the future,a tendency towards drought can be expected in the FPENC.The temporal and spatial distribution of drought and flood differed in the northwestern,northern,and northeastern segments of the FPENC,and most of the drought and flood disasters occurred in local areas.Severe and extreme drought disasters were concentrated in the northwestern and northeastern segments,and severe and extreme flood disasters were mainly in the northeastern segment.Drought was most frequent in the northwestern segment,the central part of the northeastern segment,and the northern part of the northern segment.Flood was most frequent in the western part of the northwestern segment,the eastern part of the northeastern segment,and the eastern and western parts of the northern segment.The accurate evaluation of the degrees of drought and flood disasters in the FPENC will provide scientific basis for the regional climate study and critical information on which to base decisions regarding environmental protection and socio-economic development in this region.

THE EARLY SUMMER FLOOD PERIODS OF SOUTHERN CHINA AND THE SUMMER MONSOON CIRCULATION OF EAST ASIA

Based on the thermodynamic characteristics of the summer monsoon and foe change of the lower layer wind fields, the relation between the early summer flood periods of southern China, Including the first flood period of South China and the plum rains period of the middle-lower reaches of the Yangtze River and the activities of the summer monsoon is analysed. The establishment processes of the summer monsoon circulation of East Asia are investigated. It is shown that the beginning and ending of the flood periods are exactly in accordance with the arrival and departure of the fore boundary of the summer monsoon. The establishment process of the circulation from the very beginning of the arrival of the monsoon to the time of great prosperity of development are not the same for each year. They can be classified into four categories. Each category may have four or three stages. Besides, the structure of the summer monsoon regime of East Asia is not unitary. There exist four types of structure model of the monsoon regime of East Asia.

Characteristics and Variations of the East Asian Monsoon System and Its Impacts on Climate Disasters in China

Recent advances in studies of the structural characteristics and temporal-spatial variations of the East Asian monsoon （EAM） system and the impact of this system on severe climate disasters in China are reviewed. Previous studies have improved our understanding of the basic characteristics of horizontal and vertical structures and the annual cycle of the EAM system and the water vapor transports in the EAM region. Many studies have shown that the EAM system is a relatively independent subsystem of the Asian- Australian monsoon system, and that there exists an obvious quasi-biennial oscillation with a meridional tripole pattern distribution in the interannual variations of the EAM system. Further analyses of the basic physical processes, both internal and external, that influence the variability of the EAM system indicate that the EAM system may be viewed as an atmosphere-ocean-land coupled system, referred to the EAM climate system in this paper. Further, the paper discusses how the interaction and relationships among various components of this system can be described through the East Asia Pacific （EAP） teleconnection pattern and the teleconnection pattern of meridional upper-tropospheric wind anomalies along the westerly jet over East Asia. Such reasoning suggests that the occurrence of severe floods in the Yangtze and Hualhe River valleys and prolonged droughts in North China are linked, respectively~ to the background interannual and interdecadal variability of the EAM climate system. Besides, outstanding scientific issues related to the EAM system and its impact on climate disasters in China are also discussed.

Studies on the Northern Early Summer Teleconnection Patterns, Their Interannual Variations and Relation to Drought / Flood in China

By using the one-point correlation method, calculations have been made of the northern early summer 500 hPa teleconnection patterns. Seven teleconnection patterns are revealed, namely, the Western Atlantic (WA), the Eastern Atlantic (EA), the Eurasian (EU), the Bengal / Northern Pacific (BNP), the Western Pacific (WP), the East Asian / Pacific (EAP), and the Huanghe / East Asian (HEA) patterns. Their centers are determined and their yearly intensity indices (1951-1990) are calculated. On this basis the relationship between their interannual variations and the drought / flood in China is examined. It is noted that the EU, HEA and EAP wave trains are closely related to the drought / flood in China. The HEA and EAP patterns strongly influence the precipitation in eastern China. For example, the fierce floods experienced in 1991 early summer over China are related to the weak EAP and strong HEA patterns.

Magnitude,Scale,and Dynamics of the 2020 Mei-yu Rains and Floods over China

Large parts of East and South Asia were affected by heavy precipitation and flooding during early summer 2020.This study provides both a statistical and dynamical characterization of rains and floods affecting the Yangtze River Basin(YRB).By aggregating daily and monthly precipitation over river basins across Asia,it is shown that the YRB is one of the areas that was particularly affected.June and July 2020 rainfall was higher than in the previous 20 years,and the YRB experienced anomalously high rainfall across most of its sub-basins.YRB discharge also attained levels not seen since 1998/1999.An automated method detecting the daily position of the East Asian Summer Monsoon Front(EASMF)is applied to show that the anomalously high YRB precipitation was associated with a halted northward progression of the EASMF and prolonged mei-yu conditions over the YRB lasting more than one month.Two 5-day heavy-precipitation episodes(12−16 June and 4−8 July 2020)are selected from this period for dynamical characterization,including Lagrangian trajectory analysis.Particular attention is devoted to the dynamics of the airstreams converging at the EASMF.Both episodes display heavy precipitation and convergence of monsoonal and subtropical air masses.However,clear differences are identified in the upper-level flow pattern,substantially affecting the balance of airmass advection towards the EASMF.This study contextualizes heavy precipitation in Asia in summer 2020 and showcases several analysis tools developed by the authors for the study of such events.

DIAGNOSTIC ANALYSIS OF PERSISTENT DROUGHT/FLOOD EVENTS IN SUMMER OVER THE TWO-LAKE REGION OF CHINA

Based on the daily regional mean rainfall,the Z-index method is used to identify persistent flood and drought events lasting for at least 10 days over a region where Dongting Lake and Poyang Lake sit(referred to as the"two-lake region"hereafter).The National Centers for Environmental Prediction(NCEP)reanalysis data are then utilized to perform a preliminary diagnostic analysis on these events.The results indicate that the composite standardized geopotential height at 500 hPa presents two different meridional wave trains from north to south over the East Asian-Pacific region,i.e.,a"-+-"pattern for the droughts and a"+-+"pattern for the floods,respectively.The developing,maintaining and decaying phases in the drought and flood events are closely related to the intensity and location of a subtropical high and an extra-tropical blocking high.It is shown that the East Asian summer monsoon is strong(weak)with the occurrence of persistent drought(flood)events.Droughts(floods)are accompanied by a weak(strong)tropical convergent system and a strong(weak)subtropical convergent system.Furthermore,the persistent drought(flood)events are associated with a divergence(convergence)of vertically integrated water vapor flux.In the vertical profile of water vapor flux,divergence(convergence)in the mid-and lower-levels and convergence(divergence)in the higher levels are evident in the droughts(floods).Both the divergence in the droughts and the convergence in floods are strongest at 850 hPa.

INFLUENCE OF THE KUROSHIO ON HYDROGRAPHY AND HYDROMETEOROLOGY IN THE EAST CHINA SEA NEAR-SHORE REGION

The aim of the study was l)to determine the relation between the Kuroshio meander and the intensity of the subtropic high pressure over the Pacific Ocean, and then to obtain statistical validity for the observational conclusion that the occurrence time of the Kuroshio meander leads the time of strengthened C-circulation of Europe by one or more years; 2) to develop a method to predict the occurrence time of flood or drought periods in the Changjiang River Valley from the occurrence time of the Kuroshio meander, since there is a close relation between the occurrence time of the drought or flood periods in the Changjiang River Valley and the occurrence time of the strong or weak periods of C- circulation of Europe; and 3) to develop a logical explanation verifiable by remote sensing technique and other means that the warm species phytoplanktons collected recently in the Jiaozhou Bay of Shandong Peninsula in China were carried there by a new warm current branch of the Kuroshio in the East China Sea.

THE DIRECT EFFECTS OF AEROSOLS AND DECADAL VARIATION OF GLOBAL SEA SURFACE TEMPERATURE ON THE EAST ASIAN SUMMER PRECIPITATION IN CAM3.0

Using the CAM3.0 model, we investigated the respective effects of aerosol concentration increasing and decadal variation of global sea surface temperature(SST) around year 1976/77 on the East Asian precipitation in boreal summer. By doubling the concentration of the sulfate aerosol and black carbon aerosol separately and synchronously in East Asia(100-150 °E, 20-50 °N), the climate effects of these aerosols are specifically investigated. The results show that both the decadal SST changing and aerosol concentration increasing could lead to rainfall decreasing in the center of East Asia, but increasing in the regions along southeast coast areas of China. However, the different patterns of rainfall over ocean and lower wind field over Asian continent between aerosol experiments and SST experiments in CAM3.0 indicate the presence of different mechanisms. In the increased aerosol concentration experiments, scattering effect is the main climate effect for both sulfate and black carbon aerosols in the Eastern Asian summer. Especially in the increased sulfate aerosol concentration experiment, the climate scattering effect of aerosol leads to the most significant temperature decreasing, sinking convection anomalies and decreased rainfall in the troposphere over the central part of East Asia. However, in an increased black carbon aerosol concentration experiment, weakened sinking convection anomalies exist at the southerly position. This weakened sinking and its compensating rising convection anomalies in the south lead to the heavy rainfall over southeast coast areas of China. When concentrations of both sulfate and black carbon aerosols increase synchronously, the anomalous rainfall distribution is somewhat like that in the increased black carbon concentration aerosol experiment but with less intensity.

Analysis of Precipitation and Drought-Flood in Yalu River Estuary and Donggang Offshore Area

Based on the mesoscale surface observation data,the relationship between rainfall and drought-flood in Yalu River and Donggang offshore area was analyzed. Analysis on atmospheric circulation showed that the movement of weather system affected the production of precipitation directly and resulted into the formation of drought and flood years. On the basis of analyzing general law above,a further analysis on the relationship of monsoon and drought-flood was carried out,as well as the effect of topography on rainfall.

Mantle plume,large igneous province and continental breakup——Additionally discussing the Cenozoic and Mesozoic mantle plume problems in East China

Based on the former workers' study results such as numerical simulation of fluid mechanics, seismic tomography of the whole earth and igneous rocks, the basie characteristics of mantle plumes are summarized in detail, namely the mantle plume, from the D" layer near the core-mantle boundary (CMB) of 2900 km deep, is characterized by the shape of large head and thin narrow conduit, by the physical property of high temperature and low viscosity. The LIP (large igneous province) is the best exhibition when the mantle plume ascends to the surface. According to the basie characteristics of the mantle plumes and the LIP, as well as the temporal-spatial relationships between the mantle plume and Continental breakup, the detailed research on petrology, geochemistry, temporal-spatial distribution, tectonic background of the Cenozoic-Mesozoic igneous rocks and gravity anomaly distribution in East China has been done. As a result, the Mesozoic igneous rocks in Southeast China should not be regarded as an example of typical LIP related to mantle plumes, for their related characteristics are not consistent with those of the typical LIPs related to mantle plumes. The Cenozoic igneous rocks in Northeast China have no the typical characteristics of mantle plumes and hotspots, so the Cenozoic volcanism in Northeast China might have no the direct relationships with the activity of mantle plumes.

Current Situation and Evolution of Drought and Flood in Fen-wei Plain

Based on the latest results and data of drought and flood in Fen-wei Plain, current situation and evolution of drought and flood in Fen-wei Plain were analyzed. The results show that in Fen-wei Plain drought and flood are natural disasters bringing about the most serious damage, and drought risk in east central Weihe Plain is serious. In Fen-wei Plain, precipitation tended to decrease, and temperature, drought days and intensity increased over the past 50 years. There were obvious differences between two decades in drought and flood. Drought was the severest in the 1990s, and flood was the most serious in Fenhe Plain in the 1960s and in Weihe Plain from the late 1970s to the early 1980s. Over the past ten years, precipitation and flood frequency increased, and temperature, drought days and intensity decreased. In Fen-wei Plain, temperature will rise and precipitation will increase slightly in next 20 -40 years. Monitoring and early warning capability of drought and flood in Fen-wei Plain have im- proved gradually, but some issues need to be paid more attention to and solved.