【作者】 王金艳；

【导师】 王式功；

【作者基本信息】 兰州大学 ， 气象学， 2006， 博士

【摘要】 沙尘天气不仅是干旱、半干旱区及邻近地域的一种恶劣的灾害性天气,而且已经成为影响人类健康和经济发展的重要环境问题,因而倍受关注。为了进一步探讨沙尘天气的发生机理并提高对其的预报能力,本论文在综合前人有关风蚀起沙物理机制的基础上,利用邵亚平的沙尘模式系统,讨论了风蚀起沙的各种影响因子,并修正了模式敏感的关键物理量;首次将中国气象局建立的新一代沙尘天气监测网获得的沙尘观测资料应用于数值模式中,利用近两年的新资料估计和优化数值模式中沙尘浓度的初值场,提高了沙尘数值模式系统的预报性能;分析了不同国家同一种沙尘天气类型所表征的沙尘强度的差异,对东亚地区的沙尘天气分级量化,建立了沙尘模式预报定量结果与定性观测之间的相互对应关系,进而提出了一种对沙尘模式业务预报结果定量化评估和检验的新方法,使预报产品更适用于一线预报人员。主要的研究结果如下: （1）选取4种起沙方案的数值模拟检验结果进行比较发现,Shao（1996）、Marticorena and Bergametti（1995）的模拟结果明显大于实际的沙尘天气发生范围,尤其是Marticorena and Bergametti（1995）模拟结果远高于沙尘的实际起沙量;Lu and Shao（1999）起沙方案的模拟结果明显小于实际的沙尘天气发生范围,而只有Shao（2001）起沙方案模拟结果与沙尘天气发生的实际范围和强度较为一致,且该系统的预报产品与实况观测资料有较好的吻合,说明该起沙方案模式对发生在我国的沙尘天气具有较好的预报能力。 （2）本文充分考虑气温、风速、云和降水等对土壤含水量的影响,利用这些要素估算的土壤含水量替换了模式中原有的土壤含水量,对沙尘模式的模拟结果有较明显的改进。并针对该沙尘模式系统中将沙尘初值设为0的不足,用能见度估算大气中PM₁₀浓度和TSP的浓度,优化沙尘模式中沙尘浓度的初值场,使模拟结果更加接近观测实况。初值场的优化对沙尘模式24小时和48小时的模拟都有改进,而且对24小时的模拟改进效果优于48小时的模拟。当有大面积的沙尘天气发生后,尤其大范围沙尘暴天气发生之后,初值场的优化可使模式的模拟效果显著提高。 （3）以往的研究发现,朝鲜发布的沙尘暴的频数多于中国和韩国与其邻近的地区,这些现象表明亚洲地区对同一类型的沙尘天气所表征的强度在不同国家是有差异的。本文分析结果表明:强沙尘暴、沙尘暴天气的TSP和PM₁₀浓度,在我国和日本高于其它地区;扬沙和浮尘天气的TSP和PM₁₀浓度,印度半岛高于其它地区。强沙尘暴TSP浓度的最低值出现在朝鲜;沙尘暴的TSP浓度的最低更多还原

【Abstract】 Dust events, especially severe dust storm not only are disastrous weather with extreme harm in arid, semiarid region and its surrounding area, but also become an environmental problem which causes harm to the human being health and affects economic development. In this paper, on the basis of the physical mechanisms of sand and dust emissions by wind erosion the influences of different factors on sand and dust emissions have been studied by using the dust model system. The empirical relationship between visibility and PM₁₀ concentration is established by regression analysis of visibility and PM₁₀ concentration that were taken every 5 minutes at sixteen dust event’s observation stations of northern China in springs. The prediction capability of numerical dust model is improved by optimizing dust concentration of initial field and estimating the surface soil moisture for dust model system. The difference in dust events classification in different countries in East Asia is analyzed. On the basis of TSP, PM₁₀ concentration and wind speed, a quantitative classification for dust events is proposed for East Asia. Consequently, a corresponding relation is established between results of dust model with observations. It is helpful for forecaster to using model results. The following is some conclusions:（1） The simulated results of the four schemes of sand and dust emissions of Shao（2001）, Marticorena and Bergametti（1995）, Shao（1996） , Lu and Shao（1999） are compared. It is found that the simulated results of Marticorena and Bergametti（1995）, Shao（1996） are over the range of actual dust events observation, those of Lu and Shao（1999） are less than the range of observation, that of Shao（2001） is consistent with the range of observation. So the dust model system of Shao（2001） is preferably used to predict the dust events in China.（2） By analyzing the surface soil moisture and the initial field of dust concentration in previous dust model system, it can be seen that those variables is very different from the fact. Therefore, the surface soil moisture influencing wind erosion is estimated by precipitation, cloud, air temperature and wind speed. The dust and PM₁₀ concentration are estimated from visibility. After these corrections, 24-hour and 48-hour simulated results of dust events in intensity and spatial distributions are all improved, especially for 24-hour simulated results. When the dust events occurred in larger area, the prediction capability of improved dust model system is greatlypromoted by optimizing initial field of dust concentration.（3） More dust storms were reported in North Korea in contrast with itsneighboring regions of China and South Korea in springs. This shows that the represented intensity of the same dust events is different in different countries. In China and Japan, the TSP and PMio concentrations for severe dust storm and dust storm are higher than that in other countries, while the PMio and TSP concentrations for blowing dust and floating dust over the Indian Subcontinent are highest. The minimum of TSP concentration range for severe dust storm is in North Korea. The minimum of TSP concentration range for dust storm is in South Korea. The TSP concentration range of blowing dust in south of the Korea Peninsula and parts of the Tibet Plateau are lowest. The PMio concentration ranges of severe dust storm and dust storm in Korea Peninsula and Mongolia are lowest.（4） The proposed classification standards for dust events in East Asia have been put forward for the first time by comprehensive analysis and research, severe dust storm Ptsp> 6000ug m°, Ppmio> 5000ug m"3, v > 10m s"1;dust storm: 3000ug m"3< Ptsp < 6000|ig m3, 3000ug m"3 < pPMio < 5000ug m"3, 10m s"1 < v < 15m s"1;blowing dust: 900ug m"3 < pTsp < 3000ug m"3, 200u￡ m"3 < pPMio< 2000p.g m"3, 5m s"1 < v < 10m s"1;and floating dust: 750ug m"3< pTsp< 1200ug m"3, 200ug m"3< pPMio< 600ug m’3, 2m s"1 < v < 5m s"1.（5） The sand and dust emissions by wind erosion under the La Nina phenomena and El Nino phenomena are analyzed by using the dust model system. The results are as follows: If the La Nina phenomena appears in equatorial eastern Pacific Ocean, the dust emission flux in Chinese mainland will obviously increase;if the El Nino phenomena appears in equatorial eastern Pacific Ocean, the opposite result will occure;variation range of the dust emission flux during the La Nina is exceeded that of El Nino. This is consistent with the statistical results.更多还原