Analysis and Simulation of the Stratospheric Quasi-zero Wind Layer over Korla, Xinjiang Province, China

Abstract

The stratospheric quasi-zero wind layer (QZWL) is a transition region with low zonal wind speeds in the lower stratosphere at an altitude of ∼20 km. The zonal wind direction above the QZWL layer is opposite to that below the QZWL layer and the north—south wind component is small. The atmospheric wind field near the stratospheric QZWL is an important factor affecting the flight altitude and dynamic control of stratospheric airships. It is therefore necessary to study the stratospheric QZWL to provide better environmental information for these aircraft. High-resolution radiosonde data were used to analyze the characteristics of the stratospheric QZWL over Korla, Xinjiang Province, China. A weak wind layer in which the wind direction suddenly reversed from westerly to easterly was observed at ∼20 km in the lower stratosphere, characteristic of the stratospheric QZWL. The Weather Research and Forecasting model was used to simulate the profiles of the horizontal wind speed and direction over Korla. The forcing effect of each diagnostic term in the equation on the zonal wind speed was analyzed. The results showed that the advection term was the dominant factor forcing the zonal wind speed. The wave term had a secondary forcing role, although the forcing effect of the wave term on the zonal wind speed was significant in some regions.

摘要

平流层准零风层 (Quasi-Zero Wind Layer, QZWL)是指平流层下层20km高度附近纬向风很小的大气层, 上下层纬向风风向相反, 同时南北风分量亦很小. 平流层准零风层及其附近风场是影响平流层飞行器的飞行姿态和动力控制的重要因素. 因此, 平流层准零风层的研究很有意义, 可以为平流层飞行器提供更好的环境参考. 本文利用加密的探空风数据分析了中国新疆库尔勒附近地区上空的平流层准零风层特征. 在平流层下层约20 km处观测到风向突然从西风向东风向逆转的弱风层, 即平流层准零风层. 本文利用WRF模式很好地模拟了观测站点上空水平风速和风向的廓线特征. 此外, 基于水平动量方程, 我们进一步分析了各诊断项对纬向风的强迫效应, 结果显示平流项是影响纬向风速变化的主要强迫因子; 而波动项起次要的强迫作用, 但在部分区域对纬向风的强迫效应也很显著.