酒泉市大气边界层逆温特征及其与沙尘天气的关系

Characteristics of Atmospheric Boundary Layer Inversion and the Relationship with Dust Weather in Jiuquan City

利用2009—2018年酒泉市逐日08时(北京时间,下同)和20时L波段雷达探空秒级数据资料,统计分析了近10 a酒泉市大气边界层内(5 km以下)逆温变化规律特征及其与沙尘天气的关系。结果表明:酒泉市一年四季均有逆温出现,逆温日的出现频率高达84.1%,其中接地逆温频率72.9%,悬浮逆温频率29.5%;08时逆温频率、逆温厚度高于20时,秋冬高于春夏;逆温强度08时和20时差异较小,但接地逆温平均逆温强度是悬浮逆温强度的2.2倍,>5℃·hm^(-1)的强逆温主要出现在秋季。酒泉市逆温(双层逆温)的出现频率呈增大趋势,逆温厚度呈减小趋势,逆温强度没有明显变化;沙尘天气发生时逆温层厚度增大,逆温强度减小,沙尘暴对逆温强度的削弱作用最明显,沙尘暴发生前平均逆温强度为2.73℃·hm^(-1),发生时仅为0.67℃·hm^(-1)。

In order to analyze the characteristics of temperature inversion in the boundary layer(below 5 km)over Jiuquan City,this paper used the daily L-band radar data at 08:00 and 20:00(Beijing time,BST)from 2009 to 2018.The frequency,intensity and thickness of ground temperature inversion and suspended inversion were analyzed in detail.The results showed that the frequency of temperature inversion over Jiuquan is high up to 84.1%,including 72.9%ground inversion and 29.5%suspended inversion;the frequency of temperature inversion at 08:00 is higher than that at 20:00(BST).The temperature inversion occurs mostly in autumn and winter and rarely in summer.The inversion frequency and thickness are the lowest in summer and the maximum in winter.The inversion thickness at 08:00 BST is larger than that at 20:00 BST.The thickness of suspended inversion is larger than that of ground inversion.This phenomenon is due to the change of solar radiation,which increases temperature at day time and strengthens the turbulence,resulting the inversion weakened or disappeared.On the contrary,the ground temperature gradually decreases at night with the turbulence weakening,which causes the inversion intensity and thickness strengthened.The inversion intensity is weak in summer and strong in winter,which has an obvious seasonal variation.There is a little difference in inversion intensity between 08:00 and 20:00(BST).But the average of ground inversion intensity is 2.2 times of suspended inversion intensity.Most of strong inversion with intensity higher than 5℃·hm^(-1) happens in autumn.Based on the data of dust from 2009 to 2018,the relativity of intensity dust and inversion elements(inversion intensity and inversion thickness)were analyzed.The results revealed the days of sandstorm in Jiuquan in the past 10 years were obviously fewer,the days of blowing sand were significantly weakened,and the days of floating dust were not significantly changed.The thickness of inversion increased and the intensity of inversion decreased when sand-dust weather occurred,and the intensity of inversion decreased most obviously during the period of sandstorm.