Dryness-wetness change and regional differentiation of flood-drought disasters in Guangdong during 1480-1940AD

Based on the historical records of the drought and flood disasters during 1480-1940AD, this paper reconstructs the sequences of wetness index （WI） and drought and flood disasters. We find a good identical relationship between the fluctuation of WI sequence and the δ^18O record of the GISP2 ice core in Greenland, which shows an apparent monsoonal disposal pattern of moisture and temperature. By applying the Morlet Wavelet Transform Method to deal with the data, several apparent periodicities, such as 7-8a, 11-15a, 20-23a and ca 50a, are revealed, among which some can be attributed to the solar forcing. Based on results of Cluster Analysis of dry-wet changes, we resume the regional differentiation pattern of flood-drought disasters all over Guangdong during different climatic intervals in the LIA and, find the western and northern parts of Guangdong have undergone drastic changes in drought-flood regional differentiation, but the eastern part is relatively stable, and the area of the Pearl River Delta shows stable condition of more flood disasters.

A STUDY ON REGULARITY OF DROUGHT AND FLOOD IN THE CHANGJIANG RIVER VALLEY DURING LAST 10 CENTURIES

According to historical records, there are 264 drought and flood years, occurred in the upper and middle reaches of the Changjiang (Yangtze) River during last 1020 years from 961 to 1980. The evolutionary law and developing trend of drought and flood years are studied. The distribution of drought and flood years are non-uniform and the dry and flood seasons in a year are concentrated. At the angle of monsoon circulation, at present the climate in the upper and middle reaches of the Changjiang River is just in the late stage of frequent drought period and the early stage of least flood period. In addition, the cycle of drought and flood and the feature of drought and flood occurred in the upper, middle and lower reaches of the Changjiang River are analyzed. It shows that the short period less than 10 years is in the majority, and the drought and flood occurred most frequently in the middle and lower reaches of the Changjiang River.

Change of Flood Patterns in China under the Influences of Climate Change and Human Activities

Based on the flood affected area （FA） data of the provinces in China from 1950 to 2005, the article discusses the change of the flood patterns in China, and investigates its relationship with climate change and human activities. The flood center shifted from North China and the Yangtze-Huaihe basin in the 1950s towards the south, north and west of China, and located in the south of the Yangtze River and South China after the 1990s. The FA in the western provinces was continuously on the rise since the 1950s. There are two characteristics for the future flood pattem in China. The pattern of ＂flood in the south and drought in the north＂ depends on the north-south shift of the maximum rainfall region in eastern China. The flood intensification to the west of Hu Huanyong＇s line mainly results from the increase of rainfall, extreme precipitation and the melting of glaciers under the background of human activity magnification.

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.

The Impact of Climate Change Induced Extreme Events on Agriculture and Food Security: A Review on Nigeria

The study of the climate change and the effects of climate change induced extreme events on food security are fundamental for the sustainable development of agriculture globally. Climatic factors are the primary important factors affecting agricultural production. Furthermore, the world is now experiencing more frequent and intense droughts and floods in many agricultural regions which damage and at times destroy crops. The effects of climatic change on agriculture have triggered significant trend of research during the last decade globally in order to unfold the solutions to climate change induced extreme events on agriculture. Several studies have been conducted on effects of extreme events such as droughts and flooding induced by climate change on agriculture and food security. These effects include changes in crop and livestock yields as well as the economic consequences of these potential yield changes globally. Therefore, this study reviews the effects of extreme events, including floods and drought, caused by climate change on agriculture and food security with focus on Nigeria in particular. For the study, literatures were identified for review through a comprehensive search by using electronic and non-electronic databases to identify researches conducted on effects on climate change and extreme events on agricultural productivity. From the review, it shows that extreme events such as droughts and floods impact agriculture and food security. In order to mitigate the effects of climate change especially droughts and floods, on agricultural productivity, there is an urgent need to intensity efforts and researches on climate change to mitigate and adapt to the occurrences of these extreme events when necessary in Nigeria. Several mitigation and adaptation measures need to be implemented to mitigate the effects of extreme events on agricultural productivity and food security. These measures include practicing climate-smart agriculture, construction and improvement of drainage networks to effectively dispose of flood water in order to reduce the risks of flooding in urban agriculture and drought-resistant varieties of crops should be cultivated.

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.

用CEOF分析近百年中国东部旱涝的分布及其年际变化特征

通过１８５０～１９９１年旱涝百分率的ＣＥＯＦ分析，研究了近百年来中国东部旱涝的分布特证、时空变化特点及年际演变规律。结果表明，我国东部主要有三种旱涝分布类型。第一种类型是以长江流域为中心全国大范围旱或涝，空间位相近似相同，且有１０．７年和３．１年周期性变化，振幅强度在１９２３～１９２４年间曾发生过增强突变。第二种类型为南北旱涝趋势相反的分布，空间位相自北向南变化显著，且有４．３年周期性变化，振幅强度在１８８４～１８８５年间曾有一次减弱突变。第三种类型呈江淮流域与华北和华南旱涝趋势相反的分布，空间位相从南北两个方向向中间或相反方向移动，并有３．４年周期性变化，振幅强度在１９１１～１９１２年有过增强突变。

Spatio-temporal evolution of drought and flood disaster chains in Baoji area from 1368 to 1911

Based on the collation and statistical analysis of flood and drought information in Baoji area from 1368 to 1911, and in the context of climate change, we investigated the spatio-temporal evolution characteristics of drought and flood disaster chains in this area during the Ming and Qing dynasties using the methods of moving average, cumulative anomaly and wavelet analysis. The results are as follows:(1) We found a total of 297 drought and flood events from 1368 to 1911 in Baoji. Among these events, droughts and floods occurred separately 191 and 106 times, which accounted for 64.31% and 35.69% of the total events, respectively.(2) We observed distinct characteristics of flood and drought events in Baoji in different phases. The climate was relatively dry from 1368 to 1644. A fluctuant climate phase with both floods and droughts occurred from 1645 to 1804. The climate was relatively wet from 1805 to 1911. Moreover, we observed a pattern of alternating dry and wet periods from 1368 to 1911. In addition, 3 oscillation periods of drought and flood events occurred around 70 a, 110 a and 170 a, which corresponded to sunspot cycles.(3) We also observed an obvious spatial difference in drought and flood events in Baoji. The northern and eastern parts of Weihe River basin were regions with both frequent droughts and floods.(4) The sequential appearance of drought and flood disaster chains in Baoji from 1368 to 1911 was in response to global climate change. Since the 1760s, global climatic deterioration has frequently led to extreme drought and flood events.

A Preliminary Study on the Global Land Annual Precipitation Associated with ENSO during 1948-2000

The global land monthly precipitation data (PREC / L) are used to investigate the relation between the global land annual precipitation and ENSO during 1948-2000, and the results of composite analysis are tested with Monte Carlo simulations. Results indicate that the global land annual precipitation was significantly reduced in large scale areas in warm event years; the areas were the equatorial West Pacific, North China; equatorial Central America; North Bengal Bay and Nepal; East Australia; West India and South Pakistan; the district east of the Lena River; West Europe; and Wilkes Land of Antarctica. In contrast to this, the areas where precipitation increased in warm event years were less, and mainly in Chile and Argentina of South America; Somali, Kenya, and Tanzania of East Africa; Turkey, Iraq, and Iran of the Middle East; Libya and Nigeria of North Africa; Namibia of Southwest Africa; and Botswana and Zimbabwe of southern Africa. Statistical tests show that in warm event years, the area where the land annual precipitation was reduced was larger than the area where the annual precipitation increased, and the reduction in precipitation was more significant than the increase. The results in this paper are compared with previous studies. It is also pointed out that the interdecadal change of ENSO had no significant effect on the interdecadal variation of precipitation in the above regions. However, the warm events of El Nino affected the droughts in East Australia and North China more after the 1980s than before.

The influence of anthropogenic climate change on wet and dry summers in Europe

Understanding the role of anthropogenic forcings in regional hydrological changes can help communities plan their adaptation in an informed manner.Here we apply attribution research methods to investigate the effect of human influence on historical trends in wet and dry summers and changes in the likelihood of extreme events in Europe.We employ an ensemble of new climate models and compare experiments with and without the effect of human influence to assess the anthropogenic contribution.Future changes are also analysed with projections to year 2100.We employ two drought indices defined relative to the pre-industrial climate:one driven by changes in rainfall only and one that also includes the effect of temperature via changes in potential evapotranspiration.Both indices suggest significant changes in European summers have already emerged above variability and are expected to intensify in the future,leading to widespread dryer conditions which are more extreme in the south.When only the effect of rainfall is considered,there is a distinct contrast between a shift towards wetter conditions in the north and dryer in the south of the continent,as well as an overall increase in variability.However,when the effect of warming is also included,it largely masks the wet trends in the north,resulting in increasingly drier summers across most of the continent.Historical index trends are already detected in the observations,while models suggest that what were extremely dry conditions in the pre-industrial climate will become normal in the south by the end of the century.

Future wet grasslands:ecological implications of climate change

Wet grasslands are threatened by future climate change,yet these are vital ecosystems for both conservation and agriculture,providing livelihoods for millions of people.These biologically diverse,transitional wetlands are defined by an abundance of grasses and periodic flooding,and maintained by regular disturbances such as grazing or cutting.This study summarizes relevant climate change scenarios projected by the Intergovernmental Panel on Climate Change and identifies implications for wet grasslands globally and regionally.Climate change is predicted to alter wet grassland hydrology,especially through warming,seasonal precipitation variability,and the severity of extreme events such as droughts and floods.Changes in the diversity,composition,and productivity of vegetation will affect functional and competitive relations between species.Extreme storm or flood events will favor ruderal plant species able to respond rapidly to environmental change.In some regions,wet grasslands may dry out during heatwaves and drought.C4 grasses and invasive species could benefit from warming scenarios,the latter facilitated by disturbances such as droughts,floods,and possibly wildfires.Agriculture will be affected as forage available for livestock will likely become less reliable,necessitating adaptations to cutting and grazing regimes by farmers and conservation managers,and possibly leading to land abandonment.It is recommended that agri-environment schemes,and other policies and practices,are adapted to mitigate climate change,with greater emphasis on water maintenance,flexible management,monitoring,and restoration of resilient wet grasslands.

Socio-Ecological Vulnerabilities and Major Cereal Crops Production in Bangladesh

Bangladesh enjoys food self-sufficiency or deficiency depending on crop damages by drought, floods, cyclones, storm/tidal surges and other natural hazards. Data on climate extremes were collected from literatures. Landsat images were analyzed for water availability. Arithmetic, geometric and weighted means were calculated for community vulnerability delineation using IDRISI3.2. About 12.64% populations live in disaster prone areas and their sensitivity to exposed hazards depends on financial capabilities. Crop area damages by natural hazards were the highest in Dhaka division followed by Rajshahi division during 2009-2014. The highest economic loss ($613 million) was found in Barisal division followed by Dhaka ($198.7 million) division. Flooding was the most damaging climate extreme followed by drought and hailstorm. Rice crops are frequently exposed to climate extremes and caused economic loss of $228 million during 2009-2014. Economic losses were <$110 to 1,000 ha-1 because of wheat/maize areas damaged by natural hazards. The most vulnerable areas are situated in the south-west and north-west part of the country. The most affected areas (35.4% of the country) had economic losses of $940-1,170 ha-1. About 2-4.7 million households (HH) were affected by different natural hazards in different regions of the country. Flood affected HHs were predominant in northern and north-east regions of the country. Common adaptations to natural hazard exposures are crop switching and migration. The other adaptation options could be improvement of post disaster recovery efficiency through financial support, supplying seeds and other inputs based on seasonal suitability.

中国旱涝急转事件时空变化特征

【目的】旱涝急转事件造成的社会经济和生态环境影响严重,是我国发生频繁且广泛的一种复合型事件。明确我国旱涝急转事件发生的时空变化特征,可为地区制定防灾减灾措施提供科学依据。【方法】基于1961—2021年气象观测数据,使用Penman-Monteith模型计算潜在蒸散发,然后计算逐日的标准化降水蒸散指数(daily-SPEI),分流域对中国旱涝急转事件的频次、影响范围和趋势的变化特征进行分析。【结果】结果显示:(1)时间趋势上,1961—2021年中国受旱涝急转事件影响的范围以0.6%/10a的趋势增加,且平均每年有19.8%的范围发生旱涝急转事件。(2)空间分布上,旱涝急转事件主要分布在淮河流域、黄河流域、长江流域和松花江流域,事件发生频次在30次以上地区分别占流域总面积的63.1%、20.7%、15.0%、14.6%,事件频次最高达到53次。(3)中国旱涝急转事件存在明显的季节差异,主要发生在夏季事件发生频次在5次以上的空间范围占中国总面积的一半以上;其次是春季和秋季,事件发生频次在5次以上的空间范围占比均不足15%;冬季发生最少,事件发生频次在5次以下。【结论】结果表明:中国旱涝急转事件的影响范围整体呈增加趋势,中国中东部和东北部是旱涝急转事件发生频繁地区。研究结果可为旱涝急转事件的监测与应对提供科学基础。

增氧与补肥对洞庭湖区旱涝急转下水稻减产规律的影响

【目的】阐明增氧和补肥对旱涝急转条件下水稻产量的影响。【方法】基于桶栽试验,以当地广泛种植的晚稻品种(野湘优航1573)为供试材料,设置干旱(X1,土壤含水率占田间持水率百分比)、淹涝(X2,淹没植株的高度)、增氧(X3,灌溉水溶氧量)、补肥(X4,复合肥施用量)4个因素,以当地农户水肥管理(CK)和单一旱涝急转处理(DF)为对照,采用二次饱和D-最优设计建立了四因素与产量的二次回归模型,研究了4个因素对水稻产量影响的主效应、单因素效应、交互效应及最优方案。【结果】影响水稻产量的主效应排序依次为:淹涝>增氧>补肥>干旱;交互效应强弱依次为:增氧-补肥>干旱-增氧>干旱-淹涝>干旱-补肥>淹涝-增氧>淹涝-补肥,轻旱有利于发挥增氧和补肥措施的减损效果,重度干旱与重度淹涝对水稻具有叠加减产作用。水稻产量随干旱和补肥水平的增加呈先增后减的变化趋势,随淹涝程度增加总体呈下降趋势,随增氧水平增加总体呈上升趋势。基于模型寻优得到了不同目标产量下的各因素最佳组合方案,与CK相比,增氧和补肥条件下的水稻产量平均降低了39.47%,而DF处理下的水稻产量平均降低了49.01%。【结论】4个因素与产量的二次回归模型具有良好的拟合效果(R^(2)=0.978,F=118.55,P<0.01),可为洞庭湖区水稻应对旱涝急转灾害提供理论依据。

嘉陵江流域旱涝急转演变规律及其对径流影响研究

针对气象旱涝转换对流域径流影响的问题,基于嘉陵江流域逐日降水量和流量数据,采用长、短周期旱涝急转指数方法,揭示了旱涝急转时空分布特征与演变规律,定量评估了径流变化对不同旱涝急转类型的响应程度。结果表明:1977~2022年,嘉陵江流域共发生了8次汛期旱涝急转事件,其中6次发生在2004年及之后;空间上,南部、中部以及西北部地区发生旱涝急转的频率较大,在17%以上;在月尺度上,6~7月发生旱涝急转的频率最大,超过了20%。当汛期发生涝转旱时,北碚、罗渡溪、武胜以及小河坝等站的前半汛期流量相比常年平均增长了57.52%,38.74%,85.50%和99.73%,后半汛期流量相对常年平均偏低了20.82%,49.83%,22.64%和14.53%;而在旱转涝影响下,上述站点前半汛期流量较常年平均减少了31.17%,45.77%,28.83%和26.16%,后半汛期流量较常年分别增长了31.45%,47.17%,24.31%和3.27%;月尺度上也表现出相似规律,表明旱涝急转对嘉陵江径流有着显著影响。研究成果可为梯级水库科学调度、流域水安全保障提供参考。

CHANGE TRENDS OF EXTREME CLIMATE EVENTS IN CHINA

The variations of extreme climate events such as cold wave, typhoon, hot and cold days have been discussed using the recent 45-year data. The reductions of nationwide cold wave activities and annual cold day number in northern China all have close relationship with warming winters, especially during 1980s and early 1990s. Decrements of annual hot day number are associated with cooling summers. The typhoon variation has connection with the tropical Pacific sea surface temperature conditions. The increments of drought/flood events since 1980s may be connected indirectly with climate warming up significantly since 1980s. The climate variability of these extreme climate events has decreased with time since 1980s.

1991~2020年鄂州市旱涝演变特征分析

【目的】近年来鄂州市旱涝灾害时有发生,本研究探讨了鄂州市近30a来的旱涝时空演变特征,研究结果可以为鄂州市合理构建干旱预警评估指标提供数据和理论支持。【方法】通过计算不同时间尺度的SPEI,并应用线性回归、M-K检验等统计方法分析了鄂州市旱涝的演变及持续特征,最后利用通径分析方法对影响旱涝的气象因素进行了分析。【结果】鄂州市中度及以下旱涝受旱几率高于受涝几率,而重度及以上旱涝正好相反;鄂州市整体变旱,但季节略有差异,其中春季、夏季和冬季变旱,秋季变涝;鄂州市旱涝发生季节差异明显,其中夏季易旱,但持续时间较短;春季易涝,持续时间长;降水量直接决定鄂州市旱涝程度,其次是蒸散量,而蒸散量的大小与气温关系密切。【结论】SPEI适用于研究鄂州市旱涝演变特征,可以作为气候变化和预警发布的监测指标。

论湖南省水旱灾害的地理规律性

水旱灾害是湖南省最严重的自然灾害。本文依据数十年来的水旱灾情资料，运用自然地理学的理论、方法，从灾害类型及其特点和时空尺度上揭示了湖南省水旱灾害的地理规律性，为防灾减灾决策提供科学依据。

当代新疆洪旱灾害扩大化:人类活动的影响分析

１９８０＇ｓ以来新疆洪旱灾害损失存在扩大化的趋势，这与我国及世界其它地区洪旱灾害增多的趋势相一致。造成当代新疆洪旱灾害增多、灾损扩大的原因除了全球变暖影响外，人类活动的加剧导致新疆生态环境严重退化、绿洲无度扩张致使临灾区域扩大是新疆近期洪旱灾害增多的主要原因。此外，对未来新疆的洪旱趋势进行初步展望，认为在全球和局域人类活动继续加剧的情况下，未来新疆气候会更加不稳定，降水变率增加，洪旱极端事件会增多，若能采取适当的应对措施，洪旱灾害损失会有一定程度的下降。

气候变暖背景下我国南方旱涝灾害时空格局变化

我国南方地区各季节降水异常主要包含三种优势模态:长江及其以南地区降水呈整体偏多或偏少的一致型,长江中下游流域与华南呈反相变化的南北反相型以及东南与西南呈反相变化的东西反相型。其中一致型是南方地区各季节降水变率的第一优势模态。总体而言,在1961—2013年南方地区平均降水存在明显的年代际和长期趋势变化。其中,夏季和冬季南方区域平均降水具有相似的年代际变化特征,而秋季降水的年代际演变几乎与上述两个季节的相反。不过,在近30年南方各季降水量发生年代际转折的时间不尽相同:春季和秋季降水分别在21世纪初期和20世纪80年代中后期之后进入干位相,冬季和夏季降水则分别在80年代中期和90年代初期之后进入湿位相。自21世纪初期以来,南方夏季和冬季降水逐渐转入中性位相。此外,南方春季和秋季降水均呈减少趋势;而夏季和冬季则相反,均呈增多趋势。对于西南地区,除了春季外,其他三个季节的降水均呈减少趋势,出现了季节连旱的特征,尤其是秋旱最为严重。不过,不管是季节降水量还是旱/涝日数,在我国南方大部分地区其线性变化趋势并不十分显著,这与南方降水年代际分量对降水变率存在较大贡献相关。分析还发现,我国南方区域洪涝受灾面积具有比较明显的年代际变化,而干旱受灾面积则没有明显的年代际变化特征,近十多年来西南地区干旱和洪涝受灾出现了交替互现的特点。