Numerical Study on the Effect of Air–Sea–Land Interaction on the Atmospheric Boundary Layer in Coastal Area

Zixuan Yang,Antoni Calderer,Fotis Sotiropoulos,Lian Shen,James Doyle,Brian Haus,Jamie Macmahan,Qing Wang,Hans Graber,Sida He,David Flagg

doi:10.3390/atmos9020051

Abstract

We have performed large-eddy simulations (LES) to study the effect of complex land topography on the atmospheric boundary layer (ABL) in coastal areas. The areas under investigation are located at three beaches in Monterey Bay, CA, USA. The sharp-interface immersed boundary method is employed to resolve the land topography down to grid scale. We have considered real-time and what-if cases. In the real-time cases, measurement data and realistic land topographies are directly incorporated. In the what-if cases, the effects of different scenarios of wind speed, wind direction, and terrain pattern on the momentum flux at the beach are studied. The LES results are compared with simulations using the Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS) and field measurement data. We find that the land topography imposes a critical influence on the ABL in the coastal area. The momentum fluxes obtained from our LES agree with measurement data. Our results indicate the importance of capturing the effects of land topographies in simulations.

Highlights

The present-day simulation and operational forecasting tools are limited in their ability to compute coastal land–air–sea interactions
The inhomogeneity at plane 3 can be attributed to the complex land topography in the upstream
We test the capability of large-eddy simulations (LES) in capturing the effect of complex land topographies on the atmospheric boundary layer (ABL) in coastal area

Summary

Introduction

The present-day simulation and operational forecasting tools are limited in their ability to compute coastal land–air–sea interactions. The parameterizations used by these tools are usually derived from open-ocean problems. Mesoscale numerical weather prediction (NWP) models discretize the atmosphere into horizontal scales of O(103 –104 ) m and vertical scales of O(102 –103 ) m [4,5,6]. These models are typically forced by a coarser scale regional or global model or analysis dataset, and may nest one or several meshes.

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