The present study examined the diurnal variations of summer precipitation in the Beijing area by usingsubdaily precipitation and wind observations. A combined effect of topography and urbanization on thecharacteristic...The present study examined the diurnal variations of summer precipitation in the Beijing area by usingsubdaily precipitation and wind observations. A combined effect of topography and urbanization on thecharacteristics of diurnal variations was suggested. It was shown that stations located in the plain areaexhibited typical night rain peaks, whereas those in the mountainous area exhibited clear afternoon peaks ofprecipitation diurnal variations. The precipitation peaks were associated with wind fields around the Beijingarea, which were found to be highly modulated by mountain-valley circulation and urban-country circulation.The lower-tropospheric wind exhibited a clear diurnal shift in its direction from north at 0800 LST to southat 2000 LST, which reflected mountain-valley circulation. The transitions from valley to mountain windand the opposite generally happened after sunset and sunrise, respectively, and both occurred earlier for thestations located closer to mountains. By comparing the diurnal variations of precipitation at stations in anortheast suburb, an urban area, and a southwest suburb, it was revealed that the northeast suburb grouphad the highest normalized rainfall frequency, but the southwest group had the lowest from late afternoon tolate evening. On the contrary, in the early morning from about 0200 to 1000 LST, the southwest group andurban group had the highest normalized rainfall frequency. This pattern might originate from the combinedeffects of mountain-valley topography and urbanization.展开更多
Near-surface wind measurements obtained with five 100-m meteorology towers, 39 regional automatic stations, and simulations by the Weather Research and Forecasting (WRF) model were used to investigate the spatial st...Near-surface wind measurements obtained with five 100-m meteorology towers, 39 regional automatic stations, and simulations by the Weather Research and Forecasting (WRF) model were used to investigate the spatial structure of topography-driven flows in the complex urban terrain of Urumqi, China. The results showed that the wind directions were mainly northerly and southerly within the reach of 100 m above ground in the southern suburbs, urban area, and northern suburbs, which were consistent with the form of the Urumqi gorge. Strong winds were observed in southern suburbs, whereas the winds in the urban, northern suburbs, and northern rural areas were weak. Static wind occurred more frequently in the urban and northern rural areas than in the southern suburbs. In the southern suburbs, wind speed was relatively high throughout the year and did not show significant seasonal variations. The average annual wind speed in this region varied among 1.9-5.5, 1.1-3.6, 1.2 4.3, 1.2 4.3, and 1.1 3.5 m s-1 within the reach of 100 m above ground at Yannanlijiao, Shuitashan, Liyushan, Hongguangshan, and Midong, respectively. The flow characteristics comprised more airflows around the mountain, where the convergence and divergence were dominated by the terrain in eastern and southwestern Urumqi. Further analysis showed that there was a significant mountain-valley wind in spring, summer, and autumn, which occurred more frequently in spring and summer for 10- 11 h in urban and northern suburbs. During daytime, there was a northerly valley wind, whereas at night there was a southerly mountain wind. The conversion time from the mountain wind to the valley wind was during 0800-1000 LST (Local Standard Time), while the conversion from the valley wind to the mountain wind was during 1900- 2100 LST. The influence of the mountain-valley wind in Urumqi City was most obvious at 850 hPa, according to the WRF model.展开更多
螺髻山地处青藏高原东南缘,是确切存在第四纪古冰川遗迹的典型山地之一,该区冰川地貌演化对于研究环境变化具有重要的科学意义。螺髻山东坡清水沟保存两套古冰川槽谷,分别为上槽谷和下槽谷,其中下槽谷保存完整,而上槽谷在3450~3600 m的...螺髻山地处青藏高原东南缘,是确切存在第四纪古冰川遗迹的典型山地之一,该区冰川地貌演化对于研究环境变化具有重要的科学意义。螺髻山东坡清水沟保存两套古冰川槽谷,分别为上槽谷和下槽谷,其中下槽谷保存完整,而上槽谷在3450~3600 m的阴坡部分出现缺失。采用野外地貌调查与模型分析相结合的方法,对冰川槽谷地貌进行分析,结果表明:清水沟槽谷的抛物线模型中,|A|值在1.3101~15.2064之间变动,B值变化于0.9695~3.2965之间,且随着海拔由高到低,都存在着先变小后变大的规律,A、B值同时反映出在海拔3450~3600 m处冰川槽谷的演化不符合常态。分析认为岩性差异和河流溯源侵蚀是影响上槽谷形态的主要原因。对保存在清水沟上下槽谷内的高、低侧碛进行ESR年代测定,结果显示:高侧碛形成于58-84 ka BP左右的末次冰期早期,对应深海氧同位素4阶段(MIS4);低侧碛形成于13-17 ka BP,属于于全球末次冰盛期晚期的产物。两次冰川作用分别塑造出两套冰川槽谷,即在末次冰期早期冰川作用形成上槽谷,末次冰期晚期形成下槽谷。展开更多
Performance of the fifth-generation Pennsylvania State University/National Center for Atmospheric Research Mesoscale Model(MM5) over the Lake Nam Co region of the Tibetan Plateau was evaluated based on the data from...Performance of the fifth-generation Pennsylvania State University/National Center for Atmospheric Research Mesoscale Model(MM5) over the Lake Nam Co region of the Tibetan Plateau was evaluated based on the data from five surface observation sites in 2006. The interaction between two thermally-induced circulations(lake breezes and mountain-valley winds) was also investigated. The results show that MM5 could be used to simulate 2-m air temperature; however, MM5 needs improvement in wind field simulation.Two numerical simulations were conducted to study the effect of the lake on the local weather and wind system. The original land cover of the model was used in the control experiment, and the lake was replaced with grassland resembling the area surrounding the lake in the sensitive experiment. The results of the simulations indicate that the lake enhanced the north slope mountain-valley wind and the mountain changed the offshore flow direction at the north shore. During the day, a clear convergent zone and a strong upflow were observed over the north slope of the Nyainq?entanglha Range, which may cause frequent precipitation over the north slope. During the night, the entire area was controlled by a south flow.展开更多
Geomorphological mapping plays a key role in landscape representation: it is the starting point for many applications and for the realization of thematic maps, such as hazard and risk maps, geoheritage and geotourism ...Geomorphological mapping plays a key role in landscape representation: it is the starting point for many applications and for the realization of thematic maps, such as hazard and risk maps, geoheritage and geotourism maps. Traditional geomorphological maps are useful for scientific purposes but they need to be simplified for different aims as management and education. In tourism valorization, mapping of geomorphological resources(i.e., geosites, and geomorphosites), and of geomorphic evidences of past hazardous geomorphological events, is important for increasing knowledge about landscape evolution and active processes, potentially involving geomorphosites and hiking trails. Active geomorphosites, as those widespread in mountain regions, testify the high dynamicity of geomorphic processes and their link with climatic conditions. In the present paper, we propose a method to produce and to update cartographic supports(Geomorphological Boxes)realized starting from a traditional geomorphological survey and mapping. The Geomorphological Boxes are geomorphological representation of single, composed or complex landforms drawn on satellite images, using the official Italian geomorphological legend(ISPRA symbols). Such cartographic representation is also addressed to the analysis(identification, evaluation and selection) of Potential Geomorphosites and Geotrails. The method has been tested in the upper portion of the Loana Valley(Western Italian Alps), located within the borders of the Sesia Val Grande Geopark, recognized by UNESCO in 2013. The area has a good potential for geotourism and for educational purposes. We identified 15 Potential Geomorphosites located along 2 Geotrails; they were ranked according to specific attributes also in relation with a Reference Geomorphosite located in the Loana hydrographic basin and inserted in official national and regional databases of geosites(ISPRA; Regione Piemonte). Finally, the ranking of Potential Geomorphosites allowed to select the most valuable ones for valorization or geo展开更多
The Kaghan Valley is in the territorial jurisdiction of Mansehera District, named after a tiny village Kaghan, at the end of the valley. The valley culminates in the tree-clad high mountains and glaciers in the North-...The Kaghan Valley is in the territorial jurisdiction of Mansehera District, named after a tiny village Kaghan, at the end of the valley. The valley culminates in the tree-clad high mountains and glaciers in the North-East with varying altitudes from 1 to 5 thousand meters above sea level. The region is relatively active geophysically, hydrologically and biologically diverse by virtue of the altitude and aspect-driven variability in energy and moisture. In such region a better understanding of changes in land resources, production of agronomic and horticultural crops, use of timber and non-timber products, and livestock structure/composition have important implications and understanding these changes along with the indigenous knowledge of mountain people which, is key to sustainable development of the Himalayan region. Our results showed that the main causes of lowest agriculture production in the area are poor crop management in context of the mountains, drought spells, low soil fertility, land fragmentation and tenancy status of the agricultural land. Off season vegetables cultivation on the sloppy land leads to sever soil erosion and soil land degradation of this mountain ecosystem. Overgrazing during the summer season is another problem as the pastures are visited both by the Afghan and local nomads without relating with carrying capacity of the alpine meadows. The overgrazed soil is usually subject to rainfalls and severe soil erosion. Any use of resources of such fragile rare high mountain ecosystem requires a great sense of responsibility but in this case the forest resources are being plundered and are used roughly. We recommend adequate use of agricultural inputs, specific crop management practices for mountain agriculture. Local social welfare organizations should work to create awareness about the sustainable use of natural resources. The government should resolve the ownership problem of land as common property keeping in mind the customary laws of the region to make sure the involvement of all stakeho展开更多
基金supported by grants from the National Basic Key Research Program (973) under Grant No. 2006CB403606the National Key Technology R&D Program under Grant No. 2007BAC29B04the National Science Foundation Project for Post-doctoral Scientists of China under Grant No. 20080440343
文摘The present study examined the diurnal variations of summer precipitation in the Beijing area by usingsubdaily precipitation and wind observations. A combined effect of topography and urbanization on thecharacteristics of diurnal variations was suggested. It was shown that stations located in the plain areaexhibited typical night rain peaks, whereas those in the mountainous area exhibited clear afternoon peaks ofprecipitation diurnal variations. The precipitation peaks were associated with wind fields around the Beijingarea, which were found to be highly modulated by mountain-valley circulation and urban-country circulation.The lower-tropospheric wind exhibited a clear diurnal shift in its direction from north at 0800 LST to southat 2000 LST, which reflected mountain-valley circulation. The transitions from valley to mountain windand the opposite generally happened after sunset and sunrise, respectively, and both occurred earlier for thestations located closer to mountains. By comparing the diurnal variations of precipitation at stations in anortheast suburb, an urban area, and a southwest suburb, it was revealed that the northeast suburb grouphad the highest normalized rainfall frequency, but the southwest group had the lowest from late afternoon tolate evening. On the contrary, in the early morning from about 0200 to 1000 LST, the southwest group andurban group had the highest normalized rainfall frequency. This pattern might originate from the combinedeffects of mountain-valley topography and urbanization.
基金Supported by the China Desert Meteorological Science Research Fund(Sqj2015009)Basic Business Expenses(IDM201505)China Meteorological Administration Special Public Welfare Research Fund[GYHY(QX)201506001-14]
文摘Near-surface wind measurements obtained with five 100-m meteorology towers, 39 regional automatic stations, and simulations by the Weather Research and Forecasting (WRF) model were used to investigate the spatial structure of topography-driven flows in the complex urban terrain of Urumqi, China. The results showed that the wind directions were mainly northerly and southerly within the reach of 100 m above ground in the southern suburbs, urban area, and northern suburbs, which were consistent with the form of the Urumqi gorge. Strong winds were observed in southern suburbs, whereas the winds in the urban, northern suburbs, and northern rural areas were weak. Static wind occurred more frequently in the urban and northern rural areas than in the southern suburbs. In the southern suburbs, wind speed was relatively high throughout the year and did not show significant seasonal variations. The average annual wind speed in this region varied among 1.9-5.5, 1.1-3.6, 1.2 4.3, 1.2 4.3, and 1.1 3.5 m s-1 within the reach of 100 m above ground at Yannanlijiao, Shuitashan, Liyushan, Hongguangshan, and Midong, respectively. The flow characteristics comprised more airflows around the mountain, where the convergence and divergence were dominated by the terrain in eastern and southwestern Urumqi. Further analysis showed that there was a significant mountain-valley wind in spring, summer, and autumn, which occurred more frequently in spring and summer for 10- 11 h in urban and northern suburbs. During daytime, there was a northerly valley wind, whereas at night there was a southerly mountain wind. The conversion time from the mountain wind to the valley wind was during 0800-1000 LST (Local Standard Time), while the conversion from the valley wind to the mountain wind was during 1900- 2100 LST. The influence of the mountain-valley wind in Urumqi City was most obvious at 850 hPa, according to the WRF model.
文摘螺髻山地处青藏高原东南缘,是确切存在第四纪古冰川遗迹的典型山地之一,该区冰川地貌演化对于研究环境变化具有重要的科学意义。螺髻山东坡清水沟保存两套古冰川槽谷,分别为上槽谷和下槽谷,其中下槽谷保存完整,而上槽谷在3450~3600 m的阴坡部分出现缺失。采用野外地貌调查与模型分析相结合的方法,对冰川槽谷地貌进行分析,结果表明:清水沟槽谷的抛物线模型中,|A|值在1.3101~15.2064之间变动,B值变化于0.9695~3.2965之间,且随着海拔由高到低,都存在着先变小后变大的规律,A、B值同时反映出在海拔3450~3600 m处冰川槽谷的演化不符合常态。分析认为岩性差异和河流溯源侵蚀是影响上槽谷形态的主要原因。对保存在清水沟上下槽谷内的高、低侧碛进行ESR年代测定,结果显示:高侧碛形成于58-84 ka BP左右的末次冰期早期,对应深海氧同位素4阶段(MIS4);低侧碛形成于13-17 ka BP,属于于全球末次冰盛期晚期的产物。两次冰川作用分别塑造出两套冰川槽谷,即在末次冰期早期冰川作用形成上槽谷,末次冰期晚期形成下槽谷。
基金Supported by the National(Key)Basic Research and Development(973)Program of China(2010CB951700)National Natural Science Foundation of China(41175027,91337212,and 41375022)Key Research Program of the Chinese Academy of Sciences(KZCX2-YW-Q1-02)
文摘Performance of the fifth-generation Pennsylvania State University/National Center for Atmospheric Research Mesoscale Model(MM5) over the Lake Nam Co region of the Tibetan Plateau was evaluated based on the data from five surface observation sites in 2006. The interaction between two thermally-induced circulations(lake breezes and mountain-valley winds) was also investigated. The results show that MM5 could be used to simulate 2-m air temperature; however, MM5 needs improvement in wind field simulation.Two numerical simulations were conducted to study the effect of the lake on the local weather and wind system. The original land cover of the model was used in the control experiment, and the lake was replaced with grassland resembling the area surrounding the lake in the sensitive experiment. The results of the simulations indicate that the lake enhanced the north slope mountain-valley wind and the mountain changed the offshore flow direction at the north shore. During the day, a clear convergent zone and a strong upflow were observed over the north slope of the Nyainq?entanglha Range, which may cause frequent precipitation over the north slope. During the night, the entire area was controlled by a south flow.
基金funded by the Fondi Potenziamento della Ricerca - Linea 2 - 2015 Project "Dynamic of active margins: from rift to collisional chains", leader Dr. Davide Zanoni
文摘Geomorphological mapping plays a key role in landscape representation: it is the starting point for many applications and for the realization of thematic maps, such as hazard and risk maps, geoheritage and geotourism maps. Traditional geomorphological maps are useful for scientific purposes but they need to be simplified for different aims as management and education. In tourism valorization, mapping of geomorphological resources(i.e., geosites, and geomorphosites), and of geomorphic evidences of past hazardous geomorphological events, is important for increasing knowledge about landscape evolution and active processes, potentially involving geomorphosites and hiking trails. Active geomorphosites, as those widespread in mountain regions, testify the high dynamicity of geomorphic processes and their link with climatic conditions. In the present paper, we propose a method to produce and to update cartographic supports(Geomorphological Boxes)realized starting from a traditional geomorphological survey and mapping. The Geomorphological Boxes are geomorphological representation of single, composed or complex landforms drawn on satellite images, using the official Italian geomorphological legend(ISPRA symbols). Such cartographic representation is also addressed to the analysis(identification, evaluation and selection) of Potential Geomorphosites and Geotrails. The method has been tested in the upper portion of the Loana Valley(Western Italian Alps), located within the borders of the Sesia Val Grande Geopark, recognized by UNESCO in 2013. The area has a good potential for geotourism and for educational purposes. We identified 15 Potential Geomorphosites located along 2 Geotrails; they were ranked according to specific attributes also in relation with a Reference Geomorphosite located in the Loana hydrographic basin and inserted in official national and regional databases of geosites(ISPRA; Regione Piemonte). Finally, the ranking of Potential Geomorphosites allowed to select the most valuable ones for valorization or geo
文摘The Kaghan Valley is in the territorial jurisdiction of Mansehera District, named after a tiny village Kaghan, at the end of the valley. The valley culminates in the tree-clad high mountains and glaciers in the North-East with varying altitudes from 1 to 5 thousand meters above sea level. The region is relatively active geophysically, hydrologically and biologically diverse by virtue of the altitude and aspect-driven variability in energy and moisture. In such region a better understanding of changes in land resources, production of agronomic and horticultural crops, use of timber and non-timber products, and livestock structure/composition have important implications and understanding these changes along with the indigenous knowledge of mountain people which, is key to sustainable development of the Himalayan region. Our results showed that the main causes of lowest agriculture production in the area are poor crop management in context of the mountains, drought spells, low soil fertility, land fragmentation and tenancy status of the agricultural land. Off season vegetables cultivation on the sloppy land leads to sever soil erosion and soil land degradation of this mountain ecosystem. Overgrazing during the summer season is another problem as the pastures are visited both by the Afghan and local nomads without relating with carrying capacity of the alpine meadows. The overgrazed soil is usually subject to rainfalls and severe soil erosion. Any use of resources of such fragile rare high mountain ecosystem requires a great sense of responsibility but in this case the forest resources are being plundered and are used roughly. We recommend adequate use of agricultural inputs, specific crop management practices for mountain agriculture. Local social welfare organizations should work to create awareness about the sustainable use of natural resources. The government should resolve the ownership problem of land as common property keeping in mind the customary laws of the region to make sure the involvement of all stakeho