A modified atmospheric non-hydrostatic model on low aspect ratio grids

作者：Sun Wen Yih^*; Sun Oliver M; Tsuboki Kazuhisa

来源：Tellus - Series A: Dynamic Meteorology and Oceanography , 2012, 64: 17516.

DOI：10.3402/tellusa.v64i0.17516

• non-hydrostatic model
• forward-backward
• HE-VI
• eigenvalue
• LES
• aspect ratio

It is popular to use a horizontal explicit and a vertical implicit (HE-VI) scheme in the compressible nonhydrostatic (NH) model. However, when the aspect ratio becomes small, a small time-interval is required in HE-VI, because the Courant-Fredrich-Lewy (CFL) criterion is determined by the horizontal grid spacing. Furthermore, simulations from HE-VI can depart from the forward-backward (FB) scheme in NH even when the time interval is less than the CFL criterion allowed. Hence, a modified non-hydrostatic (MNH) model is proposed, in which the left-hand side of the continuity equation is multiplied by a parameter delta (4 %26lt;= delta %26lt;= 16, in this study). When the linearized MNH is solved by FB (can be other schemes), the eigenvalue shows that MNH can suppress the frequency of acoustic waves very effectively but does not have a significant impact on the gravity waves. Hence, MNH enables to use a longer time step than that allowed in the original NH. When the aspect ratio is small, MNH solved by FB can be more accurate and efficient than the NH solved by HE-VI. Therefore, MNH can be very useful to study cloud, Large Eddy Simulation (LES), turbulence, flow over complex terrains, etc., which require fine resolution in both horizontal and vertical directions.

• 出版日期2012
• 单位中央民族大学