【摘要】：城市化作為人類活動對水循環(huán)影響的重要表現(xiàn)形式，一方面通過改變下墊面屬性，對地表產(chǎn)匯流特征產(chǎn)生直接影響，另一方面通過地表能量分配及其他城市環(huán)境要素（如氣溶膠，人為熱源等）改變區(qū)域降雨特性，從而對地表的水文過程產(chǎn)生間接影響。論文圍繞城市地區(qū)夏季暴雨及洪水問題，基于多源觀測數(shù)據(jù)和數(shù)值模擬手段，開展城市下墊面對降雨以及洪水過程影響規(guī)律的研究，對理解城市地區(qū)陸氣耦合反饋機制以及建立防洪減災體系有重要的科學價值與實踐意義。 論文從我國夏季降雨整體時空格局及其與東亞夏季風的關系出發(fā)，分析了北京夏季降雨年際變化特征，發(fā)現(xiàn)北京夏季降雨在年際上呈波動減少的趨勢，與東亞夏季風變化一致；但城區(qū)夏季降雨在2000年之后顯著增加，與北京建成區(qū)面積急劇增加的變化趨勢一致。同時，揭示了2008~2012年北京夏季累積降雨量和強降雨頻次在空間上有兩個聚集中心，分別位于城區(qū)以及城市下風向的懷柔、密云和平谷地區(qū)�；隈詈铣鞘泄趯幽Ｐ偷闹谐叨葰庀竽Ｊ絎RF對北京地區(qū)2008~2012年夏季降雨的空間格局進行了分析和模擬，從氣候角度揭示了城市下墊面對北京地區(qū)夏季降雨的影響機制。開發(fā)了基于雷達反射回波強度的暴雨云團識別算法SCI-2D，，并將其用于分析夏季暴雨云團通過城區(qū)時的演變規(guī)律，研究表明城市下墊面對暴雨云團有分離和激發(fā)的作用�；跉鈮K浮升理論發(fā)現(xiàn)城區(qū)地表的熱量傳輸過程改變了大氣邊界層厚度、抬升凝結(jié)高度以及自由對流高度，為對流活動提供了良好的動力和水汽條件，從而使得城區(qū)降雨強度和頻次得到顯著增強。 對于典型湖濱城市而言，城市地表熱量傳輸過程對降雨的影響還與湖陸風環(huán)流有關。以美國密爾沃基市-密歇根湖地區(qū)為例，通過對該地區(qū)夏季典型降雨事件的數(shù)值模擬和分析，揭示了城市熱島環(huán)流和湖陸風環(huán)流的耦合效應及其對湖濱城市夏季降雨的影響機制�；诒┯暝茍F追蹤算法TITAN，識別了暴雨云團通過城區(qū)時形態(tài)和結(jié)構(gòu)的演變特征，進一步驗證了北京地區(qū)研究得到的結(jié)論。 以城市化流域為研究對象，定量分析了城市下墊面以及城市化引起的降雨空間分布的改變對流域洪水響應的影響。通過設置虛擬流域及數(shù)值實驗，發(fā)現(xiàn)忽略降雨的空間分布會低估城市化引起的流域洪水量級的增幅，最高可低估50%。此外，降雨空間分布特征對流域年徑流量的年際變異性也有顯著影響。論文綜合了下墊面改變和陸氣耦合反饋機制，完善了城市化流域水文響應規(guī)律的分析框架。
[Abstract]:Urbanization, as an important form of human activity affecting the water cycle, on the one hand, has a direct impact on the characteristics of surface production and confluence by changing the properties of the underlying surface. On the other hand, the surface energy distribution and other urban environmental factors (such as aerosol, artificial heat source, etc.) change the regional rainfall characteristics, thus have an indirect impact on the surface hydrological process. On the basis of multi-source observation data and numerical simulation method, this paper studies the effects of urban underlying rainfall and flood process on summer rainstorm and flood in urban areas. It is of great scientific value and practical significance to understand the coupling feedback mechanism between land and atmosphere in urban areas and to establish a flood control and disaster reduction system. Based on the analysis of the interannual variation of summer rainfall in Beijing and its relationship with the East Asian summer monsoon, it is found that the summer rainfall in Beijing tends to fluctuate and decrease, which is consistent with the change of the East Asian summer monsoon. However, the summer rainfall in urban areas increased significantly after 2000, which is consistent with the trend of sharp increase in the area of Beijing's built-up areas. At the same time, it is revealed that there are two gathering centers in Beijing from 2008 to 2012, which are located in Huairou and Miyun Heping Valley, respectively, in the urban area and the wind direction under the city. Based on the mesoscale meteorological model (WRF) coupled with urban canopy model, the spatial pattern of summer rainfall in Beijing from 2008 to 2012 was analyzed and simulated, and the influence mechanism of urban underlay on summer rainfall in Beijing was revealed from the point of view of climate. A rainstorm cloud cluster recognition algorithm based on radar echo intensity (SCI-2D,) is developed and applied to analyze the evolution of storm cloud cluster in summer. The research shows that the urban underlay can separate and excite the storm cloud cluster. Based on the theory of air mass floatation, it is found that the heat transfer process on the surface of the urban area changes the thickness of the atmospheric boundary layer, uplift condensation height and free convection height, which provides good power and water vapor conditions for the convective activity. As a result, the intensity and frequency of rainfall in urban areas are significantly enhanced. For typical lakeshore cities, the effect of urban surface heat transfer on rainfall is also related to lake-land wind circulation. Taking the Milwaukey-Lake Michigan area as an example, the typical summer rainfall events in the area are simulated and analyzed. The coupling effect of urban heat island circulation and lake-land monsoon circulation and its influence mechanism on summer rainfall in lakeside cities are revealed. Based on the rainstorm cloud tracking algorithm (TITAN,), the evolution characteristics of the morphology and structure of the storm cloud cluster passing through the urban area are identified, which further verifies the conclusion of the research in Beijing area. Taking the urbanized watershed as the research object, the influence of the urban underlying surface and the change of the spatial distribution of rainfall caused by urbanization on the flood response of the watershed is analyzed quantitatively. By setting up virtual watershed and numerical experiments, it is found that the increase of flood magnitude caused by urbanization can be underestimated by neglecting the spatial distribution of rainfall, and the maximum value can be underestimated by 50%. In addition, the spatial distribution of rainfall also has a significant impact on the annual variability of runoff. In this paper, the change of underlying surface and the coupling feedback mechanism between land and atmosphere are integrated to perfect the analytical framework of the hydrological response law of the urbanized watershed.
【學位授予單位】：清華大學
【學位級別】：博士
【學位授予年份】：2014
【分類號】：TV122

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