The evolution analysis of flood and drought in Huai River Basin of China based on monthly precipitation characteristics

Based on the daily precipitation data of 38 weather stations in the Huai River Basin from 1961 to 2010, this study used SPI index, P-III curve to determine the flood/drought years, under what situations for droughts and floods easily happen, and to analyze the evolution law of flood and drought during inter-annual and intra-annual based on the characteristic of monthly precipitation. The results showed that: (1) annual rainfall of the Huai River Basin presented decreasing trend, maximum rainfall appeared from June to August, and multi-year average precipitation increased gradually from north to south; (2) the variation of monthly precipitation during flood years was more severe than other typical years, and precipitation in drought years showed nearly 50 % decline compared with normal years; (3) high rainfall of flood years was mainly caused by the increase in rainfall in flood season, and the strategy of flood control and drought relief was “short-term flood prevention and long-term drought relief”; (4) while precipitation of most months in drought year was reduced, the relevant strategies “annual basin-wide of long-term drought prevention” should be carried out; (5) combination events of floods and droughts occurred frequently. Persistent drought dominated in spring and summer while droughts and floods that happened alternately were mainly in summer and autumn.     

公元1500—2000年印度尼西亚—菲律宾强火山喷发对中国中东部旱涝格局的影响*

强火山活动是气候变化的重要自然驱动因素,可导致中国降水出现年际或年代际变化,甚至极端的旱涝现象。探究位于中国邻域的印度尼西亚—菲律宾一带的强火山喷发与中国旱涝分布格局的关系,有助于阐释中国旱涝发生的时空规律及机制,为预测未来火山爆发可能导致的降水异常提供借鉴。本文基于1500—2000年期间世界强火山活动和中国旱涝资料,运用时序叠加分析的方法辨识了印度尼西亚—菲律宾一带的强火山喷发后中国旱涝在年际尺度上的时空变化特征,并对1815年Tambora火山喷发进行案例分析。结果表明印度尼西亚—菲律宾一带的强火山喷发对中国的旱涝格局有一定的影响:强火山喷发后第0年至第2年,中国中东部各站点的整体变化为偏涝;在第3年,整体出现了偏旱的转变,且变化幅度相比其他年份较大;就地区而言,喷发后华北、华南地区分别出现了由旱转涝、由涝转旱的变化,并且这些变化大概持续了2~3年,随后2个区域均恢复了喷发前的旱涝趋势;印度尼西亚1815年Tambora火山喷发后0~3年,中国以涝情为主,但发生涝情的区域逐年在发生变化。     

Large-scale interannual variation of the summer monsoon over India and its empirical prediction

Large-scale interannual variability of the northern summer southwest monsoon over India is studied by examining its variation in the dry area during the period 1871–1984. On the mean summer monsoon rainfall (June to September total) chart the 800 mm isohyet divides the country into two nearly equal halves, named as dry area (monsoon rainfall less than 800 mm) and wet area (monsoon rainfall greater than 800 mm). The dry area/wet area shows large variations from one year to another, and is considered as an index for assessing the large-scale performance of the Indian summer monsoon. Statistical and fluctuation characteristics of the summer monsoon dry area (SMDA) are reported. To identify possible causes of variation in the Indian summer monsoon, the correlation between the summer monsoon dry area and eleven regional/global circulation parameters is examined. The northern hemisphere surface air temperature, zonal/hemispheric/global surface air and upper air temperatures, Southern Oscillation, Quasi-biennial oscillation of the equatorial lower stratosphere, April 500-mb ridge along 75°E over India, the Indian surface air temperature and the Bombay sea level pressure showed significant correlation. A new predictor parameter that is preceding year mean monsoon rainfall of a few selected stations over India has been suggested in the present study. The stations have been selected by applying the objective technique ‘selecting a subset of few gauges whose mean monsoon rainfall of the preceding year has shown the highest correlation coefficient (CC) with the SMDA’. Bankura (Gangetic West Bengal), Cuddalore (Tamil Nadu) and Anupgarh (West Rajasthan) entered the selection showing a CC of 0.724. Using a dependent sample of 1951–1980 a predictive model (multiple CC = 0.745) has also been developed for the SMDA with preceding year mean monsoon rainfall of the three selected stations and the sea level pressure tendency at Darwin from Jan–Feb to Mar–May as independent parameters.     

Riverine flood assessment in Jhang district in connection with ENSO and summer monsoon rainfall over Upper Indus Basin for 2010

Pakistan has experienced severe floods over the past decades due to climate variability. Among all the floods, the flood of 2010 was the worst in history. This study focuses on the assessment of (1) riverine flooding in the district Jhang (where Jhelum and Chenab rivers join, and the district was severely flood affected) and (2) south Asiatic summer monsoon rainfall patterns and anomalies considering the case of 2010 flood in Pakistan. The land use/cover change has been analyzed by using Landsat TM 30 m resolution satellite imageries for supervised classification, and three instances have been compared, i.e., pre-flooding, flooding, and post-flooding. The water flow accumulation, drainage density and pattern, and river catchment areas have been calculated by using Shutter Radar Topography Mission digital elevation model 90 m resolution. The standard deviation of south Asiatic summer monsoon rainfall patterns, anomalies and normal (1979–2008) has been calculated for July, August, and September by using rainfall data set of Era interim (0.75° × 0.75° resolution). El Niño Southern Oscillation has also been considered for its role in prevailing rainfall anomalies during the year 2010 over Upper Indus Basin region. Results show the considerable changing of land cover during the three instances in the Jhang district and water content in the rivers. Abnormal rainfall patterns over Upper Indus Basin region prevailed during summer monsoon months in the year 2010 and 2011. The El Niño (2009–2010) and its rapid phase transition to La Niña (2011–2012) may be the cause of severity and disturbances in rainfall patterns during the year 2010. The Geographical Information System techniques and model based simulated climate data sets have been used in this study which can be helpful in developing a monitoring tool for flood management.     

近40年中国平均气候与极值气候变化的概述

随着中国气象局对近50年来逐日气象观测资料的释放,人们从不同的角度对中国平均气候和极端气候的分布特征有了更多的了解.从目前研究的结果来看,这些认识需要有一个集成,即需要有一个总体的归纳和解释.通过中国近40年来的温度极值和降水极值事件的分析认识到全球增暖和区域环流异常决定着气候极值事件的分布格局.与全球增暖相联系的是:我国微量降水在空间上表现为一致的减少趋势,我国北方寒潮事件显著减少,冷夜和冷日的减少与暖夜和暖日的增多并存,以及极端强降水有增多的趋势.与东亚季风气流和西风带气流异常对应的我国有效降水在区域分布上发生了显著变化,东部季风区中的"北涝南旱"从1970年代末转型为"南涝北旱",与华南的偏干一起形成了东部季风区降水从华南、长江到华北的"-、 、-"异常分布型,但华南在1991年出现了转湿的突变;东北和西北先后从1983年和1987年前后转为暖湿气候.极端温度和极端降水趋势的空间分布与平均温度和平均降水趋势的空间分布一致.     

宁夏春、夏、秋季干旱与降水集中期及集中度的关系

应用宁夏气象台站1961-2010年逐候降水量序列资料, 计算了春、夏、秋季3个季降水的集中期、集中度和干旱Z指数, 运用趋势分析、相关分析、合成分析讨论了3季的集中期、集中度与旱涝程度的时空变化特征及其相互关系. 结果表明: 50 a来宁夏春夏秋干旱等级均呈加剧趋势, 秋季加剧更明显, 3季中中部干旱带加剧最严重, 南部山区次之, 北部最小. 春季集中期无明显变化趋势, 但集中度有上升趋势, 夏季集中期、集中度缓慢下降, 秋季集中期、集中度变化不明显;近10 a来3季集中度明显增大, 春夏两季集中期推迟. 春季降水集中度对干旱没有显著影响, 但首场透雨出现早晚对干旱影响显著, 透雨出现偏早, 干旱等级低, 反之亦然;夏季集中期对干旱影响不显著, 但集中度显著影响干旱, 集中度高, 雨涝发生概率越大, 集中度低, 干旱发生概率大;秋季集中期、集中度对干旱都有影响, 集中度高, 集中期早, 雨涝发生概率大, 反之干旱出现概率大.     

中国干旱-半干旱区当代气候变化

本文在作者近年有关研究工作的基础上，结合最新资料和有关成果，对我国干旱－半干旱区当代气候变化做了比较系统的分析。结果表明，中国干旱－半干旱区气候变化与全国和北半球气候变化相比有一定的特点。冬夏温度变化不同，干旱－半干旱区降水变化趋势不同。     

历史极端雨涝事件研究——1823年我国东部大范围雨涝

1823年(清道光三年)我国发生大范围、多流域的严重雨涝,这是在小冰期寒冷气候背景下的重大气象灾害和极端气候事件.文章依据历史文献记载复原了1823年的气候实况并绘图显示,指出该年我国华北夏季雨期长、多大雨,北京6～8月雨日53天、降水量663mm超过现代(1971～2000年)平均值5成;长江中下游全年多雨,梅雨期长...     

中国周降雨量与相关海域周平均海面水温

应用旋转主成分分析和复变量莫莱特小波变换分析了1982～1995年中国境内实测周降雨量和1982～1994年美国环境预报中心周平均海面水温资料,研究其时空变化特征及其相互关系。结果表明:海面水温乃至降雨量的周年变化,主要源于太阳直射点在南北回归线之间的往复运动和海面云雾覆盖量及其相关联的季风周年变化;依降雨量的周年变化可将中国自然地分为12个降水区,从海气相互作用的角度来看其年际变化主要取决于太阳辐射强度、有效日照率和亚洲夏季风的年际变化;厄尔尼诺只对黄河河套北部和两广降水区年降雨量有较大影响;西太平洋暖池以东海面水温的年际变化仅对黄河河套北部年降雨量有一定影响。     

2500多年来的太阳活动与温度变化

利用Schove推算出的2500多年太阳黑子极值出现的年份得到了2500多年来的太阳黑子周期长度，将其与北半球部分地区温度对比，发现太阳黑子周期长时北半球温度低，太阳黑子周期短时北半球温度高；快周期持续时间越长暖期持续时间也越长，反之亦然。最后，利用太阳黑子周期长度和万年尺度的温度变化趋势拟合了2500多年来的温度变化，它与我国温度和极区温度有一定的可比性。     

LGM时期气候背景下中国区域植被变化对东亚夏季降水影响的模拟

利用CCM3/NCAR全球气候模式在21kaB.P.(2.1万年前)的末次盛冰期(LGM)气候背景下,对中国区域植被变化对夏季(6～7月)东亚季风降水的影响进行了模拟,结果表明： 在LGM时期气候背景下,植被退化会使得中国东南部夏季降水减少,其中东南沿海减少超过20mm,而在 100°E 以东的中国北方大部分地区降水增加,其中心值大于50mm,从而导致降水南少北多的现象,植被的这种影响可以从物理上得到解释。在LGM气候背景下,植被退化在暖季起着增温的作用,即通过影响地表热状况使夏季大陆增温,增强了夏季东亚大陆与其周边海域的热力差异,从而使夏季东亚地区的西南风增强,35°～45°N的北方地区对流层低层的空气辐合和对流层上升运动加强,伴随着在 30°N 以南的中国南方地区出现异常下沉运动; 同时,西南季风的加强也导致夏季在 30°～40°N 之间的华北地区低层水汽输送加大。在这些因子的共同作用下,中国北方夏季降水增多,而东南部降水减少。这些结果说明使用LGM时期中国区域不同的重建植被资料可以对东亚季风气候模拟产生一定的不确定性。因此,重建可信度高的东亚植被对于降低对气候模拟的不确定性是十分重要的。     

Inter-annual variability of summer monsoon rainfall over Orissa (India) in relation to cyclonic disturbances

The summer monsoon rainfall over Orissa, a state on the eastern coast of India, is more significantly related than Indian summer monsoon rainfall (ISMR) to the cyclonic disturbances developing over the Bay of Bengal. Orissa experiences floods and droughts very often due to variation in the characteristics of these disturbances. Hence, an attempt was made to find out the inter-annual variability in the rainfall over Orissa and the frequencies of different categories of cyclonic disturbances affecting Orissa during monsoon season (June–September). For this purpose, different statistical characteristics, such as mean, coefficient of variation, trends and periodicities in the rainfall and the frequencies of different categories of cyclonic disturbances affecting Orissa, were analysed from 100 years (1901–2000) of data. The basic objective of the study was to find out the contribution of inter-annual variability in the frequency of cyclonic disturbances to the inter-annual variability of monsoon rainfall over Orissa. The relationship between summer monsoon rainfall over Orissa and the frequency of cyclonic disturbances affecting Orissa shows temporal variation. The correlation between them has significantly decreased since the 1950s. The variation in their relationship is mainly due to the variation in the frequency of cyclonic disturbances affecting Orissa. The variability of both rainfall and total cyclonic disturbances has been above normal since the 1960s, leading to more floods and droughts over Orissa during recent years. The inter-annual variability of seasonal rainfall over Orissa and the frequency of cyclonic disturbances affecting Orissa during monsoon season show a quasi-biennial oscillation period of 2–2.8 years. There is least impact of El Nino southern oscillation (ENSO) on inter-annual variability of both the seasonal rainfall over Orissa and the frequencies of monsoon depressions/total cyclonic disturbances affecting Orissa.     

Characteristics of glacier outburst flood in the Yarkant river,Karakorum mountains

Conclusions 1. The drainage of the Kyagar glacier dammed lake and the Tram Kangri glacier dammed lake at the upper Shaksgam is the main reason for glacier outburst floods in the Yarkant river. The Kyagar glacier dammed lake is characterized by subglacial drainage, while the Tram Kangri glacier dammed lake by mainly lateral drainage and, secondly, by subglacial drainage. 2. The drainage mechanism of the Tram Kangri ice dam determines the main characteristics of flood hydrography of the Kagun station, while the Kyagar glacier dammed lake plays an important role in the formation of floods. 3. Glacier outburst floods in the Yarkant river are characterized mainly by high peak discharge, big rising rate, small total volume and short duration. The floods happen mostly from late summer to early autumn. A period of 6 to 10 years in occurrence of large scale glacier outburst floods exist. The periodicity depends mainly on large scale drainage in the Kyagar ice-dammed lake. 4. Formation and dimensions of glacier dams at the upper Shaksgam were determined by long-term variations of the regional climate, whereas the changes of storage capacity in the lake reflect cold and warm changes of alpine region. Therefore, frequent glacier outburst floods indicate glacier advance and climatic variations.     

全球变暖、长江水灾与可能损失

全球大幅度变暖,使得水循环加快,蒸发和降水增强。长江中下游地区在20世纪90年代已呈现出明显增温趋势,达到 0．2～0．8℃,最大增温区域在长江三角洲地区。降水在长江流域中下游地区增加明显,增加值为5％～20％。20世纪90年代是继50年代后,长江流域性洪水灾害高发的10年。长江流域是我国经济发展的核心地区,对长江流域725个县洪水灾害脆弱性分析结果表明,近 1／3的地区是洪水灾害高脆弱性地区。按照1998年社会经济状况,若遭遇1954年型、1991年型、1996年型和1998年型的洪水时,洪水灾害造成的可能损失分别为589、55、70和196亿美元。气候模拟预测表明,21世纪长江流域地区的增温可能达到 2．7℃,导致降水可能增加 10％,径流可能增加37％。在全球变暖的趋势,以及区域社会经济可持续发展造成不透水面积增大和单位经济价值升高的共同影响下,长江流域发生相当于1870年、1954年和1998的千年、百年和20年一遇洪水的可能性增大,甚至可能发生超过上述频率的特大洪水。     

Relationship between South Asia High Low Frequency Oscillation and the Drought and Flood in the Middle and Lower Reaches of the Yangtze River

Based on the NCEP/NCAR daily reanalysis data and the daily rainfall data of ground observation at 164 weather stations in the middle and lower reaches of the Yangtze River from 1960 to 2013, the relationship between South Asia high low frequency oscillation and the drought and flood in the middle and lower reaches of the Yangtze River were analyzed using a composite analysis, wavelet analysis and band-pass filtering analysis method. The results indicated that in the typical drought and flood years, the Qinghai-Tibet Plateau 200 hPa atmosphere u, v low-frequency primary cycle and the summer rainfall cycle over the middle and lower reaches of the Yangtze River were the same. In more summer rainfall, from the Qinghai-Tibet Plateau to east China and west Pacific coast, there existed a cycle-anticyclone-cycle low frequency wave train. Low-frequency anticyclone controlled eastern China and the low-frequency cyclone controlled the northern Qinghai-Tibet Plateau. In drought years, results were opposite. In flood years, the precipitation of low frequency over the middle and lower reaches of the Yangtze River and that of 200 hPa atmospheric low frequency change of the Qinghai-Tibet Plateau was closely related. When the northerly wind in the northeast part of the the Qinghai-Tibet Plateau and in the middle and lower reaches of the Yangtze River was strong, and Lake Baikal southerly wind was strong, there was more precipitation. On the contrary, precipitation was less. The low frequency oscillation wave train was mainly spread from the northeast of China and Japan's southern to China’s southwest. However, in drought years, the relationship between them was not clear and needed to be further studied.     

长江流域历史洪水的周期地理学研究

从周期地理学的角度,探讨长江历史洪水的频发特点和周期规律,认为影响长江历史洪水的基本周期因子,与近日点日月交食年周期、太阳黑子活动周期和历史气候周期等因素有较大的关联性。而近几个世纪以来长江洪水频率的不断加快,表明人类活动扰乱和改变了历史洪水原有的周期值,使长江历史洪水周期打上了人类活动的深刻烙印。     

Rainfall Variability and Changes in Southern Africa during the 20th Century in the Global Warming Context

Rainfall variability and changes in Southern Africa over the 20th century areexamined and their potential links to the global warming discussed. After a shortreview of the main conclusions of various experiments with Global AtmosphericModels (GCM) forced by increased concentrations of greenhouse gases for SouthernAfrica, a study of various datasets documents the observed changes in rainfall featuresat both daily and seasonal time steps through the last century. Investigations of dailyrainfall parameters are so far limited to South Africa. They show that some regionshave experienced a shift toward more extreme rainfall events in recent decades.Investigations of cumulative rainfall anomalies over the summer season do notshow any trend to drier or moister conditions during the century. However, closeexamination reveals that rainfall variability in Southern Africa has experiencedsignificant modifications, especially in the recent decades. Interannual variabilityhas increased since the late 1960s. In particular, droughts became more intense andwidespread. More significantly, teleconnection patterns associated with SouthernAfrican rainfall variability changed from regional before the 70s to near global after,and an increased statistical association to the El Niño – Southern Oscillation (ENSO) phenomenon is observed. Numerical experiments with a French GCM indicate that these changes in teleconnections could be related to long-term variations in the Sea-Surface-Temperature background, which are part of the observed global warming signal.     

长链烷基二醇及其指标在南海北部粤东沿海上升流地区的环境指示

本文以南海北部粤东沿海夏季上升流三个短柱状岩心为研究对象,通过二醇化合物分布分析测试和二醇环境参数的定量化重建,初步探讨了过去80年来海水表层温度(SST)、上升流活动和沉积环境演变过程及其交互关系。二醇温度指标(LDI)在粤东沿海地区较好地指示了年均SST,在三个岩心中均显示了整体增加的分布特征和相似的多年尺度变化趋势。此外,LDI SST和二醇参数2具有非常好的线性关系(R2=0.85,n=49),其整体分布、多年尺度变化均和ENSO旋回一致,并且大部分高/低值和ENSO暖/冷年、南海夏季风强/弱年具有很好的对应关系,表明了二醇参数2可以作为粤东上升流强度变化(多年/单年尺度)的替代性指标。而1,14 二醇含量和ENSO指标在多年尺度上显示了相似的波动特征,但大部分高/低值和南海夏季风指数、ENSO指标呈反相分布,说明了仅用1,14 二醇含量不可反演粤东上升流。据此,利用二醇参数2初步重建了过去80年来粤东上升流演变信息：上升流强度整体上显示加强的分布趋势,大体上呈约2~5年周期变化。此外,三个岩心中1,15 C30(二醇/二醇+酮醇)比值和二醇参数2在整体上和多年尺度上均呈现相反的分布特征,可能与上升流活动导致的1,15 C30二醇母源再悬浮再氧化有关,而普遍较高的1,15 C30二醇比值(≥0.82)反映的强还原环境则和上升流地区水体中含氧量普遍偏低相关。     

An analysis of the drought and flood hazard characteristics and risks during the pre-rainy season in South China

Based on the daily precipitation data provided by the National Meteorological Information Center recorded at 89 representative stations in South China, as well as the reanalyzed monthly average 850-hPa wind field and sea surface temperature (SST) data from the National Centers for Environmental Prediction and the National Center for Atmospheric Research between 1969 and 2008, we studied the inter-annual variations and the causes of flood and drought hazards during the pre-rainy season in South China. Moreover, we assessed the hazard risks. The results indicate the following. (1) Most areas in Guangdong, the north and southwest of Guangxi, and the junction of Jiangxi and Fujian are at high risk of severe flooding. (2) The inter-annual variations of the pre-rainy season flood and drought hazards are evident in South China; specifically, consistent anomalies exist in Guangdong, Guangxi, central and north Fujian, and central and south Jiangxi. An inverse distribution of anomalies occurred in central and south Guizhou. Since the 1990s, inter-annual drought and flood hazards have accrued, particularly in south Guangxi, the southern and northern regions of Guangdong, and the north and central of Fujian where the risk of severe drought and flood is high. (3) The “El-Niño-Southern-Oscillation-like” (ENSO-like) SST anomaly and the corresponding atmospheric circulation anomaly are the major causes of the inter-annual variation of the pre-rainy season drought and flood hazards in South China. From the preceding winter to the pre-rainy season, the ENSO-like positive (negative) SST anomaly regulates the South China Sea and western Pacific anti-cyclonic (cyclonic) airflow to control the South China Sea. This effect increases (or decreases) the warm, humid vapor input in South China and causes severe pre-rainy season floods (or droughts) hazards in South China. It should be noted that because of the asymmetry in the anomalous local low-level circulation and the rainfall patterns, the floods and droughts hazards region in South China are also asymmetry between El Niño and La Niña.     

Seasonality of European warming: Influence of the tropics

This paper describes seasonal peculiarities of modern climate warming in the European region. It is shown that warming scenarios considerably differ in cold and warm periods of the year. The warming is accompanied with growth and considerable change in the phase of the yearly cycle in solarity data. A strong half-year cycle is recognized in seasonal variation of long-term trends over the last few years. Peculiarities of climate change in Europe and the increased influence of the tropics are discussed in view of the results obtained.