Seasonal Variations in the Southern Hemisphere Storm Tracks and Jet Streams as Revealed in a Reanalysis Dataset

Abstract A 30-yr climatology of Rossby wave breaking (RWB) on the Southern Hemisphere (SH) tropopause is formed using 30 yr of reanalyses. Composite analysis of potential vorticity and meridional fluxes of wave activity show that RWB in the SH can be divided into two broad categories: anticyclonic and cyclonic events. While there is only weak asymmetry in the meridional direction and most events cannot be classified as equatorward or poleward in terms of the potential vorticity structure, the position and structure of the fluxes associated with equatorward breaking differs from those of poleward breaking. Anticyclonic breaking is more common than cyclonic breaking, except on the lower isentrope examined (320 K). There are marked differences in the seasonal variations of RWB on the two surfaces, with a winter minimum for RWB around 350 K but a summer minimum for RWB around 330 K. These seasonal variations are due to changes in the location of the tropospheric jets and dynamical tropopause. During winter the subtropical jet and tropopause at 350 K are collocated in the Australian–South Pacific Ocean region, resulting in a seasonal minimum in the 350-K RWB. During summer the polar front jet and 330-K tropopause are collocated over the Southern Atlantic and Indian Oceans, inhibiting RWB in this region.

Download Full-text

A meridional structure of static stability and ozone vertical gradient around the tropopause in the Southern Hemisphere extratropics

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-10-19175-2010 ◽

2010 ◽

Vol 10 (8) ◽

pp. 19175-19194 ◽

Cited By ~ 1

Author(s):

Y. Tomikawa ◽

T. Yamanouchi

Keyword(s):

Southern Hemisphere ◽

Seasonal Variations ◽

Inversion Layer ◽

Polar Vortex ◽

Vertical Gradient ◽

Static Stability ◽

Radiative Heating ◽

Stratospheric Polar Vortex ◽

Close Relationship ◽

The Antarctic

Abstract. An analysis of the static stability and ozone vertical gradient in the ozone tropopause based (OTB) coordinate is applied to the ozonesonde data at 10 stations in the Southern Hemisphere (SH) extratropics. The tropopause inversion layer (TIL) with a static stability maximum just above the tropopause shows similar seasonal variations at two Antarctic stations, which are latitudinally far from each other. Since the sunshine hour varies with time in a quite different way between these two stations, it implies that the radiative heating due to solar ultraviolet absorption of ozone does not contribute to the seasonal variation of the TIL. A meridional section of the static stability in the OTB coordinate shows that the static stability just above the tropopause has a large latitudinal gradient between 60° S and 70° S in austral winter because of the absence of the TIL over the Antarctic. It is accompanied by an increase of westerly shear with height above the tropopause, so that the polar-night jet is formed above this latitude region. This result suggests a close relationship between the absence of the TIL and the stratospheric polar vortex in the Antarctic winter. A vertical gradient of ozone mixing ratio, referred to as ozone vertical gradient, around the tropopause shows similar latitudinal and seasonal variations with the static stability in the SH extratropics. In a height region above the TIL, a small ozone vertical gradient in the midlatitudes associated with the Antarctic ozone hole is observed in a height region of the subvortex but not around the polar vortex. This is a clear evidence of active latitudinal mixing between the midlatitudes and subvortex.

Download Full-text

Observed Associations Among Storm Tracks, Jet Streams and Midlatitude Oceanic Fronts

Earth's Climate - Geophysical Monograph Series ◽

10.1029/147gm18 ◽

2013 ◽

pp. 329-345 ◽

Cited By ~ 120

Author(s):

Hisashi Nakamura ◽

Takeaki Sampe ◽

Youichi Tanimoto ◽

Akihiko Shimpo

Keyword(s):

Storm Tracks ◽

Jet Streams ◽

Oceanic Fronts

Download Full-text

The Response of the Northern Hemisphere Storm Tracks and Jet Streams to Climate Change in the CMIP3, CMIP5, and CMIP6 Climate Models

Journal of Geophysical Research Atmospheres ◽

10.1029/2020jd032701 ◽

2020 ◽

Vol 125 (23) ◽

Author(s):

B. J. Harvey ◽

P. Cook ◽

L. C. Shaffrey ◽

R. Schiemann

Keyword(s):

Climate Change ◽

Northern Hemisphere ◽

Climate Models ◽

Storm Tracks ◽

Jet Streams

Download Full-text

Exploring the sensitivity of Northern Hemisphere atmospheric circulation to different surface temperature forcing using a statistical–dynamical atmospheric model

Nonlinear Processes in Geophysics ◽

10.5194/npg-26-1-2019 ◽

2019 ◽

Vol 26 (1) ◽

pp. 1-12 ◽

Cited By ~ 1

Author(s):

Sonja Totz ◽

Stefan Petri ◽

Jascha Lehmann ◽

Erik Peukert ◽

Dim Coumou

Keyword(s):

Temperature Gradient ◽

Large Scale ◽

Planetary Waves ◽

Hadley Cell ◽

Storm Tracks ◽

Meridional Temperature Gradient ◽

Jet Streams ◽

Global Mean Temperature ◽

Mean Temperature ◽

Global Mean

Abstract. Climate and weather conditions in the mid-latitudes are strongly driven by the large-scale atmosphere circulation. Observational data indicate that important components of the large-scale circulation have changed in recent decades, including the strength and the width of the Hadley cell, jets, storm tracks and planetary waves. Here, we use a new statistical–dynamical atmosphere model (SDAM) to test the individual sensitivities of the large-scale atmospheric circulation to changes in the zonal temperature gradient, meridional temperature gradient and global-mean temperature. We analyze the Northern Hemisphere Hadley circulation, jet streams, storm tracks and planetary waves by systematically altering the zonal temperature asymmetry, the meridional temperature gradient and the global-mean temperature. Our results show that the strength of the Hadley cell, storm tracks and jet streams depend, in terms of relative changes, almost linearly on both the global-mean temperature and the meridional temperature gradient, whereas the zonal temperature asymmetry has little or no influence. The magnitude of planetary waves is affected by all three temperature components, as expected from theoretical dynamical considerations. The width of the Hadley cell behaves nonlinearly with respect to all three temperature components in the SDAM. Moreover, some of these observed large-scale atmospheric changes are expected from dynamical equations and are therefore an important part of model validation.

Download Full-text