平流层准零风层统计特征及准两年周期振荡对其影响分析

根据形成机制的不同将平流层准零风层（Quasi-Zero Wind Layer，QZWL）划分为由平流层准两年周期振荡（Quasi-Biennial Oscillation，QBO）各高度处于不同位相形成的第一类QZWL和由于平流层低层经向温度梯度逆转而形成的第二类QZWL；利用ERA-40再分析资料分析了两类QZWL在不同季节中空间结构的变化规律，讨论了平流层QBO对两类QZWL年际变化产生的影响。研究结果表明：第一类QZWL集中出现在冬季赤道附近地区，第二类QZWL在夏季热带外地区和冬季20°N～40°N太平洋地区上空；QZWL夏季高度比冬季低约3 km，夏季QZWL出现高度比冬季稳定，约在50～70 hPa之间；由于受到QBO的直接影响，第一类QZWL出现的高度和纬度范围存在明显的年际变化，第二类QZWL受到QBO的影响主要体现在QBO西风位相年和东风位相年相比，冬季20°N～40°N范围内存在第二类QZWL的概率较高。

Analysis of the Characteristics of the Stratospheric Quasi-Zero Wind Layer and the Effects of the Quasi-Biennial Oscillation on it

According to the different forming mechanisms,the stratospheric Quasi-Zero Wind Layers(QZWL) are classified into two categories.The first kind of QZWL is due to the transition between two phases of the Quasi-Biennial Oscillation(QBO),and the second kind of QZWL is caused by the reversal of meridional temperature gradient in lower stratosphere.Then based on the ERA-40 reanalysis data,the three-dimension structures of the two kinds of QZWL in different seasons are analyzed,further the influence of QBO on them are studied.The results show that the first kind of QZWL can be found at tropical zone in winter,whereas the second kind exists at extratropical areas in summer and over the Pacific Ocean in middle and lower latitude(20°N-40°N) in winter.The height of QZWL in summer is lower and more stable than that in winter.The barometric heights of it in summer are settled from 70 hPa to 50 hPa.Because of the direct effect of QBO,the first kind of QZWL has an obviously interannual variation.The influence of QBO on the second kind of QZWL is that the frequency of QZWL occurring within 20°N-40°N in winter in the westerly phase of QBO is more than in the easterly phase of QBO.