气象极值变化及其导致的农业气象灾害趋势分析——以甘肃省为例

依据甘肃省62个气象站1960-2005年的地面气候资料, 分析农作物生育期(3-10月)内气象要素极值的变化趋势, 并用主成分分析方法研究了该变化对农业气象灾害发生趋势的影响.结果表明: 与温度相关的气象要素极值表现出了同平均气温类似的显著上升趋势,其中降水相关的气象要素极值变化说明甘肃省降水结构发生了改变, 极端性有所减弱;其他相关要素中, 最大风速存在明显下降趋势, 蒸发量呈下降趋势、日照时数呈上升趋势, 但都不够显著.大部分气象极值的变化与农业气象灾害的变化呈正相联系, 只有很少部分气象极值的变化与农业气象灾害的变化呈反相联系.综合分析这些气象极值在甘肃省范围内的变化趋势, 揭示出未来甘肃省干旱灾害倾向于加剧, 而洪涝灾害趋于减轻.     

Modelling direct,diffuse, and total solar radiation for cloudless days

A simple form of solar radiation model was analysed for cloudless days for Goose, Nfld., Port Hardy, B.C., and Edmonton, Alta. Performance for daily values of total solar radiation was satisfactory; however, data for Goose indicated that the model over‐and under‐estimated the direct and diffuse components of solar radiation, respectively. Modifications, including solving for an aerosol parameter k and substituting 0.6 forward scattering instead of the more commonly used 0.5, improved model performance for direct and diffuse radiation.     

梅雨期江淮地区极端高温事件的非均匀性特征及其与环流系统的配置

本文基于集中度和集中期的定义方法,利用1960~2007年的48年江淮地区站点的日平均温度资料和累积频率的阈值统计方法,分析梅雨期江淮地区极端高温事件的非均匀分布特征.结果表明,集中度和集中期的方法能够定量地表征梅雨期江淮地区极端高温事件的非均匀分布特征.集中期的异常型为全场一致和南北异常型,集中度的异常分布主要为南北异常和东西异常.进一步比较集中度和集中期异常与同期环流系统的配置关系得知,当集中期南北异常变化时,在高纬度的北太平洋区域出现一对正负的异常模态,且随高度增加而增强,为相当正压结构.海温的异常集中在北太平洋的北美沿岸的显著负异常中心.当集中度为东西异常时,主要环流异常型为约在160°W左右出现 "+ - + -" 的200 hPa纬向西风异常波列形式从低纬度到高纬度地区传播以及与ENSO的显著负相关.     

Extremely high temperatures in France at the end of the century

Power plant construction requires anticipation to achieve a liable dimensioning on the long functioning time of the installation. In the present climate change context, dimensioning towards extremely high temperature for installations intended to run until the 2070s or later implies an evaluation of plausible extreme values at this time scale. This study is devoted to such an estimation for France, using both observation series and climate model simulation results. The climate model results are taken from the European PRUDENCE (Prediction of Regional scenarios and Uncertainties for Defining European Climate change risks and Effects) project database of regional climate change scenarios for Europe. Comparison of high summer temperature distributions given by observations and climate models under current climate conditions, conducted using Generalized Extreme Value distribution, reveals that only a few models are able to correctly reproduce it. For these models, climate change under IPCC A2 and B2 scenarios leads to differences in the variability of high values, whose proportion has an important impact on future 100-year return levels. This study was first presented at the EGU General Assembly in Vienna, 2–7 April 2006.     

Changing properties of hydrological extremes in south China: natural variations or human influences?

Extreme events are drawing increasing concerns in recent decades due to their catastrophic nature. In this case, we thoroughly analysed the statistical behaviours of hydrological extremes in the south China by taking Guangdong province as a case study because of its unshakable position in the economic development in China. Our results further corroborated the fact that the hydrological changes are the integrated consequences of various external factors, basically the human activities and climate changes. Generally, decreasing annual maximum water (AMW) level was observed mainly in the seaward regions characterized by decreasing occurrence frequency of higher AMW level. Streamflow variations are influenced mainly by precipitation changes. Increasing annual maximum streamflow (AMS) can be attributed to the increasing precipitation intensity in recent years. However, in the East River basin, hydrological regulation function of the water reservoirs greatly reduced the AMS. In the lower East River, however, downcutting river channel and notable increases in the cross‐section area caused larger magnitude of decrease in AMW level when compared to AMS. The time when the relations between AMW level and streamflow start to change matches well the time when massive in‐channel sand dredging occurred, showing tremendous influences of human activities on hydrological processes in the lower Pearl River basin. This study will be of great scientific and practical merits in better understanding the statistical behaviours of hydrological extremes under the changing environment and also help to improve human mitigation to natural hazards in south China. Copyright © 2010 John Wiley & Sons, Ltd.     

How to improve attribution of changes in drought and flood impacts

ABSTRACT

For the development of sustainable, efficient risk management strategies for the hydrological extremes of droughts and floods, it is essential to understand the temporal changes of impacts, and their respective causes and interactions. In particular, little is known about changes in vulnerability and their influence on drought and flood impacts. We present a fictitious dialogue between two experts, one in droughts and the other in floods, showing that the main obstacles to scientific advancement in this area are both a lack of data and a lack of commonly accepted approaches. The drought and flood experts “discuss” available data and methods and we suggest a complementary approach. This approach consists of collecting a large number of single or multiple paired-event case studies from catchments around the world, undertaking detailed analyses of changes in impacts and drivers, and carrying out a comparative analysis. The advantages of this approach are that it allows detailed context- and location-specific assessments based on the paired-event analyses, and reveals general, transferable conclusions based on the comparative analysis of various case studies. Additionally, it is quite flexible in terms of data and can accommodate differences between floods and droughts.     

基于情景的1951-2011年中国极端降水风险评估

随着全球气候变暖,极端降水的风险评估研究成为学界和各国政府广泛关注的热点问题,开展中国极端降水的风险评估研究可以为中国防灾减灾提供参考依据。本文从灾害风险评估视角,依据国际减灾战略（ISDR）的灾害风险评估模型,开展了中国极端降水的风险评估研究。首先,利用1951-2011年全国各站点逐日降水数据,采用Pearson-III方法,模拟不同重现期情景下极端降水量和频次分布,评估中国不同重现期下的极端降水危险性及空间分布;其次,基于人口和GDP指标,分析极端降水脆弱性及空间分布特征;在此基础上,评估了5年、10年、50年、100年一遇情景下中国极端降水风险及其空间分布特征。结果表明：① 中国极端降水危险性等级从东南沿海向西北内陆递减,5年一遇情景下,极端降水高危险区和低危险区的分界线大致与400 mm等降水线相同。② 中国极端降水脆弱性高的地区主要分布在人口稠密且经济发达的东部沿海大城市地区,特别是经济发达的长三角、珠三角和京津冀等城市群地区,以及中部地区的一些大城市。③ 不同情景下,中国极端降水风险等级均呈现由东南向西北方向降低。风险等级高和较高的地区主要位于黑河—腾冲线以东,中和低风险区位于该线以西,这与中国人口密度分布的胡焕庸线大体一致。     

Quo vadis,hydrology?

This is an invited essay by the Dooge Medallist of the 2017 International Hydrological Prize. The paper reflects a broad perspective on hydrology, as a result of the author’s long experience. It is suggested that transgressing the traditional hydrological perspective, by increasing the scale of research, as well as interdisciplinarization have been, and are likely to remain, key drivers of the development of hydrology. Gaps in knowledge and research challenges are reviewed, and the interlinked areas of stationarity, extremes and projections for the future are discussed. Finally, after reviewing the achievements of Jim Dooge, examples of others following in his footsteps are presented.     

Effects of urbanization on daily temperature extremes in North China简

The regional changes of daily temperature extremes in North China caused by ur- banization are studied further from observed facts and model estimates on the basis of ho- mogenized daily series of maximum and minimum temperature observations from 268 mete- orological stations, NCEP/DOE AMIP- Ⅱ reanalysis data （R-2）, and the data of simulations by regional climate model （RegCM3）. The observed facts of regional warming on long time scales are obtained by analyzing the indices of temperature extremes during two time periods of 1961-2010 and 1951-2010. For urbanization effect, the contributions to decreases in an- nual and winter diurnal temperature range （DTR） are 56.0% and 52.9%, respectively, and increases in the lowest minimum temperature （TNn） are 35.7% and 26.2% by comparison of urban and rural observations. Obtained by R-2 data with observations for contrast, on the other hand, increase in the number of annual warm nights （TN90p） contributed by urbaniza- tion is 60.9%. And observed facts of regional warming in daily temperature extremes are also reflected in the simulations, but what difference is urbanization progress at rural areas in North China would be prominent in the next few years relative to urban areas to some extent from model estimates.