流域生态水文模型研究进展   总被引：3，自引：1，他引：2  

陈腊娇  朱阿兴  秦承志  李润奎  刘京  刘军志 《地理科学进展》2011,30(5):535-544

流域生态水文模型是全球变化下流域生态水文响应研究的重要工具,通过定量刻画植被与水文过程的相互作用及全球变化对流域生态水文过程演变的影响机制,为流域水资源管理和生态恢复提供科学支撑,是生态水文研究的前沿和热点.基于植被与水文过程相互作用规律,流域生态水文模型一方面要充分描述植被与水文过程相互作用和互为反馈机制,另一方面要...  相似文献   

近30年中国极地气象科学研究进展   总被引：1，自引：0，他引：1       下载免费PDF全文

陆龙骅  卞林根 《极地研究》2011,23(1):1-10

南极和北极是地球上的气候敏感地区,也是研究全球变化的关键区域.中国的南极和北极实地科学考察研究,分别始于20世纪80年代和90年代.作为国家行为,到2010年底,已经组织了27次南极考察、4次北极北冰洋考察和7次北极陆地考察;在南北极建立了4个科学考察站、5个(中澳/中美)合作自动气象站;初步形成了以有人考察站、无人自...  相似文献   

From Soda Bottles To Super Labs: An Analysis Of North America's Dual Methamphetamine Production Networks          下载免费PDF全文

Aaron H. Gilbreath 《Geographical review》2015,105(4):511-527

This article uses the global production network perspective to analyze the various actors involved in the production and distribution of methamphetamine in North America. The paper analyzes the organization and operation of the two dominant network typologies at work in the United States: small toxic labs and Mexican drug‐trafficking organizations. Particular emphasis is placed on how the networks have adapted to changes in the regulatory context in which they operate. I conclude with potential policy recommendations for curtailing methamphetamine production within both networks.  相似文献   

Global cities,cosmopolitanism, and geographies of tolerance     

Barney Warf 《Urban geography》2015,36(6):927-946

Scholarly attention devoted to global cities has emphasized their economic and political significance. Yet global cities are also deeply cultural and ideological in nature. Contrary to a long tradition of urban studies that views urban life as inherently alienating, this essay argues that the social and cultural diversity of global cities renders them mechanisms for the generation of tolerance and empathy. It opens with a brief review of global cities. Second, it traces the contours of cosmopolitanism as an ideology that fosters respect for social and cultural differences and a wider community of caring. Third, it reviews the empirical evidence of American global cities to make the case that their diversity leads them to generate a progressive cosmopolitan ethnics. It draws on the literature of social psychology, the work of Richard Florida, and indices of immigration, religious and linguistic diversity, homophobia, and voting patterns to substantiate the claim that cosmopolitan values are most evident and deeply rooted in globalized metropolitan centers.  相似文献   

气候变暖情景下黄河上游径流的可能变化   总被引：15，自引：3，他引：12  

蓝永超  丁永建  朱云通  马建华  魏智 《冰川冻土》2004,26(6):668-673

根据水文气象台站观测资料, 分析了全球变暖情景下黄河上游唐乃亥以上流域温度、降水和径流的变化状况, 并采用假定气候组合对未来数十年黄河上游唐乃亥以上流域的径流变化进行了预测. 结果表明: 黄河上游的温度与全球变暖有着明显的对应关系, 近几十年来, 流域各个地方的温度有不同程度的上升. 降水变化因流域各地所处位置、地势、地形的不同而差异较大, 受温度上升和主要产流区域降水大幅减少的影响, 近10余年来黄河上游的径流量呈持续递减的态势. 在未来几十年, 如果遭遇到气温升幅与降水减幅较大的"暖-干"气候组合时, 流域产水量将有较大的减幅; 当气温变化不大而降水增幅较大时, 流域产水量将有明显的增加, 同时由于冰雪及冻土融水的补给, 此气候情景下黄河上游唐乃亥以上流域径流量的增幅还将略大于降水量的增幅.  相似文献   

Poleward expansion of the hadley circulation in CMIP5 simulations   总被引：1，自引：0，他引：1  

胡永云  陶利军  刘骥平 《大气科学进展》2013,30(3):790-795

Observational analyses have demonstrated that the Hadley circulation has expanded poleward in recent decades. Important issues are what caused the widening of the Hadley circulation and whether the observed widening is related to anthropogenic forcing. In the present study, we use currently available simulations of the Coupled Model Intercomparison Project Phase-5 (CMIP5) to analyze changes in the width of the Hadley circulation. It is found that CMIP5 historical simulations with greenhouse gas (GHG) forcing generate a total widening of ～0.15o0.06o in latitude (10 yr)-1 for the period 1979--2005, and the widening in CMIP5 historical simulations with all forcings is ～0.17o0.06o per decade. Similar to that in CMIP3, the simulated poleward expansion in CMIP5 is much weaker than the observational reanalyses. In CMIP5 projection simulations for the 21st century, magnitudes of widening of the Hadley circulation increase with radiative forcing. For the extreme projected radiative forcing of RCP8.5, the total annual-mean widening of the Hadley circulation is ～0.27o0.04o(10 yr)-1 in the 21st century. Although CMIP5 underestimates observed poleward expansion of the Hadley circulation, the results of this study suggest that the observed trends in the width of the Hadley circulation are caused by anthropogenic forcing and that increasing GHGs play an important role in the observed poleward expansion of the Hadley circulation, in addition to other forcings emphasized in previous studies.  相似文献   

C‐band SAR backscatter characteristics of Arctic sea and land ice during winter     

Konrad Steffen  John Heinrichs 《大气与海洋》2013,51(3):289-299

Abstract

Synthetic Aperture Radar (SAR) data has become an important tool for studies of polar regions, due to high spatial resolution even during the polar night and under cloudy skies. We have studied the temporal variation of sea and land ice backscatter of twenty‐four SAR images from the European Remote Sensing satellite (ERS‐1) covering an area in Lady Ann Strait and Jones Sound, Nunavut, from January to March 1992. The presence of fast ice in Jones Sound and glaciers and ice caps on the surrounding islands provides an ideal setting for temporal backscatter studies of ice surfaces. Sample regions for eight different ice types were selected and the temporal backscatter variation was studied. The observed backscatter values for each ice type characterize the radar signatures of the ice surfaces. This time series of twenty‐four SAR images over a 3‐month period provides new insights into the degree of temporal variability of each surface. Ice caps exhibit the highest backscatter value of ‐3.9 dB with high temporal variability. Valley glacier ice backscatter values decrease with decreasing altitude, and are temporally the most stable, with standard deviations of 0.08–0.10 dB over the 90‐day period.

First‐year ice and lead ice show a negative trend in backscatter values in time and a positive correlation of up to 0.59 with air temperature over the 90‐day period. For first‐year ice and lead ice, episodes of large temperature fluctuations (±12°C) are associated with rapid changes in backscatter values (±2 dB). We attribute the backscatter increase to a temperature‐induced increase in brine volume at the base of the snow pack. Multi‐year ice, conglomerate ice and shore ice are relatively stable over the 3‐month period, with a backscatter variation of only a few dBs. An observed lag time of up to three days between backscatter increase/decrease and air temperature can be attributed to the insulation effect of the snow cover over sea ice. The net range of the backscatter values observed on the most temporally stable surface, valley glacier ice, of about 0.30 dB indicates that the ERS‐1 SAR instrument exceeds the 1 dB calibration accuracy specified for the Alaska SAR Facility processor for the three winter months.  相似文献   

Influence of Changes in Solar Radiation on Changes of Surface Temperature in China          下载免费PDF全文

ZHANG Hu  YIN Qing  Teruyuki NAKAJIMA  Nakata Mukai MAKIKO  LU Peng  HE Jinhai 《Acta Meteorologica Sinica》2013,27(1):87-97

The long-term trends of total surface solar radiation(SSR),surface diffuse radiation,and surface air temperature were analyzed in this study based on updated 48-yr data from 55 observational stations in China,and then the correlation between SSR and the diurnal temperature range(DTR) was studied.The effect of total solar radiation on surface air temperature in China was investigated on the basis of the above analyses.A strong correlation between SSR and DTR was found for the period 1961-2008 in China.The highest correlation and steepest regression line slope occurred in winter,indicating that the solar radiation effect on DTR was the largest in this season.Clouds and water vapor have strong influences on both SSR and DTR,and hence on their relationship.The largest correlations between SSR and DTR occurred in wintertime in northern China,regardless of all-day(including clear days and cloudy days) or clear-day cases.Our results also showed that radiation arriving at the surface in China decreased significantly during 1961-1989(dimming period),but began to increase during 1990-2008(brightening period),in agreement with previous global studies.The reduction of total SSR offset partially the greenhouse warming during 1961-1989.However,with the increase of SSR after 1990,this offsetting effect vanished;on the contrary,it even made a contribution to the accelerated warming.Nonetheless,the greenhouse warming still played a controlling role because of the increasing of minimum and mean surface temperatures in the whole study period of 1961-2008.We estimated that the greenhouse gases alone may have caused surface temperatures to rise by 0.31-0.46℃(10 yr) 1 during 1961-2008,which is higher than previously estimated.Analysis of the corresponding changes in total solar radiation,diffuse radiation,and total cloud cover indicated that the dimming and brightening phenomena in China were likely attributable to increases in absorptive and scattering aerosols in the atmosphere,respectively.  相似文献   

Intensified Eastward and Northward Propagation of Tropical Intraseasonal Oscillation over the Equatorial Indian Ocean in a Global Warming Scenario     

YANG Jing  BAO Qing  WANG Xiaocong 《大气科学进展》2013,30(1):167-174

Northward propagation in summer and eastward propagation in winter are two distinguished features of tropical intraseasonal oscillation(TISO) over the equatorial Indian Ocean.According to numerical modeling results,under a global warming scenario,both propagations were intensified.The enhanced northward propagation in summer can be attributed to the enhanced atmosphere-ocean interaction and the strengthened mean southerly wind;and the intensified eastward propagation in winter is associated with the enhanced convection-wind coupling process and the strengthened equatorial Kevin wave.Future changes of TISO propagations need to be explored in more climate models.  相似文献   

Intraseasonal Oscillation in Global Ocean Temperature Inferred from Argo     

HU Ruijin  WEI Meng 《大气科学进展》2013,30(1):29-40

The intraseasonal oscillation(ISO;14-97-day periods) of temperature in the upper 2000 m of the global ocean was studied based on Argo observations from 2003-2008.It is shown that near the surface the ISO existed mainly in a band east of 60 E,between 10 S and 10 N,and the region around the Antarctic Circumpolar Current(ACC).At other levels analyzed,the ISOs also existed in the regions of the Kuroshio,the Gulf Stream,the Indonesian throughflow,the Somalia current,and the subtropical countercurrent(STCC) of the North Pacific.The intraseasonal signals can be seen even at depths of about 2000 m in some regions of the global ocean.The largest amplitude of ISO appeared at the thermocline of the equatorial Pacific,Atlantic and Indian Ocean,with maximum standard deviation(STD) exceeding 1.2 C.The ACC,the Kuroshio,and the Gulf Stream regions all exhibited large STD for all levels analyzed.Especially at 1000 m,the largest STD appeared in the south and southeast of South Africa-a part of the ACC,with a maximum value that reached 0.5 C.The ratios of the intraseasonal temperature variance to the total variance at 1000 m and at the equator indicated that,in a considerable part of the global deep ocean,the ISO was dominant in the variations of temperature,since such a ratio exceeded even 50% there.A case study also confirmed the existence of the ISO in the deep ocean.These results provide useful information for the design of field observations in the global ocean.Analysis and discussion are also given for the mechanism of the ISO.  相似文献