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

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.

Mechanical and Thermal Impacts of the Tibetan–Iranian Plateau on the North Pacific Storm Track: Numerical Experiments by FGOALS‐f3‐L

“…We find that the strength and position of the East Asian trough (Gong et al., 2014; Leung & Zhou, 2015) are faithfully reproduced by FGOALS‐f3‐L. Previous studies identified that there is an interaction between the East Asian trough and the winter NPST and that an enhanced East Asian trough attenuates the winter NPST (Song et al., 2016; Yang et al., 2020b). More specifically, the intensified East Asian trough accompanied by the strengthened East Asian winter monsoon (Wang & Chen, 2010) guides the cold air behind the trough southward, which weakens the winter NPST by impacting the atmospheric baroclinicity at higher latitudes (Lee et al., 2010; Song et al., 2016).…”

Inconsistent Variations Between the Northern and Southern North Pacific Storm Track

“…In fact, apart from the meridional dipole of anomalous PST related to the subtropical jet, there is a meridional dipole of anomalous upper‐level zonal wind associated with the PST (Figure S2 in Supporting Information ), which can also be found in some previous studies (e.g., Lee et al., 2010; Ma & Zhang, 2018; Yang et al., 2020). For example, by using regionally averaged variances of upper‐tropospheric filtered meridional winds, Lee et al.…”

“…In addition, they suspected that a pair of storm tracks may only exist at the surface and in the low‐level troposphere. When investigating variations in the PST, most previous studies have regarded the PST as a whole (e.g., Ma & Zhang, 2018; Nakamura et al., 2002; Yang et al., 2020; Zhang & Luo, 2017). Given that the storm source regions of the NPST and SPST are different, we cannot ensure the consistency of the variations in the NPST and SPST.…”

Interdecadal Variation in Available Potential Energy of Stationary Eddies in the Midlatitude Northern Hemisphere in Response to the North Pacific Gyre Oscillation

“…The energy budget is widely used as a diagnostic tool to investigate regional and global climate variation. Energy conversion is also applied to explain the relation among East Asian trough intensity, atmospheric blocking, and North Pacific storm tracks in winter (Yang et al., 2020, 2021). In addition, enhancement of synoptic temperature variation after 2010 is caused by strengthened baroclinic energy conversion from the mean flow to transient eddies in South China and surrounding regions (Leung et al., 2019).…”

“…Hence, there are interactions among atmospheric eddies, mean westerly flow, and the decadal mode in the North Pacific.The energy budget is widely used as a diagnostic tool to investigate regional and global climate variation. Energy conversion is also applied to explain the relation among East Asian trough intensity, atmospheric blocking, and North Pacific storm tracks in winter (Yang et al, 2020(Yang et al, , 2021. In addition, enhancement of synoptic temperature…”