Intraseasonal Variability of Air Temperature Over East Asia in Boreal Summer
Intraseasonal Variability of Air Temperature Over East Asia in Boreal Summer
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DOI：
10.3389/feart.2017.00063
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发表时间：
2017-08
影响因子：
2.9
通讯作者：
Chen Zhao;Tim Li;Suxiang Yao;S. Behera;T. Nasuno
中科院分区：
文献类型：
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作者：
Chen Zhao;Tim Li;Suxiang Yao;S. Behera;T. Nasuno
利用1979-2013年NCEP-NCAR再分析资料，研究了东亚北部夏季2m高空大气温度的季节内振荡(ISO)特征。结果表明，东亚地区的地面气温具有10-30天的优势周期，并呈现出向东南传播的特征。季内气温异常的纬向和经向平均相速度分别约为2.6经度和1.7纬度/日。温度收支的诊断表明，季节内温度扰动的传播主要归因于平均风的平流和季节内风对夏季平均温度的平流。高空对流层位势正(负)高度异常与低层暖(冷)气温异常密切相关，这两种异常以相似的方式向东南传播。波活动通量分析表明，中纬度Rossby波能量也向东南传播，与对流层高层位势高度传播一致。这表明，除了低层平流机制外，通过静力关系的对流层高层强迫是另一种可能的机制。进一步的统计分析表明，EA夏季的热波受东南向传播的季内温度模的调制。
The intraseasonal oscillation (ISO) of atmospheric temperature at 2m over East Asia (EA) in boreal summer is investigated through NCEP-NCAR reanalysis data for the period of 1979-2013. It is found that the surface air temperature in EA has a dominant period of 10-30 days and exhibits a southeastward propagation characteristic. The average zonal and meridional phase speed of the intraseasonal air temperature anomaly is about 2.6 longitudes and 1.7 latitudes per day, respectively. A diagnosis of the temperature budget suggests that the propagation of the intraseasonal temperature perturbation is primarily attributed to the advection by the mean wind and the advection of the summer mean temperature by the intraseasonal wind. An upper-tropospheric geopotential positive (negative) height anomaly is closely associated with a low-level warmer (cooler) air temperature anomaly and both anomalies propagate southeastward in a similar way. A wave activity flux analysis reveals that mid-latitude Rossby wave energy also propagates southeastward, consistent with the upper-tropospheric geopotential height propagation. This indicates that in addition to low-level advection mechanism, upper-tropospheric forcing through the hydrostatic relationship is another possible mechanism. A further statistical analysis indicates that heat waves in EA summer are modulated by the southeastward-propagating intraseasonal temperature mode.