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风蚀起沙的影响因子及其变化特征 总被引：19，自引：4，他引：15
以敦煌地区的戈壁和绿洲为例,对地表土壤风蚀起沙的临界摩擦速度及其变化特征和风蚀起沙过程中地表土壤的粒子尺度分布及其对垂直尘粒通量的影响进行了分析研究。结果表明,地表土壤风蚀起沙的临界摩擦速度随土壤水分含量和植被覆盖度的增大而增大,随粒子尺度的变化是先减小后增大,在中间某一尺度处有一最小值;土壤的人工利用和管理对临界摩擦速度也有着相当大的影响,风蚀起沙过程中,地表土壤的粒子尺度分布随时间发生变化,瞬时的粒子尺度分布不同于平均的粒子尺度分布,利用前者计算得到的垂直尘粒通量对摩擦速度的变化更敏感,利用后者计算得到的垂直尘粒通量偏大。 相似文献
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全球变暖对甘肃省经济、社会和生态环境的影响及其对策 总被引：15，自引：7，他引：8
根据相关资料,分析了全球变暖的事实以及在全球变暖的大背景下对甘肃省生态环境和社会、经济的影响,并提出了应对气候变化、实现可持续发展的对策。这些对策对甘肃省而言,归纳起来主要是两个问题：一是用好水、管好水、节约用水,开发利用祁连山空中云水资源,实施人工增雨(雪);二是沙的问题。关键是遏制沙漠化进程,使用“区域气候—生态模式”,根据各地的地形、地貌、气候、水文、土壤等生态环境,定量计算各地林、草种植的品种、布局、走向、承载力,以提出恢复植被的最优方案。 相似文献
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三江源冻土、植被二者之间存在着强烈的相互作用的关系,并通过改变土壤水热特性以及地表-大气间的能量和水分交换过程影响局地气候,加快或减缓气候变化,源区的生态安全面临挑战。本文综述了近几十年来三江源区冻土、植被特征及变化趋势、冻土-植被相互作用过程以及冻土、植被变化的气候效应,在此基础上对未来研究方向进行了展望。主要认知如下：三江源地区是季节性冻土和多年冻土的交汇带。植被类型有高寒草甸、高寒草原、高寒荒漠等,植被生长季较短。近几十年来,在全球变化影响下,源区冻土和植被经历了快速的变化。冻土土壤温度明显升高;多年冻土面积减小而季节性冻土面积增加;多年冻土活动层厚度及融化期增加而季节性冻土最大冻结深度及冻结期减小。植被物候整体表现出返青期提前,黄枯期推迟,生长季延长的特征;同时高寒植被生态系统的结构和功能也发生了明显变化。土壤的水、热状态是连接冻土和植被相互作用的重要纽带。冻土的冻融状态,土壤的水、热过程对高寒植被的生长有着密切的影响;同时位于冻土上层的植被,又通过植被特征和生态系统的变化,影响土壤温度、湿度,反作用于冻土的形成和发展。冻土和高寒植被作为三江源两种典型的下垫面,在陆-气相互作用... 相似文献
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土壤-植被-大气系统水分散失机理的数值模拟 总被引：8，自引：0，他引：8
以Eeardorff(1978)提出的陆面参数化方案和Noilhan等人(1989)土壤水分参数化方案为基础,对陆面物理过程参数化方案进行了改进,在模式中较详细地考虑了植被和地面的各种物理参量如地面和叶面的反射率和发射率,净叶面面积指数,植被的物理阻抗等,并与大气边界层模式耦合。应用该模式模拟了沙漠及绿洲地区不同植被覆盖率情况下的蒸散量、土壤含水量和表面温度的日变化和连续变化特征;对不同植被覆盖率的热量平衡特征进行了比较。结果表明该模式较好地反映了地表蒸散3阶段的变化趋势特征,揭示出下垫面热量平衡分量间的相互转换过程。该模式可以用于中尺度的气象和区域气候模式,模拟和预测不同植被覆盖情况下近地层的热量输送和水分散失情况。 相似文献
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土壤-植被-大气系统水分能量传输模拟和验证 总被引：21，自引：0，他引：21
本文建立了包括地下水的土壤－植被－大气系统水分能量传输综合模型,并对模型中冠层动量湍流交换反梯度传输现象的描述进行了改进。在此基础上,依据冠层内动量和热量的交换以及辐射传输过程,同时求解地表、冠层能量平衡方程,进而模拟饱和－非饱和土壤的水热传输。用浅地下水地区冬小麦田间试验资料对模型进行验证,结果表明,系统能量平衡各分量和土壤含水量的模拟与观测结果相当一致。模型敏感性分析发现,叶面积指数对总蒸散量的影响随叶面积指数的增加而逐渐减弱;叶片最小气孔阻力对总蒸散量的影响,在该阻力较小时更显著;地下水位对蒸散量的影响在它小于１．５ｍ时不显著,而在１．５～１．７５ｍ之间时,蒸散减小较快,主要由于土壤蒸发减小显著,冠层蒸腾稍有增加。 相似文献
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采用生物-大气传输模式（BATS模型）模拟了淮河流域山丘区和平原区在1998年汛期的暴雨洪水过程,从陆地-大气间水量交换的角度揭示了径流量、土壤含水量、土壤质地、植被分布的内在联系。结果表明：对于山丘区和平原区而言,根系层土壤含水量、土壤质地以及土壤颜色的变化对径流量的影响具有相似性,但是敏感性不同;而山丘区和平原区深层土壤含水量和植被覆盖率变化对径流量影响的作用正好相反。这些结果显示,由于山丘区与平原区的不同气候和下垫面条件,而造成两者水文性质的差异性,反映了大气-水文之间关系与作用的不同特征。 相似文献
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The few systematic international comparisons of climate policy strength made so far have serious weaknesses, particularly those that assign arbitrary weightings to different policy instrument types in order to calculate an aggregate score for policy strength. This article avoids these problems by ranking the six biggest emitters by far – China, the US, the EU, India, Russia, and Japan – on a set of six key policy instruments that are individually potent and together representative of climate policy as a whole: carbon taxes, emissions trading, feed-in tariffs, renewable energy quotas, fossil fuel power plant bans, and vehicle emissions standards. The results cast strong doubt on any idea that there is a clear hierarchy on climate policy with Europe at the top: the EU does lead on a number of policies but so does Japan. China, the US, and India each lead on one area. Russia is inactive on all fronts. At the same time climate policy everywhere remains weak compared to what it could be.
Policy relevance
This study enables climate policy strength, defined as the extent to which the statutory provisions of climate policies are likely to restrict GHG emissions if implemented as intended, to be assessed and compared more realistically across space and time. As such its availability for the six biggest emitters, which together account for over 70% of global CO2 emissions, should facilitate international negotiations (1) by giving participants a better idea of where major emitters stand relative to each other as far as climate policy stringency is concerned, and (2) by identifying areas of weakness that need action. 相似文献
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Stephen F. Wathen 《Climatic change》2011,108(1-2):333-356
This paper provides both a detailed history of environmental change in the Sierra Nevada over the past 1,800 years and evidence for climate teleconnections between the Sierra Nevada and Greenland during the late Holocene. A review of Greenland ice core data suggests that the magnitudes of abrupt changes in temperature and precipitation increased beginning c. 3,700 and 3,000 years ago, respectively. Precipitation increased abruptly 1,300 years ago. Comparing paleotemperature data from Cirque Peak, CA with paleoprecipitation data from Pyramid Lake, NV suggests that hot temperatures occurred at the beginnings of most severe droughts in the Sierra Nevada over the past 1,800 years. Severe fires and erosion also occurred at Coburn Lake, CA at the beginning of all severe droughts in the Sierra Nevada over the past 1,800 years. This suggests that abrupt climate change during the late Holocene caused vegetation and mountain slopes in some areas to be out of equilibrium with abruptly changed climates. Finally, the ending of drought conditions in Greenland coincided with the beginning of drought conditions in the Sierra Nevada over the past 1,800 years, perhaps as a result of the rapidly changed locations of the Earth??s major precipitation belts during abrupt climate change events. 相似文献
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Anthony H. McDaniel Chris A. Cantrell James A. Davidson Richard E. Shetter Jack G. Calvert 《Journal of Atmospheric Chemistry》1991,12(3):211-227
The infrared absorption cross-sections for eight commonly used halogenated methanes and ethanes have been measured as a function of temperature from 203 to 293 K. High resolution spectra (0.03 cm-1) have been used to derive integrated band strengths and peak cross-sections associated with the spectral features in the infrared region from 600 to 1500 cm-2. The values obtained in this study are compared to those from previous reports, and recommendations are made for uses in atmospheric sensing and radiative energy transfer models. The observed temperature dependence in the spectral features is also discussed. 相似文献
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Wind-driven, double-gyre, ocean circulation in a reduced-gravity, 2.5-layer, lattice boltzmann model
A coupled lattice Boltzmann （LB） model with second-order accuracy is applied to the reduced-gravity, shallow water, 2.5-layer model for wind-driven double-gyre ocean circulation. By introducing the secondorder integral approximation for the collision operator, the model becomes fully explicit. The Coriolis force and other external forces are included in the model with second-order accuracy, which is consistent with the discretization accuracy of the LB equation. The feature of the multiple equilibria solutions is found in the numerical experiments under different Reynolds numbers based on this LB scheme. With the Reynolds number increasing from 3000 to 4000, the solution of this model is destabilized from the anti-symmetric double-gyre solution to the subtropic gyre solution and then to the subpolar gyre solution. The transitions between these equilibria states are also found in some parameter ranges. The time-dependent variability of the circulation based on this LB simulation is also discussed for varying viscosity regimes. The flow of this model exhibits oscillations with different timescales varying from subannual to interannual. The corresponding statistical oscillation modes are obtained by spectral analysis. By analyzing the spatiotemporal structures of these modes, it is found that the subannual oscillation with a 9-month period originates from the barotropic Rossby basin mode, and the interarmual oscillations with periods ranging from 1.5 years to 4.6 years originate from the recirculation gyre modes, which include the barotropic and the baroclinic recirculation gyre modes. 相似文献
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B. Kochtubajda 《Atmospheric Research》1995,35(2-4)
Physical experiments designed to explore the potential of rain augmentation through airborne glaciogenic seeding on small, isolated non-precipitating cumuliform clouds near Red Deer, Alberta were carried out during the period 1982–1985. The microstructure of 90 cumulus congestus clouds have been documented through repeated in-situ sampling using a cloud physics instrumented aircraft platform. Observations from the inspection passes of 57 clouds seeded with either dry ice pellets or silver iodide pyrotechnics, and all the passes of 33 natural clouds are presented.Measurements of the cloud droplet concentration indicate that Alberta cumulus clouds are typically continental in nature, with an average droplet concentration of 535 cm−3 and an average droplet diameter of 10.6 μm. Alberta clouds have average liquid water contents of 0.57 g m−3, with a peak 1-sec value of 3.17 g m−3. The 1-km average liquid water contents are 0.83 g m−3, with a peak value of 2.81 g m−3. Cloud lifetimes vary between 11 and 20 minutes. Concentrations of naturally occurring ice crystals are found to be low. The average maximum 1-km ice concentration was 31−1, and the peak 1-km concentration was 73.11−1 in the natural cloud dataset. Evidence of precipitation-sized particles was detected in 21% (7 of 33) of the clouds, and precipitation below cloud base was detected in 6% (2 of 33) of the clouds.A comparison of the Alberta cloud characteristics to the cumulus clouds from different locations showed that there are some distinct differences between Alberta clouds and the clouds from the other regions. 相似文献
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利用常规观测资料和NCEP/NCAR(1°×1°)逐6 h再分析资料,对承德市2017年5月5—6日大风天气的环流形势和物理量进行分析,结果表明气旋的快速发展(气旋加深率0.84 B)导致锋生加强,引发气压和变压梯度加大是导致大风的直接原因。500 hPa高压脊东移迫使冷空气向南堆积,高空槽不断发展成为冷涡,温度平流为地面气旋的发展提供热力条件,高低层涡度平流的差异,也是地面气旋快速发展的重要原因;当1.5 PVU位涡面伸展至对流层低层时,局地位涡异常在气旋的发展过程中不可忽视;高空急流出口区发生质量调整,出口区左侧的辐散强度达10×10~(-5) s~(-1),使低层大气减压,有利于气旋发展。 相似文献
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Governance,complexity, and resilience 总被引：1，自引：0，他引：1
Andreas Duit Victor Galaz Katarina Eckerberg Jonas Ebbesson 《Global Environmental Change》2010,20(3):363-368
This special issue brings together prominent scholars to explore novel multilevel governance challenges posed by the behavior of dynamic and complex social-ecological systems. Here we expand and investigate the emerging notion of “resilience” as a perspective for understanding how societies can cope with, and develop from, disturbances and change. As the contributions to the special issue illustrate, resilience thinking in its current form contains substantial normative and conceptual difficulties for the analysis of social systems. However, a resilience approach to governance issues also shows a great deal of promise as it enables a more refined understanding of the dynamics of rapid, interlinked and multiscale change. This potential should not be underestimated as institutions and decision-makers try to deal with converging trends of global interconnectedness and increasing pressure on social-ecological systems. 相似文献
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利用气象业务中使用的L波段探空数据和毫米波云雷达观测资料,分析探空相对湿度在入云和出云时的变化规律,提出一种基于探空相对湿度阈值与梯度相结合的云区边界识别改进算法,并利用云雷达观测数据对算法识别结果进行验证.利用北京市南郊观象台2019年1—6月层状云样本验证分析,结果表明:改进算法相比相对湿度阈值法,对云区边界识别更... 相似文献
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利用常规观测资料和NCEP 1°×1°再分析资料,通过对发生在江苏的三次不同量级的区域性暴雪、大雪和中雪过程典型个例进行对比分析,发现降雪时,700hPa低空急流的位置和强度是影响降雪量级的主要因素之一;降雪区上空涡度的垂直分布遵循低层负涡度、中层正涡度和高层负涡度的配置,暴雪时正涡度强且正涡度区最为深厚,动力抬升作用强,中雪发生时正涡度区相对最为浅薄,不利于形成强辐合抬升,动力抬升作用弱。且暴雪和大雪发生时基本上整层都为垂直螺旋度正值区,中雪时没有出现明显的正值区;暴雪和大雪过程时中低层都具有明显的逆温层,中高层西南急流造成的对流层中层的爆发性增温是逆温层形成的关键,中雪发生时不一定有逆温层结;降雪强度与湿位涡分量绝对值存在一定的正相关关系。 相似文献
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D.T. Patterson J.K. Westbrook R.J.V. Joyce† P.D. Lingren J. Rogasik 《Climatic change》1999,43(4):711-727
The geographic distribution, vigor, virulence, and agricultural impact of weeds, insects, and plant pathogens will be affected by climatic changes accompanying the global "greenhouse effect." Weed/crop competitive interactions, particularly among species differing in photosynthetic pathway (C3 v C4), may be altered, with the C3 species favored by increasing CO2. Physiological and biochemical changes induced in host crop plants by rising CO2 may affect feeding patterns of pest insects. Compilation of climatic thresholds for phenological development of pest insects reveals the potential for shifts in pest behavior induced by global warming and other climatic change. Generation times may be reduced, enabling more rapid population increases to occur. Poleward migration may be accelerated during the crop season. The epidemiology of plant diseases also will be altered. Prediction of disease outbreaks will be more difficult in periods of rapidly changing climate and unstable weather. Environmental instability and increased incidence of extreme weather may reduce the effectiveness of pesticides on targeted pests or result in more injury to non-target organisms. Biological control may be affected either negatively or positively. Overall, the challenge to agriculture from pests probably will increase. 相似文献