Seasonal differences in extratropical potential vorticity variability at tropopause levels
Seasonal differences in extratropical potential vorticity variability at tropopause levels
复制标题
对流层顶温带位涡变化的季节差异
DOI：
10.1029/2004jd004639
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发表时间：
2004
影响因子：
--
通讯作者：
H. Davies
中科院分区：
文献类型：
--
作者：
M. Liniger;H. Davies
[1] 横切对流层顶的等熵表面上的温带位涡 (PV) 分布是行星尺度遥相关模式、天气尺度天气系统和中尺度平流层-对流层交换的关键特征。这里使用所谓的欧洲中期天气预报中心再分析 15 (ERA-15) 数据集展示了北半球 1 月和 7 月的气候学，用于了解 PV 的平均值和变化模式。它的推导考虑了对流层顶高度的强烈季节性循环和等熵表面上PV的尖锐准纬度梯度以及伴随的正负异常的规模和幅度的双峰性。通过将变异性的传统标准偏差测量与正异常和负异常的概率密度函数结构的单独描述进行比较，既强调又避免了双峰性。结果表明，冬季纬向异质性明显，变化（例如风暴路径）模式表现出丰富的空间结构，太平洋和大西洋之间存在显着差异。相比之下，在夏季，等熵表面平流层下部部分的异质性要弱得多，但表面对流层部分的海洋区域仍然存在高变异性区域。结果与风暴路径的结构和动态及其空间和季节变化直接相关。
[1] The distribution of extratropical potential vorticity (PV) on isentropic surfaces that transect the tropopause is a key feature of planetary-scale teleconnection patterns, synoptic-scale weather systems, and mesoscale stratosphere-troposphere exchange. Here a Northern Hemisphere January and July climatology is presented for the mean and variability patterns of the PV using the so-called European Centre for Medium-Range Weather Forecasts reanalysis-15 (ERA-15) data set. It is derived taking into account the strong seasonal cycle of the tropopause height and the sharp quasi-latitudinal gradient of PV on the isentropic surfaces together with the accompanying bimodality in the scale and amplitude of positive and negative anomalies. The bimodality is both emphasized and circumvented by comparing conventional standard deviation measures of the variability with those of separate depictions of the probability density function structures of positive and negative anomalies. It is shown that in winter the zonal heterogeneity is pronounced and the variability (e.g., storm track) patterns exhibit a rich spatial structure with marked differences between the Pacific and Atlantic. In contrast, in summer the heterogeneity on the lower stratospheric portion of the isentropic surfaces is much weaker, but there remain regions of high variability over oceanic regions on the tropospheric portion of the surfaces. The results relate directly to the structure and dynamics of storm tracks and their spatial and seasonal variation.