Further inquiry into the interaction between the winter North Pacific storm track and the East Asian trough

Minghao Yang,Peilong Yu,Yanke Tan,Xin Li,Chongyin Li,Xiong Chen

doi:10.1007/s00382-020-05279-2

Abstract

Based on the daily ERA-Interim reanalysis, interactions between the winter North Pacific storm track (WNPST) and the East Asian trough (EAT) on the interannual scale are further explored from the perspective of energy conversion and the simplified quasi-geostrophic potential vorticity equation. There is a prominent out-of-phase relationship between the EAT and WNPST on the interannual scale. It is baroclinic energy conversion rather than barotropic energy conversion that is the main physical process that the EAT affects the WNPST. When the EAT is intensified, the energy conversion from mean available potential energy to eddy available potential energy decreases; further, the energy conversion from eddy available potential energy to eddy kinetic energy is attenuated, which leads directly to remarkable weakening in the strength of the WNPST in its peak area and the region west of the date line. In addition, when the WNPST is enhanced, the WNPST dynamic forcing contributes to lowering the geopotential height near the EAT and thus profits to recover the strength of the EAT, while the thermal forcing of WNPST is opposite. However, their joint effect is still to strengthen the EAT, indicating that the impact of WNPST dynamic forcing on the EAT is stronger than that of thermal forcing. The interaction between the WNPST and EAT may be a way for the WNPST to maintain itself.

Highlights

The East Asian trough (EAT), located off the east coast of the Eurasian continent, is a large-scale topographic wave formed by the thermal contrast between cold land and warm sea and the dynamic effect of the Qinghai-Tibet Plateau topography on the east coast of Eurasia (Held et al 2002)
Based on the daily ERA-Interim reanalysis data spanning 1979 to 2010 and the standard deviation of geopotential height at 500 hPa to represent the winter North Pacific storm track (WNPST), this article investigates the influences of the EAT on the WNPST from the perspective of energy conversion and the impact of the WNPST on the EAT through the simplified quasi-geostrophic potential vorticity equation to further analyze the interaction between the EAT and WNPST on the interannual scale
When the EAT is intensified, the energy conversion from mean available potential energy to eddy available potential energy is lessened; further, the energy conversion from eddy available potential energy to eddy kinetic energy is attenuated, which directly leads to remarkable weakening in the strength of the WNPST in its peak area and the region west of the dateline

Summary

Introduction

The East Asian trough (EAT), located off the east coast of the Eurasian continent, is a large-scale topographic wave formed by the thermal contrast between cold land and warm sea and the dynamic effect of the Qinghai-Tibet Plateau topography on the east coast of Eurasia (Held et al 2002). As one of the most energetic regions of synoptic-scale disturbance in the Northern Hemisphere (Blackmon 1976; Chang et al 2002), the winter North Pacific storm track (WNPST) is located downstream of the EAT, acts as an important bridge in the interactions between the tropics and the middle-high latitudes through heat, water and momentum transport (Chang and Fu 2002; Luo et al 2011), and has a significant impact on the maintenance of atmospheric circulation and climate change in East Asia (Jin 2010; Kug et al 2010; Lee et al 2012). Song et al (2016) investigated the impact of synoptic-scale transient eddies on intraseasonal variations in the strength of the EAT through the three-dimensional quasi-geostrophic potential vorticity equation.

Data and methods

Relationship between WNPST and EAT

The influence of EAT on WNPST

The impact of WNPST on EAT

Findings

Conclusion and discussion