Response of Westerly Jet Over the Northern Hemisphere to Astronomical Insolation During the Holocene

Peng Zhou,Zhengguo Shi,Xinzhou Li,Weijian Zhou

doi:10.3389/feart.2020.00282

Abstract

The westerly jet (WJ) in the upper troposphere, an important atmospheric circulation system, is critical for influencing global climate by changes of its north-south migration and intensity. However, its variations during the Holocene across the Eurasian and North America are not well evaluated, which restricts our understanding of climate change in those regions. Using general circulation model experiments, here we simulate the variations of WJ over the past 10ka to show its intensity and position of WJ responding to astronomical insolation. Our results suggest that the summer WJ gradually migrates southward and strengthens over the Central Asia, Japan and North America from the early to late Holocene; meanwhile, the positions of the winter WJ barely move and its intensity slightly change. These seasonally asymmetric changes can be attributed to the temperature structure, in which the surface latent and sensible heat flux both contribute.

Highlights

The westerly jet (WJ), located in the upper troposphere, is the strong and narrow westerly wind belt with horizontal and vertical wind shears over the Northern Hemisphere (NH) throughout whole year
In this study, based on the Community Earth System Model (CESM) with a relatively high horizontal resolution, we explore the seasonal characteristics of WJ in the NH, especially the Asia, during the Holocene responding to astronomical insolation
In order to evaluate the changes of WJ, we focus on three center areas including: the Central Asia (CA; 70–100◦E, 15–55◦N), the Japan (125–155◦E, 15–55◦N), and Northern America (NA; 60– 100◦W, 15–55◦N)

Summary

Introduction

The westerly jet (WJ), located in the upper troposphere, is the strong and narrow westerly wind belt with horizontal and vertical wind shears over the Northern Hemisphere (NH) throughout whole year. It is an important planetary-scale atmospheric circulation system affecting weather and climate anomalies; especially, its variations in the intensity and position play a vital role in affecting precipitation patterns in the middle and low latitudes (Yang et al, 2002; Schiemann et al, 2009; Zhao et al, 2014). In view of the blocking effect of the Tibet Plateau, the south branch of the WJ is located at the south side of the Tibet Plateau in spring and winter with gradually northward migration in May; whereas it rapidly jumps to north site of Tibetan Plateau in June with continually northward migration in July away from the Tibetan

Results

Discussion

Conclusion