Mechanisms Setting the Strength of Orographic Rossby Waves across a Wide Range of Climates in a Moist Idealized GCM
Mechanisms Setting the Strength of Orographic Rossby Waves across a Wide Range of Climates in a Moist Idealized GCM
复制标题
在潮湿理想化 GCM 中设定各种气候条件下地形罗斯贝波强度的机制
DOI：
10.1175/jcli-d-17-0700.1
复制
发表时间：
2018
影响因子：
4.9
通讯作者：
T. Schneider
中科院分区：
文献类型：
--
作者：
Robert C.J. Wills;T. Schneider
地形定常Rossby波对大气大尺度环流有重要影响，尤其是在北方冬季。全球变暖引起的驻波变化有可能改变地表温度和降水的模式。本文提出了一个分析的定常波强迫中纬度地形在一个潮湿的理想化的GCM，潜热加热和瞬变涡被允许反馈的定常涡动动力学在很大范围内的气候。定常涡振幅依赖于地表风对地形的主导阶次，导致不同纬度山地对气候变化的响应不同。潜加热被发现阻尼地形驻波，而瞬态涡流被发现加强他们。随着气候变暖，潜热加热的阻尼变得更加有效，而瞬态涡旋的增强变得不那么有效，导致地形驻波振幅的整体减少。这些影响压倒了减少的纬向温度梯度和增加的干静态稳定度的影响，这两者都增加了自由对流层对地形强迫的敏感性。随着中纬度纬向温度梯度的降低，地形驻波的减弱导致温暖潮湿气候中温度和净降水的纬向不对称性降低。虽然在这个理想化的模型中，环流的变化不能指望与真实的世界的变化在数量上一致，但所确定的关键物理过程是广泛相关的。
Orographic stationary Rossby waves are an important influence on the large-scale circulation of the atmosphere, especially in Northern Hemisphere winter. Changes in stationary waves with global warming have the potential to modify patterns of surface temperature and precipitation. This paper presents an analysis of the forcing of stationary waves by midlatitude orography across a wide range of climates in a moist idealized GCM, where latent heating and transient eddies are allowed to feed back on the stationary-eddy dynamics. The stationary-eddy amplitude depends to leading order on the surface winds impinging on the orography, resulting in different climate change responses for mountains at different latitudes. Latent heating is found to damp orographic stationary waves, whereas transient eddies are found to reinforce them. As the climate warms, the damping by latent heating becomes more effective while the reinforcement by transient eddies becomes less effective, leading to an overall reduction in orographic stationary wave amplitude. These effects overwhelm the influences of a reduced meridional temperature gradient and increased dry static stability, both of which increase the sensitivity of the free troposphere to orographic forcing. Together with a reduction in the midlatitude meridional temperature gradient, the weakening of orographic stationary waves leads to reduced zonal asymmetry of temperature and net precipitation in warm, moist climates. While circulation changes in this idealized model cannot be expected to agree quantitatively with changes in the real world, the key physical processes identified are broadly relevant.