北京地区一次强沙尘暴过程的大气边界层结构和湍流通量输送特征

Characteristics of Atmospheric Boundary-Layer Structure and Turbulent Flux Transfer during a Strong Dust Storm Weather Process over Beijing Area

利用中国科学院大气物理研究所北京325m气象塔的风速和温度平均场观测资料和湍流资料，以及北京市气象台地面常规气象资料和逐日08：00和20：00（北京时间）的探空资料，分析了2002年3月18-22日沙尘暴过境前后北京城市边界层结构特征和湍流输送特征，结果表明：1）在沙尘暴爆发前，边界层中水平风速一直较小；气温较高，大气层结稳定，在边界层上部有强大的逆温层。随着冷锋过境，沙尘暴爆发，边界层中水平风速和平均湍流速度急剧增强；温度也突然变化，先迅速增强后又持续下降，逆温层迅速被破坏。2）沙尘暴初期，280m上为系统性上升气流，而47和120m则为系统性的下沉气流。随着沙尘暴爆发，湍流动能、向下传输的动量以及向上传输的感热也迅速增大，并且120m高度的湍能、动量通量以及感热通量明显高于47和280m，这与北京的局地环流有关。3）本次沙尘暴过程中，120和47m层的摩擦速度都明显超过了北京的临界摩擦速度，表明局地起沙也是本次沙尘暴过程中北京沙尘的一个重要沙源。

Based on the mean wind, temperature and humidity data and turbulent data observed at the Beijing 325 m Meteorological Tower, and the surface conventional meteorological data and sounding data collected at Beijing Meteorology Observatory, some characteristics of atmospheric boundary layer structure and turbulence transfer during the strong dust storm weather from 18 to 22 March 2002 was investigated. The results showed that, 1） before the dust storm broke out, the mean wind speed was very slow and the temperature was comparatively high. And strong inversion layers existed in the upper atmospheric boundary layer （ABL）. While after the dust storm broke out, the wind speed increased sharply and the temperature changed greatly. The temperature increased sharply in advance, and then decreased continuously. Consequently the inversion layer was rapidly destroyed. 2） During the initial stages of the synoptic process, there were systematic upward flows at the 280 m height in the ABL, but systematic downward flows occurred at the heights of 47 m and 120 m during the synoptic process. The turbulence energy, the momentum transportation and the sensible heat transportation were increasing sharply. The turbulence energy and the fluxes of turbulent momentum and sensible heat collected at 120 m height was larger than those collected at the heights of 47 m and 280 m, perhaps which was caused by the local circumfluence of Beijing. 3） In this dust storm process, the friction velocities collected at 47 m and 120 m heights were larger than the critical friction velocity of Beijing, consequently we got the conclusion that the local dust emission is one of the important source of dust particles of Beijing in this synoptic process.