利用2012 -2017年逐小时风速资料， 分析了华山景区大风天气不同时间尺度的变化特征， 并以春秋季对景区索道运行产生严重影响的两次偏南大风为例， 分析了大风形成机制。结果表明： 以17 m·s^-1作为大风阈值， 景区大风多发生在21:00（北京时）至次日凌晨， 相反午后到黄昏大风较少发生。华山南峰站位置偏南， 海拔高， 偏南气流与秦岭北坡夜间下山风作用， 导致偏南大风多。华山站靠北， 海拔低， 除偏南大风外， 冷锋后偏北气流影响， 西北大风频次也较高。两次偏南大风前环流一致呈“东高西低”形势， 华山位于华北高压向西北低压过渡的南北向等高线密集带中， 梯度风原理是风速加大的动力机制。大风发生前， 陕西关中为-4 hPa的强3 h变压区， 变压风引起辐合上升， 与高压后部偏南风越过秦岭后的干绝热下沉运动， 加上关中不稳定上升运动， 诱导夜间下山风增强， 是偏南大风形成的热力因子。分析气象要素的变化， 大风前3 h华山站降温5 ℃以上， 前7 h降压4 hPa以上； 且大风前温度露点差大于10 ℃， 气压和气温的超前降低可作为大风预警的有效因子。大风时景区附近的雷达图像有片状弱回波， 但没有大风速区， 表明受地形遮蔽， 距离景区最近的泾河雷达不足以反映大风特征。

This paper analyzed the variations on different time scales of gales in the Huashan mountain scenic spot of Shaanxi， by using the hourly observations from the year of 2012 to 2017 in the Huashan’s station.Two representative southerly events were analyzed in this paper to get the mechanism of gales of Huashan.The main conclusions were as follows.Taking the wind velocity of more than 17 m·s^-1 as a thread， the gales of Huashan tended to occur from 21:00 （Beijing Time the same as affer） to the next early morning frequently， on the contrary， less gales occurred after noon and before 20:00.The southern peak located at higher altitude and more southward position， so it encountered more southerly gales.The Huashan station meet with not only southerly gale， but also northwestern strong wind， because of its northerly position and lower altitude.During the two gale southerly events， the similar circulation of characterized by ‘East High and West Low’ at the low-level was explored.Huashan was located in the contour-intensive transition region of from North China High to Northwest Low.The dynamic theory of gradient wind resulted in the high velocity.Before the gales， the 3h variable pressure field displayed a strong negative center of lower than -4 hPa in central Shaanxi， which made the convergence and ascending motion.At the same time， the southerly alee was accelerated in the night and enforces the gales， accompanied with the instability-ascending motion.The significant temperature and pressure changes were found before the strong wind.In the autumn gale， the temperature decreased by 5 °C 3 hours before the maximum velocity， accompanying the pressure decreased by 4 hPa about 7 hours before.The early changed pressure and temperature can be the important factors of wind forecasting.From the observations of Jinghe radar site， 100 km away from Huashan， the echoes in the Huashan gale were weakened and cannot display the extreme velocity， because of the terrain occlusion of high mountain peaks.