This paper,using a revised Penman-Monteith model,computed the terrestrial surface humidity index of the Loess Plateau(China) based on climatic factors of monthly mean temperature,maximum temperature,minimum temperature,relative humidity,precipitation,wind speed and sunshine duration observed on the plateau from 1961 to 2008.The temporal-spatial distribution,anomaly distribution and sub-regional temporal variations of the terrestrial surface dry and wet conditions were analyzed as well.The results showed a decreasing trend in the annual average surface humidity from the southeast to the northwest in the research area.Over the period of 1961-2008,an aridification tendency appeared sharply in the central interior region of the Loess Plateau,and less sharply in the middle part of the region.The border region showed the weakest tendency of aridification.It is clear that aridification diffused in all directions from the interior region.The spatial anomaly distribution of the terrestrial surface dry and wet conditions on the Loess Plateau can be divided into three key areas:the southern,western and eastern regions.The terrestrial annual humidity index displayed a significantly descending trend and showed remarkable abrupt changes from wet to dry in the years 1967,1977 and 1979.In the above mentioned three key areas for dry and wet conditions,the terrestrial annual humidity index exhibited a fluctuation period of 3-4 years,while in the southern region,a fluctuation period of 7-8 years existed at the same time.
YuBi YAORunYuan WANGJinHu YANGPing YUEDengRong LUGuo,Ju XIAOYang WANGLinChun LIU
A socio-economic data set on China's historical flood losses for the period 1984e2012 was compiled to analyze the exposed population,economy,and crop area as well as the vulnerabilities of the population and economy to floods.The results revealed that the exposed population was approximately 126 persons km 2per year when taking China as a whole;in terms of the economy,potential losses due to floods were estimated to be approximately 1.49 million CN$km 2and the crop area exposed to floods covered 153 million hm2per year.China's total exposure to floods significantly increased over the analysis period.The areas that showed the higher exposure were mainly located along the east coast.The population's vulnerability to floods showed a significantly increasing trend,however,the economic vulnerability showed a decreasing trend.The populations and economies that were most vulnerable to floods were in Hunan,Anhui,Chongqing,Jiangxi,and Hubei provinces.The municipalities of Shanghai,Beijing,and Tianjin showed the lowest vulnerabilities to floods.
WANG Yan-JunGAO ChaoZHAI Jian-QingLI Xiu-CangSU Bu-daHARTMANN Heike
基于1983—2011年月总降水量、环流和海温的再分析资料,给出了20世纪90年代末东亚夏季降水的年代际调整的区域特征,及其对应的大气环流内部过程和可能的海温外强迫的年代际变化.研究结果表明,在20世纪90年代末期东亚北部夏季降水比东亚南部夏季降水由湿向干的表现更为明显,东亚南部地区夏季降水则是在20世纪90年代初和21世纪初发生年代际的转折.此外,东亚地区夏季的500 h Pa高度场、850 h Pa风场、U200风场、水汽输送场和东亚太平洋遥相关型指数和东亚夏季风指数等在20世纪90年代末期也表现出明显的年代际变化特征.进而从大气内部过程的角度验证了20世纪90年代末东亚夏季降水发生的年代际调整.与此同时,北太平洋和西太平洋海表温度表现出由偏低向偏高的转变,这可能是导致20世纪90年代末期东亚夏季气候年代际变化的重要外部成因之一.
