| 大气边界层强风的阵性和相干结构 |
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| 引用本文： | 程雪玲,曾庆存,胡非,彭珍.大气边界层强风的阵性和相干结构[J].气候与环境研究,2007,12(3):227-243. |
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| 作者姓名： | 程雪玲 曾庆存 胡非 彭珍 |
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| 作者单位： | 中国科学院大气物理研究所,北京,100029 |
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| 摘 要： | 我国北方春季冷锋过境后,常骤发强风,甚至起沙扬尘,持续数小时甚至一二天,通过对边界层超声风温仪的资料分析,可知大风常叠加有周期为3～6 min的阵风,较有规律,且有明显的相干结构:阵风风速峰期有下沉运动,谷期有上升运动;阵风扰动以沿平均流的顺风方向分量为主,横向和垂直方向的分量都较小,其本质是低频次声波和重力波的混合;阵风沿顺风向且向下传播.周期小于1 min的脉动在水平面上基本是各向同性的不规则的湍涡.大风期间,无论是平均流、阵风和湍流脉动,至少在120 m高度以下,主要都有西风和北风动量下传,感热上传.平均流的动量下传强于由脉动下传的量,与一般天气情况不同,而且阵风与湍流的动量下传的量值差不多.平均流和阵风在动量传送上起相当大的作用.
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| 关 键 词： | 大气边界层 强风 阵风 相干结构 动量下传 沙尘暴 |
| 文章编号： | 1006-9585（2007）03-0227-17 |
| 修稿时间： | 2007-04-052007-04-19 |
Gustness and Coherent Structure of Strong Wind in the Atmospheric Boundary Layer |
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| CHENG Xue-Ling,ZENG Qing-Cun,HU Fei and PENG Zhen.Gustness and Coherent Structure of Strong Wind in the Atmospheric Boundary Layer[J].Climatic and Environmental Research,2007,12(3):227-243. |
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| Authors: | CHENG Xue-Ling ZENG Qing-Cun HU Fei and PENG Zhen |
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| Institution: | Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029 |
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| Abstract: | Spring in the northern China after the passage of cold front there is often outbreak of strong wind and even with accompany of dust emission.The strong wind is lasted for several hours up to two days.By the analyses of the date obtained by the ultra-sonic anemometer-thermometer monitoring in the atmospheric boundary layers during some typical cases,it is revealed: there are rather regular wavetrains of gustwind superimposed on the basic wind flow(i.e.,time mean flow,for example,averaged for every 20 min).1)The gustwind wavepaket is very different and separable from the turbulent addies.It is with frequency equal to about 3 to 6 min.and with coherent stracture,i.e.,there is descending(ascending)motion in the period of wind speed peak(wind speed valley).2)The major component of the gustwind velocity is along the direction of mean wind flow,but the component perpendigular to the flow and the vertical velocity are rather weak.This indicates that the gustwind is essentially a subsonic wave with very low frequency and mixed with gravity wave.3)The gustwind trains propagate along the mean wind flow direction and downwards in the vertical.4)The hight frequency turbulent fluctuations(with period less than 1 min) is almost isotropic in the horizontal space.5)During the period of strong wind,there are downward vertical transport of momentum and upward(in the daytime)vertical transport of sensible heat by fluctuations(both the gustwind and turbulence).6)It is very interesting to point out that as the vertical transport of momentum is decomposed separatedly into transports by a)mean motion, b)eddy motion(gustwind disturbances plus turbulent eddies),c)gustwind,and d)turbulence separatedly,they are all downwards in the lower levels of the atmospheric boundary layer and in the most period.However,that by the mean motion is the largest,and that by c) and d) are comparable.All these are very different from the case of normal weather,and the friction velocity owing to the fluctuations is also much larger than that of normal weather case.7)Even in the lowest levels of atmospheric boundary layer the vertical transports of momentum by mean flow and by gustwind are both very important,hence can not be neglected in the strong wind case. |
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| Keywords: | atmospheric boundary layer strong wind gustwind coherent structure downward transport of momentum duststorm |
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