Large-scale length and time-scales for use with stochastic convective parametrization
Large-scale length and time-scales for use with stochastic convective parametrization
复制标题
用于随机对流参数化的大尺度长度和时间尺度
DOI：
10.1002/qj.992
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发表时间：
2011
影响因子：
8.9
通讯作者：
Keane R
中科院分区：
文献类型：
--
作者：
Keane R
许多用于天气预报和气候研究的数值模式的分辨率太粗，无法明确地解决对流问题，但又太精细，无法证明传统对流参数化所假定的局地平衡。本文发展的Plant-Craig(PC)随机对流参数化方案，去掉了一个给定的网格尺度的情况必须总是产生相同的亚网格尺度对流响应的假设，从而解决了这个问题。取而代之的是，对于每个时间点和网格点，从许多可能的对流响应中随机选择一个与大范围情况一致的对流响应。该方案需要大尺度状态作为输入，而不是瞬时网格尺度状态，但仍然必须能够考虑大尺度情况下的真实变化。在这里，我们研究了PC方案在辐射-对流平衡的三维模拟中的行为，特别是证明了产生输入大尺度状态的良好表示所需的必要的时空平均与捕捉大尺度变化的要求并不冲突。所得到的平衡廓线与已建立的确定性方案以及相应的云分辨模式模拟结果吻合得很好。与常规方案不同的是，PC方案对质量通量和降水变率的统计也与相关理论吻合较好，并随空间尺度的变化而变化。进一步表明，该方案能够自动适应网格长度和强迫强度的变化。
Many numerical models for weather prediction and climate studies are run at resolutions that are too coarse to resolve convection explicitly, but too fine to justify the local equilibrium assumed by conventional convective parameterizations. The Plant-Craig (PC) stochastic convective parameterization scheme, developed in this paper, solves this problem by removing the assumption that a given grid-scale situation must always produce the same sub-grid-scale convective response. Instead, for each timestep and gridpoint, one of the many possible convective responses consistent with the large-scale situation is randomly selected. The scheme requires as input the large-scale state as opposed to the instantaneous grid-scale state, but must nonetheless be able to account for genuine variations in the largescale situation. Here we investigate the behaviour of the PC scheme in three-dimensional simulations of radiative-convective equilibrium, demonstrating in particular that the necessary space-time averaging required to produce a good representation of the input large-scale state is not in conflict with the requirement to capture large-scale variations. The resulting equilibrium profiles agree well with those obtained from established deterministic schemes, and with corresponding cloud-resolving model simulations. Unlike the conventional schemes the statistics for mass flux and rainfall variability from the PC scheme also agree well with relevant theory and vary appropriately with spatial scale. The scheme is further shown to adapt automatically to changes in grid length and in forcing strength.