Sensitivity of Gravity Wave Fluxes to Interannual Variations in Tropical Convection and Zonal Wind
Sensitivity of Gravity Wave Fluxes to Interannual Variations in Tropical Convection and Zonal Wind
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DOI：
10.1175/jas-d-17-0044.1
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发表时间：
2017-09-01
影响因子：
3.1
通讯作者：
Kim, Ji-Eun
中科院分区：
文献类型：
--
作者：
Alexander, M. Joan;Ortland, David A.;Kim, Ji-Eun
使用一个理想化的模式框架与来自全球卫星观测的降水和云的高频热带潜热加热变率，作者研究了平流层下部重力波的性质和影响，对比厄尔尼诺年和拉尼娜年的条件。该模式产生了一个广泛的热带波，包括行星尺度波通过中尺度重力波。作者比较了模拟的月平均风和温度的区域变化与再分析，并使用基于卫星和气球的重力波动量通量估计来验证模拟的重力波。在模式中发现了动量通量重力谱的一些有趣的变化，并从云、降水和大尺度风的年际变化方面对这些变化进行了讨论。虽然云，降水和风的区域变化是戏剧性的，平均重力波纬向动量通量进入平流层的差异只有11%。重力波动量通量的建模的不稳定性被证明是非常现实的观测相比，和最大振幅波相关的显着的重力波阻力在最低平流层。由于重力波不透明度参数化的不足，这种强不透明度在气候模式中通常不存在或很弱。这些结果提出了一种改进平流层最低准两年振荡风和遥相关的模式表示的方法。
Using an idealized model framework with high-frequency tropical latent heating variability derived from global satellite observations of precipitation and clouds, the authors examine the properties and effects of gravity waves in the lower stratosphere, contrasting conditions in an El Nino year and a La Nina year. The model generates a broad spectrum of tropical waves including planetary-scale waves through mesoscale gravity waves. The authors compare modeled monthly mean regional variations in wind and temperature with reanalyses and validate the modeled gravity waves using satellite-and balloon-based estimates of gravity wave momentum flux. Some interesting changes in the gravity spectrum of momentum flux are found in the model, which are discussed in terms of the interannual variations in clouds, precipitation, and large-scale winds. While regional variations in clouds, precipitation, and winds are dramatic, the mean gravity wave zonal momentum fluxes entering the stratosphere differ by only 11%. The modeled intermittency in gravity wave momentum flux is shown to be very realistic compared to observations, and the largest-amplitude waves are related to significant gravity wave drag forces in the lowermost stratosphere. This strong intermittency is generally absent or weak in climate models because of deficiencies in parameterizations of gravity wave intermittency. These results suggest a way forward to improve model representations of the lowermost stratospheric quasi-biennial oscillation winds and teleconnections.