Impact of a Convectively Forced Gravity Wave Drag Parameterization in NCAR CCM3
Impact of a Convectively Forced Gravity Wave Drag Parameterization in NCAR CCM3
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NCAR CCM3 中对流强迫重力波阻力参数化的影响
DOI：
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发表时间：
2004
期刊：
影响因子：
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通讯作者：
Young‐joon Kim
中科院分区：
文献类型：
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作者：
H. Chun;In‐Sun Song;Jong‐Jin Baik;Young‐joon Kim
将Chun和Baik提出的次网格尺度积云对流（GWDC）引起的重力波阻力参数化方案应用到美国国家大气研究中心社区气候模式（NCAR CCM 3）中，研究其对1月和7月气候的影响。云顶重力波应力主要集中在热带辐合区，那里存在着持续的深积云。对流强迫重力波破碎产生的纬向风加速度主要出现在热带低平流层，在云顶上方有西风加速度，在云顶下方有东风加速度，由于参数化重力波相对于对流云是静止的，所以波破碎主要发生在热带低平流层，那里的纬向风足够弱，足以使波饱和。结果表明，GWDC参数化显著地消除了纬向平均纬向风场和温度场的系统偏差。特别是，过多的东风在热带平流层和热带低平流层过冷的温度减少了50%以上，包括GWDC参数化。热带对流层上部和平流层下部的水平风散度场也得到了显著的改善。GWDC参数化的影响通过冬季半球的行星波活动延伸到中高纬度地区。1月北方半球纬向波数3的振幅增加和7月南半球纬向波数2的振幅增加导致模式性能的显著改善。在热带外，尤其是北方半球冬季，GWDC参数化对定常波和瞬变波的Eliassen-Palm（EP）通量散度强迫的影响是相反的。因此，纬向平均纬向风变化的GWDC参数化主要发生在热带地区的直接重力波拖曳强迫。
A parameterization of gravity wave drag forced by subgrid-scale cumulus convection (GWDC) proposed by Chun and Baik is implemented into the National Center for Atmospheric Research Community Climate Model (NCAR CCM3) and its effect on perpetual January and July climate is investigated. The cloud-top gravity wave stress is concentrated in the intertropical convergence zone where persistent deep cumulus clouds exist. The resultant zonal wind acceleration due to the breaking of convectively forced gravity waves is predominantly found in the tropical lower stratosphere with westerly acceleration above cloud top and easterly acceleration just below it. Since the parameterized gravity waves are stationary relative to convective clouds, wave breaking occurs mainly in the tropical lower stratosphere where the zonal wind is weak enough for wave saturation. It is shown that the GWDC parameterization significantly alleviates the systematic model biases of zonal-mean zonal wind and temperature. In particular, excessive easterlies in the tropical stratosphere and excessive cold temperatures in the tropical lower stratosphere are reduced by more than 50% by including the GWDC parameterization. The horizontal wind divergence field in the tropical upper troposphere and lower stratosphere is also significantly improved with the GWDC parameterization. The impact of the GWDC parameterization extends to mid- to high latitudes through planetary wave activity in the winter hemisphere. The increased amplitude of zonal wavenumber 3 in the January Northern Hemisphere and the increased amplitude of zonal wavenumber 2 in the July Southern Hemisphere lead to significant improvements in model performance. The impact of the GWDC parameterization on Eliassen‐Palm (EP) flux divergence forcing by stationary waves is generally opposite to that by transient waves in the extratropics, especially in the Northern Hemisphere wintertime. Hence, the zonal-mean zonal wind change by the GWDC parameterization occurs mainly in the Tropics by direct gravity wave drag forcing.