基于标准化降水蒸散指数（SPEI）的毛乌素沙地1981—2020年干旱特征研究

大气干旱是影响半干旱沙区植被建设、生态恢复及社会经济可持续发展的重要因素。基于1981—2020年毛乌素沙地10个气象站点的逐月气象资料,计算了月、季和年尺度的标准化降水蒸散指数（SPEI）,分析了该沙区近40年降水和气温的变化趋势、干旱事件及其频率的时空特征。结果表明：（1）毛乌素沙地近40年降水量和气温均呈现显著的上升趋势（P<0.05）;秋季和冬季降水量呈现显著的上升趋势（P<0.05）,四季气温均呈现显著的上升趋势（P<0.05）。（2）毛乌素沙地总体上呈现出不显著的湿润化趋势（P>0.05）,但秋季呈显著的湿润化趋势（P<0.05）;中、西部地区呈现出湿润化趋势,而东部地区则呈现干旱化趋势。（3）近40年毛乌素沙地的月尺度下干旱总频率达32.71%,各等级发生频率为轻旱>中旱>重旱>特旱,季节发生频次为冬季>夏季、秋季>春季;轻旱主要发生在毛乌素沙地的北部、中部、东南和西南部,中旱在东部、北部和西部边缘,重旱在东部、中部以及南部地区,特旱在西北部、南部和东南部区域。     

四川盆地东部再生稻高温伏旱区腋芽萌发期气象适宜度

以四川盆地东部再生稻高温伏旱区为研究区,基于气象条件对腋芽萌发期再生稻生长发育的影响机理,采用结构方程模型探明了腋芽萌发的影响因素、影响路径及影响强度。进一步结合隶属函数和层次分析法,构建了再生稻腋芽萌发气象适宜度模型,并分析了1981—2021年研究区腋芽萌发期气象影响因素及气象适宜度的变化特征。结果表明：气温、空气湿度、降水是四川盆地东部再生稻高温伏旱区腋芽萌发的关键影响因素,基于以上因素的气象适宜度模型能较好地评价再生稻腋芽萌发期的气象影响。1981—2021年研究区气温适宜度、空气湿度适宜度及综合气象适宜度均呈下降趋势,降水适宜度没有表现出明显的变化趋势。气温适宜度、空气湿度适宜度及综合气象适宜度总体呈“西高东低”的空间分布特征,降水适宜度则表现为“东西高、中部低”。1981—2021年研究区气温上升趋势与空气湿度下降趋势显著,导致致害高温（日平均气温≥32℃）积温和致害低湿（日平均相对湿度≤65％）日数明显增加,这是再生稻腋芽萌发期气象适宜度总体呈下降趋势的诱因。     

两种判断月干旱过程的方法在黄河流域的对比研究

利用黄河流域160个气象站1961-2010年逐日综合气象干旱指数(CI)指数, 对比分析两种用逐日CI指数判断月干旱过程的方法. 结果表明: 对重大干旱事件个例来说, 两种方法都能大体描述事件的月干旱过程, 但干旱的强度和范围有所不同. 从干旱发生的范围来看, 两种结果的差别较小, 方法I的识别结果范围更大、更连续, 特别是对青海旱情的判断常常比实际范围大;而方法II的识别结果范围稍小, 大体上能反应干旱的整体范围, 但有时也偶尔会遗漏小部分旱区;从干旱发生的强度来看, 方法I对干旱事实的描述偏轻, 而方法II以重-特旱为主, 与实际情况更相符. 从对黄河流域近50 a月干旱频率的分析结果来看, 两种方法一致表明黄河流域分界线以西的地区常年不容易发生干旱, 而对于分界线以东地区, 两种方法的统计结果有较大差异. 方法I的结果表明, 分界线以东地区干旱的月发生频率较大, 其中, 轻旱的月发生频率最大, 其次为中旱, 而重旱和特旱的发生频率很小;方法II的结果表明, 分界线以东地区干旱的月发生频率在60%~80%左右, 其中重旱的月发生频率最大, 其次为中旱, 轻旱和特旱的发生频率很小. 总体来说, 方法II对黄河流域月干旱情况的评估结果与干旱实际情况更一致.     

浅析广义干旱与狭义干旱的联系与区别

指出干旱研究的基础是以区域水资源承载力为前提。利用陆地水文学知识分析了自然界水循环运动的每个环节和特点,剖析了水资源承载力在陆面蒸发和径流衰退过程中形成干旱的机制。定义了广义干旱,并简析了与气象、农业等各种狭义干旱的区别与联系。强调了陆地水文学是唯一可以给干旱以科学、严谨和充分定义的学科。     

Spatial and temporal pattern of precipitation and drought in Gansu Province, Northwest China

Drought is one of the most harmful natural hazards in Gansu Province in Northwest China. The changes of precipitation affect the severity of drought. In order to recognize the trend of precipitation and understand the effect of rainfall change on water resources management and drought severity, Mann–Kendall test was used. Standardized Precipitation Index (SPI) was calculated to reconstruct the drought at different time scales and analyze the frequency of drought occurrence in the recent 50 years. The results show that the SPI is applicable in Gansu Province. The number of severe droughts differs among regions: it is more obvious as a 3-month drought in the Yellow River Basin and the Yangtze River Basin than in the Inland River Basin, and other droughts at 6-, 9-, and 12-month time scales have the same effect in the three regions. Mann–Kendall test results show that there is an upward trend in the summer periods and a downward trend in the autumn-winter-spring intervals ranging from 10.5 mm/10 years to −37.4 mm/10 years, which affect the local water resources management, droughts mitigation, and agriculture decision making. This situation poses challenges for future study.     

盐肤木对岩溶干旱环境的适应性研究:叶片解剖结构的启示

通过石蜡切片和扫描电镜观察,研究了岩溶环境下生长的盐肤木叶片结构特征.结果表明,在水分胁迫下,叶片表现了一系列的旱生特征.表皮由一层排列致密的不规则细胞组成.上表皮覆盖一层较厚的角质层,下表皮表面有表皮毛丛生.气孔着生在下表皮,陷入表皮以下.叶肉内栅栏组织发达,海绵组织松散.栅栏组织与海绵组织比约为4:1.部分叶肉细胞中含有胶状结晶物质.叶脉中犀壁组织发达,木质部外纤维数量众多,在气腔周围有单宁结晶分布.这些特征表明,盐肤木采用以保护型为主的多种方式适应岩溶干旱环境.     

ENSO事件对长江上游1470-2003年旱涝灾害影响分析

对长江上游旱涝灾害时间序列(1470-2003年)及SST指数序列(1868-2003年)作统计相关与谱分析,探讨了长江上游旱涝灾害与ENSO事件的遥相关关系.结果表明:长江上游旱涝灾害主周期要大于ENSO事件的主周期,前者主周期主要为16.69a,5.09a以及10.47a,而后者主周期主要为5a,～10～12年以及～10a.交叉谱分析结果表明,长江上游旱涝灾害与SST在约5a以及约10～12a周期上呈现出显著的相关性.可以认为ENSO事件发生周期与生存周期的长短直接影响着长江上游旱涝灾害发生的周期与频率,并在5a以及10～12a的周期上表现出高的统计相关性.SST指数与长江上游旱涝灾害相关分析表明,ElNiño事件的发生使长江上游发生旱灾机率增大,而LaNiña事件的发生则使长江上游发生涝灾的机率增大.     

Recent Precipitation Trends in Hungary in the Context of Larger Scale Climatic Changes

The time series of monthly precipitation totals from 14 Hungarian observing stations (1901–1998) were analysed to reveal the long term changes in precipitation characteristics occurred in the 20th century. A particular attention was given to the changes in the recent decades and their links with the larger scale climatic and circulation changes over Europe and the Atlantic.The statistical significancesof systematic changes are controlled by linear trend analysis and the Mann–Kendall test. The long term fluctuations are illustrated applying a 15-point Gaussian filter on the time series. The Standardised Precipitation Index is used to evaluate the changes in the drought event frequency. The relationships with larger scale changes are mostly discussed relying on contemporary papers, and the Grosswetterlagen Catalogue is used as well.The annual precipitation total decreased by 15–20% in Hungary during the 20th century. The decline is substantial in both halves of the century, but the precipitation sums in the transition seasons declined in the first 50 years, and the winter precipitation decreased in the latest decades. The precipitation total of the period November–February declined significantly in the last 50 years. In the same time the mean winter value of the North Atlantic Oscillation Index (NAOI) increased, the positions of the main pressure patterns over the Atlantic are shifted northeastward, and lot of other coherent changes detected in the winter climate of the European–Atlantic region. The mean summer precipitation total has hardly changed, but the frequency of summer drought events increased. There are some signs of a shift of the Hungarian summer climate towards a Mediterranean like climate.     

Response of the hydrological regime of the Yellow River to the changing monsoon intensity and human activity

Abstract

In the past 50 years, influenced by global climate change, the East Asian summer monsoon intensity (SMI) changed significantly, leading to a response by the water cycle of the Yellow River basin. The variation in SMI has three stages: (1) 1951–1963, SMI increased; (2) 1963–1965, SMI declined sharply, a feature that may be regarded as an abrupt change; and (3) 1965–2000, SMI remained at low levels and showed a tendency to decline slowly. The decreased SMI led to a reduction in water vapour transfer from the ocean to the Yellow River basin, and thus precipitation decreased and the natural river runoff of the Yellow River also decreased. Due to the increase in population and therefore in irrigated land area, the ratio of net water diversion to natural river runoff increased continuously. Comparison of the ratio of net water diversion to natural river runoff before and after the abrupt change in SMI indicates some discontinuity in the response of the man-induced lateral branch of the water cycle to the abrupt change in SMI. The frequently occurring flow desiccation in the lower Yellow River can be regarded as a response of the water cycle system to the decreasing summer monsoon intensity and increasing population. When the ratio of net water diversion exceeded the ratio of natural runoff of the low-flow season to the annual total natural runoff, flow desiccation in the lower Yellow River would occur. When the ratio of net water diversion is 0.3 larger than the ratio of the natural runoff of the low-flow season to the annual total natural runoff, an abrupt increase in the number of flow desiccation events is likely to occur.     

A drought outlook study in Korea

Abstract

Techniques are proposed for developing a monthly and weekly drought outlook and the drought outlook components are evaluated. A drought index, the surface water supply index (SWSI) was modified and used for the drought outlook. A water balance model (abcd) was successfully calibrated using a regional regression, including monthly and weekly factors, and was used to convert meteorology to hydrology. For the monthly drought outlook, an ensemble technique was applied, both with and without monthly industrial meteorology information (MIMI). For the weekly drought outlook, a deterministic forecasting technique was applied employing the Global Data Assimilation and Prediction System (GDAPS). The methodologies were applied to the Geum River basin in Korea. While only the weekly outlook using the GDAPS has sufficient forecasting capability to suggest it might be useful, the accuracy of the monthly drought outlook is expected to improve as the climate forecast accuracy increases.

Editor Z.W. Kundzewicz; Associate editor D. Hughes

Citation Kim, Y.-O., Lee, J.-K., and Palmer, R.N., 2012. A drought outlook study in Korea. Hydrological Sciences Journal, 57 (6), 1141–1153.