共查询到19条相似文献，搜索用时 343 毫秒
1.
沙漠绿洲陆面物理过程和地气相互作用数值模拟 总被引：1，自引：0，他引：1
利用一个已发展的陆面物理过程参数化方案与大气边界层数值模式耦合, 模拟了半干旱区沙漠绿洲非均匀下垫面的陆面物理过程及其与大气边界层的相互作用过程, 成功地模拟了局地气候效应和地表温度、净辐射、感热和潜热通量特征并与实测资料进行了比较. 给出“绿洲效应”这一自然现象的垂直剖面上更为清晰准确和细致的结构特征, 结果表明: “绿洲效应”具有明显的“冷岛效应”和“湿岛效应”; 它表现为在绿洲区域比戈壁沙漠区域环境温度低、湿度大、湍流动能输送弱, 具有下沉气流而导致与周围戈壁沙漠区域产生水平输送环流. 这些结果对于深入了解绿洲气候的形成和绿洲的维持机理具有重要的意义. 相似文献
2.
本文在MSPAS(Modified Soil-Plant-Atmosphere Scheme)的基础上,引入了一个有效的晴天大气辐射传输方案,建立了一个能在物理上真实地模拟陆气相互作用及其反馈机制的二维模式MLAIM（Modified Land Atmosphere Interaction Model）.本文利用HEIFE实验的观测资料对MLAIM的模拟结果进行了检验,对其中不合理的部分进行了分析,指出了在干旱半干旱区陆面过程参数修正的必要性,对干旱半干旱区土壤水分传输以及大气近地面层湍流输送的参数化方案进行了改进.改进后的模式能够较好地模拟夏季连续晴天条件下沙漠的地表能量收支,因此,本文利用MLAIM研究了绿洲对其周围沙漠地表能量收支的影响,并对地表能量收支各分量之间的相互作用进行了分析.结果表明,绿洲向其下风向沙漠的水汽输送是导致其上下风向沙漠间地表能量收支差异的最重要的因子. 相似文献
3.
大气边界层是地球大气重要物理特征之一.干旱气候背景下的大气边界层特征与人们以往对典型大气边界层的认识有很大不同,其形成机制也比较特殊.本文利用冬、夏两季典型时段在极端干旱区敦煌开展的大气边界层和陆面过程综合观测试验,对大气边界层厚度与净辐射、地-气温差和感热通量等陆面热力因素的日变化特征进行了对比分析,研究了大气边界层的发展和维持衰退过程与陆面热力和动力过程的关系,发现发展过程消耗的能量要比维持衰退过程高得多,而且进入残余层后对流边界层发展对陆面热力作用更敏感,发展也更迅速.风速的动力作用对大气边界层发展也有一定的影响,尤其对冬季稳定大气边界层影响较大.极强的陆面热力作用是我国干旱区形成深厚大气边界层的主导因素. 相似文献
4.
青藏高原地-气过程动力、热力结构综合物理图象 总被引：40，自引：2，他引：40
根据第二次青藏高原大气科学试验（ＴＩＰＥＸ）３个边界层观测基地（改则、当雄。昌都）及相关的卫星、探空、地面等加密观测（ＩＯＰ）资料，综合分析了青藏高原地－气物理过程及其动力学模型，揭示了高原边界层动力学特征和高原湍流运动规律；发现高原边界层低层风向、风速具有多层次变化特征，高原边界层对流混合层较为深厚，高原边界层大气密度远小于平原特征相联系的高原湍流运动“强浮力”效应。高原深厚边界层Ｅｋｍａｎ螺线及高原边界层动力“抽吸泵”效应。研究了高原近地层局地水汽静态分布状况和水汽的侧边界平流输送特征。分析了高原近地层与边界层异常热力结构，其中包括高原强辐射现象、高原中部地面强热源特征等。综合上述青藏高原近地层与行星边界层动力、热力结构特征，提出了描述高原边界层湍流与对流混合机制的综合物理图象。揭示了显著影响中国长江流域洪涝的青藏高原对流云团的生成、发展和移动的特征，给出与高原“爆米花”云系频发相关的湍流运动和对流泡动力、热力结构概念模型。 相似文献
5.
21世纪开始,随着天气气候模式和超算机计算能力的发展,加之气象精细化预报服务需求日益增长,气象数值模拟迈入“百米级”发展阶段.本文系统回顾并归纳了近20年来百米级气象数值模式研发和模拟应用两方面的研究进展.重点关注百米级大气模式资料同化和浅积云对流、云微物理、边界层和城市陆面等物理参数化方案的研发进展,以及模式对天气系统、边界层特征、降水、雾和城市化效应的模拟研究.基于百米级模式的研发和应用现状,指出该研究领域的五个重点发展方向,包括有限域高分辨率资料同化方法、云和边界层作用反馈、百米级城市陆面模式、人工智能方法对参数化方案的改进、模式分辨率与计算资源的平衡配置,以期为系统开展百米级气象数值模拟研究与应用提供参考. 相似文献
6.
《中国科学:地球科学》2015,(10)
陆面过程模式中有关土壤水热传输、植被冠层和空气动力学等过程的关键参数的不确定性严重制约着地表-大气相互作用模拟能力的提高.本文利用架设在我国吉林通榆和甘肃榆中典型半干旱区陆-气相互作用野外试验站的观测资料,结合大气边界层理论,利用多种方法系统估算了上述试验站地表空气动力学粗糙度(z0m)以及热传输附加阻尼(?B?1)的量值.结果表明,z0m在半干旱区具有明显的季节变化和年际变化特征,且在植被低矮的下垫面与现行通用的陆面模式中的默认值相差较大;而?B?1的日变化和季节变化特征明显.将修正后的z0m和?B?1参数化方案引入陆面过程模式,发现能够明显改善模式对于半干旱区地表感热通量的模拟能力.这些结果说明有必要进一步结合半干旱区的野外观测试验对陆面模式在该地区的缺省参数设置进行更广泛的评估,而基于外场观测试验和大气边界层理论估算的关键地表参数对于改进陆气相互作用的模拟体现出较大的应用潜力. 相似文献
7.
采用WRFV2.2中尺度数值模式对鄱阳湖地区200 km×200 km范围内,2009年11月5日00∶00至2009年11月6日12∶00不同高度的气象要素进行了数值模拟,得到了水平分辨率为1 km的鄱阳湖地区大气边界层风、温、湿度场和廓线分布的大气边界层物理特征.模拟结果发现:白天鄱阳湖面上空存在着冷岛效应并伴随湖风,而夜间湖面上空存在着热岛效应并伴随陆风,湖面与陆地之间最大温差可达6 ℃;同时地形以及下垫面类型对鄱阳湖区风场的分布具有很大影响,夜间存在一条东北西南走向的低空辐合带,白天逐渐消失;此外受风场和地形作用湖面上空的湿度分布也不均匀,白天湿度层厚度低而夜晚湿度层厚度高,湖中心右侧湿度值大于左侧湿度值.模拟结果能较好地反映鄱阳湖的大气边界层物理特征,有助于了解鄱阳湖地区区域气候的特点,以及由于地形、地理环境、地表特征所形成的不同高度上的风、温、湿的分布规律和大气边界层物理特征,为鄱阳湖地区局地天气预报、风能资源开发、环境保护等提供了科学依据. 相似文献
8.
三工河流域绿洲时空变异及其稳定性研究 总被引：21，自引：7，他引：21
根据三工河流域1978, 1987年的航片和1998年TM影像以及气象水文观测资料, 利用GIS, RS和景观生态学的理论与方法, 从绿洲土地覆被、景观格局变化和绿洲冷岛效应, 研究了冲洪积扇-冲积平原型绿洲时空变异和稳定性.结果表明: (1) 流域绿洲上部、中部和下部土地覆被变化的幅度大且速度很快, 并且存在明显的空间变异性; (2) 1978~1987年期间, 绿洲景观的多样性和异质性增加, 绿洲景观稳定性降低, 而1987年后, 绿洲景观的多样性降低, 绿洲景观稳定性提高; (3) 60年代以来, 三工河绿洲的冷岛效应逐步加强, 从气候角度来说, 绿洲稳定性显著提高. 相似文献
9.
城市群落大气污染源影响的空间结构及尺度特征 总被引：29，自引：1，他引：29
以迅速发展的城市群落-北京及周边区域为样本, 利用2003年冬季(2月)、夏季(8月)北京城市大气环境现场科学试验(BECAPEX, Beijing City Air Pollution Observation Experiment)建筑群边界层大气污染动力-化学过程观测资料以及相关的气象要素、卫星反演气溶胶光学厚度等综合资料, 进行“点-面”空间结构动力-统计合成分析, 剖析北京大城市及周边区域大气污染影响域的空间结构及多尺度特征. 结果表明, 冬、夏季不同污染排放源对大气污染成分特征的贡献率具有显著差异, 统计模型主成分分析结果亦表明, 冬季气溶胶颗粒物成分结构以SO2和NOx影响为主; 夏季粒子成分结构则以CO, NOx影响为主. 冬、夏季北京城区不同方位测点近地层大气动力、热力结构及建筑群上边界各类污染物种均具有“同位相”变化及其“影响域”空间尺度特征. 功率谱分析发现冬、夏季颗粒物浓度和大气风场动力结构的周期谱相吻合, 冬季以长周期为主, 夏季则多为短周期, 揭示出冬、夏季大气环流季节性尺度特征对大气污染变化周期特征的影响效应. 分析城市区域热力非均匀性特征, 可发现北京地区热岛多尺度效应与高层建筑群面积非均匀扩展特征存在相关关系. 城市大气动力、热力特征空间结构中城市边界层群筑群湍流尺度特征对城市大气污染多尺度特征具有重要影响. 晴空、稳定天气条件下MODIS气溶胶变分订正分析场和污染源追踪相关合成风矢场综合分析模型均表明, 冬季北京大气污染气溶胶颗粒物的排放源可远距离追溯到北京南部周边的河北、山东及天津等地更大尺度空间范围, 气溶胶指数高值区与北京及周边地区居民户数高值区(采暖面源)空间分布存在关联. 冬、夏季空气质点后向轨迹特征呈类似上述多尺度特征, 且描述出不同季节污染源空间分布的尺度特征差异, 城区大气污染周边源轨迹路径主体来自城市近郊固定工业面源或采暖面源, 且冬季周边污染源扩散输送距离较夏季呈更远的空间尺度, 上述结论描述出城市区域大气污染源影响和大气动力结构引起的多尺度空间影响域及季节性特征. 冬季TOMS气溶胶光学厚度高值区域位于北京地区并向南延伸, 且呈南北向带状分布, 可描述出周边地形分布对区域尺度大气污染源扩散的动力影响效应. 研究分析表明: 北京周边大地形“谷地”内冬季污染程度与南部周边地区的污染排放源密切相关; 北京及周边地区冬季的气溶胶光学厚度和日照时数的“反位相”变化特征显著, 冬季云量、雾日数与气溶胶呈区域尺度相关特征, 反映了该区域尺度气溶胶影响的局地气候效应. 另外, 流域面尺度的大气干、湿沉降分布对密云水库区域尺度空间水体的影响分析亦反映了夏季水、土、气多圈层污染源影响多尺度空间结构对密云水库水质影响的可能性. 相似文献
10.
渭干河平原绿洲适宜规模 总被引：1，自引：0，他引：1
荒漠和绿洲长期共存,绿洲系统的生存发展需要有较好的绿洲植被生态系统支撑.干旱区平原绿洲,应以水为中心确定绿洲规模,防止水资源不足情况下土地过度开发造成的荒漠化和沙漠化.良性循环的稳定绿洲必须具有合理的农林牧用地结构.开展绿洲适宜规模与发展空间研究,将为绿洲的有效建设提供理论和应用依据.本文通过水热、水土平衡分析,建立了适宜绿洲数学模型.根据渭干河平原绿洲多年的水文气象资料,依据水量平衡原理,计算了该绿洲可供蒸发蒸腾的水资源量、适宜的绿洲和耕地面积.结果表明,渭干河平原绿洲可供蒸发蒸腾的水资源量为22.32×108 m3,在常规地面灌溉条件下适宜的绿洲面积为3716.06 km2,其中适宜的耕地面积为1564.79 km2;在节水灌溉条件下,适宜的绿洲面积5515.49 km2,其中适宜的耕地面积为2322.31 km2.世界银行贷款项目--渭干河流域农业灌溉排水工程结束后达到的绿洲面积为4123km2,农田耕地面积为1507 km2,绿洲和耕地面积比较适宜,如果采取节水灌溉措施可适度扩大绿洲规模. 相似文献
11.
LIU ShuHua ? LIU HePing HU Yu ZHANG ChengYi LIANG FuMing & WANG JianHua Department of Atmospheric Sciences School of Physics Peking University Beijing China Laboratory of Climate Research National Climatic Center China Meteorological Administration Beijing China 《中国科学D辑(英文版)》2007,50(2):290-295
A land-surface physical process model was coupled with a mesoscale atmospheric model. This cou- pled model was then used to simulate the interactions between land and the atmosphere, including surface temperature, net radiation, sensible heat flux and latent heat flux over a desert/Gobi with an oasis in northwestern semiarid regions in China. Comparisons between observations and simulations were made over the oasis and the desert/Gobi, respectively. Both cold island effect and wet island ef- fect, the so-called oasis effect, were observed and simulated. Lower temperature, higher specific hu- midity and weaker turbulent transfer were present over the oasis than the desert/Gobi. A subsidence occurred over the oasis, leading to a thermally-generated mesoscale circulation. 相似文献
12.
In this paper, the process of oasis-desert circulation (ODC) is simulated by MM5V3.5 model through designing an ideal oasis-desert scheme and assuming that initial atmosphere is at rest (V = 0). The findings showed that the key of forming special oasis boundary structure is the difference of energy and water between oasis and desert. The evaporation of oasis surface consumes heat energy, and the low temperature of oasis causes an oasis breeze circulation (OBC), which drives an ODC with a downdraft over the oasis and an updraft over the desert. Later, the cold, dry and stable boundary over oasis is gradually formed, on the contrary,the atmospheric boundary over desert on the edge of oasis is hot, humid and unstable and its height is about 600 hPa. The updraft over the desert forms a wet ring that acts as a vertical wall weakening the low-level moisture exchange between the oasis and desert. The downdraft of OBC increases the atmospheric stability that reduces the oasis evaporation. The low-level outflow from the oasis (into the desert) prevents the dry, hot air flowing from the desert into the oasis.Thus an oasis self-preservation mechanism may be formed due to OBC. The horizontal area influenced by oasis is twice as oasis area and the vertical range is four times as oasis. The ODC is strong in the daytime and reaches the strongest at 17:00, and the influenced area is the largest at 20:00. 相似文献
13.
In this paper, the process of oasis-desert circulation (ODC) is simulated by MM5V3.5 model through designing an ideal oasis-desert scheme and assuming that initial atmosphere is at rest (V= 0). The findings showed that the key of forming special oasis boundary structure is the difference of energy and water between oasis and desert. The evaporation of oasis surface consumes heat energy, and the low temperature of oasis causes an oasis breeze circulation (OBC), which drives an ODC with a downdraft over the oasis and an updraft over the desert. Later, the cold, dry and stable boundary over oasis is gradually formed, on the contrary, the atmospheric boundary over desert on the edge of oasis is hot, humid and unstable and its height is about 600 hPa. The updraft over the desert forms a wet ring that acts as a vertical wall weakening the low-level moisture exchange between the oasis and desert. The downdraft of OBC increases the atmospheric stability that reduces the oasis evaporation. The low-level outflow from the oasis (into the desert) prevents the dry, hot air flowing from the desert into the oasis. Thus an oasis self-preservation mechanism may be formed due to OBC. The horizontal area influenced by oasis is twice as oasis area and the vertical range is four times as oasis. The ODC is strong in the daytime and reaches the strongest at 17:00, and the influenced area is the largest at 20:00. 相似文献
14.
The surface energy balance algorithm for land method was used in this study to calculate the evapotranspiration (ET) rate for the middle reaches of the Heihe River Basin, Gansu Province, China, to analyse ET distribution within the oasis and the surrounding desert and, especially, on the edge zone of the oasis. Five profile graphs were created vertical to the river. Because of the inverse humidity phenomenon, the least amount of evapotranspiration occurred on the desert close to the oasis. The average evapotranspiration rate was roughly proportioned from the edge of the oasis to inside and outside its boundary. Two meteorological ground stations located close to the oasis edge showed a notable difference in net radiation flux that led to the difference found in ET. The primary reason for the significant differences observed in net radiation may be largely the result of differences in flux reflectivity and surface temperature. Meteorological data show that water supply also played an important role. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
15.
沙漠地区植被稀疏、干旱少雨,其陆面物理过程具有与全球其它地区显著不同的特点.本文利用巴丹吉林沙漠观测资料,分析和计算了地表反照率、比辐射率、粗糙度和土壤热容量、热传导系数等关键陆面过程参数,建立了适合于沙漠地区的陆面过程模式DLSM (Desert Land Surface Model),并与NOAH陆面过程模式的模拟结果和观测资料进行了比较.结果表明:巴丹吉林沙漠地表反照率为0.273,比辐射率为0.950,地表粗糙度为1.55×10-3 m,土壤热容量和热扩散系数分别为1.08×106 J·m-3·K-1和3.34×10-7 m2·s.辐射传输、感热输送和土壤热传导过程是影响沙漠地区地表能量平衡的主要物理过程.通过对这三种过程的准确模拟检验,DLSM能够较准确地模拟巴丹吉林沙漠地气能量交换特征;短波辐射、长波辐射和感热通量的模拟结果与观测值间的标准差分别为7.98,6.14,33.9 W·m-2,与NOAH陆面过程模式的7.98,7.72,46.6 W·m-2的结果接近.地表反照率是沙漠地区最重要的陆面过程参数,地表反照率增大5%,向上短波辐射通量随之增加5%,感热通量则减小2.8%.本文研究结果对丰富陆面过程参数化方案,改进全球陆面过程模式、气候模式具有参考意义. 相似文献
16.
Modelling and analysis of the impact of irrigation on local arid climate over northwest China 总被引：1，自引：0，他引：1
This study focuses on how irrigation processes affect local climate over arid areas. The chosen study area is northwest China, a typical arid region where three dominant land‐use types are irrigated cropland, grassland, and desert. Observational analysis indicates that the highest precipitation, the coolest surface temperatures, and the slowest warming trend are seen over irrigated cropland from 1979 to 2005. The single column atmospheric model (SCAM), developed by the National Center for Atmospheric Research (NCAR), was used to investigate and better understand the differences in long‐term climate conditions and change over the above three land‐use types. The results indicate that local climate conditions are predominantly controlled by large‐scale forcing in this arid region and that local land surface forcing related to vegetation cover change and irrigation processes also has a significant impact. This study strongly suggests that a realistic climate forecast for this region can be achieved only with both accurate large‐scale and local climate forcing. The irrigated cropland of the region generates stronger evaporation that cools the surface and slows the warming trend more than does the evaporation from the natural grassland and desert. Stronger evaporation also significantly increases precipitation, potentially alleviating the stress of irrigation demands in arid regions. A series of sensitivity SCAM simulations indicate that a drier and warmer climate occurs with decreasing vegetation cover in the irrigated cropland region. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
17.
Temporal and spatial variation and stability of the oasis in the Sangong River Watershed, Xinjiang, China 总被引：5，自引：0，他引：5
The unique ecological landscapes are composed of the mountain systems with the obviousvertical differentiation, vast natural desert systems, and oasis systems on which the human beings rely for the existence in the arid areas in West China. Oases are the … 相似文献
18.
By using the theories and methods of landscape ecology and the technology of GIS and RS, a study has been carried out on the responses of distribution pattern of desert riparian forest to hydrologic process on the basis of the hydrologic data from 1990 to 2000 and the TM image of 2001 year. The results showed that: (1) there appears an even distribution pattern for the relative forest area in oasis, however, the degenerated forest diaplays an increasing tendency from west to east; (2) the desert riparian forest in Ejina is in completely degenerated process at the patch scale; (3) the number of patch is influenced not only by hydrologic process,but also by agricultural activity such as cultivation. The severe deterioration of the degraded vegetation in whole oasis initiates from lower reaches, and gradually impels to upstream; the fragmentation of landscape in the terminal site is more obvious, which is influenced by river shape and decreasing flux of water. It is found that the influence of surface hydrologic process to the ground hydrologic process of desert riparian forest in Ejina oasis is little for the recent ten years. The relative area of the degenerated forest increased with increasing ground water depth in the direction of parallel to river channel. On the contrary, in the direction perpendicular to river channel, there is a decreasing tendency for the average patch area of the forest and the degenerated forest with increasing ground water depth. 相似文献
19.
By using the theories and methods of landscape ecology and the technology of GIS and RS, a study has been carried out on the responses of distribution pattern of desert riparian forest to hydrologic process on the basis of the hydrologic data from 1990 to 2000 and the TM image of 2001 year. The results showed that: (1) there appears an even distribution pattern for the relative forest area in oasis, however, the degenerated forest diaplays an increasing tendency from west to east; (2) the desert riparian forest in Ejina is in completely degenerated process at the patch scale; (3) the number of patch is influenced not only by hydrologic process, but also by agricultural activity such as cultivation. The severe deterioration of the degraded vegetation in whole oasis initiates from lower reaches, and gradually impels to upstream; the fragmentation of landscape in the terminal site is more obvious, which is influenced by river shape and decreasing flux of water. It is found that the influence of surface hydrologic process to the ground hydrologic process of desert riparian forest in Ejina oasis is little for the recent ten years. The relative area of the degenerated forest increased with increasing ground water depth in the direction of parallel to river channel. On the contrary, in the direction perpendicular to river channel, there is a decreasing tendency for the average patch area of the forest and the degenerated forest with increasing ground water depth. 相似文献