The Influence of Large-Scale Circulation on the SummerHydrological Cycle in the Haihe River Basin of China

In this study,we focus on changes in three important components of the hydrological-cycle in the Haihe River basin (HRB) during 1957-2005:precipitation (Prep),actual evaportranspiration (ETa),and pan evaporation (PE)- a measure of potential evaporation.The changes in these components have been evaluated in relation to changes in the East Asian summer monsoon.Summer Prep for the whole basin has decreased significantly during 1957-2005.Recent weakening of the convergence of the integrated water vapor flux,in combination with a change from cyclonic-like large-scale circulation conditions to anti-cyclonic-like conditions,led to the decrease in the summer Prep in the HRB.ETa is positively correlated with Prep on the interannual timescalc.On longer timescales,however,ETa is less dependent on Prep or the large-scale circulation.We found negative trends in ETa when the ERA40 reanalysis data were used,but positive trends in ETa when the NCEP/NCAR reanalysis data were used.PE declined during the period 1957 2001.The declining of PE could be explained by a combination of declining solar radiation and declining surface wind.Howevcr,the declining solar radiation may itself be related to the weakening winds,due to weaker dispersion of pollution.If so,the downward trend of PE may be mainly caused by weakening winds.     

东亚季风边缘带上的植被变化

早期的工作在全球和区域尺度上对气候与植被之间的关系进行了研究,表现在区域上存在差异. 本文集中于东亚季风边缘带上植被变化与季风季节与年际变化的关系分析,分季风区、非季风区和季风边缘区等3个区域做比较分析,结果得出季风边缘区域的植被生长对气候变化的响应较为敏感.