冬季北太平洋与北大西洋上空风暴轴特征比较与分析

Comparisons and Analysis of the Characteristics of Winter Storm Tracks over the North Pacific and North Atlantic

采用1948—2007年NCEP/NCAR再分析资料,选取850,700,600,500,250hPa层风场(u,v)、垂直运动场(ω)、位势高度场(H)和温度场(T),对北半球冬季(12、1、2月)太平洋和大西洋上空风暴轴的特征及影响因素进行了分析和比较。结果表明,北半球冬季风暴轴最强中心位于北大西洋上空,北太平洋高空急流的强度明显大于大西洋高空西风急流的强度。通过诊断分析北太平洋与北大西洋上空风暴轴的影响因素,发现北太平洋和北大西洋上空风暴轴强度的影响因素具有明显的差异:在北太平洋上空,涡度平流随高度的变化和厚度平流项对风暴轴的作用较大西洋而言更明显,而涡动能量的向上输送对北大西洋风暴中心的作用更大。对风暴轴年际变化的分析发现,两大洋风暴轴在1980年代之后均有明显的增强现象,而在空间分布的时间演化上,两大洋风暴轴有着相反的演化:太平洋风暴轴有向西南方向移动的趋势,而大西洋风暴中心则略微向东北方向移动。

By using the NCEP / NCAR reanalysis data from 1948 to 2007, and selecting the winds （u, v）, potential height （H）, air temperature （T） and vertical velocity （w）, （ including level 850, 700, 500 and 250hPa）, the characteristics and the factors of the storm tracks over the North Pacific and North At- lantic in winter （Dec, Jan and Feb） were analyzed. The result shows that the storm track＇s center in win- ter is located in the North Atlantic, while the jet center is located in the North Pacific. Using the co-equa- tion to diagnose the factors which influence the storm tracks over the both oceans, we found that there are some differences between the two storm tracks. Over the North Pacific, vorticity advection and thickness advection are major factors, while diabatic heating plays the more important role over the North Atlantic. In the energy feature, the instable energy supported by the diabatic heating is stronger over the North At- lantic than the North Pacific, which means thermal effect produced by latent heating plays the most im- portant role to storm tracks. The paper shows with the storm track＇s analysis of inter-annual variation that, storm tracks over the two oceans have enhanced since 1980s. The storm track over the Pacific has shifted south-west, while the Atlantic storm track has moved to the northeast.