高原低涡与OLR、风场的气候变化及低频信号特征

Climate Change and Low-frequency Signal Characteristics of Plateau Vortex,OLR and Wind Fields

为进一步探讨高原低涡与高原大气的基本状况及其联系,通过对1981-2015年低涡频次及OLR、500 h Pa经纬向风场的统计,分析其气候变化及低频振荡特征,并初步探讨了低涡频次与其他三者低频信号之间的联系。结果表明:4-8月是低涡的频发时段;低涡频次呈逐年增加的趋势,存在显著的2 a、4 a变化周期和55 d、30 d低频振荡周期;在低涡频发期内,OLR平均值为212.2 W·m^(-2),存在显著的10~12 a变化周期和45 d、20 d低频振荡,滤波中心存在东进和西退的移动特征,在纬向上表现为向南移动,500 h Pa纬向风均值为3.56 m·s^(-1),其逐年及逐日变化均呈下降趋势,存在4 a、10 a的变化周期和75 d、45 d的低频振荡周期,30~60 d滤波信号中心以西退和北进为主要移动特征,60~90 d滤波信号中心向南移动特征明显,500 h Pa经向风以北风分量为主,其逐年及逐日变化均为减小趋势,存在4 a变化周期和10-20 d低频振荡;低涡频次与500 h Pa纬向风区域平均值在1996年发生突变;低涡频次与大气低频振荡存在密切联系,其与500 h Pa经向风呈负相关性,7-8月尤为显著,与OLR和500 h Pa纬向风在4月至7月中旬呈显著正相关,7月中旬至8月转为负相关,其中与OLR 30-60 d滤波信号呈高度负相关性;500 h Pa纬向风滤波信号中心的移动能较好的对应低涡频次空间分布的变化。

In order to further discuss the basic situations and relations between plateau vortex and plateau atmosphere, the characteristics of climate change and low frequency oscillation are analyzed by the statistics of the low vortex frequency and the OLR and 500hPa wind field of the 1981-2015 years. Moreover, the relationships between the frequency of the plateau vortex and the other three＇ s low frequency signals are also discussed. The results are showed as follows： The plateau vor-tex is active from April to August. The frequency of the plateau vortex has an increasing trend, which has significant oscil-lations of 2 a and 4 a and low frequency oscillations of 55 d and 20 d. In the active period of plateau vortex, the average value of OLR is 212.2 W · m^-2, there is a significant 10-12 a change cycle and low frequency oscillation of 45 d and 20 d in OLR. The filter centers exist moving characteristics of eastward or westward movement, and southward movement at lati-tude. The mean value of the 500 hPa zonal wind is 3.56 m · s^-1 , and the trend of the zonal wind has a decreasing trend in annual and daily change. The change has variation periods of 4 a and 10 a and the low frequency oscillation periods of 75 d and 45 d. The filtering signal centers of 30-60 d is mainly moving westward and northward, and the 60-90 d filter signal centers have a tendency to move southward. The north wind component is the main component of the of 500 hPa me-ridional wind and 500 hPa meridional wind has a 4 a variation period and 10-20 d low frequency oscillation. The muta-tions of annual variation of the vortex frequency and the zonal wind mean value of 500 hPa both exist in 1996. The low vor-tex frequency is closely related to the low frequency oscillations of the atmosphere, it is negatively correlated with the 500 hPa meridional wind, especially in 7-8 months. The low vortex frequency has a significant positive correlation with the OLR and 500 hPa zonal wind from April to mid July and turns negative correlation from mid July to August, which is highly negatively correlated with the OLR 30-60 d filtering signal. The movement of 500 hPa zonal wind filtering signal centers can better correspond to the spatial distribution of low vortex frequency.