Dependence of aqua‐planet simulations on time step
Dependence of aqua‐planet simulations on time step
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DOI：
10.1256/qj.02.62
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发表时间：
2003-04
影响因子：
8.9
通讯作者：
D. Williamson;J. Olson
中科院分区：
文献类型：
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作者：
D. Williamson;J. Olson
使用欧拉和半拉格朗日动力核心与 NCAR CCM3 参数化套件相结合的 Aqua-Planet 模拟产生了截然不同的区域平均降水模式。具有欧拉核心的模型形成了以海面温度 (SST) 最大值为中心的狭窄单一降水峰。具有半拉格朗日核心的结构通常具有横跨海温最大值的双峰，降水量最小值以海温最大值为中心。不同的结构主要是由每个核心采用的不同时间步长及其对参数化的影响引起的，而不是由动态核心本身引入的不同截断误差引起的。通过较长的离散时间步长，表面交换参数化在单个时间步长内在大气中沉积更多的水分，导致对流在距离赤道更远、更接近最大源的地方开始。与不同光谱分辨率相关的不同扩散平滑是影响双结构强度的次要效应。当半拉格朗日核心配置为与具有相同时间步长、三时间水平公式和相同光谱截断的欧拉相匹配时，它会产生与欧拉相似的降水场。
Aqua‐planet simulations with Eulerian and semi‐Lagrangian dynamical cores coupled to the NCAR CCM3 parametrization suite produce very different zonal average precipitation patterns. The model with the Eulerian core forms a narrow single precipitation peak centred on the sea surface temperature (SST) maximum. The one with the semi‐Lagrangian core forms a broad structure often with a double peak straddling the SST maximum with a precipitation minimum centred on the SST maximum. The different structure is shown to be caused primarily by the different time step adopted by each core and its effect on the parametrizations rather than by different truncation errors introduced by the dynamical cores themselves. With a longer discrete time step, the surface exchange parametrization deposits more moisture in the atmosphere in a single time step, resulting in convection being initiated farther from the equator, closer to the maximum source. Different diffusive smoothing associated with different spectral resolutions is a secondary effect influencing the strength of the double structure. When the semi‐Lagrangian core is configured to match the Eulerian with the same time step, a three‐time‐level formulation and same spectral truncation it produces precipitation fields similar to those from the Eulerian.