scholarly journals A dissection of the topographic effects from Eurasia and North America on the isentropic meridional mass circulation in Northern Winter

2022 ◽  
Author(s):  
Yueyue Yu ◽  
Rongcai Ren ◽  
Xin Xia ◽  
Ruxue Liang ◽  
Jian Rao
Keyword(s):  
North America ◽  
Topographic Effects ◽  
Northern Winter ◽  
Meridional Mass Circulation ◽  
Mass Circulation

A Dissection of the Topographic Effects from Eurasia and North America on the Isentropic Meridional Mass Circulation in Northern Winter

2021 ◽  
Author(s):  
Yueyue Yu ◽  
Rongcai Ren ◽  
Xin Xia ◽  
Ruxue Liang ◽  
Jian Rao
Keyword(s):  
North America ◽  
Stationary Flow ◽  
Independent Effect ◽  
Gradient Force ◽  
Pressure Gradient Force ◽  
Stationary Waves ◽  
Topographic Effects ◽  
Mean Flow ◽  
Meridional Mass Circulation ◽  
Mass Circulation

Abstract The topographic dynamical effect from Eurasia (EA_Topo) and North America (NA_Topo) on the winter isentropic meridional mass circulation (IMMC) is investigated using the WACCM. The independent effect of EA_Topo and that of NA_Topo, with the former much stronger, are both to strengthen the IMMC that is composed of the lower equatorward cold air branch (CB) and the upper poleward warm air branch in the extratropical tropopshere (WB_TR) and stratosphere (WB_ST). Further investigation of the individual contributions from changes in stationary vs. transient and zonal-mean flow vs. waves reveals that, due to the topography-forced mass redistribution, changes in the low-level meridional pressure gradient force a zonal-mean counter-clockwise/ clockwise meridional cell in the southern/northern side of topography. This weakens/strengthens the IMMC south/north of 30°N from the troposphere to lower stratosphere, acting as a dominant contributor to the IMMC changes south of 50°N. Meanwhile, the EA/NA_Topo-forced amplification of stationary waves constructively interacts with those determined by land-sea contrast, making the dominant/minor contributions to the strengthening of CB and WB_TR north of 50°N. The related increase in the upward wave propagation further dominates the WB_ST strengthening in the subpolar region. Meanwhile, transient eddy activities are depressed by EA/NA_Topo along with the weakened background westerly, which partly-offset/dominate-over the contribution from stationary flow in midlatitudes and subpolar region. The coexistence of the other topography (NA/EA_Topo) yields destructive mutual interferrence, which can weaken/offset the independent-EA/NA_Topo-forced meridional mass transport mainly via changing the zonal-mean as well as the downstream wave pattern of mass and meridional wind.

Topographic forcing from East Asia and North America in the northern winter stratosphere and their mutual interference

2020 ◽  
Author(s):  
Rongcai Ren ◽  
Xin Xia ◽  
Jian Rao
Keyword(s):  
North America ◽  
East Asia ◽  
Climate Model ◽  
Polar Vortex ◽  
Wave Pattern ◽  
Mutual Interference ◽  
Mean Flow ◽  
Stratospheric Polar Vortex ◽  
Northern Winter ◽  
Topographic Forcing

<p>This study uses the stratosphere-resolved Whole Atmosphere Community Climate Model to demonstrate the “independent” and “dependent” topographic forcing from the topography of East Asia (EA) and North American (NA), and their “joint” forcing in the northern winter stratosphere. The mutual interference between the EA and NA forcing is also demonstrated. Specifically, without EA, an independent NA can also, like EA, induce a severe polar warming and weakening of the stratospheric polar vortex. While EA favors a displacement of the polar vortex toward Eurasia, NA favors a displacement toward the North America–Atlantic region. However, the independent-EA-forced weakening effect on the polar vortex can be largely decreased and changes to a location displacement when NA exists, and the interference the other way around is even more critical, being able to completely offset the independent-NA-forced effect, because EA can substantively obstruct NA’s effect on the tropospheric wave pattern over the Eurasia–Pacific region. The much stronger/weaker interference of EA/NA is associated with its stronger/weaker downstream weakening effect on the zonal flow that impinges on NA/EA. The mutual interference always tends to further destruct the upward wave fluxes over the eastern North Pacific and enhance the downward wave fluxes over NA. The overall changes in upward wave fluxes, as well as that in the Rossby stationary wavenumber responsible for the stratospheric changes, are related to changes in the zonal-mean flow pattern. The joint effects of EA and NA, rather than being a linear superimposition of their independent effects, are largely dominated by the effects of EA.</p>

scholarly journals Topographic Forcing from East Asia and North America in the Northern Winter Stratosphere and Their Mutual Interference

2019 ◽  
Vol 32 (24) ◽  
pp. 8639-8658 ◽  
Author(s):  
Rongcai Ren ◽  
Xin Xia ◽  
Jian Rao
Keyword(s):  
North America ◽  
East Asia ◽  
Climate Model ◽  
Polar Vortex ◽  
Wave Pattern ◽  
Mutual Interference ◽  
Mean Flow ◽  
Stratospheric Polar Vortex ◽  
Northern Winter ◽  
Topographic Forcing

Abstract This study uses the stratosphere-resolved Whole Atmosphere Community Climate Model to demonstrate the “independent” and “dependent” topographic forcing from the topography of East Asia (EA) and North America (NA), and their “joint” forcing in the northern winter stratosphere. The mutual interference between the EA and NA forcing is also demonstrated. Specifically, without EA, an independent NA can also, like EA, induce a severe polar warming and weakening of the stratospheric polar vortex. While EA favors a displacement of the polar vortex toward Eurasia, NA favors a displacement toward the North America–Atlantic region. However, the independent-EA-forced weakening effect on the polar vortex can be largely decreased and changes to a location displacement when NA exists, and the interference the other way around is even more critical, being able to completely offset the independent-NA-forced effect, because EA can substantively obstruct NA’s effect on the tropospheric wave pattern over the Eurasia–Pacific region. The much stronger (weaker) interference of EA (NA) is associated with its stronger (weaker) downstream weakening effect on the zonal flow that impinges on NA (EA). The mutual interference always tends to further destruct the upward wave fluxes over the eastern North Pacific and enhance the downward wave fluxes over North America. The overall changes in upward wave fluxes, as well as that in the Rossby stationary wavenumber responsible for the stratospheric changes, are related to changes in the zonal-mean flow pattern. The joint effects of EA and NA, rather than being a linear superimposition of their independent effects, are largely dominated by the effects of EA.

The impact of air mass circulation dynamics on Late Holocene paleoclimate in northwestern North America

2003 ◽  
Vol 108 (1) ◽  
pp. 77-83 ◽  
Author(s):  
I.S Spooner ◽  
S Barnes ◽  
K.B Baltzer ◽  
R Raeside ◽  
G.D Osborn ◽  
...  
Keyword(s):  
North America ◽  
Late Holocene ◽  
Air Mass ◽  
Holocene Paleoclimate ◽  
Mass Circulation ◽  
Northwestern North America ◽  
The Impact ◽  
Circulation Dynamics ◽  
Late Holocene Paleoclimate

scholarly journals Dynamic Linkage between Cold Air Outbreaks and Intensity Variations of the Meridional Mass Circulation

2015 ◽  
Vol 72 (8) ◽  
pp. 3214-3232 ◽  
Author(s):  
Yueyue Yu ◽  
Rongcai Ren ◽  
Ming Cai
Keyword(s):  
Mass Transport ◽  
Western Europe ◽  
Peak Time ◽  
Cold Air ◽  
Continental Scale ◽  
Icelandic Low ◽  
Meridional Mass Circulation ◽  
Azores High ◽  
Mass Circulation ◽  
Cold Air Outbreaks

Abstract This study investigates the dynamical linkage between the meridional mass circulation and cold air outbreaks using the ERA-Interim data covering the period 1979–2011. It is found that the onset date of continental-scale cold air outbreaks coincides well with the peak time of stronger meridional mass circulation events, when the net mass transport across 60°N in the warm or cold air branch exceeds ~88 × 109 kg s−1. During weaker mass circulation events when the net mass transport across 60°N is below ~71.6 × 109 kg s−1, most areas of the midlatitudes are generally in mild conditions except the northern part of western Europe. Composite patterns of circulation anomalies during stronger mass circulation events greatly resemble that of the winter mean, with the two main routes of anomalous cold air outbreaks being along the climatological routes of polar cold air: namely, via East Asia and North America. The Siberian high shifts westward during stronger mass circulation events, opening up a third route of cold air outbreaks through eastern Europe, where lies the poleward warm air route in the winter-mean condition. The strengthening of the Icelandic low and Azores high during stronger mass circulation events acts to close off the climatological-mean cold air route via western Europe; this is responsible for the comparatively normal temperature there. The composite pattern for weaker mass circulation events is generally reversed, where the weakening of the Icelandic low and Azores high, corresponding to the negative phase of the North Atlantic Oscillation (NAO), leads to the reopening and strengthening of the equatorward cold air route through western Europe, which is responsible for the cold anomalies there.

A Mass Budget Analysis on the Interannual Variability of the Polar Surface Pressure in the Winter Season

2014 ◽  
Vol 71 (9) ◽  
pp. 3539-3553 ◽  
Author(s):  
Yueyue Yu ◽  
Rongcai Ren ◽  
Jinggao Hu ◽  
Guoxiong Wu
Keyword(s):  
Interannual Variability ◽  
Surface Pressure ◽  
Winter Season ◽  
Arctic Region ◽  
The Arctic ◽  
Mass Budget ◽  
Budget Analysis ◽  
Meridional Mass Circulation ◽  
Mass Circulation ◽  
The Arctic Region

Abstract This study reports a mass budget analysis on the year-to-year variability of the winter [December–February (DJF)]-mean Arctic (60°–90°N) surface pressure (Ps) using the 33-yr daily Interim ECMWF Re-Analysis (ERA-Interim; 1979–2011). The analysis reveals that the interannual variability of mass transported into the Arctic region in upper layers plays a dominant role in the interannual variability of the winter-mean Arctic Ps anomalies. When winter-mean Arctic Ps anomalies are positive, both the transport of mass into the Arctic region in the upper layer by the poleward branch of meridional mass circulation and the transport of mass out of the Arctic region in the lower layer by the equatorward branch tend to strengthen and vice versa. In the earlier winter months from November to December, mass anomalies transported in overwhelm those transported out, explaining the mass source of winter-mean Arctic Ps anomalies. The coupling between adiabatic mass transport by meridional mass circulation and diabatic processes explains why, over the Arctic region, yearly variations of winter Ps are positively correlated with mass anomalies in the upper layer (above 290 K) and near the surface (below 260 K) but negatively correlated with mass anomalies in the middle and lower troposphere (between 260 and 290 K). In winters with positive (negative) Arctic Ps anomalies, wave activity, particularly in wavenumbers 1 and 2, is stronger (weaker) in the extratropical stratosphere in the earlier winter months from November to January, coincident with the interannual variability of the meridional mass circulation intensity in winter seasons.

Sub-seasonal prediction skill for the stratospheric meridional mass circulation variability in CFSv2

2019 ◽  
Vol 53 (1-2) ◽  
pp. 631-650 ◽  
Author(s):  
Yueyue Yu ◽  
Ming Cai ◽  
Chunhua Shi ◽  
Ruikai Yan ◽  
Jian Rao
Keyword(s):  
Seasonal Prediction ◽  
Prediction Skill ◽  
Meridional Mass Circulation ◽  
Mass Circulation

scholarly journals Zonally Symmetric Adjustment in the Presence of Artificial Relaxation

2014 ◽  
Vol 71 (11) ◽  
pp. 4349-4368 ◽  
Author(s):  
Peter Hitchcock ◽  
Peter H. Haynes
Keyword(s):  
Boundary Condition ◽  
General Circulation ◽  
Circulation Model ◽  
Companion Paper ◽  
Reference State ◽  
Effective Boundary ◽  
Effective Boundary Condition ◽  
Meridional Mass Circulation ◽  
Sponge Layer ◽  
Mass Circulation

Abstract Numerical experiments, presented in a companion paper, have been performed in which the zonal-mean state of the stratosphere in a comprehensive, stratosphere-resolving, general circulation model is strongly relaxed (or “nudged”) toward the evolution of a reference sudden warming event in order to investigate its influence on the freely evolving troposphere below. Similar approaches have been used in a number of other studies. This raises the question of whether such an artificial relaxation induces the adiabatic and diabatic adjustments expected below the region of nudging, even in the absence of the stratospheric wave driving responsible for the reference event. Motivated by this question, the zonally symmetric quasigeostrophic diabatic response to zonal forces (representing wave driving) in a system nudged to a time-dependent reference state is studied. In the presence of wave driving in the nudging region that differs from the reference state, the meridional mass circulation of the reference state is reproduced only in the region below the nudging up to a correction that is inversely proportional to the strength of the nudging. The anomalous circulation is confined because of an effective boundary condition at the interface of the nudging layer. The nudging also produces an artificial “sponge-layer feedback” immediately below the region of the nudging in response to differences in the tropospheric wave driving. The strength of this artificial feedback is closely related to the strength of the effective boundary condition; however, the time scale required for the sponge-layer feedback to be established is typically much longer than that required for the confinement.

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