To analyze the characteristics of drought and flood variations in Quanzhou during recent 55 years, the standardized precipitation index (SPI) and Empirical Orthogonal Function (EOF) and Rotated Empirical Orthogonal Fu...To analyze the characteristics of drought and flood variations in Quanzhou during recent 55 years, the standardized precipitation index (SPI) and Empirical Orthogonal Function (EOF) and Rotated Empirical Orthogonal Function (REOF) were calculated by using the monthly precipitation data from 6 meteorological bureaus across Quanzhou for 1960-2014. Results showed that: 1) During 1960-2014, the drought and flood showed Periodic variation characteristics in Quanzhou, the specific period of frequent drought was 1963-1972, 1977-1986 and 2009-2011, and the specific period of frequent flood was 1961-1962, 1972-1975, 1990-1992 and 1997-2007;the drought and flood did not have significant tendency of variation in Spring and Summer, and the drought and flood showed a non-significant downward trend in Autumn and Winter. 2) The drought and flood variation had relatively consistent trend in Quanzhou, but there was a big difference on the northwest mountainous area, the middle semi-mountainous area and the southeast coast area in some periods. 3) The precipitation cell and distribution in every season were Nan’an and Anxi, but there was a big difference in rainfall less area: it was Yongchun and Dehua in Spring, Chongwu and Jinjiang in Summer, Chongwu in Autumn, Dehua and Chongwu in Winter.展开更多
On the basis of large amount of historical and measured data,this paper analyzed the regional,periodic,frequency,continuing,and response characteristics of droughts and floods in Zhejiang and proposed the conception o...On the basis of large amount of historical and measured data,this paper analyzed the regional,periodic,frequency,continuing,and response characteristics of droughts and floods in Zhejiang and proposed the conception of ratio of peak runoff.Main characteristics of droughts and floods in Zhejiang are as follows:1)The western Zhejiang region is plum rain major control area,and the eastern coastal region of Zhejiang is typhoon major control area.2)Within a long period in the future,Zhejiang will be in the long period that features droughts.3)In Zhejiang the 17th century was frequent drought and flood period,the 16th,19th,and 20th centuries were normal periods,while the 18th century was spasmodic drought and flood period.4)The severe and medium floods in Zhejiang were all centered around the M-or m-year of the 11-year sunspot activity period.5)There are biggish years of annual runoff occurred in El Ni?o year(E)or the following year(E+1)in Zhejiang.The near future evolution trend of droughts and floods in Zhejiang is as follows:1)Within a relatively long period in the future,Zhejiang Province will be in the long period of mostly drought years.2)Between 1999 and 2009 this area will feature drought years mainly,while the period of 2010-2020 will feature flood years mostly.3)Zhejiang has a good response to the sunspot activities,and the years around 2009,2015,and 2020 must be given due attention,especially around 2020 there might be an extremely severe flood year in Zhejiang.4)Floods in Zhejiang have good response to El Ni?o events,in El Ni?o year or the following year much attention must be paid to.And 5)In the future,the first,second,and third severe typhoon years in Zhejiang will be 2009,2012,and 2015,respectively.展开更多
Simultaneous stresses of salinity and drought often coincide during rice-growing seasons in saline lands,primarily due to insufficient water resources and inadequate irrigation facilities.Consequently,combined salinit...Simultaneous stresses of salinity and drought often coincide during rice-growing seasons in saline lands,primarily due to insufficient water resources and inadequate irrigation facilities.Consequently,combined salinity-drought stress poses a major threat to rice production.In this study,two salinity levels(NS,non-salinity;HS,high salinity)along with three drought treatments(CC,control condition;DJ,drought stress imposed at jointing;DH,drought stress imposed at heading)were performed to investigate their combined influences on leaf photosynthetic characteristics,biomass accumulation,and rice yield formation.Salinity,drought,and their combination led to a shortened growth period from heading to maturity,resulting in a reduced overall growth duration.Grain yield was reduced under both salinity and drought stress,with a more substantial reduction under the combined salinity-drought stress.The combined stress imposed at heading caused greater yield losses in rice compared with the stress imposed at jointing.Additionally,the combined salinity-drought stress induced greater decreases in shoot biomass accumulation from heading to maturity,as well as in shoot biomass and nonstructural carbohydrate(NSC)content in the stem at heading and maturity.However,it increased the harvest index and NSC remobilization reserve.Salinity and drought reduced the leaf area index and SPAD value of flag leaves and weakened the leaf photosynthetic characteristics as indicated by lower photosynthetic rates,transpiration rates,and stomatal conductance.These reductions were more pronounced under the combined stress.Salinity,drought,and especially their combination,decreased the activities of ascorbate peroxidase,catalase,and superoxide dismutase,while increasing the contents of malondialdehyde,hydrogen peroxide,and superoxide radical.Our results indicated a more significant yield loss in rice when subjected to combined salinity-drought stress.The individual and combined stresses of salinity and drought diminished antioxidant enzyme activities,inhibited leaf photosynthetic functions,accelerated leaf senescence,and subsequently lowered assimilate accumulation and grain yield.展开更多
To study non-structural carbohydrate character-istics and nutrient utilization strategies of Pinus yunnanen-sis under continuous drought conditions,2-year-old seed-lings were planted in pots with appropriate water,lig...To study non-structural carbohydrate character-istics and nutrient utilization strategies of Pinus yunnanen-sis under continuous drought conditions,2-year-old seed-lings were planted in pots with appropriate water,light and moderate and severe drought treatments[(80±5),(65±5),(50±5),and(35±5)%of field water-holding capacity].Non-structural carbohydrates,carbon(C),nitrogen(N),and phosphorus(P)concentrations were measured in each plant component.The results show that:(1)With increasing drought,non-structural carbohydrates gradually increased in leaves,stems,and coarse roots,while gradually decreased in fine roots;(2)C concentrations of all were relatively stable under different stress levels.Phosphorous utilization of each component increased under light and moderate drought conditions,while N and P utilization efficiency of each plant component decreased under severe drought.Growth was mainly restricted by N,first decreasing and then increasing with increased drought;(3)There was a correlation between the levels of non-structural carbohydrates and C,N,and P in each component.Changes in N concentration affected the interconversion between soluble sugar and starch,which play a regulatory role in the fluctuation of the concentration of non-structural carbohydrates;and,(4)Plasticity analysis showed that P.yunnanensis seedlings responded to drought mainly by altering starch concentration,the ratio of soluble sugar to starch in leaves and stems,and further by alter-ing N and P utilization efficiencies.Overall,these results suggest that the physiological activities of all organs of P.yunnanensis seedlings are restricted under drought and that trade-offs exist between different physiological indicators and organs.Our findings are helpful in understanding non-structural carbohydrate and nutrient adaptation mechanisms under drought in P.yunnanensis seedlings.展开更多
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 Standardiz...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.展开更多
Based on the data of annual average precipitation in Deyang area and its five stations (Mianzhu, Deyang, Zhongjiang, Shifang and Guanghan) from 1984 to 2013, the annual precipitation anomaly percentage was calculated,...Based on the data of annual average precipitation in Deyang area and its five stations (Mianzhu, Deyang, Zhongjiang, Shifang and Guanghan) from 1984 to 2013, the annual precipitation anomaly percentage was calculated, and then the flood and drought situation in Deyang area was graded to discuss the variation characteristics of droughts and floods in the past 30 years. The results show that the cycle of droughts and floods in Deyang was about 3-5 a. The precipitation anomaly percentage indicates that the climate in Deyang area of Sichuan tended to be dry slowly in the past 30 years, and Deyang gradually entered a dry and warm period.展开更多
The spatial distribution of summer precipitation anomalies over eastern China often shows a dipole pattern,with anti-phased precipitation anomalies between southern China and northern China,known as the“southern floo...The spatial distribution of summer precipitation anomalies over eastern China often shows a dipole pattern,with anti-phased precipitation anomalies between southern China and northern China,known as the“southern flooding and northern drought”(SF-ND)pattern.In 2015,China experienced heavy rainfall in the south and the worst drought since 1979 in the north,which caused huge social and economic losses.Using reanalysis data,the atmospheric circulation anomalies and possible mechanisms related to the summer precipitation anomalies in 2015 were examined.The results showed that both El Niño and certain atmospheric teleconnections,including the Pacific Japan/East Asia Pacific(PJ/EAP),Eurasia pattern(EU),British–Baikal Corridor pattern(BBC),and Silk Road mode(SR),contributed to the dipole pattern of precipitation anomalies.The combination of these factors caused a southwards shift of the western Pacific subtropical high(WPSH)and a weakening of the East Asian summer monsoon.Consequently,it was difficult for the monsoon front and associated rain band to migrate northwards,which meant that less precipitation occurred in northern China while more precipitation occurred in southern China.This resulted in the SF-ND event.Moreover,further analysis revealed that global sea surface temperature anomalies(SSTAs)or sea-ice anomalies were key to stimulating these atmospheric teleconnections.展开更多
The pilot test of infilling polymer-surfactant-preformed particle gel(PPG)flooding has been successfully implemented after polymer flooding in Ng3 block of Gudao Oilfield in China.However,the production characteristic...The pilot test of infilling polymer-surfactant-preformed particle gel(PPG)flooding has been successfully implemented after polymer flooding in Ng3 block of Gudao Oilfield in China.However,the production characteristics and displacement mechanisms are still unclear,which restricts its further popularization and application.Aiming at this problem,this paper firstly analyzes the production performance of the pilot test and proposed four response types according to the change of water cut curves,including W-type,U-type,V-type response,and no response.Furthermore,the underlying reasons of these four types are analyzed from the aspects of seepage resistance and sweep efficiency.The overall sweep efficiency of gradual-rising W-type,gradual-decreasing W-type,and early V-type response increases from 0.81 to 0.93,0.55 to 0.89,and 0.94 to 1,respectively.And the sum of seepage resistance along the connection line between production well and injection well for U-type and delayed V-type response increases from 0.0994 to 0.2425,and 0.0677 to 0.1654,respectively.Then,the remaining oil distribution after polymer flooding is summarized into four types on the basis of production and geological characteristics,namely disconnected remaining oil,streamline unswept remaining oil,rhythm remaining oil,and interlayer-controlled remaining oil.Furthermore,the main displacement mechanisms for each type are clarified based on the dimensionless seepage resistance and water absorption profile.Generally,improving connectivity by well pattern infilling is the most important for producing disconnected remaining oil.The synergistic effect of well pattern infilling and polymer-surfactant-PPG flooding increases the dimensionless seepage resistance of water channeling regions and forces the subsequent injected water to turn to regions with streamline unswept remaining oil.The improvement of the water absorption profile by polymer-surfactant-PPG flooding and separated layer water injection contributes to displacing rhythm remaining oil and interlayer-controlled remaining oil.Finally,the paper analyzes the relationships between the remaining oil distribution after polymer flooding and production characteristics of infilling polymer-surfactant-PPG flooding.The study helps to deepen the understanding of infilling polymer-surfactant-PPG flooding and has reference significance for more commercial implementations in the future.展开更多
A smart response fluid was designed and developed to overcome the challenges of gas channeling during CO_(2)flooding in low-permeability,tight oil reservoirs.The fluid is based on Gemini surfactant with self-assembly ...A smart response fluid was designed and developed to overcome the challenges of gas channeling during CO_(2)flooding in low-permeability,tight oil reservoirs.The fluid is based on Gemini surfactant with self-assembly capabilities,and the tertiary amine group serves as the response component.The responsive characteristics and corresponding mechanism of the smart fluid during the interaction with CO_(2)/oil were studied,followed by the shear characteristics of the thickened aggregates obtained by the smart fluid responding to CO_(2).The temperature and salt resistance of the smart fluid and the aggregates were evaluated,and their feasibility and effectiveness in sweep-controlling during the CO_(2)flooding were confirmed.This research reveals:(1)Thickened aggregates could be assembled since the smart fluid interacted with CO_(2).When the mass fraction of the smart fluid ranged from 0.05%to 2.50%,the thickening ratio changed from 9 to 246,with viscosity reaching 13 to 3100 mPas.As a result,the sweep efficiency in low-permeability core models could be increased in our experiments.(2)When the smart fluid(0.5%to 1.0%)was exposed to simulated oil,the oil/fluid interfacial tension decreased to the level of 1×10^(-2)mN/m.Furthermore,the vesicle-like micelles in the smart fluid completely transformed into spherical micelles when the fluid was exposed to simulated oil with the saturation greater than 10%.As a result,the smart fluid could maintain low oil/fluid interfacial tension,and would not be thickened after oil exposure.(3)When the smart fluid interacted with CO_(2),the aggregates showed self-healing properties in terms of shear-thinning,static-thickening,and structural integrity after several shear-static cycles.Therefore,this fluid is safe to be placed in deep reservoirs.(4)The long-term temperature and salt resistance of the smart fluid and thickened aggregates have been confirmed.展开更多
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 ...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.展开更多
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 (PC...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.展开更多
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 pro...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.展开更多
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...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.展开更多
NCEP/NCAR data are utilized to analyze an extreme flood year(1998) and an extreme dry year(2006) in the Sichuan-Chongqing region(SCR) and the results are as follows. The positive divergence of South Asia High(SAH) is ...NCEP/NCAR data are utilized to analyze an extreme flood year(1998) and an extreme dry year(2006) in the Sichuan-Chongqing region(SCR) and the results are as follows. The positive divergence of South Asia High(SAH) is stronger in the flood year; the position of the ridge line of SAH is southward compared with the annual average; Western Pacific Subtropical High(WPSH) extends westward and its ridge line is southward. In the drought year, the positive divergence of SAH is weaker, its ridge line is northward, and the position of WPSH is also northward. As shown in the dynamics, in drought(flood) years, negative(positive) vorticity advection in the upper atmosphere can cause the atmosphere to ascend(descend), and anomalous circulation of SAH displays divergence(convergence), and anomalous circulation of the lower atmosphere shows convergence(divergence). Thermal structure of the atmosphere shows that there is warm(cold) temperature advection in the lower atmosphere, and the vertical distribution of diabetic heating causes SAH's local circulation to display convergence(divergence) and affects vertical motion of the lower atmosphere circulation eventually. To some extent, the two extreme years in the SCR is closely related to the vertical motion of atmosphere circulation and the variation of such vertical motion is caused by differences of interactions between SAH and lower atmosphere circulations.展开更多
This study aims to apply a hydrogeological approaches and analysis of the 2021 flood event of Tasi-Tolu Lagoon to achieve four specific goals. Firstly, the study seeks to determine the natural characteristics of the l...This study aims to apply a hydrogeological approaches and analysis of the 2021 flood event of Tasi-Tolu Lagoon to achieve four specific goals. Firstly, the study seeks to determine the natural characteristics of the lagoon, which include factors such as size, depth, water quality, and ecosystem composition. Secondly, the influence of precipitation on the water volume in the lagoon will be examined. This analysis involves assessing historical rainfall patterns in the region, as well as the amount and frequency of precipitation during the 2021 flood event. Thirdly, the hydrogeologic and geologic conditions of the lagoon will be evaluated. This involves examining factors such as the type and structure of the soil and bedrock, the presence of aquifers or other underground water sources, and the movement of water through the surrounding landscape. Finally, the study seeks to assess the risk of future flooding in Tasi-Tolu Lagoon, based on the insights gained from the previous analyses. Overall, this study’s goal is to provide a comprehensive understanding of the hydrogeological factors that contribute to flooding in Tasi-Tolu Lagoon. This knowledge could be used to inform flood mitigation strategies or to improve our ability to predict and respond to future flooding events in the region.展开更多
Spatio-temporal analysis of drought provides valuable information for drought management and damage mitigation. In this study, the Standardized Precipitation Index at the time scale of 6 months (SPI-6) is selected to ...Spatio-temporal analysis of drought provides valuable information for drought management and damage mitigation. In this study, the Standardized Precipitation Index at the time scale of 6 months (SPI-6) is selected to reflect drought conditions in the North-Eastern coastal region of Vietnam. The drought events and their characteristics from 1981 to 2019 are detected at 9 meteorological stations and 10 Chirps rainfall stations. The spatio-temporal variation of drought in the study region is analyzed on the basis of the number, duration, severity, intensity, and peak of the detected drought events at the 19 stations. The results show that from 1981 to 2019 the drought events mainly occurred with 1-season duration and moderate intensity and peak. The number, duration, severity, and peak of the drought events were the greatest in the period 2001-2010 and were the smallest in the period 2011-2019. Among the 19 stations, the drought duration tends to decrease at 11 stations, increase at 7 stations, and has a slight variant at 1 station;the drought severity tends to decrease at 14 stations, increase at 4 stations, and has not a significant trend at 1 station;the drought intensity tends to decrease at 17 stations, increase at 1 station, and has a slight variant at 1 station;and the drought peak tends to decrease at 18 stations and increase at 1 station.展开更多
This study investigates the impact of global warming on drought/flood patterns in China at the end of the 21st century based on the simulations of 22 global climate models and a regional climate model(RegCM3) under th...This study investigates the impact of global warming on drought/flood patterns in China at the end of the 21st century based on the simulations of 22 global climate models and a regional climate model(RegCM3) under the SRES(Special Report on Emissions Scenarios) A1B scenario.The standardized precipitation index(SPI),which has well performance in monitoring the drought/flood characteristics(in terms of their intensity,duration,and spatial extent) in China,is used in this study.The projected results of 22 coupled models and the RegCM3 simulation are consistent.These models project a decrease in the frequency of droughts in most parts of northern China and a slight increase in the frequency in some parts of southern China.Considering China as a whole,the spatial extents of droughts are projected to be significantly reduced.In contrast,future flood events over most parts of China are projected to occur more frequently with stronger intensity and longer duration than those prevalent currently.Additionally,the spatial extents of flood events are projected to significantly increase.展开更多
文摘To analyze the characteristics of drought and flood variations in Quanzhou during recent 55 years, the standardized precipitation index (SPI) and Empirical Orthogonal Function (EOF) and Rotated Empirical Orthogonal Function (REOF) were calculated by using the monthly precipitation data from 6 meteorological bureaus across Quanzhou for 1960-2014. Results showed that: 1) During 1960-2014, the drought and flood showed Periodic variation characteristics in Quanzhou, the specific period of frequent drought was 1963-1972, 1977-1986 and 2009-2011, and the specific period of frequent flood was 1961-1962, 1972-1975, 1990-1992 and 1997-2007;the drought and flood did not have significant tendency of variation in Spring and Summer, and the drought and flood showed a non-significant downward trend in Autumn and Winter. 2) The drought and flood variation had relatively consistent trend in Quanzhou, but there was a big difference on the northwest mountainous area, the middle semi-mountainous area and the southeast coast area in some periods. 3) The precipitation cell and distribution in every season were Nan’an and Anxi, but there was a big difference in rainfall less area: it was Yongchun and Dehua in Spring, Chongwu and Jinjiang in Summer, Chongwu in Autumn, Dehua and Chongwu in Winter.
基金Under the auspices of Zhejiang Provincial ScienceTechnology Foundation of China(No.2006C23066)
文摘On the basis of large amount of historical and measured data,this paper analyzed the regional,periodic,frequency,continuing,and response characteristics of droughts and floods in Zhejiang and proposed the conception of ratio of peak runoff.Main characteristics of droughts and floods in Zhejiang are as follows:1)The western Zhejiang region is plum rain major control area,and the eastern coastal region of Zhejiang is typhoon major control area.2)Within a long period in the future,Zhejiang will be in the long period that features droughts.3)In Zhejiang the 17th century was frequent drought and flood period,the 16th,19th,and 20th centuries were normal periods,while the 18th century was spasmodic drought and flood period.4)The severe and medium floods in Zhejiang were all centered around the M-or m-year of the 11-year sunspot activity period.5)There are biggish years of annual runoff occurred in El Ni?o year(E)or the following year(E+1)in Zhejiang.The near future evolution trend of droughts and floods in Zhejiang is as follows:1)Within a relatively long period in the future,Zhejiang Province will be in the long period of mostly drought years.2)Between 1999 and 2009 this area will feature drought years mainly,while the period of 2010-2020 will feature flood years mostly.3)Zhejiang has a good response to the sunspot activities,and the years around 2009,2015,and 2020 must be given due attention,especially around 2020 there might be an extremely severe flood year in Zhejiang.4)Floods in Zhejiang have good response to El Ni?o events,in El Ni?o year or the following year much attention must be paid to.And 5)In the future,the first,second,and third severe typhoon years in Zhejiang will be 2009,2012,and 2015,respectively.
基金financed by the National Key Research and Development Program,China(Grant Nos.2022YFE0113400 and 2022YFD1500402)National Natural Science Foundation of China(Grant No.32001466)+3 种基金Scientific and Technological Innovation Fund of Carbon Emissions Peak and Neutrality of Jiangsu Provincial Department of Science and Technology,China(Grant Nos.BE2022304 and BE2022305)Joints Funds of the National Natural Science Foundation of China(Grant No.U20A2022)Postdoctoral Research Foundation of China(Grant No.2020M671628)the Priority Academic Program Development of Jiangsu Higher Education Institutions,China.
文摘Simultaneous stresses of salinity and drought often coincide during rice-growing seasons in saline lands,primarily due to insufficient water resources and inadequate irrigation facilities.Consequently,combined salinity-drought stress poses a major threat to rice production.In this study,two salinity levels(NS,non-salinity;HS,high salinity)along with three drought treatments(CC,control condition;DJ,drought stress imposed at jointing;DH,drought stress imposed at heading)were performed to investigate their combined influences on leaf photosynthetic characteristics,biomass accumulation,and rice yield formation.Salinity,drought,and their combination led to a shortened growth period from heading to maturity,resulting in a reduced overall growth duration.Grain yield was reduced under both salinity and drought stress,with a more substantial reduction under the combined salinity-drought stress.The combined stress imposed at heading caused greater yield losses in rice compared with the stress imposed at jointing.Additionally,the combined salinity-drought stress induced greater decreases in shoot biomass accumulation from heading to maturity,as well as in shoot biomass and nonstructural carbohydrate(NSC)content in the stem at heading and maturity.However,it increased the harvest index and NSC remobilization reserve.Salinity and drought reduced the leaf area index and SPAD value of flag leaves and weakened the leaf photosynthetic characteristics as indicated by lower photosynthetic rates,transpiration rates,and stomatal conductance.These reductions were more pronounced under the combined stress.Salinity,drought,and especially their combination,decreased the activities of ascorbate peroxidase,catalase,and superoxide dismutase,while increasing the contents of malondialdehyde,hydrogen peroxide,and superoxide radical.Our results indicated a more significant yield loss in rice when subjected to combined salinity-drought stress.The individual and combined stresses of salinity and drought diminished antioxidant enzyme activities,inhibited leaf photosynthetic functions,accelerated leaf senescence,and subsequently lowered assimilate accumulation and grain yield.
基金This study was supported by the National Natural Science Foundation of China(31960306).
文摘To study non-structural carbohydrate character-istics and nutrient utilization strategies of Pinus yunnanen-sis under continuous drought conditions,2-year-old seed-lings were planted in pots with appropriate water,light and moderate and severe drought treatments[(80±5),(65±5),(50±5),and(35±5)%of field water-holding capacity].Non-structural carbohydrates,carbon(C),nitrogen(N),and phosphorus(P)concentrations were measured in each plant component.The results show that:(1)With increasing drought,non-structural carbohydrates gradually increased in leaves,stems,and coarse roots,while gradually decreased in fine roots;(2)C concentrations of all were relatively stable under different stress levels.Phosphorous utilization of each component increased under light and moderate drought conditions,while N and P utilization efficiency of each plant component decreased under severe drought.Growth was mainly restricted by N,first decreasing and then increasing with increased drought;(3)There was a correlation between the levels of non-structural carbohydrates and C,N,and P in each component.Changes in N concentration affected the interconversion between soluble sugar and starch,which play a regulatory role in the fluctuation of the concentration of non-structural carbohydrates;and,(4)Plasticity analysis showed that P.yunnanensis seedlings responded to drought mainly by altering starch concentration,the ratio of soluble sugar to starch in leaves and stems,and further by alter-ing N and P utilization efficiencies.Overall,these results suggest that the physiological activities of all organs of P.yunnanensis seedlings are restricted under drought and that trade-offs exist between different physiological indicators and organs.Our findings are helpful in understanding non-structural carbohydrate and nutrient adaptation mechanisms under drought in P.yunnanensis seedlings.
基金Under the auspices of the National Social Science Foundation of China (No.19CGL045)。
文摘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.
文摘Based on the data of annual average precipitation in Deyang area and its five stations (Mianzhu, Deyang, Zhongjiang, Shifang and Guanghan) from 1984 to 2013, the annual precipitation anomaly percentage was calculated, and then the flood and drought situation in Deyang area was graded to discuss the variation characteristics of droughts and floods in the past 30 years. The results show that the cycle of droughts and floods in Deyang was about 3-5 a. The precipitation anomaly percentage indicates that the climate in Deyang area of Sichuan tended to be dry slowly in the past 30 years, and Deyang gradually entered a dry and warm period.
基金sponsored by the National Natural Science Foundation of China(Grant Nos.41991281,42130613 and 41705073)the UK-China Research and Innovation Partnership Fund through the Met Office Climate Science for Service Partnership(CSSP)China as part of the Newton Fundthe Jiangsu Collaborative Innovation Center for Climate Change.
文摘The spatial distribution of summer precipitation anomalies over eastern China often shows a dipole pattern,with anti-phased precipitation anomalies between southern China and northern China,known as the“southern flooding and northern drought”(SF-ND)pattern.In 2015,China experienced heavy rainfall in the south and the worst drought since 1979 in the north,which caused huge social and economic losses.Using reanalysis data,the atmospheric circulation anomalies and possible mechanisms related to the summer precipitation anomalies in 2015 were examined.The results showed that both El Niño and certain atmospheric teleconnections,including the Pacific Japan/East Asia Pacific(PJ/EAP),Eurasia pattern(EU),British–Baikal Corridor pattern(BBC),and Silk Road mode(SR),contributed to the dipole pattern of precipitation anomalies.The combination of these factors caused a southwards shift of the western Pacific subtropical high(WPSH)and a weakening of the East Asian summer monsoon.Consequently,it was difficult for the monsoon front and associated rain band to migrate northwards,which meant that less precipitation occurred in northern China while more precipitation occurred in southern China.This resulted in the SF-ND event.Moreover,further analysis revealed that global sea surface temperature anomalies(SSTAs)or sea-ice anomalies were key to stimulating these atmospheric teleconnections.
基金The authors greatly appreciate the financial support of the National Natural Science Foundation of China(Grant No.52104027)the Project supported by the Joint Funds of the National Natural Science Foundation of China(Grant No.U21B2070)the Shandong Provincial Natural Science Foundation(Grant No.ZR2021ME072).
文摘The pilot test of infilling polymer-surfactant-preformed particle gel(PPG)flooding has been successfully implemented after polymer flooding in Ng3 block of Gudao Oilfield in China.However,the production characteristics and displacement mechanisms are still unclear,which restricts its further popularization and application.Aiming at this problem,this paper firstly analyzes the production performance of the pilot test and proposed four response types according to the change of water cut curves,including W-type,U-type,V-type response,and no response.Furthermore,the underlying reasons of these four types are analyzed from the aspects of seepage resistance and sweep efficiency.The overall sweep efficiency of gradual-rising W-type,gradual-decreasing W-type,and early V-type response increases from 0.81 to 0.93,0.55 to 0.89,and 0.94 to 1,respectively.And the sum of seepage resistance along the connection line between production well and injection well for U-type and delayed V-type response increases from 0.0994 to 0.2425,and 0.0677 to 0.1654,respectively.Then,the remaining oil distribution after polymer flooding is summarized into four types on the basis of production and geological characteristics,namely disconnected remaining oil,streamline unswept remaining oil,rhythm remaining oil,and interlayer-controlled remaining oil.Furthermore,the main displacement mechanisms for each type are clarified based on the dimensionless seepage resistance and water absorption profile.Generally,improving connectivity by well pattern infilling is the most important for producing disconnected remaining oil.The synergistic effect of well pattern infilling and polymer-surfactant-PPG flooding increases the dimensionless seepage resistance of water channeling regions and forces the subsequent injected water to turn to regions with streamline unswept remaining oil.The improvement of the water absorption profile by polymer-surfactant-PPG flooding and separated layer water injection contributes to displacing rhythm remaining oil and interlayer-controlled remaining oil.Finally,the paper analyzes the relationships between the remaining oil distribution after polymer flooding and production characteristics of infilling polymer-surfactant-PPG flooding.The study helps to deepen the understanding of infilling polymer-surfactant-PPG flooding and has reference significance for more commercial implementations in the future.
基金Supported by the PetroChina Science and Technology Major Project(2019-E2607)PetroChina Exploration and Production Company Science and Technology Project(KS2020-01-09).
文摘A smart response fluid was designed and developed to overcome the challenges of gas channeling during CO_(2)flooding in low-permeability,tight oil reservoirs.The fluid is based on Gemini surfactant with self-assembly capabilities,and the tertiary amine group serves as the response component.The responsive characteristics and corresponding mechanism of the smart fluid during the interaction with CO_(2)/oil were studied,followed by the shear characteristics of the thickened aggregates obtained by the smart fluid responding to CO_(2).The temperature and salt resistance of the smart fluid and the aggregates were evaluated,and their feasibility and effectiveness in sweep-controlling during the CO_(2)flooding were confirmed.This research reveals:(1)Thickened aggregates could be assembled since the smart fluid interacted with CO_(2).When the mass fraction of the smart fluid ranged from 0.05%to 2.50%,the thickening ratio changed from 9 to 246,with viscosity reaching 13 to 3100 mPas.As a result,the sweep efficiency in low-permeability core models could be increased in our experiments.(2)When the smart fluid(0.5%to 1.0%)was exposed to simulated oil,the oil/fluid interfacial tension decreased to the level of 1×10^(-2)mN/m.Furthermore,the vesicle-like micelles in the smart fluid completely transformed into spherical micelles when the fluid was exposed to simulated oil with the saturation greater than 10%.As a result,the smart fluid could maintain low oil/fluid interfacial tension,and would not be thickened after oil exposure.(3)When the smart fluid interacted with CO_(2),the aggregates showed self-healing properties in terms of shear-thinning,static-thickening,and structural integrity after several shear-static cycles.Therefore,this fluid is safe to be placed in deep reservoirs.(4)The long-term temperature and salt resistance of the smart fluid and thickened aggregates have been confirmed.
基金The Second Tibetan Plateau Scientific Expedition and Research(STEP)Program(2019QZKK0105)the Science and Technology Development Fund of the Chinese Academy of Meteorological Sciences(2022KJ022)+2 种基金Special Fund for the Basic Scientific Research Expenses of the Chinese Academy of Meteorological Sciences(2021Z013)the Science and Technology Development Fund of the Chinese Academy of Meteorological Sciences(2022KJ021)Major Projects of the Natural Science Foundation of China(91337000)。
文摘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.
基金National Foundation for Outstanding Young Scientists (40825008)National Natural Science Foundation of China (40975020)Models and Technical Composites for Comprehensive Improvement of Ecological and Environmental Conditions in the Basin of Qinghai Lake (2007BAC30B05-4)
文摘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.
基金This study was financially supported by the National Natural Science Foundation of China(41871097).
文摘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.
基金Essential Scientific Research Project in the national 9th five-year development plan (96-908-05-06-08)
文摘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.
基金National Key Basic Research Development Program Project of China(2012CB417202)Key Project of National Natural Science Foundation(91337215)National Natural Science Foundation of China(41275051)
文摘NCEP/NCAR data are utilized to analyze an extreme flood year(1998) and an extreme dry year(2006) in the Sichuan-Chongqing region(SCR) and the results are as follows. The positive divergence of South Asia High(SAH) is stronger in the flood year; the position of the ridge line of SAH is southward compared with the annual average; Western Pacific Subtropical High(WPSH) extends westward and its ridge line is southward. In the drought year, the positive divergence of SAH is weaker, its ridge line is northward, and the position of WPSH is also northward. As shown in the dynamics, in drought(flood) years, negative(positive) vorticity advection in the upper atmosphere can cause the atmosphere to ascend(descend), and anomalous circulation of SAH displays divergence(convergence), and anomalous circulation of the lower atmosphere shows convergence(divergence). Thermal structure of the atmosphere shows that there is warm(cold) temperature advection in the lower atmosphere, and the vertical distribution of diabetic heating causes SAH's local circulation to display convergence(divergence) and affects vertical motion of the lower atmosphere circulation eventually. To some extent, the two extreme years in the SCR is closely related to the vertical motion of atmosphere circulation and the variation of such vertical motion is caused by differences of interactions between SAH and lower atmosphere circulations.
文摘This study aims to apply a hydrogeological approaches and analysis of the 2021 flood event of Tasi-Tolu Lagoon to achieve four specific goals. Firstly, the study seeks to determine the natural characteristics of the lagoon, which include factors such as size, depth, water quality, and ecosystem composition. Secondly, the influence of precipitation on the water volume in the lagoon will be examined. This analysis involves assessing historical rainfall patterns in the region, as well as the amount and frequency of precipitation during the 2021 flood event. Thirdly, the hydrogeologic and geologic conditions of the lagoon will be evaluated. This involves examining factors such as the type and structure of the soil and bedrock, the presence of aquifers or other underground water sources, and the movement of water through the surrounding landscape. Finally, the study seeks to assess the risk of future flooding in Tasi-Tolu Lagoon, based on the insights gained from the previous analyses. Overall, this study’s goal is to provide a comprehensive understanding of the hydrogeological factors that contribute to flooding in Tasi-Tolu Lagoon. This knowledge could be used to inform flood mitigation strategies or to improve our ability to predict and respond to future flooding events in the region.
文摘Spatio-temporal analysis of drought provides valuable information for drought management and damage mitigation. In this study, the Standardized Precipitation Index at the time scale of 6 months (SPI-6) is selected to reflect drought conditions in the North-Eastern coastal region of Vietnam. The drought events and their characteristics from 1981 to 2019 are detected at 9 meteorological stations and 10 Chirps rainfall stations. The spatio-temporal variation of drought in the study region is analyzed on the basis of the number, duration, severity, intensity, and peak of the detected drought events at the 19 stations. The results show that from 1981 to 2019 the drought events mainly occurred with 1-season duration and moderate intensity and peak. The number, duration, severity, and peak of the drought events were the greatest in the period 2001-2010 and were the smallest in the period 2011-2019. Among the 19 stations, the drought duration tends to decrease at 11 stations, increase at 7 stations, and has a slight variant at 1 station;the drought severity tends to decrease at 14 stations, increase at 4 stations, and has not a significant trend at 1 station;the drought intensity tends to decrease at 17 stations, increase at 1 station, and has a slight variant at 1 station;and the drought peak tends to decrease at 18 stations and increase at 1 station.
基金supported by the National Basic Research Program of China (Grant No. 2012CB955401)the National Natural Science Foundation of China (Grant No. 41275078)supported by the "Strategic Priority Research Program-Climate Change:Carbon Budget and Relevant Issues" of the Chinese Academy of Sciences (Grant No. XDA05090306)
文摘This study investigates the impact of global warming on drought/flood patterns in China at the end of the 21st century based on the simulations of 22 global climate models and a regional climate model(RegCM3) under the SRES(Special Report on Emissions Scenarios) A1B scenario.The standardized precipitation index(SPI),which has well performance in monitoring the drought/flood characteristics(in terms of their intensity,duration,and spatial extent) in China,is used in this study.The projected results of 22 coupled models and the RegCM3 simulation are consistent.These models project a decrease in the frequency of droughts in most parts of northern China and a slight increase in the frequency in some parts of southern China.Considering China as a whole,the spatial extents of droughts are projected to be significantly reduced.In contrast,future flood events over most parts of China are projected to occur more frequently with stronger intensity and longer duration than those prevalent currently.Additionally,the spatial extents of flood events are projected to significantly increase.
