摘要
利用NCEP客观分析资料、卫星观测资料和中尺度化学模式(WRF-Chem),对2007年4月17日发生在青藏高原(下称高原)北侧塔克拉玛干沙漠地区的一次沙尘过程进行分析,研究了高原及附近地区沙尘气溶胶从地面向对流层上部和平流层下部传输的特征和机制,以及不同粒径沙尘粒子在传输中的差异。结果表明,沙尘粒子的垂直传输高度与背景水平风场的垂直分布特征密切相关,在没有云微物理过程参与的情况下,当高原上空出现深厚南北风交汇,形成穿透对流层顶的上升运动时,源于塔克拉玛干沙漠地区的沙尘气溶胶粒子,能到达高原上空,在辐合上升运动的作用下传输至下平流层,且具有明显的倾斜向上传输的特征。进一步分析表明,到达平流层下层的沙尘在空间上并不与地面沙尘源的位置相匹配。不同粒径的沙尘粒子的传输表现出不同的特征,粒径小的沙尘气溶胶粒子更容易在上升气流的作用下传至下平流层,而粒径>8.0μm的沙尘粒子则在重力沉降作用影响下无法传至下平流层。敏感性数值试验结果表明,降低高原地形会使得高原上空沙尘气溶胶粒子向南和向上的传输变弱。
Using NCEP reanalysis data and satellite observations,together with a mesoscale chemical transport model(WRF- Chem),a dust event occurred in the Taklimakan desert,north of the Qinghai- Xizang Plateau on April 17,2007 is analyzed in an attempt to understand the characteristics and mechanisms of dust aerosol transport from the surface to the upper troposphere and the lower stratosphere over Qinghai-Xizang Plateau and its vicinity. Differences in the transport of particles with different sizes are also discussed. The results indicate that:Vertical transport of dust aerosols is closely related to background horizontal winds. In the absence of the cloud microphysical processes,when a deep convergence zone of northerly and southerly winds forms over Qinghai-Xizang Plateau,the vertical motions resulted from the convergence could transport dust aerosols,originated from the Taklimakan desert,to the lower stratosphere with an evident inclined transport pathway. The result implies that the position of the dust reached the lower stratosphere may not collocate with the surface dust source. In addition,dust particles with different sizes present different transfer characteristics. Small dust particles can be transported to the stratosphere relative easily by upward motions,while particles with size larger than 8.0 μm could not be transported to the lower stratosphere due to strong deposition process. The results from a sensitivity experiment with decreased orography height showthat the upward and southward transport of dust aerosols is depressed when orography height is decreased.
出处
《高原气象》
CSCD
北大核心
2015年第4期991-1004,共14页
Plateau Meteorology
基金
国家自然科学基金项目(41175042
41225018
41275006)
