Contrast of Evolution Characteristics of Boreal Summer and Winter Intraseasonal Oscillations over Tropical Indian Ocean
Contrast of Evolution Characteristics of Boreal Summer and Winter Intraseasonal Oscillations over Tropical Indian Ocean
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热带印度洋北半球夏季和冬季季节内振荡演化特征对比
DOI：
10.1007/s13351-019-9015-z
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发表时间：
2019-08
影响因子：
3.2
通讯作者：
Liu Jia
中科院分区：
文献类型：
--
作者：
Zhang Qingchi;Li Tim;Liu Jia
赤道印度洋季节内振荡(ISO)演变的一个最显着的夏季-冬季差异是北半球夏季为准稳态振荡，而北半球冬季为东向传播。这一特征与北半球夏季ISO方差最大仅出现在东印度洋，而北半球冬季则遍及整个盆地的观测事实是一致的。 1982-2012年,发现印度洋东部出现ISO对流时,北半球冬季(夏季)对流以东出现正(负)水汽趋势。正是水汽趋势的差异造成了夏季和冬季不同的传播行为。对水汽收支的进一步诊断表明,主要差异在于平均流量的异常水汽平流。此外,海-气相互作用也发挥了作用。而北半球冬季ISO开始结束西印度洋地区,北半球夏季ISO在中东部赤道印度洋上空因边界层增湿而启动。水汽增加主要是由于前期东印度洋上空ISO抑制阶段引起的异常东风的平均比湿水平平流所致。此外,延迟的海表温度反馈也发挥了作用。夏季和冬季ISO演变的总体差异受包括平均海表温度和水汽含量在内的季节平均状态的调节。
A most striking summer-winter difference of evolution of the intraseasonal oscillation (ISO) over the equatorial Indian Ocean is a quasi-stationary oscillation in boreal summer but eastward propagation in boreal winter.This feature is consistent with the observational fact that maximum ISO variance appears only in the eastern Indian Ocean in boreal summer while it appears across the entire basin in boreal winter.The cause of the distinctive propagation and initiation characteristics is investigated through the diagnosis of observational and reanalysis data for the period of 1982-2012.It is found that when the ISO convection appears over eastern Indian Ocean,a positive (negative) moisture tendency appears to the east of the convection in boreal winter (summer).It is the moisture tendency difference that is responsible for different propagation behavior in the summer and winter.A further diagnosis of the moisture budget indicates that the major difference lies in anomalous moisture advection by the mean flow.In addition,air-sea interaction also plays a role.While boreal winter ISO starts over western Indian Ocean,boreal summer ISO is initiated over central-eastern equatorial Indian Ocean,due to boundary layer moistening.The moisture increase is caused primarily by the horizontal advection of mean specific humidity by anomalous easterlies induced by preceding suppressed-phase ISO over eastern Indian Ocean.Besides,a delayed SST feedback also plays a role.The overall difference of ISO evolution between the summer and winter is regulated by the seasonal mean state including the mean SST and water vapor content.
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影响因子：
0.8
作者：
Tim Li;Bin Wang
通讯作者：
Tim Li;Bin Wang
影响因子：
3.1
作者：
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作者：
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通讯作者：
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影响因子：
5.8
作者：
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通讯作者：
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