Evaluating the Conservation of Energy Variables in Simulations of Deep Moist Convection
Evaluating the Conservation of Energy Variables in Simulations of Deep Moist Convection
复制标题
评估深层潮湿对流模拟中能量变量的守恒
DOI：
10.1175/jas-d-20-0351.1
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发表时间：
2021
影响因子：
3.1
通讯作者：
Chavas, Daniel R.
中科院分区：
文献类型：
--
作者：
Peters, John M.;Chavas, Daniel R.
在包裹理论计算、数值模型和积云参数化中，通常假设湿静态能量 (MSE) 是绝热守恒的。然而，由于流体静力平衡的假设，MSE 的绝热守恒只是近似的。这里评估两个替代变量：MSE − IB 和 MSE + KE，其中 IB 是浮力 (B) 的路径积分，KE 是动能。这两个变量都放宽了流体静力学假设，并且比 MSE 更精确地守恒。本文量化了假设上述变量在无组织和有组织深对流的大涡模拟 (LES) 中守恒而产生的误差。结果表明，MSE − IB 和 MSE + KE 比单独使用 MSE 更好地预测沿轨迹的数量。 MSE − IB 在孤立的深对流中更守恒，而 MSE − IB 和 MSE + KE 在飑线模拟中表现相当。这些结果可以通过飑线和孤立对流的压力扰动行为之间的差异来解释。当假设 MSE – IB 绝热守恒时，上升气流诊断中的误差普遍最小化，但只有当考虑到热容的湿度依赖性和潜热的温度依赖性时。当使用不太准确的潜热和热容公式时，由于补偿误差，MSE − IB 产生的 B 预测结果比 MSE 差。我们的结果表明，使用 MSE − IB 或 MSE + KE 代替具有正确配制的热容和潜热的 MSE 将使各种应用受益。
It is often assumed in parcel theory calculations, numerical models, and cumulus parameterizations that moist static energy (MSE) is adiabatically conserved. However, the adiabatic conservation of MSE is only approximate because of the assumption of hydrostatic balance. Two alternative variables are evaluated here: MSE − IB and MSE + KE, wherein IB is the path integral of buoyancy (B) and KE is kinetic energy. Both of these variables relax the hydrostatic assumption and are more precisely conserved than MSE. This article quantifies the errors that result from assuming that the aforementioned variables are conserved in large-eddy simulations (LES) of both disorganized and organized deep convection. Results show that both MSE − IB and MSE + KE better predict quantities along trajectories than MSE alone. MSE − IB is better conserved in isolated deep convection, whereas MSE − IB and MSE + KE perform comparably in squall-line simulations. These results are explained by differences between the pressure perturbation behavior of squall lines and isolated convection. Errors in updraftBdiagnoses are universally minimized when MSE − IB is assumed to be adiabatically conserved, but only when moisture dependencies of heat capacity and temperature dependency of latent heating are accounted for. When less accurate latent heat and heat capacity formulae were used, MSE − IB yielded poorerBpredictions than MSE due to compensating errors. Our results suggest that various applications would benefit from using either MSE − IB or MSE + KE instead of MSE with properly formulated heat capacities and latent heats.