Climatic impacts of historical wetland drainage in Switzerland   总被引：1，自引：0，他引：1  

N. Schneider  W. Eugster 《Climatic change》2007,80(3-4):301-321

The effects of historical land-use and land-cover changes on the climate of the Swiss Plateau in the different seasons were investigated. In the 19th century, a civil engineering project was initiated to reshape the lake and river system on the Swiss Plateau in order to ban the frequent flooding during extreme weather events. The landscape modifications consisted primarily of a conversion of wetlands with extended peat soils into a highly productive agricultural landscape. Historical maps (1800–1850) served as a basis for the reconstruction of the past land use. The “Lokal-Modell” of the Consortium for Small-Scale Modelling was used to conduct eight one-month long high-resolution simulations (1.5 × 1.5 km²) with present and past landscape conditions. The modified soil and surface properties led to distinctly altered energy and moisture exchanges at the surface and as a consequence affected the local and regional climate. The climatic changes show different characteristics and magnitudes in the cold (October – March) as compared to the warm season (April – September). The landscape modifications led to an average daytime cooling between −0.12 °C (January) and −0.61 °C (April) and a night-time warming of 0.19 °C−0.34 °C. The differences in the mean monthly temperatures show a warming of 0.1 °C−0.2 °C in the cold season and a cooling of similar magnitude in most of the study area in the warm season. The modification of the radiation budget and the surface energy balance distinctly affected the convective activity in the study area in the warm season, but had only a weak effect on convectivity in the cold season. The cloud coverage in the warm season is therefore distinctly reduced compared to the past.  相似文献   

Long-Term Trend and Abrupt Change for Major Climate Variables in the Upper Yellow River Basin   总被引：7，自引：0，他引：7  

ZHAO Fangfang  XU Zongxue  HUANG Junxiong 《Acta Meteorologica Sinica》2007,21(2):204-214

On the basis of the mean air temperature, precipitation, sunshine duration, and pan evaporation from 23 meteorological stations in the upper Yellow River Basin from 1960 to 2001, the feasibility of using hypothesis test techniques to detect the long-term trend for major climate variables has been investigated. Parametric tests are limited by the assumptions such as the normality and constant variance of the error terms. Nonparametric tests have not these additional assumptions and are better adapted to the trend test for hydro-meteorological time series. The possible trends of annual and monthly climatic time series are detected by using a non-parametric method and the abrupt changes have been examined in terms of 5-yr moving averaged seasonal and annual series by using moving T-test (MTT) method, Yamamoto method, and Mann-Kendall method. The results show that the annual mean temperature has increased by 0.8℃in the upper Yellow River Basin during the past 42 years. The warmest center was located in the northern part of the basin. The nonlinear tendency for annual precipitation was negative during the same period. The declining center for annual precipitation was located in the eastern part and the center of the basin. The variation of annual precipitation in the upper Yellow River Basin during the past 42 years exhibited an increasing tendency from 1972 to 1989 and a decreasing tendency from 1990 to 2001. The nonlinear tendencies for annual sunshine duration and pan evaporation were also negative. They have decreased by 125.6 h and 161.3 mm during the past 42 years, respectively. The test for abrupt changes by using MTT method shows that an abrupt wanning occurred in the late 1980s. An abrupt change of the annual mean precipitation occurred in the middle 1980s and an abrupt change of the mean sunshine duration took place in the early 1980s. For the annual mean pan evaporation, two abrupt changes took place in the 1980s and the early 1990s. The test results of the Yamamoto method show that the abrupt changes mostly occurred in the 1980s, and two acute abrupt changes were tested for the spring pan evaporation in 1981 and for the annual mean temperature in 1985. According to the Mann-Kendall method, the abrupt changes of the temperature mainly occurred in the 1990s, the pan evaporation abrupt changes mostly occurred in the 1960s, and the abrupt changes of the sunshine duration primarily took place in the 1980s. Although the results obtained by using three methods are different, it is undoubted that jumps have indeed occurred in the last four decades.  相似文献   

Impacts of Coastal SST Variability on the East Asian Summer Monsoon   总被引：4，自引：0，他引：4  

黄安宁  张耀存  高新房 《大气科学进展》2007,24(2):259-270

The impacts of the seasonal and interannual SST variability in the East Asia coastal regions （EACRSST） on the East Asian summer monsoon （EASM） have been examined using a regional climate model （PδRCM9） in this paper. The simulation results show that the correlation between the EACRSST and the EASM is strengthened after the mid-1970s and also the variability of the EACRSST forcing becomes much more important to the EASM interannual variability after the mid-1970s. The impacts of the EACRSST on the summer precipitation over each sub-region in the EASM region become weak gradually from south to north, and the temporal evolution features of the summer precipitation differences over North and Northeast China agree well with those of the index of EASM （IEASM） differences.
The mechanism analyses show that different EACRSST forcings result in the differences of sensible and latent heat flux exchanges at the air-sea interface, which alter the heating rate of the atmosphere. The heating rate differences induce low level air temperature differences over East Asia, resulting in the differences of the land-sea thermal contrast （LSTC） which lead to 850 hPa geopotential height changes. When the 850 hPa geopotential height increases over the East Asian continent and decreases over the coast of East China and the adjacent oceans during the weakening period of weakens consequently. On the contrary, the EASM enhances during the strengthening period of the LSTC.  相似文献   

基于数字地价模型的地价监测点配置研究   总被引：1，自引：0，他引：1  

胡石元  李德仁  刘耀林 《武汉大学学报(信息科学版)》2007,32(9):838-841

从数字地价模型的建立、格网数字地价模型向TIN转化、TIN节点与宗地图层叠加拟合完成地价监测点的定位配置、结合市场比较法的监测点地价更新、TIN数字地价模型更新等几个方面详细阐述了数字地价模型运用于地价监测点配置的具体方法。并将这一配置模式与以标准宗地为载体的配置模式进行了比较分析。  相似文献   

Climatic change and human activities of northeastern sahara in Holocene   总被引：1，自引：0，他引：1  

张虎才 《中国地理科学(英文版)》1998,8(4):377-382

ＧｅｏｌｏｇｉｃａｌｒｅｃｏｒｄｓｒｅｖｅａｌｅｄｔｈａｔｔｈｅＨｏｌｏｃｅｎｅｅｎｖｉｒｏｎｍｅｎｔｓｈａｄｅｘｐｅｒｉｅｎｃｅｄｄｒａｓｔｉｃｃｈａｎｇｅｓ,ｗｈｉｃｈｗａｓｃｌｏｓｅｌｙｒｅｌａｔｅｄｔｏｈｕｍａｎｅｖｏｌｕｔｉｏｎａｎｄｆｉｎ...  相似文献   

Tropical Deforestation and Climate Change: What Does the Record Reveal?     

Karen L. O'Brien 《The Professional geographer》1998,50(1):140-153

Tropical deforestation is widely believed to directly influence the climate at a number of scales. Yet while much has been written about the tropical forest-climate relationship, there is little empirical evidence showing if and how local and regional climates are modified by deforestation. This study presents the results of an analysis of deforestation and climate change in a rain forest in southern Mexico. Records from 18 climate stations in the Selva Lacandona of Chiapas, Mexico were examined and related to an analysis of deforestation based on Landsat images. The area surrounding some stations has been deforested since the stations were established, while the area surroundings others has remained forested. Strong climatic trends were generally evident at the deforested stations, including decreases in the average daily maximum temperature and temperature range. No precipitation changes were observed. A comparison of the results with microclimatic experiments and modeling studies suggests that the climatic impacts of deforestation are overgeneralized at the local scale. Landscape heterogeneity appears to influence the biophysical mechanisms linking tropical forests and climate, and should be explicitly represented in modeling studies.  相似文献   

拉斯曼丘陵的短期气候特征   总被引：15，自引：5，他引：10       下载免费PDF全文

卞林根  薛正夫  逯昌贵  陆龙骅  贾朋群 《极地研究》1998,10(1):40-49

利用中山站１９８９年以来的气象资料,对拉斯曼丘陵的短期气候特征进行了初步分析。结果表明,拉斯曼丘陵的气候特点与东南极沿岸其它绿洲区相似,共同受大尺度气候过程的影响,同时还具有许多局地气候特征。  相似文献   

策勒绿洲与荒漠交错带达木沟剖面近4ka来干湿波动记录   总被引：13，自引：3，他引：10  

钟巍  熊黑钢 《中国沙漠》1998,18(3):205-209

位于塔克拉玛干沙漠南缘策勒绿洲与荒漠交错带的达木沟剖面高分辨率地记录了这一区域近４ｋａ来的环境演变历史。虽然,可以反映干湿波动的Ｒｂ／Ｓｒ比值曲线明显地反映了近４ｋａ来本地区持续干旱化的特征,且有后期加剧的趋势。但年代学及剖面沉积特征的研究还表明,在此期间仍有若干次相对湿润与干旱化加剧时期的波动。  相似文献   

城市空间结构演变的空间过程和动力因子分析   总被引：6，自引：0，他引：6  

王开泳  王淑婧  薛佩华 《云南地理环境研究》2004,16(4):65-69

城市空间结构是城市地理学、城市规划学的核心研究内容之一。城市空间结构的演变作为一个十分复杂的社会现象，一直受到各方面学者的关注。通过着重分析城市空间结构演变的主要空间过程：空间竞争、空间演替、空间扩散、空间均衡等，并对这些空间经济过程做出横向分析，讨论城市空间结构与城市经济运行之间的内在联系。分析城市空间结构演变的主要动力因子：包括完善的服务和基础设施、土地集约利用、城市产业的人口需求等集聚因子和环境承载力、级差地租、现代技术的发展等离散因子，从而论证集聚力和离心力的交互作用对城市空间结构演变产生深刻影响。  相似文献   

曲靖烤烟气候分析及产量年景趋势预测   总被引：2，自引：0，他引：2  

浦吉存  蓝光汉 《云南地理环境研究》2004,(Z1)

烤烟因其商品率高、经济效益高,是一种特殊的叶用经济作物,它以“适产优质”为栽培目标而区别于其它收果实作物,是曲靖市的支柱产业,地方财税的主要来源。利用烤烟产量、气候资料进行相关分析,探明气候要素在烤烟生育期内的变化对产量的形成和影响。其中3月平均最高气温、6月平均气温、6～8月积温、6～7月日照、5～9月干燥度、6～7月干燥度、夏季干旱等对产量形成呈正效应,3月降水量、6月降水量、盛夏洪涝呈负效应。利用关键时段气候要素变化对产量的影响进行判别分析预测烤烟年景趋势,此方法用于1997～2003年曲靖烤烟单产趋势预测,除1997年趋势预测错误外,其余6年全部预测正确。  相似文献