The effect of a well-resolved stratosphere on East Asian winter climate

Ke Wei,Luyang Xu,Zelin Cai,Wen Chen

doi:10.1007/s00382-016-3419-6

Abstract

This study performs a comparison between models with and without well-resolved stratosphere on the simulation of the East Asian winter climate. The results reveal that the Fifth Coupled Model Inter-comparison Project (CMIP5) models with model top above the stratopause have a better simulation of the distribution of surface air temperature, sea level pressure and precipitation than the models with a low-top below the stratopause. The discrepancy of the East Asian winter climate between high-top (HT) and low-top (LT) CMIP5 models is also evident in the future projection under higher (RCP85) and midrange (RCP45) emission scenarios. The HT models present about 1.3 and 1.7 °C higher surface air temperature in East Asian region under RCP45 and RCP 85 scenarios by the end of this century than that of the LT models. Therefore, the insufficient representation of the stratosphere may lead to underestimation of the anthropogenic global warming in regional scale and hence have the potential to lead to insufficient response action and mitigation measures.

Highlights

The stratosphere is conventionally believed to be passively influenced by the tropospheric circulation anomalies
We examine the performance of the CMIP5 models with a well-resolved stratosphere in East Asian region, and compare with the models with a low model top
In order to assess the performance of CMIP5 models with and without full stratosphere in charactering EAWM, we examined in several key parameters that are usually used as the strength or state of the EAWM

Summary

Introduction

The stratosphere is conventionally believed to be passively influenced by the tropospheric circulation anomalies. In the models which were used in the fourth climate change assessment report (AR4) of the Intergovernmental Panel on Climate Change (IPCC), half of the model have model top beneath 2 hPa (upper stratosphere around 48.5 km) These models show a significant cold bias in their upper levels (~10 hPa) compared to the reanalysis data, possibly due to low model top or insufficient stratospheric levels (Cordero and Forster 2006). There have been several evaluation studies with focus on the model reproduction of East Asian summer and winter monsoon climate (e.g., Boo et al 2011; Gong et al 2014; Wei and Bao 2012; Wei et al 2014). We examine the performance of the CMIP5 models with a well-resolved stratosphere in East Asian region, and compare with the models with a low model top.

Models and data

CMIP5 models and experiments

The model climatology of EAWM

Discrepancy of the EAWM between high‐top and low‐top CMIP5 models

The EAWM projection

Discussion and conclusions