水平螺旋度与沙尘暴的动力学关系研究  

Dynamic relationships between the horizontal helicity and the sandstorm

作　　者：李岩瑛[1,2,3] 张强[1,2] 李耀辉[2] 孙爱芝[4] 尚宝玉[1] 陈龙泉 

机构地区：[1]兰州大学大气科学学院,甘肃省干旱气候变化与减灾重点实验室,兰州730000 [2]中国气象局兰州干旱气象研究所,兰州730020 [3]甘肃省武威市气象局,武威733000 [4]西南大学地理科学学院,重庆400715

出　　处：《地球物理学报》2008年第3期692-703,共12页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目“西北沙尘暴关键区近地面起沙特征的观测与数值研究”(40645027);国家重点基础研究项目(G2000048703)共同资助

摘　　要：应用2002～2006年高空流场和地面观测资料,计算近地面至500hPa水平螺旋度的大小.结果表明:水平螺旋度负值中心值越大,500hPa到近地面风速越大,西风增强,风速垂直切变越大,辐合上升运动越强,形成沙尘暴的强度就越强.水平螺旋度负值中心常常在河西走廊附近最强,导致其下游东南方发生沙尘暴.水平螺旋度负值中心与其下游沙尘暴发生强度有一致的对应关系:当水平螺旋度负值中心≤-200m2/s2时,未来24小时内该区下游将有沙尘天气出现,当≤-600m2/s2时,6小时内该区下游将有能见度小于500m的强沙尘暴天气出现,当≤-1000m2/s2时,6小时内该区下游将有能见度小于50m的特强沙尘暴天气出现.We calculated the average horizontal helicities from the surface to 500 hPa based on daily 08h and 20h upper wind and surface wind data obtained in 2002-2006. The calculated results show that the more negative the horizontal helicity is, the higher the wind velocities from the surface to 500 hPa are and the stronger the westerly wind is. Consequently, the shear strength of the vertical air flow increases and the convergent vertical air flow is thus enhanced, resulting in the formation of extremely severe dust storms. The negative core （or center） of the aforementioned horizontal helicity is often strongest near the Hexi Corridor, leading to the frequent occurrence of sandstorms in its downstream areas towards the southeast. Our calculated results demonstrate a strong relationship between the negativity of the helicities and the intensity of the resulted sandstorms. For example, if the horizontal helicity in its core is ≤-200 m^2/s^2,sand-dust will probably occur within 24 hours with a better （〉500 m） visibility. When the horizontal helicity in its core is ≤- 600 m^2/s^2 , strong sandstorms are likely to occur within 6 hours with a visibility of less than 500 m. When the horizontal helicity in its core （or center） is ≤-1000 m^2/s^2,extremely strong sandstorms are most likely to occur within 6 hours with a visibility of less than 50 m.

关 键 词：水平螺旋度 近地面风场 沙尘暴 强度 动力学关系 

分 类 号：P445[天文地球—大气科学及气象学]