Knowledge Resource Center for Ecological Environment in Arid Area
| 兰州市两山绿化气候效应的数值模拟 | |
| 安兴琴 | |
| 出版年 | 2001 |
| 学位类型 | 硕士 |
| 导师 | 陈玉春 |
| 学位授予单位 | 中国科学院寒区旱区环境与工程研究所 |
| 中文摘要 | 山谷城市兰州位于青藏高原的东北边缘，属于中纬度干旱、半干旱气候区，生态环境相当脆弱，干旱少雨、荒漠化始终困扰着本地区的人民。植树造林，增加陆面植被覆盖度，通过改变地表反射率、地面粗糙程度及土壤湿度的途径改善区域气候环境更显得尤为重要。兰州冬季地面静风频率很高，一年中约有310天出现逆温，同时兰州市又是一座工业城市。其特殊的山谷地形及与此相联系的气象条件是造成兰州市大气污染严重的重要因素。如何科学合理地治理兰州市的大气污染及改善城市气候环境是一项艰巨而具有现实意义的工作。在兰州市既有高山河谷又有水域城市，如此复杂的非均匀下垫面上研究大气边界层特征和陆气相互作用，更是要综合考虑山谷地形与城市下垫面等各方面的因素，全面揭示兰州市的大气边界层特征及其污染气候特征，以及南北两山绿化后对于局地气候环境的影响和小区域绿洲对于城市气候和环境影响的机理。本文主要是利用三维流体非静力平衡中尺度模式MM5V3，一方面，对山谷城市兰州冬季的大气边界层进行了数值模拟试验，分析了兰州的风场、温度场及湿度场特征，着重分析了兰州市逆温形成机理及其污染气候特征。另一方面，模拟研究改变兰州市周围山体的地表植被状况，对于局地气候的影响。通过以上工作，得到的主要结论如下：1、MM5V3模式在高分辨率(1KM)的情况下，模式积分稳定，能够较好地模拟兰州的大气边界层特征，模拟结果与现有理论及观测事实基本一致。模式模拟出了山谷城市典型的山谷风特征，及冬季逆温、逆湿等边界层特征。2、通过三个绿化对比方案的冬季模拟结果表明：(1)在兰州市南北两山不同高度、不同范围的绿化，冬季气温与地表温度的变化各不相同。一般来说白天(14时)，绿化区内气温都有所升高，而绿化区域内海拔高的山体，地表温度降低，海拔低的河谷，地表温度有升高的情况；傍晚(20时)，绿化区域地表温度都有所升高；早晨，在绿化区域内温度都有所减小。(2)不同的绿化方案，比湿增加的时间、区域及空间位置以及对于市区的影响都不相同，这主要与兰州市特殊的南高北低的山谷地形及其局地的山谷风环流和高空环流密切相关。因此，在兰州既有高山河谷又有水域，如此复杂的下垫面上绿化，需要综合考虑山谷边界层与城市边界层的影响；植被在海拔较高的南山与海拔较低的北山与北部河谷具有不同甚至完全相反的气候效应，这是由于兰州特殊山谷地形条件下，山谷、山坡及山顶的辐射差异及复杂的热量平衡差异所造成。(3)绿化后，兰州市晚上20时，逆温强度及大气稳定度有明显减小，这对于兰 州市污染物的向外输送比较有利，而且随着绿化后，对流层下部大气湿度的增加，从而也增加了大气中污染物湿沉降过程的可能性。3、两山绿化夏季气候效应模拟结果：(1)MM5V3模式能够很好地模拟兰州夏季近地面气温与地表温度及相对湿度的日变化规律。(2)绿化与控制试验模拟结果对比分析表明，绿化后，夏季白天植被覆盖区域地表温度降低1℃，相对湿度的增加最大是在模拟区域上空600Hpa的对流层下部，增加最大时间是白天14时，增加最大值为19％，增加次大时间是晚上20时，高度稍低于14时的高度；与冬季C绿化方案比较表明，夏季比湿最大增值中心位置高于冬季，并且增加值大于冬季。 |
| 英文摘要 | The valley city Lanzhou lies on the North east margin of Qinghai_Xizang Plateau and belongs to median latitude dry and half-dry climate area. Local people are puzzled at frail environment, drought and desertness. So it is especially important to improve local climate and environment, if only we afforest on mountains aronud Lanzhou to induce albedo, to enhance roughness and soil moisture. The surface wind velocity of Lanzhou is almost aero in winter, there are 310 inverse temperature days in a year. The special valley environment and related meteorologic condition are important factors related with air pollution. It is a hard and realism work to handle air pollution and improve city climate sientificaly and reasonably. The numerical simulation study on the atmospheric boundary layer structure and the interaction process between land-surface and atmosphere is complex especially on heterogeneous terrain of Lanzhou where have valley, river and city. We should considerate overall. In this paper, nonhydrostatic meso-scale MM5V3 model is on one hand used to simulate many characters of winter atmospheric boundary of Lanzhou such as wind, temperature and humidity field. The dissertation is aimed at analysing the reason of inverse temperature in hanzhou and the character of polluted climate. On the other hand, the model is also used to simulate the influence on local climate while changing the vegetations on mountains around Lanzhou. In summary, the major conclusions of the paper are as follows: 1. When using high resolution, MM5V3 model is stable to simulate the characters of atmospheric boundary of Lanzhou such as mountain-valley wind, inverse temperature and inverse humidity in winter, and the simulations are consistent with theories and observations. 2. After having compared three green test with control test, we get the conclusions as follows: (1) Temperature and ground temperature are varied according to the vegetations planted on different height and range of north and south mountains around Lanzhou. Generally, at noon, temperature of more vegetation is higher than that of less vegetations and ground temperature of higher mountains is lower and that of lower mountains is the opposite. Ground temperature of all afforested areas is higher at dusk and lower at morning than that of less vegetation. (2) At different green test, the time, area and space that the humidity increased most are varied related with the special terrain of Lanzhou and mountain-valley wind and upper air circulation. So when planting trees on such complicated terrain of Lanzhou, we should take the valley and city boundary into account. Because the vegetations on higher south mountain and lower north mountain have different even contrary climatic effect caused by the variation of net radiation and of heat balance at mountain valley, slope and top. (3) After afforesting, the intensity of atmospheric inversion and stability reduce at dusk, which benefits to the diffusion of pollution. Simultaneously, the humidity of low troposhere increases, which enlarges the possibility of pollution sedimentation. 3. For summer, after green C test compared with control test, the climatic effects are as follows: (1) MM5V3 model can simulate the change rule of surface temperature, ground temperature and relative humidity. (2) It shows that the ground temperature with more vegetation is lower in summer daytime and the area where relative humidity increased is at low troposhere of 600hPa. The time when humidity increased biggest is at 14 and bigger is at 20 and the height is slightly lower than that of 14. Compared with winter test, the location where humidity increased biggest is heigher than that of winter and the increased quantity is bigger than that of winter. |
| 中文关键词 | 山谷城市 ; 大气边界层 ; 陆气相互作用 ; 数值模拟 ; 山谷风 ; 逆温 ; 逆湿 ; 大气稳定度 |
| 英文关键词 | MM5V3 valley city atmospheric boundary layer land atmosphere interaction numerical simulation mountain and valley breeze inverse temperature inverse humidity atmospheric stability |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源机构 | 中国科学院西北生态环境资源研究院 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/286272 |
| 推荐引用方式 GB/T 7714 | 安兴琴. 兰州市两山绿化气候效应的数值模拟[D]. 中国科学院寒区旱区环境与工程研究所,2001. |
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