The quasi‐2 day wave activities during 2007 boreal summer period as revealed by Whole Atmosphere Community Climate Model
The quasi‐2 day wave activities during 2007 boreal summer period as revealed by Whole Atmosphere Community Climate Model
复制标题
DOI：
10.1002/2016ja022867
复制
发表时间：
2016-07
期刊：
影响因子：
--
通讯作者：
Sheng‐yang Gu;Han L. Liu;N. Pedatella;X. Dou;Zhifeng Shu
中科院分区：
文献类型：
--
作者：
Sheng‐yang Gu;Han L. Liu;N. Pedatella;X. Dou;Zhifeng Shu
利用美国国家大气研究中心（NationalCenterforAtmosphericResearch）开发的全大气共同体气候模式（WholeAtmosphericCommunityClimateModel）+资料同化研究试验床（DataAssimilationResearchTestbed）的集合资料同化版本，对2007年夏季准二日波（QTDW）活动进行了研究。QTDW振荡在不同时刻间歇性地以向西波数3（W3）和4（W 4）模态为主。从第172天到第224天，W3达到4次峰值，其中在第199-206天左右的主峰比其他峰强得多。在整个夏季期间，W 4也表现出四重结构，但它们的振幅彼此相当。W 4周期从186天（东风急流较强）的42 h增加到225天（东风急流较弱）的56 h，而W3周期较稳定，最大扰动出现在52 h左右。因此，W3比W 4表现出更多的简正模特征。进一步的诊断分析表明，中低纬的正压/斜压不稳定区对W3的放大作用更强，不稳定性越强，强迫越大。此外，与背景风相关的W 4折射率和临界层的时间变化是其周期变化的原因。我们还发现，在2007年北半球夏季没有向西波数2（W2）的QTDW是由于东风急流较弱，在南半球夏季。
The ensemble data assimilation version of the Whole Atmosphere Community Climate Model + Data Assimilation Research Testbed developed at National Center for Atmospheric Research is utilized to study the quasi‐2 day wave (QTDW) activities during boreal summer period of 2007. The westward wave number 3 (W3) and 4 (W4) modes intermittently dominated the QTDW oscillations at different times. The W3 peaked 4 times from day 172 to day 224 with the major peak at around days 199–206 being much stronger than the others. The W4 also showed a quadruple structure during the whole summer period but with their amplitudes comparable with each other. The period of W4 increases from ~42 h on day 186 (with stronger easterly jet) to 56 h on day 225 (with weaker easterly jet), while the W3 period is more stable with the maximum perturbation occurring at ~52 h. Thus, the W3 exhibits more normal mode features than W4. Further diagnostic analysis shows that the barotropically/baroclinically unstable regions at middle and low latitudes are more effective for the amplification of W3 with stronger instabilities providing larger forcing. Moreover, the temporal variability of the refractive indexes and critical layers of W4, which are related to the background wind, are responsible for its period variations. We also find that the absence of a westward wave number 2 (W2) QTDW during boreal summer of 2007 is due to the weaker easterly jet compared with that during austral summer.