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An Observational and Numerical Study on the Topographic Influence on Dust Transport in East Asia
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Based on observations and numerical simulations, the topographic impacts on dust transport in East Asia were studied. Two regions frequently attacked by dust storms have been confirmed: one is the western part of Inner Mongolia and the southern Mongolia (namely the Mongolia Plateau), and the other is the Tarim Basin. The most frequent dust storm occurrence area within the first region appears in its hinterland while that of the second one lies in its southern boundary. Moreover, the region from the northeastern edge of the Tibetan Plateau (TP) to the Loess Plateau is attacked by dust storms second frequently. The dust storms frequently occurring over the Mongolia Plateau axe related not only to the abundant sand and dust sources, but also to the special topographic conditions of East Asia. The most significant factor that influences the dust storms forming in the hinterland of the Mongolia Plateau is the canyon low level jet (CLLJ), which dominates around the southern areas of the Altay-Sayan Mountains with an east-west direction in the beginning of its formation, and is accompanied by significantly enhanced surface wind afterwards. Due to the obstructive effects of the CLLJ, a lot of dust particles carried by the southward down-slope cold air mass would pile up over the southern slope of the Sayan Mountains. Meanwhile, uneven surface conditions are favorable for the dust particles to go up into the upper atmosphere. With the dust particles piling up continuously, a dust layer is formed in the troposphere and can be recognized as a '!dust accumulating container", which provides abundant dust particles to be transported later to the downstream areas. Additionally, the topographic features of East Asia also exert a great influence on dust transport. Generally, the easterly CLLJ enhances the easterly dust transport. The down-slope air current over the southern Sayan Mountains and the air flow surrounding the TP near its northeastern edge enhance the southward dust transport. Lastly, weather system influences are also examined. The weathers associated with cold fronts frequently appear over the areas of Mongolia and North China in springtime. The cold front system, in general, carries the sand and dust southwards. Among all topographic influencing elements, the rounding effect of the TP is the strongest. Under the combined influences of the cold front and the rounding effect of topography, most sand and dust particles are transported and then deposited over the Loess Plateau. 相似文献
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基于Landsat遥感影像,提取蒙古高原2000—2020年每年1 km2以上湖泊面积信息,分析其时空变化特征。结果表明:(1)2009年之前湖泊面积和数量呈减少趋势,2009年之后呈增加趋势,整体上2000—2020年湖泊面积和数量呈减少趋势。(2)不同等级湖泊变化差异较大,特大型和中型湖泊变化相对稳定,大型湖泊减少幅度最大。(3)不同区域湖泊变化也不同,西北部湖泊变化较稳定,中东部湖泊变化较剧烈。(4)研究区湖泊空间分布集聚性呈异因同向的减弱趋势。(5)湖泊面积与年均气温、年降水量、年蒸发量、植被指数和4层土壤水分的相关关系较为显著,且2个时间段内表现的影响程度有明显差异。掌握蒙古高原湖泊时空变化情况及其原因,对蒙古高原乃至全球的气候调节和生物多样性保护研究提供可参考依据。 相似文献
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A Dipole Pattern of Summer Precipitation over Mid-high Latitude Asia and Related Snow Cover Anomalies in the Preceding Spring
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A dipole pattern of summer precipitation over the mid-high latitudes of Asia, which is characterized by opposing summer precipitation variations between the Mongolian and Northeast China (MNC) region and the West Siberian Plain (WSP), is found to be clear and stable on both interdecadal and interannual scales during 1981- 2011. Spring snow cover anomalies over a small region within the WSP and the Heilongjiang River (HR) region are closely related to the variation of this dipole mode during the subsequent summer, and they can therefore be considered as forecasting factors. Our statistical results imply a potential process explaining the relationship between the spring snow anomalies and the summer rainfall dipole. Corresponding to the snow anomalies, Rossby waves propagate along a path from the WSP region, via the Mongolian Plateau, to the Stanovoy Range during summer. At the same time, Rossby-wave energy divergences and convergences along this path maintain and reinforce an anomalous cyclone and anticyclone pairing over the Asian continent, which is significantly linked to opposite summer precipitation anomalies between the MNC and WSP regions. Numerical experiments are need- ed to further confirm the above conjecture and demonstrate the detailed physical mechanisms linking the spring snow cover anomalies and summer precipitation dipole. 相似文献
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内蒙古二连浩特市,"一座异域风情的魅力边城,一个世界闻名的恐龙之乡"。这里是蒙古高原最早发现恐龙化石和恐龙蛋化石的地方,早在20世纪20年代,举世瞩目的中亚考察团就在这里取得了一系列重要考察成果,此后的近百年间,我国古生物学者在这里先后发现并命名了十余个新属种的恐龙化石。新千 相似文献
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蒙古高原NDVI的空间格局及空间分异 总被引:12,自引:2,他引:10
基于GIMMS NDVI多年最大值合成数据,采用空间统计学方法,利用Moran’ s I系数分析、半变异函数分析以及分维分析等3种方法,对蒙古高原NDVI空间格局及空间分异特征进行研究。结果表明:(1)蒙古高原NDVI的空间分布在全局范围内呈现正的空间自相关,相似的NDVI值倾向于聚集在一起,这表明蒙古高原植被具有较好的整体性,地表植被无显著破碎化;(2)蒙古高原NDVI的空间分布虽然同时受到结构性因子和随机性因子的影响,但结构性因子占据绝对控制地位,结构性因子引起的空间变异占系统总变异的88.7%;(3)蒙古高原NDVI存在各向异性的分布特征,具有相似NDVI值的像元主要沿着西北-东南方向展布;全局NDVI空间自相关距离约为1178km,西北-东南方向与东北-西南方向的空间自相关距离比可达2.4 ∶ 1。 相似文献
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青藏高原隆升对亚洲乃至全球气候演化的影响是古气候学热点问题之一。青藏高原的热力和动力效应一直以来受到人们的广泛重视,其中高原对大气环流的阻碍作用被认为在亚洲冬季气候形成中扮演着极其重要的作用。过去的理论及重建研究大都强调青藏高原主体的贡献,忽略了高原边缘中小尺度地形的可能贡献。以青藏高原北边缘蒙古地形为例,现代大气流场显示蒙古地形对冬季对流层低层西风具有明显的阻碍作用。本研究利用一个海气耦合模式评估了蒙古地形对亚洲冬季气候的影响及其同青藏高原主体的相对贡献。结果显示,蒙古高原地形对亚洲西风急流和东亚冬季风具有非常显著的影响。蒙古高原存在时,东亚大槽加深,日本上空的西风急流增强,东亚冬季风环流也增强。该效应主要源自于亚洲大气热力结构的变化,对流层低层西风在蒙古地形的动力强迫下向北绕流,在下游产生强烈的北风异常,有利于极地冷空气南下。该温度冷平流最终导致西风急流和冬季风环流的响应。值得注意的是,青藏高原主体对西风急流和冬季风的贡献要明显弱于蒙古高原。该结果启示我们,传统认识的青藏高原动力效应可能被一定程度高估,亚洲各地形的动力效应不仅同其规模和高度有关,也与其所处位置有关,处于敏感区域的较小尺度地形同样会对亚洲气候形成有不可忽略的影响。 相似文献
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白云鄂博位于绥远之西北,包头之北北东约一七○公里之蒙古高原上,附近为极缓之波状丘陵,地质主要由结晶质石灰岩,变质矽质页岩,片状石英岩及黑云母花岗岩所成,前三者 相似文献
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青藏高原、伊朗高原和蒙古高原属于亚洲高海拔地区,3个高原热力作用对同期和后期中国天气气候有重要影响。首先,介绍了3个高原地表感热时空变化特征,结果表明在全球变暖的背景下,3个高原地表感热经历了明显的年际和年代际变化,基本都在20世纪末到21世纪初出现年代际转折,之后探讨了它们之间地表感热可能存在的联系。其次,归纳总结了3个高原春季和夏季地表热力状况对中国天气气候的影响研究进展,结果显示:青藏高原感热对高原低涡的生成、发展和东移有重要作用,在适当的背景环流下会给中国东部地区带来暴雨天气;青藏高原和伊朗高原的“感热气泵”为亚洲季风区提供有利的大尺度上升背景场,而且这2个高原的热力协同作用对中国南方夏季降水的贡献要大于二者的线性叠加;青藏高原、伊朗高原和蒙古高原地表加热激发的次级环流下沉支与中国北方暖干化关系密切,且3个高原感热异常会引起其上空大气环流异常,通过大气遥相关调节中国北方天气气候。最后,在此基础上讨论了现有研究的不足,并对未来关于青藏高原、伊朗高原和蒙古高原感热的天气气候效应的研究进行了展望。 相似文献