Improved Simulation of the Antarctic Stratospheric Final Warming by Modifying the Orographic Gravity Wave Parameterization in the Beijing Climate Center Atmospheric General Circulation Model

Yixiong Lu,Li Zhang,Tongwen Wu,Xin Xu,Min Chu

doi:10.3390/atmos11060576

Abstract

The Antarctic stratospheric final warming (SFW) is usually simulated with a substantial delay in climate models, and the corresponding temperatures in austral spring are lower than observations, implying insufficient stratospheric wave drag. To investigate the role of orographic gravity wave drag (GWD) in modeling the Antarctic SFW, in this study the orographic GWD parameterization scheme is modified in the middle-atmosphere version of the Beijing Climate Center Atmospheric General Circulation Model. A pair of simulations are conducted to compare two orographic GWD schemes in simulating the breakdown of the stratospheric polar vortex over Antarctica. The control simulation with the default orographic GWD scheme exhibits delayed vortex breakdown and the cold-pole bias seen in most climate models. In the simulation with modified orographic GWD scheme, the simulated vortex breaks down earlier by 8 days, and the associated cold-pole bias is reduced by more than 2 K. The modified scheme provides stronger orographic GWD in the lower stratosphere, which drives an accelerated polar downwelling branch of the Brewer–Dobson circulation and, in turn, produces adiabatic warming. Our study suggests that modifying orographic GWD parameterizations in climate models would be a valid way of improving the SFW simulation over Antarctica.

Highlights

Climate models have evolved into the stage of “Earth System Models” (ESMs), in which various components of physics, chemistry, and biology are fully coupled to serve multiple purposes, including the simulation of air quality, stratospheric ozone, tropospheric chemistry, and global climate
Our study suggests that modifying orographic gravity wave drag (GWD) parameterizations in climate models would be a valid way of improving the stratospheric final warming (SFW) simulation over Antarctica
It is shown in this study that modifying the orographic gravity waves (GWs) parameterization results in an improved simulation of the SFW over Antarctica

Summary

Introduction

Climate models have evolved into the stage of “Earth System Models” (ESMs), in which various components of physics, chemistry, and biology are fully coupled to serve multiple purposes, including the simulation of air quality, stratospheric ozone, tropospheric chemistry, and global climate. As a major model hierarchy of ESMs, chemistry-climate models (CCMs) combine physical climate models with an explicit representation of atmospheric chemistry and have been used in investigating the Antarctic ozone depletion problem [1,2]. The Antarctic SFW simulated by a number of climate models is 1–2 weeks later than observations at 50 hPa [3,4,5]. The polar temperatures in climate models are Atmosphere 2020, 11, 576; doi:10.3390/atmos11060576 www.mdpi.com/journal/atmosphere

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