Restricting 32-128 km horizontal scales hardly affects the MJO in the Superparameterized Community Atmosphere Model v.3.0 but the number of cloud-resolving grid columns constrains vertical mixing
Restricting 32-128 km horizontal scales hardly affects the MJO in the Superparameterized Community Atmosphere Model v.3.0 but the number of cloud-resolving grid columns constrains vertical mixing
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DOI：
10.1002/2014ms000340
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发表时间：
2014-09-01
影响因子：
6.8
通讯作者：
DeMott, Charlotte A.
中科院分区：
文献类型：
--
作者：
Pritchard, Michael S.;Bretherton, Christopher S.;DeMott, Charlotte A.
通过减小其嵌入的云解析模型（CRM）阵列的范围，在超级参数化社区大气模式第3.0版中探究了人为限制32 - 128千米水平尺度范围对 Madden - Julian振荡（MJO）动力学的影响。CRM范围缩小两倍和四倍（从128千米到64千米以及32千米）所产生的统计合成MJO特征，在空间尺度、纬向相速度以及固有风 - 对流异常结构方面，都与标准超级参数化社区大气模式（SPCAM）的MJO极为相似。这表明在32 - 128千米尺度上的中尺度对流组织的物理过程对SPCAM中的MJO动力学并非至关重要，并且减小CRM范围可能是一种可行的策略，能使超级参数化MJO动力学的计算效率提高400%。然而，一些意想不到的基本态响应提醒我们，极端的CRM区域缩小可能会导致超级参数化模型中出现系统性的平均态问题。我们假设，垂直上升气流混合效率的人为限制是由嵌入的CRM阵列中可用于补偿下沉的网格列数量所设定的。这可能会导致水汽通风减少，从而支持过多的液态云，进而产生过强的云短波辐射强迫，特别是在深对流区域。
The effects of artificially restricting the 32-128 km horizontal scale regime on MJO dynamics in the Superparameterized Community Atmosphere Model v. 3.0 have been explored through reducing the extent of its embedded cloud resolving model (CRM) arrays. Two and four-fold reductions in CRM extent (from 128 to 64 km and 32 km) produce statistical composite MJO signatures with spatial scale, zonal phase speed, and intrinsic wind-convection anomaly structure that are all remarkably similar to the standard SPCAM's MJO. This suggests that the physics of mesoscale convective organization on 32-128 km scales are not critical to MJO dynamics in SPCAM and that reducing CRM extent may be a viable strategy for 400% more computationally efficient analysis of superparameterized MJO dynamics. However several unexpected basic state responses caution that extreme CRM domain reduction can lead to systematic mean state issues in superparameterized models. We hypothesize that an artificial limit on the efficiency of vertical updraft mixing is set by the number of grid columns available for compensating subsidence in the embedded CRM arrays. This can lead to reduced moisture ventilation supporting too much liquid cloud and thus an overly strong cloud shortwave radiative forcing, particularly in regions of deep convection.