共查询到17条相似文献，搜索用时 140 毫秒
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黄土高原陆面水分的凝结现象及收支特征试验研究 总被引：7，自引：2，他引：5
中国黄土高原是全球独特的地理区域,其陆面水分过程比较特殊。利用黄土高原陆面过程试验研究(LOPEX)的陇中黄土高原定西陆面过程综合观测站的资料,分析了陆面水分凝结现象及其出现频率与局地微气象条件的关系,研究了露水(霜)量及其出现频率的季节分布特征以及受降水和天气阴、晴的影响规律。同时,对比分析了降水、露水、雾水和土壤吸附水对陆面水分的贡献率,讨论了涡动相关法、蒸渗计和蒸发皿观测的陆面蒸发量的差别及其与陆面水分来源的年平衡关系,给出了半干旱区陆面水分平衡的日循环特征。发现露水对风速、大气湿度、近地层温度梯度的依赖很强,一般在风速为1.5 m/s、相对湿度大于80%和逆温强度为0.25℃的情况下露水(霜)量最大;刚降水后的晴天露水量比较大;实际蒸散量与蒸发力的差距十分明显,陆面水分平衡特征表现为一个"呼吸"过程。 相似文献
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霍文 《沙漠与绿洲气象(新疆气象)》2016,10(5):87-96
陆面过程是影响大气环流和气候变化的基本物理、生化过程之一。沙漠陆面过程及相应的小气候效应已经成为当前沙漠气象研究的热门问题。近年来,在沙漠陆面过程野外观测、陆面过程特征及参数化、陆面过程模拟、小气候及陆面过程对小气候影响等方面已取得重大进展。本文对于沙漠小气候、沙漠陆面过程及沙漠陆面过程参数化进行了简要概述,重点总结了国内外在沙漠地区气候考察、沙漠边界层高度、沙漠热力环流、绿洲效应、塔克拉玛干沙漠气候特征、沙漠陆面过程野外观测试验及结果、沙漠陆面过程对气候的影响、沙漠陆面过程参数化方案方面的成果,回顾了近年来利用地面观测设备和数值模式等对气候效应和陆面过程直接观测和数值模拟所获得的观测事实和模拟试验,并讨论了其陆面过程参数化对模拟的影响,在总结前人研究成果的基础上对未来的研究方向进行了讨论。 相似文献
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干旱区天气、气候数值模拟的研究进展 总被引：5，自引：0，他引：5
干旱区的气候模拟有着很强特殊性。气候模式是研究和探讨干旱区形成物理机制的有效手段和工具。介绍了近年来国内外干旱气候数值模拟和试验的研究与进展．总结和评述了陆面过程中地表反照率、土壤湿度、植被状况的参数化和对气候的影响．讨论和阐述陆面过程在气候模拟中的重要性。对干旱区的气候和天气灾害的数值模式模拟研究作了一些评述，并对干旱区数值模拟的有关问题进行了讨论和展望。指出干旱区陆面过程的深入研究和干旱区陆面参数的标定，是改进干旱区气候模拟的重要途径。 相似文献
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利用ERA-Interim再分析资料作为边界条件,基于耦合陆面模式Noah-MP的区域气候模式WRF在东亚区域进行了动力降尺度模拟(简称WRF2),对比格点观测资料,评估了动力降尺度对青藏高原极端气温指数的模拟能力,在此控制试验基础上,分别将WRF的陆面模式替换为Noah LSM,边界条件替换为CCSM4,进行了两组敏感性试验(分别是WRF1和WRF3),通过与控制试验的比较,分析了边界条件和陆面模式对极端气温指数模拟的影响。结果表明,WRF2能较好地模拟青藏高原极端气温指数气候态的空间分布,但存在一定的冷偏差;受边界条件影响WRF3模拟的极端气温指数的气候倾向率存在负偏差。同时,尽管采用不同的边界条件,耦合相同陆面过程的两次数值试验对极端气温空间分布的模拟能力相似,相比WRF2,WRF1表现出更强的冷偏差;但边界条件对极端气温指数气候倾向率的影响大于陆面模式,WRF3模拟的极端气温指数气候倾向率与观测结果更为接近。 相似文献
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《高原气象》2016,(3)
利用ERA-Interim再分析资料作为边界条件,基于耦合陆面模式Noah-MP的区域气候模式WRF在东亚区域进行了动力降尺度模拟(简称WRF2),对比格点观测资料,评估了动力降尺度对青藏高原极端气温指数的模拟能力,在此控制试验基础上,分别将WRF的陆面模式替换为Noah LSM,边界条件替换为CCSM4,进行了两组敏感性试验(分别是WRF1和WRF3),通过与控制试验的比较,分析了边界条件和陆面模式对极端气温指数模拟的影响。结果表明,WRF2能较好地模拟青藏高原极端气温指数气候态的空间分布,但存在一定的冷偏差;受边界条件影响WRF3模拟的极端气温指数的气候倾向率存在负偏差。同时,尽管采用不同的边界条件,耦合相同陆面过程的两次数值试验对极端气温空间分布的模拟能力相似,相比WRF2,WRF1表现出更强的冷偏差;但边界条件对极端气温指数气候倾向率的影响大于陆面模式,WRF3模拟的极端气温指数气候倾向率与观测结果更为接近。 相似文献
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陇中黄土高原陆面辐射分量年际变化及其对气候波动的响应 总被引：1，自引：1，他引：0
本文利用兰州大学半干旱气候与环境观测站(SACOL站)2006—2012年陆面过程观测资料以及榆中站气象资料,分析了陆面各辐射收支分量对于气候波动的响应,并且研究了地表反照率年际波动变化,讨论了各陆面过程参数对于黄土高原气候背景年际波动的反馈。并且根据黄土高原降水类型将全年分为冬夏半年讨论,以得到更为显著的年际变化特征和相关关系。结果显示,2006—2012年气温降水的趋势与近年来黄土高原暖干化总趋势相吻合。地表浅层土壤湿度和温度都与气温、降水呈现很好的响应。气候因素的综合影响是地表反照率变化波动的原因。通过冬夏半年资料区分探究得到,长波辐射分量与气候要素的相关较短波辐射分量与气候要素的相关性更强。但总体而言,陆面过程对于该地区气候背景波动的响应机制是较为复杂的。 相似文献
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Urban and rural dewfall,surface moisture,and associated canopy-level air temperature and humidity measurements for vancouver,canada 总被引：1，自引：0，他引：1
Canopy-level humidity is often less at night during fine weather in a mid-latitude city, compared to its rural surroundings. This feature has been attributed, in part, to reduced urban dew, but links are largely unproven, because urban dew data are rare. In this study, surface moisture (i.e., dew + guttation by blotting) and dewfall (by mini-lysimeter) were measured at rural and urban residential sites in Vancouver, Canada, during the summer of 1996. Air temperature and humidity were measured at both sites, and on rural-to-urban vehicle traverses. Weather and location effects were evident. Humidity data suggested the small (< 1 g m–3) urban moisture excess observed on fine nights was linked to reduced urban dew. For grass, the frequency of moisture events, and surface moisture amounts, were similar for both sites. However, on grass, rural dewfall (mean=0.10 mm per night) was more than urban dewfall (mean=0.07 mm per night). On the other hand, data for a roof lysimeter (mean dewfall=0.12 mm per night) showed that an urban roof could rival rural grass as a favoured location for dewfall in Vancouver. 相似文献
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Effects of global irrigation on the near-surface climate 总被引：3，自引：0，他引：3
William J. Sacks Benjamin I. Cook Nikolaus Buenning Samuel Levis Joseph H. Helkowski 《Climate Dynamics》2009,33(2-3):159-175
Irrigation delivers about 2,600 km3 of water to the land surface each year, or about 2% of annual precipitation over land. We investigated how this redistribution of water affects the global climate, focusing on its effects on near-surface temperatures. Using the Community Atmosphere Model (CAM) coupled to the Community Land Model (CLM), we compared global simulations with and without irrigation. To approximate actual irrigation amounts and locations as closely as possible, we used national-level census data of agricultural water withdrawals, disaggregated with maps of croplands, areas equipped for irrigation, and climatic water deficits. We further investigated the sensitivity of our results to the timing and spatial extent of irrigation. We found that irrigation alters climate significantly in some regions, but has a negligible effect on global-average near-surface temperatures. Irrigation cooled the northern mid-latitudes; the central and southeast United States, portions of southeast China and portions of southern and southeast Asia cooled by ~0.5 K averaged over the year. Much of northern Canada, on the other hand, warmed by ~1 K. The cooling effect of irrigation seemed to be dominated by indirect effects like an increase in cloud cover, rather than by direct evaporative cooling. The regional effects of irrigation were as large as those seen in previous studies of land cover change, showing that changes in land management can be as important as changes in land cover in terms of their climatic effects. Our results were sensitive to the area of irrigation, but were insensitive to the details of irrigation timing and delivery. 相似文献
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On the contribution of atmospheric moisture to dew formation 总被引：4，自引：0，他引：4
The relative contributions of dewfall (a flux of water vapour from air to surface) and distillation (a flux of water vapour from soil to canopy) to dew formation on closed canopy and bare soil surfaces are assessed, and the dependence of dew amount upon wind speed, absolute temperature, atmospheric stability, relative humidity, soil characteristics and cloudiness, all of which are significant factors, is evaluated. Some of these evaluations provide refinements to similar ones given in Monteith (1961). High dewfall rates are usually 0.06 mm hr–1 over canopy or bare soil, though upon a canopy under soil-saturated and air-saturated conditions, rates of dew formation may reach 0.07–0.09 mm hr–1 with contributions from distillation. Various sets of observations are reanalyzed to illustrate the importance of the horizontal advection of moisture in the nocturnal boundary layer (NBL) to observed high rates of dew formation arising from the atmospheric contribution of water vapour (dewfall). These locally observed high dewfall rates must be the result of small-scale or mesoscale horizontal advection of moisture in the NBL, since the humidity changes within the typically shallow NBL required to balance the loss of water at the surface are not observed. Over extensive areas of uniform surface (horizontal scales 10 km), such continuously high dewfall rates could only be balanced by a local supply of atmospheric moisture since advection of moisture would necessarily be small. 相似文献
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Roy Darwin 《Climatic change》1999,41(3-4):371-411
During the past few years two new methods, each based on the analogous region concept, have been developed to account for farmer adaptation in response to global climatic change. The first, called 'Ricardian' by Mendelsohn, Nordhaus, and Shaw (1994), econometrically estimates the impact of climatic and other variables on the value of farm real estate. Under some conditions, estimates of climate-induced changes in farm real estate capture first-round adaptations by farmers and represent the economic value of climatic change on agriculture. The second method, promulgated by Darwin et al. (1994) in the Future Agricultural Resources Model (FARM), uses a geographic information system to empirically link climatically derived land classes with other inputs and agricultural outputs in an economic model of the world. FARM provides estimates of economic impacts that fully account for all responses by economic agents under global climate change as well as estimates of Ricardian rents. The primary objective of this analysis is to evaluate how well changes in Ricardian rents measure agricultural or other effects of climatic change after all economic agents around the world have responded. Results indicate that changes in Ricardian rents on agricultural land are poor quantitative, but good qualitative, measures of how global climatic change is likely to affect the welfare of agricultural landowners, if one recognizes that increases in Ricardian rents actually indicate losses in landowner welfare and vice versa. Results also indicate that regional changes in Ricardian rents on all land are good qualitative measures of changes in regional welfare. They are poor quantitative welfare measures because they systematically overestimate both benefits and losses and are on average upwardly biased because inflated benefits are larger than exaggerated losses. Results also indicate that, when based on existing land-use patterns, changes in Ricardian rents on all the world's land are poor quantitative and qualitative measures of changes in world welfare. Despite these shortcomings, changes in Ricardian rents can provide useful information when other measures are not available. In this analysis, for example, estimated changes in Ricardian rents on all land indicate that climatic change would likely have detrimental effects in Latin America and Africa, beneficial effects in the former Soviet Union, and either detrimental or beneficial impacts in eastern and northern Europe and western and southern Asia. This is consistent with previous studies showing that climatic change would likely have detrimental, beneficial, and mixed effects on economic welfare in, respectively, equatorial, high latitude, and temperate areas. Estimated changes in Ricardian rents also indicate that aggregating Africa, Latin America, the former Soviet Union, eastern and northern Europe, and western and southern Asia into one region causes FARM's economic model to generate upwardly biased changes in world welfare. Modified results from scenarios with moderately flexible land-use change and which account for current land-use patterns indicate that world welfare may increase if the average surface land temperature does not increase by more than 1.0 or 2.0°C. If the average surface land temperature increases by 3.0°C or more, however, then world welfare may decline. 相似文献
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Climatic responses to anthropogenic groundwater exploitation: a case study of the Haihe River Basin,Northern China 总被引：5，自引：0，他引：5
In this study, a groundwater exploitation scheme is incorporated into the regional climate model, RegCM4, and the climatic responses to anthropogenic alteration of groundwater are then investigated over the Haihe River Basin in Northern China where groundwater resources are overexploited. The scheme models anthropogenic groundwater exploitation and water consumption, which are further divided into agricultural irrigation, industrial use and domestic use. Four 30-year on-line exploitation simulations and one control test without exploitation are conducted using the developed model with different water demands estimated from relevant socioeconomic data. The results reveal that the groundwater exploitation and water consumption cause increasing wetting and cooling effects on the local land surface and in the lower troposphere, along with a rapidly declining groundwater table in the basin. The cooling and wetting effects also extended outside the basin, especially in the regions downwind of the prevailing westerly wind, where increased precipitation occurs. The changes in the four exploitation simulations positively relate to their different water demands and are highly non-linear. The largest changes in climatic variables usually appear in spring and summer, the time of crop growth. To gain further insights into the direct changes in land-surface variables due to groundwater exploitation regardless of the atmospheric feedbacks, three off-line simulations using the land surface model Community Land Model version 3.5 are also conducted to distinguish these direct changes on the land surface of the basin. The results indicate that the direct changes of land-surface variables respond linearly to water demand if the climatic feedbacks are not considered, while non-linear climatic feedbacks enhance the differences in the on-line exploitation simulations. 相似文献
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Influences of Climate Change and Its Interannual Variability on Surface Energy Fluxes from 1948 to 2000 总被引：1，自引：0，他引：1
Understanding changes in land surface processes over the past several
decades requires knowledge of trends and interannual variability in surface
energy fluxes in response to climate change. In our study, the Community
Land Model version 3.5 (CLM3.5), driven by the latest updated hybrid
reanalysis-observational surface climate data from Princeton University, is
used to obtain global distributions of surface energy fluxes during 1948 to
2000. Based on the climate data and simulation results, long-term trends and
interannual variability (IAV) of both climatic variables and surface energy
fluxes for this span of 50+ years are derived and analyzed. Regions with
strong long-term trends and large IAV for both climatic variables and
surface energy fluxes are identified. These analyses reveal seasonal
variations in the spatial patterns of climate and surface fluxes; however,
spatial patterns in trends and IAV for surface energy fluxes over the past
～50 years do not fully correspond to those for climatic variables,
indicating complex responses of land surfaces to changes in the climatic
forcings. 相似文献