Knowledge Resource Center for Ecological Environment in Arid Area
| 东亚沙尘循环及其气候效应的数值模拟研究 | |
| 其他题名 | Numerical simulation of atmospheric dust cycles and their climatic effects over East Asia |
| 孙辉 | |
| 出版年 | 2014 |
| 学位类型 | 博士 |
| 导师 | 刘晓东 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 东亚沙尘暴活动频繁，每年春季伴随着沙尘暴的爆发，大量沙尘气溶胶被卷入大气层。沙尘暴不但直接危害人们日常生活和生命财产，而且其爆发过程产生的沙尘气溶胶对气候和环境有重要影响，由于其特殊的物理化学特性。然而，目前对沙尘循环过程的观测非常有限，难以满足人们更透彻的理解东亚沙尘暴活动规律和沙尘气溶胶对气候影响的需求。因此，耦合沙尘模块的气候模式，包括起沙、传输、沉降被应用于预测沙尘暴活动，沙尘循环过程以及沙尘对气候的影响。同时，改善和发展用于预测沙尘暴的模式至关重要。尽管一些学者利用不同的模式研究了东亚沙尘气溶胶特性。由于模式内核和起沙参数化方案不同，得到的结论不同。另外，人们对东亚沙尘气溶胶时空分布的模拟仍存在差异，而且沙尘气溶胶对东亚气候的影响，尤其是对大气环流的影响至今极少。因此开展东亚沙尘循环以及其气候效应的模拟至关重要。我们首先检验了耦合沙尘模块的区域气候模式(Regional Climate Model version 3, RegCM3/Dust)对中国西北地区沙尘暴爆发过程的模拟效果，然后利用最新版的RegCM4/Dust对东亚地区进行了两个有无耦合沙尘模块的数值试验。耦合沙尘模块的试验输出用于分析沙尘的时空分布特征，两个试验之差被用于分析沙尘对东亚气候的影响。本文的主要结论如下：1.RegCM3/Dust模式已成功地用于东亚强沙尘暴的个例研究。与实际观测相比，RegCM3/Dust较好地模拟出了2006年4月9日-11日爆发于中国西北的一次强沙尘暴爆发区域、天气形势及相应的沙尘气溶胶光学厚度(AOD)分布。2006年4月9日6时，沙尘暴首先爆发于塔里木和吐鲁番盆地。受蒙古气旋的影响，24小时后甘肃中部及内蒙古西部地区也开始爆发沙尘暴。源区地面起沙率大于3 mg m-2 s-1，单位面积上的沙尘载荷量高于3 000 mg m-2。对流层中低层沙尘主要向东输送，可影响我国华北绝大部分地区，本次沙尘暴过程造成中国北方主要城市空气质量的下降。模拟的AOD分布特征与地面起沙率和载荷量分布特征相对应，并与TOMS 卫星观测的气溶胶指数(AI)的区域和中心值具有较好的一致性。AOD分布由西向东呈递减的趋势，且有两个大于2的高值中心，一个位于新疆塔里木、吐鲁番盆地和古尔班通古特沙漠地区；另一个位于河西走廊和内蒙古交界地区。对比他人研究结果，RegCM3对沙尘的起沙、传输等过程以及AOD的时空分布模拟合理。沙尘暴在源区引起的地面和大气顶(TOA)辐射强迫能够达到-150 W m-2和50 W m-2左右2.利用最新版区域气候模式RegCM4/Dust对东亚地区气候平均的大气沙尘循环进行了数值模拟并于观测资料进行了对比。模拟的沙尘AOD与同期卫星观测的气溶胶AOD对比发现，RegCM4/Dust较好的抓住了东亚地区沙尘气溶胶的时空分布特征，而这些特征在以前全球模式模拟结果较差。其次，RegCM4/Dust模拟出了3个沙尘浓度高值中心，它们分别位于塔克拉玛干沙漠，内蒙古西部沙漠和北疆，在全年沙尘活动最强盛的春季，源区中心沙尘浓度高达1000 ?g m-3。另外，模拟的沙尘柱含量在三个沙尘源区均高于0.6 g m-2。相比湿沉降，沙尘主要通过干沉降消除，且干沉降中的主要贡献来源于粒径大于5 μm的沙尘颗粒，沉降通量在源区可达800 mg m-2 day-1。3.利用耦合与不耦合沙尘模块的两个长达10年(2000-2009)的数值试验，对比分析了沙尘对东亚区域气候的影响，模拟结果表明，沙尘的局地效应主要表现为春季在源区对太阳短波辐射起强的削弱作用，使地面降温。沙尘使地面获得的短波辐射通量减少12 %左右，使TOA净向外的长波辐射通量减少1.2 %。在沙尘暴活动最强的春季，地面短波辐射强迫为负，中心位于沙尘源区，可达-20 W m-2左右。沙尘的强消光作用能够使沙尘源区地面温度降低0.8 ℃左右，降温趋势可一直延续到夏季。而TOA短波辐射强迫也为负，在-8 W m-2左右，中心位于华北地区。4.模拟结果还表明，东亚春季沙尘能够影响到随后夏季的东亚大气环流，进而影响下游的大气降水，表现为沙尘影响的一种滞后和非局地效应。沙尘的降温效应从春季可以一直维持到夏季，使得在中国西北沙尘源区、黄河下游和中国东海依次形成了气旋-反气旋-气旋（C-A-C）耦合环流异常。在华北反气旋异常与东海气旋异常共同作用下，夏季中国偏北风增强，进而减弱了东亚夏季风。这样的环流特征增加了中国西北沙尘源区和东海的降水，减弱了中国华北和华南地区的降水。 |
| 英文摘要 | East Asia is a region where dust storms occur frequently. Millions of tons of dust can be injected into atmosphere accompanying with the explosion of dust storms every year, especially in spring. Dust storms not only can cause huge damage to human lives and production activities, but also can influence the climate and environment due to physical and chemical effects of dust aerosols produced in sandstorm. However, available observations of the dust cycle are too limited to satisfy need of scientific research for in-depth understanding dust activities and its climatic effect in East Asia. So climate models incorporate with dust schemes including the emission, transport and deposition are often used to explore processes of dust activities, dust cycle and its climatic effect. Meanwhile, it is important to improve or develop a model which can be used to forecast a dust storm. Although some scientists used different models to investigate dust storms in East Asia, previous results were discrepant based on different model kernels and dust emission parameterizations. On the other hand, the differences of simulated dust aerosol spatial-temporal distribution in East Asia still exist and the research about dust aerosol effect on the climate of East Asia, particularly on the impact of atmospheric circulation is not reported. So it is important to carry out the simulation of dust cycle and its climatic effect in East Asia. Above all, the regional climate model version 3 (RegCM3), developed by the Abdus Salam International Centre for Theoretical Physics (ICTP, Italy) has been coupled with a desert dust module to test its performance on the simulation of strong dust strom process in East Asia. Then, the latest regional climate model version 4 (RegCM4) is used to simulated the spatial-temporal distribution of dust aerosol and its climatic impact through direct radiative forcing over East Asia. Two experiments are carried out. One is coupled dust module, the other is not. The output of coupled dust experiment is used to analyze the distribution of dust aerosol, and the difference of the above two experiment is used to research the dust aerosol climatic effect in East Asia. The main conclusions are summarized as follows:1. The RegCM3/Dust has been successfully used in case studies of severe dust stroms over East Asia. Simulated results show that the outbreak sites, synoptic situation and pattern of the corresponding AOD of the dust storm which outbroke on April 9-11 in 2006 are successfully simulated, comparing with observation. This severe dust storm extensively exploded in Tarim Basin and Turpan Basin at 6:00 a.m. on April 9 in 2006. 24 hours later, the sandstorm began to outbreak in central Gansu and the western Inner Mongolia under the effect of Mongolia Cyclone. The dust emission rate and column burden of those places were greater than 3 mg m-2 s-1 and 3 000 mg m-2, respectively. The transportation of dust in lower and middle troposphere was eastward and its effect can reach most provinces of east China. This dust storm caused the air quality decline of the cities in north China. In addition, distribution characteristics of AOD, which were well consistent with the distribution and values of TOMS AI, corresponded with those of dust emission rate and column burden. The AOD showed a decline trend from west to east with two maximums which was great than 2. One was located in the desert area of Tarim Basin, Turpan Basin and Gurbantonggut. The other was close to the border between Gansu corridor and western Inner Mongolia. Comparing with results from other models, the dust emission rate, transport and spatial-temporal distribution of AOD were reasonably simulated. The surface and TOA radiative forcing induced by this dust strom over the sources region can reach -150 W m-2 and 50 W m-2 respectively. 2. The averaged atmospheric dust cycle over East Asia is simulated by using the latest version of the regional climate model RegCM4/Dust and simulate |
| 中文关键词 | 东亚 ; 沙尘气溶胶 ; 直接辐射强迫 ; 夏季风 ; 区域气候模式 |
| 英文关键词 | East Asia dust aerosol direct radiative forcing summer monsoon regional climate model (RegCM) |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 环境科学 |
| 来源机构 | 中国科学院地球环境研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287329 |
| 推荐引用方式 GB/T 7714 | 孙辉. 东亚沙尘循环及其气候效应的数值模拟研究[D]. 中国科学院大学,2014. |
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