Long‐term observations of the quasi two‐day wave by Hawaii MF radar
Long‐term observations of the quasi two‐day wave by Hawaii MF radar
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DOI：
10.1002/2013ja018858
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发表时间：
2013-12
期刊：
影响因子：
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通讯作者：
Sheng‐yang Gu;Tao Li;X. Dou;Ning Wang;D. Riggin;D. Fritts
中科院分区：
文献类型：
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作者：
Sheng‐yang Gu;Tao Li;X. Dou;Ning Wang;D. Riggin;D. Fritts
分析了1991-2006年期间由夏威夷考艾岛（22°N，160°W）中频（MF）雷达测量的中层水平风数据集，以检查准两日波（QTDW）的长期变化。夏威夷上空的QTDW每年放大两次，1月和7月的事件最有可能分别代表纬向波数3和4模态。1月份经向风和纬向风的月平均QTDW以及7月份经向风的月平均QTDW的振幅几乎与太阳周期同相，但太阳极大值领先QTDW极大值1或2年。而纬向风的7月平均QTDW与太阳活动周的位相相反。1998年1月两个风分量的QTDW振荡都明显增强，这可能与1997/1998年冬季的强厄尔尼诺事件有关。与平流层夏季东风急流增强有关的重力波活动增强和正压/斜压/惯性不稳定性增加可能提供额外的强迫来放大QTDW。此外，在温暖的厄尔尼诺-南方涛动事件期间，增强的迁移日潮也可能通过增加折射率和QTDW的增长率而导致异常强的QTDW。在2006年1月平流层突然变暖期间，观测到了QTDW的进一步增强，其时间短至43 h。
A mesospheric horizontal wind data set measured during 1991–2006 by the medium frequency (MF) radar at Kauai, Hawaii (22°N, 160°W) is analyzed to examine the long‐term variability of the quasi two‐day wave (QTDW). The QTDW over Hawaii is amplified twice a year, with the January and July events most likely being the representation of zonal wave numbers 3 and 4 modes, respectively. The amplitudes of the January monthly mean QTDW in both meridional and zonal winds and the July monthly mean QTDW in meridional component are nearly in phase with the solar cycle but with the solar maxima leading the QTDW maxima by 1 or 2 years. However, the July monthly mean QTDW in zonal wind is more antiphase with the solar cycle. Enhanced QTDW oscillations are evident in both wind components in January 1998, which is likely related to the strong El Niño event during the winter of 1997/1998. The enhanced gravity wave activity and the increased barotropic/baroclinic/inertial instability related to the strengthened stratosphere summer easterly jet might provide additional forcing to amplify the QTDW. Moreover, the enhanced migrating diurnal tide during warm El Niño‐Southern Oscillation events could also contribute to the abnormally strong QTDW by increasing the refractive index and thus the growth rate of the QTDW. Additional enhancement of the QTDW with a short period of ~43 h is observed during the major sudden stratospheric warming in January 2006.