Seasonal cycle of orographic gravity wave occurrence above small islands in the Southern Hemisphere: Implications for effects on the general circulation
Seasonal cycle of orographic gravity wave occurrence above small islands in the Southern Hemisphere: Implications for effects on the general circulation
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南半球小岛屿上方地形重力波发生的季节周期：对大气环流影响的影响
DOI：
10.1002/2013jd020526
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
A. Grimsdell
中科院分区：
文献类型：
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作者：
M. Alexander;A. Grimsdell
利用AQUA卫星上的大气红外探测仪从轨道上观测到南大洋小岛地形上方流动产生的地形重力波。我们研究了这些波在14个岛屿上方40公里处∼平流层中的出现频率，并研究了地理和季节变化。我们的结果表明，这些小岛山波在5-9月季节在平流层中普遍出现，但不是每天都发生。不同岛屿的季节变化明显不同，季节变化与纬度和盛行风型密切相关。我们还检验了2a资料的年际变化，以及出现频率、动量通量、平流层和地面风之间的关系。结果表明，平流层风对大气红外测深仪(AIRS)观测到的这些岛状山波具有一阶限制作用。地面风向和海岛地形起伏对AIRS资料中的海岛山波出现频率有附加但次要的影响。其含义是，这些波动事件非常常见，在AIRS数据中没有观测到这些波动的许多天，它们很可能已经消散，并在40公里观测层以下对大气产生了阻力。对这些波动事件期间的动量通量的观测也可以初步估计它们对南半球大气环流的重要性。
Orographic gravity waves generated by flow over the topography of small islands in the southern oceans have been observed from orbit with the Atmospheric Infrared Sounder on the Aqua satellite. We examine the occurrence frequencies of these waves in the stratosphere at ∼40km above 14 islands and examine geographical and seasonal changes. Our results show that these small island mountain waves occur commonly in the stratosphere in the May–September season, though not every day. Differing seasonal variations are evident at different islands, and the seasonal variations are closely related to latitude and prevailing wind patterns. We also examine interannual variability in 2years of data and the relationships between occurrence frequencies, momentum fluxes, and stratospheric and surface winds. The results suggest that stratospheric winds have a first‐order limiting effect on the observations of these island mountain waves in Atmospheric Infrared Sounder (AIRS) data. Surface wind direction and island orographic relief have an additional but secondary influence on the island mountain wave occurrence frequencies in AIRS data. The implications are that these wave events are extremely common and that on many days when the waves are not observed in AIRS data they have likely dissipated and induced a drag force on the atmosphere below the 40km observation level. Observations of momentum flux during these wave events also permit a first estimate of their importance to the general circulation of the Southern Hemisphere.