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- Title
Explicit Representation of Orographic Anisotropy for All Directions Improves Nanling Mountain Rainfall Simulation.
- Authors
Xie, Jinbo; Zhang, Minghua
- Abstract
Climate models exhibit significant rainfall bias in mountainous regions. One reason is the insufficient representation of orographic anisotropy in these models. In this study, we implement the orographic drag scheme with 3‐D orographic anisotropy (all flow directions (AFD)) into a general circulation model and investigate its impact on Nanling rainfall simulation where models have systematic dry bias in the summer. It is shown that the AFD alleviated the Nanling mountain rainfall bias by over 60%. This is through an anomalous "lower‐convergence‐higher‐divergence" deceleration pattern of the flow windward of the Nanling Mountains that enhanced vertical motion and low‐level moisture convergence. The results suggest the importance of explicit orographic anisotropy representation in rainfall simulation in mountainous regions. Plain Language Summary: Simulation of the Nanling mountain summer rainfall has shown significant dry bias. In this study, we implemented a scheme considering fully impact of direction‐dependent change of orographic height on mountain flow in a global climate model to examine its effect on this bias. It is shown that the new scheme led to better simulation of the orographic rainfall compared to the original scheme due to improvement in moisture transport and vertical motion. This demonstrates that explicit representation of this effect for all flow directions is important in climate modeling especially in the simulation of the orographic rainfall. Hence, it should be necessary to represent this effect in the drag parameterization. Key Points: Nanling mountain rainfall simulation is improved when an orographic drag scheme is used with anisotropy for all flow directionsThe impact is due to anomalous drag windward of the Mountains that enhanced vertical motion and low‐level moisture convergenceThe results suggest the importance of explicit orographic anisotropy in climate simulations
- Subjects
CLIMATE change models; GENERAL circulation model; ANISOTROPY; VERTICAL motion; ATMOSPHERIC models; RAINFALL; MOUNTAIN soils
- Publication
Geophysical Research Letters, 2023, Vol 50, Issue 22, p1
- ISSN
0094-8276
- Publication type
Article
- DOI
10.1029/2023GL106353