沙尘气溶胶输送及其辐射反馈效应的数值模拟研究

【作者】 陈勇；

【导师】 陈德辉； 王宏；

【作者基本信息】 中国气象科学研究院 ， 气象学， 2006， 硕士

【摘要】 本文首先基于中国气象科学研究院研发的GRAPES_DAM沙尘气溶胶模式,结合Goddard短波辐射参数化方案,利用我国沙漠地区最新的辐射特性参数,对沙尘气溶胶模式实时输出的沙尘空间分布进行辐射参数化,把沙尘短波辐射效应引起的大气温度变化同步反馈到天气模式中,从而初步建立了GRAPES₂W_SDM天气-沙尘双向模式。然后根据天气系统的典型性、局地持续时间长短、范围大小等,主要选取了造成我国沙尘天气的典型天气过程,分别为2006年3月南疆东灌冷锋和2002年3月蒙古气旋两次沙尘天气过程。通过对比考虑（RAD）与未考虑（CTL）沙尘短波辐射效应的两组试验,分析比较沙尘短波辐射效应对天气系统及沙尘输送的影响,进而对沙尘气溶胶短波辐射的反馈效应有了进一步的认识,得出以下主要结论:（1）GRAPES_DAM模式在未考虑沙尘辐射时,在72h内对天气形势场、地面大风及沙尘输送的模拟较为理想,为考虑沙尘辐射的试验提供了理想的基础。（2）沙尘辐射效应影响到达地面短波辐射量、短波辐射加热率、温度、风及边界层特征量等的变化。在沙尘浓度定量模拟较为理想的条件下,考虑沙尘辐射效应对沙尘区内地面气温、气压的模拟较好。（3）沙尘辐射效应影响沙尘模块的起沙、输送、沉降等。在特殊的地形、气象场下,沙尘辐射效应的累积可能会引起风向的变化,使堆积的沙尘重新逆着原方向输送。（4）沙尘辐射效应对天气-沙尘的综合影响可以对沙尘体的不同区域分别进行讨论,本文主要将沙尘体分为中上部、中下部、移动前沿和中心底层四个区域。除了起沙外,同时可以结合沙尘输送、沉降来考虑沙尘辐射反馈效应。通过模拟发现并提出一个沙尘辐射引起的正反馈机制:沙尘加热爬升效应。即沙尘体中上部吸收太阳短波辐射增大,产生加热效应,使温度升高,温度升高使得沙尘体中上部的向上垂直速度加强,气团将较大沙尘浓度的空气向上输送,使得中上部沙尘浓度增大。该机制在沙尘体中上部随着短波辐射的累积,逐步使沙尘浓度和垂直速度共同增大;机制随着短波辐射的消失而消失。该机制主要发生在沙尘体中上部的弱上升运动区。（5）沙尘辐射效应对蒙古气旋海平面气压影响程度不大,主要表现在对蒙古气旋路径和强度的影响不大。只有当沙源处于蒙古气旋中心后部、沙尘有条件向气旋中心输送时,其对强度的影响才显著。更多还原

【Abstract】 To study the radiative effect of dust aerosols on synoptic-scale system and the dusttransport, an interactive weather-dust model （GRAPES₂W_SDM） was developed. Themodel based on the GRAPES_DAM dust aerosol model which developed by CAMS,including the shortwave radiative transfer scheme for dust aerosols, and the dust aerosolparameterization. Based on the dust aerosol concentration which output from dust aerosolmodel, and using the new Chinese desert parameter, the radiative effects of dust aerosol wascalculated. The change of temperature caused by radiative effect of dust aerosol was returnedto the weather model on-line.According to the representative of synoptic-scale systems which caused dust weather, theduration, and the range of the dust weather process, two case happened in China were chose,one caused by the cold front happened in south of Xinjiang, the other caused by the Mongoliacyclone. Two parallel simulation, one including the radiative effects of dust aerosol （RAD）and the other without them （CTL）. A comparison of the two experiments shows that:（1） GRAPES_DAM model which didn’t consider radiative effects of dust aerosol, cansimulated the synoptic situation, the surface wind, and the dust aerosol transport very wellduring the 72h. It established a good foundation for the RAD experiment.（2） Radiative effects of dust aerosol impacted the solar radiation flux arrived the floor,solar heating rate, temperature, wind, and the physic quantity of boundary layer. If the dustaerosol concentration simulate very well, the experiment which consider the radiative effectsof dust aerosol can simulate the surface temperature and the pressure much better. （3） Radiative effects of dust aerosol also impacted the dust production, transport, and thedeposition. In the special terrain and weather case, radiative effects of dust aerosol can changethe wind direction, and transport the dust back.（4）The impact on weather-dust which caused by the radiative effects of dust aerosolshould be divided into different areas to discussed. In this paper, four areas was chose todiscuss, including the upper of dust body, the lower of the dust body, foreside of the dust bodyand the bottom of the dust body. Besides the dust production, it should also include the dusttransport and deposition.The simulation also shows that it existed a positive feedback mechanism caused by theradiative effects of dust aerosol: dust heating and raising effect. The mechanism happened inthe middle and upper of the sand-dust body, if there have a weak raising area. The dustaerosol over there absorbed the solar radiation, heated the layer, and then improved the raisingvertical velocity. The increase of raising vertical velocity raised more dust into the upper areain turn. Finally, both the raising vertical velocity and dust aerosol concentration increased.Along with the solar radiation cumulating, the mechanism also enhanced;and along with thesolar radiation disappearing, the mechanism also disappeared.（5） The impact on sea level pressure of Mongolia cyclone which caused by the radiativeeffects of dust aerosol not remarkable, including the route and the intensity of the cyclone.Only when there were some dust source behind the Mongolia cyclone, and the dust cantransport into the center of the cyclone, the impact would be remarkable.更多还原