Intraseasonal variability of air temperature over the mid-high latitude Eurasia in boreal winter
Intraseasonal variability of air temperature over the mid-high latitude Eurasia in boreal winter
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欧亚大陆中高纬度地区冬季气温的季节内变化
DOI：
10.1007/s00382-015-2956-8
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发表时间：
2016-01
期刊：
影响因子：
4.6
通讯作者：
李天明
中科院分区：
文献类型：
--
作者：
杨双艳;李天明
利用NCEP-NCAR再分析资料研究了欧亚大陆中高纬冬季气温的季节内振荡。结果表明，季节内温度扰动在50° ~ 75 ° N，80° ~ 120°E附近的近地面区域表现出最大变率，并以平均纬向和纬向相速度分别为3.2和2.5 m s-1向东南方向传播。低层温度信号与对流层高层高度异常紧密耦合，两者以相似的相速向东南方向传播。诊断的温度收支表明，东南传播主要归因于平流的温度异常的平均风。波活动通量分析表明，向东南传播的波列可能是Rossby波能量传播的结果。Rossby波列的源出现在高纬度欧洲/大西洋部门，最大的波活动通量收敛驻留。在向东南移动的过程中，ISO扰动通过动能和势能转换从平均气流中获得能量。建立了一个基于物理的中国东南部地区季节内气温异常的经验模式。主要的可预报源是向东南传播的ISO信号。以1979 ~ 2003年的数据作为训练期，构建了实证模型。一个10年（2004年至2013年）的独立预测表明，该模型达到了一个有用的技能，长达25天。
The intraseasonal oscillation (ISO) of air temperature over the mid- and high-latitude Eurasia in boreal winter was investigated by NCEP-NCAR reanalysis data. It is found that the intraseasonal temperature disturbances exhibit maximum variability near the surface in the region of 50°–75°N, 80°‒120°E and they propagate southeastwards at average zonal and meridional phase speeds of 3.2 and 2.5 m s−1, respectively. The low-level temperature signal is tightly coupled with upper-tropospheric height anomalies, and both propagate southeastward in a similar phase speed. A diagnosis of the temperature budget reveals that the southeastward propagation is primarily attributed to the advection of the temperature anomaly by the mean wind. A wave activity flux analysis indicates that the southeastward propagating wave train is likely a result of Rossby wave energy propagation. The source of the Rossby wave train appears at the high latitude Europe/Atlantic sector, where maximum wave activity flux convergence resides. During its southeastward journey, the ISO perturbation gains energy from the mean flow through both kinetic and potential energy conversions. A physics-based empirical model was constructed to predict the intraseasonal temperature anomaly over southeast China. The major predictability source is the southeastward-propagating ISO signal. The data for 1979‒2003 were used as a training period to construct the empirical model. A 10-yr (2004‒2013) independent forecast shows that the model attains a useful skill of up to 25 days.
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