Simulation of orographic effects with a Quasi‐3‐D Multiscale Modeling Framework: Basic algorithm and preliminary results

• Published in: Journal of advances in modeling earth systems Vol. 8; no. 4; pp. 1657 - 1673
• Main Author: Jung, Joon‐Hee
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 01.12.2016; American Geophysical Union (AGU)
• Subjects: Atmospheric models; Atmospheric precipitations; Banks (topography); ENVIRONMENTAL SCIENCES; Frameworks; Horizontal distribution; Mathematical models; Modelling; Mountains; Multi-scale models; Ocean surface topography; Orographic effects; Orographic precipitation; Orography; Precipitation; Q3D MMF; Rainfall; Simulation; Slope; subgrid orographic effects; superparameterization (or MMF); Topography; Topography (geology); Wind fields
• ISSN: 1942-2466; 1942-2466
• DOI: 10.1002/2016MS000783

The global atmospheric models based on the Multi‐scale Modeling Framework (MMF) are able to explicitly resolve subgrid‐scale processes by using embedded 2‐D Cloud‐Resolving Models (CRMs). Up to now, however, those models do not include the orographic effects on the CRM grid scale. This study shows that the effects of CRM grid‐scale orography can be simulated reasonably well by the Quasi‐3‐D MMF (Q3D MMF), which has been developed as a second‐generation MMF. In the Q3D framework, the surface topography can be included in the CRM component by using a block representation of the mountains, so that no smoothing of the topographic height is necessary. To demonstrate the performance of such a model, the orographic effects over a steep mountain are simulated in an idealized experimental setup with each of the Q3D MMF and the full 3‐D CRM. The latter is used as a benchmark. Comparison of the results shows that the Q3D MMF is able to reproduce the horizontal distribution of orographic precipitation and the flow changes around mountains as simulated by the 3‐D CRM, even though the embedded CRMs of the Q3D MMF recognize only some aspects of the complex 3‐D topography. It is also shown that the use of 3‐D CRMs in the Q3D framework, rather than 2‐D CRMs, has positive impacts on the simulation of wind fields but does not substantially change the simulated precipitation. Key Points: A limited‐area version of the Q3D MMF, which is a second‐generation MMF, is used to simulate the orographic effects over a steep mountain The results show that the distribution of orographic precipitation and the flow changes can be simulated reasonably well by the Q3D MMF Its ability to explicitly simulate the subgrid‐scale processes in the presence of topography can be useful for global modeling