Projection of the summer northern East Asian low under global warming in CMIP5 models

Zhong-Da Lin,Yuan-Hai Fu

doi:10.1080/16742834.2017.1358053

Abstract

AbstractThe East Asian summer climate is modulated by a low-pressure system over northern East Asia (NEAL) and a subtropical high over the western North Pacific. Many studies have focused on the subtropical high, but little is known about NEAL, especially its change in the future under global warming scenarios. This study investigates the projected change in NEAL in the late twenty-first century, using the outputs of 20 models from Phase 5 of the Coupled Model Intercomparison Project — specifically, their historical climate simulations (HIST) and future climate projections under the Representative Concentration Pathway 4.5 (RCP4.5) and 8.5 (RCP8.5) scenarios. The results show that the models capture the NEAL well in HIST. The NEAL is weakened in the late twenty-first century under the two RCP scenarios, with a stronger weakening under RCP8.5 than under RCP4.5. The weakened NEAL increases the geopotential height zonal gradient in the west and causes a southerly anomaly, which may bring more moisture and ra...

Highlights

The East Asian summer monsoon is modulated by a meridional land–sea thermal contrast between northern East Asia (NEA) and the western North Pacific (Han and Wang 2007; Lin 2014; Du, Lin, and Lu 2017), in addition to a planetary-scale thermal contrast between the Asian continent and North Pacific in the zonal direction (Guo 1983; Shi and Zhu 1996; Zhao and Zhou 2005; Zhu et al 2005)
The projected change in NEAL is investigated in this study by analyzing the historical climate simulations (HIST), RCP4.5 and RCP8.5 outputs of 20 CMIP5 models
The results show that the models can capture NEAL well in HIST, with a low H850 trough over northern East Asia during 1981–2000

Summary

Introduction

The East Asian summer monsoon is modulated by a meridional land–sea thermal contrast between northern East Asia (NEA) and the western North Pacific (Han and Wang 2007; Lin 2014; Du, Lin, and Lu 2017), in addition to a planetary-scale thermal contrast between the Asian continent and North Pacific in the zonal direction (Guo 1983; Shi and Zhu 1996; Zhao and Zhou 2005; Zhu et al 2005). The meridional thermal contrast is depicted by a low over continental northern East Asia (NEAL) and a subtropical high over the western North Pacific (Du, Lin, and Lu 2016; Lin and Wang 2016). Understanding the variability of the NEAL and the western North Pacific subtropical high is vital for predicting change in the East Asian summer climate. Kamae et al (2014a) investigated the summertime land–sea thermal contrast over East Asia under global warming. The enhanced land–sea thermal contrast, especially the warming in continental East Asia induced by the increase in greenhouse gases (Zhu et al 2012; Kamae et al 2014b), may change the intensity of NEAL (Du, Lin, and Lu 2016). Summer refers to the mean of June, July, and August

Evaluation of the NEAL in HIST

Possible impact of the change in NEAL on the East Asian summer monsoon

Summary and discussion