Projections of the 21st Century Changjiang-Huaihe River Basin Extreme Precipitation Events

Based on the 1961-1990 observed daily precipitation in the Changjiang-Huaihe River Basin, the NCEP/NCAR reanalysis data, and the HadCM3 model data for IPCC SRES A1B climate projections, the simulation capabilities of the BP-CCA downscaling approach for extreme precipitation indices of the current climate are assessed by applying canonical correlation analysis (CCA). In addition, future extreme precipitation indices in the middle and late 21st century are projected. The results show that simulation capability of the HadCM3 for regional climate characteristics can be effectively improved by the downscaling approach, with 30%-100% reduction of the relative errors of the climatological mean state of extreme precipitation indices. However, the downscaling results still show wetter winter and dryer summer than the observation. Under the SRES A1B emission scenario, frequency and intensity of extreme precipitation events are projected to increase, and the estimated increasing rate is higher for extreme precipitation indices than for mean precipitation index; and in summer than in winter. Extreme precipitations in the middle and late 21st century are expected to increase by 14% and 25% respectively in winter, and by 24% and 32% respectively in summer.

论西周外缘区域——建立在考古材料基础上的分析

西周时期,今山东地区、南方的淮河—长江流域,太行山东侧的冀北平原和西部的泾河、渭河上游等四个地区构成西周外缘疆域。考古发现揭示,西周疆域的形成有以下策略与规律,即:分封建国、以点带面,最大限度占有领土,并通过王室与诸侯国的配合或诸侯国的自发行为进行领土的扩张;注意自然地理环境的特殊性,分封边疆地区诸侯国,以占据极为重要的战略地带,集中防卫力量于最有效的部位,保障西周王朝核心地带和王室的安全;武力征服之外,加强先进文化影响力的辐射,将土著族群吸纳进西周王国的政治体制之中,实现疆域的拓展。

A comparative study of the atmospheric circulations associated with rainy-season floods between the Yangtze and Huaihe River Basins

Here we present the results from the composite analyses of the atmospheric circulations and physical quantity fields associated with rainy-season for the selected floods cases over the Yangtze and Huaihe River basins for the 21 years(1990–2010),using the daily rain gauge measurements taken in the 756 stations throughout China and the NCEP/reanalysis data for the rainyseasons(June–July)from 1990 to 2010.The major differences in the atmospheric circulations and physical quantity fields between the Yangtze and Huaihe River basins are as follows:for flooding years of the Yangtze River Basin,the South Asia high center is located further east than normal,the blocking high over the Urals and the Sea of Okhotsk maintains,and the Meiyu front is situated near 30°N whereas for flooding years of the Huaihe River Basin,the South Asia high center is further west than normal,the atmospheric circulations over the mid and high latitudes in the Northern Hemisphere are of meridional distribution,and the Meiyu front is situated near 33°N.In addition,there are distinct differences in water vapor sources and associated transports between the Yangtze and Huaihe River basins.The water vapor is transported by southwesterly flows from the Bay of Bengal and monsoon flows over the South China Sea for flooding years of the Yangtze River Basin whereas by southeast monsoons from the eastern and southern seas off China and monsoon flows over the South China Sea for flooding years of the Huaihe River Basin.