scholarly journals Wave Packets and Life Cycles of Troughs in the Upper Troposphere: Examples from the Southern Hemisphere Summer Season of 1984/85

2000 ◽  
Vol 128 (1) ◽  
pp. 25-50 ◽  
Author(s):  
Edmund K. M. Chang
Keyword(s):  
Southern Hemisphere ◽  
Wave Packets ◽  
Life Cycles ◽  
Summer Season ◽  
Upper Troposphere

Intraseasonal Periodicity in the Southern Hemisphere Circulation on Regional Spatial Scales

2017 ◽  
Vol 74 (3) ◽  
pp. 865-877 ◽  
Author(s):  
David W. J. Thompson ◽  
Brian R. Crow ◽  
Elizabeth A. Barnes
Keyword(s):  
Southern Hemisphere ◽  
Time Scales ◽  
Spatial Scales ◽  
Wave Packets ◽  
Lower Troposphere ◽  
Wave Activity ◽  
Heat Fluxes ◽  
Time Structure ◽  
Upper Troposphere ◽  
Activity Form

Abstract Wave activity in the Southern Hemisphere extratropical atmosphere exhibits robust periodicity on time scales of ~20–25 days. Previous studies have demonstrated the robustness of the periodicity in hemispheric averages of various eddy quantities. Here the authors explore the signature of the periodicity on regional spatial scales. Intraseasonal periodicity in the Southern Hemisphere circulation derives from out-of-phase anomalies in wave activity that form in association with extratropical wave packets as they propagate to the east. In the upper troposphere, the out-of-phase anomalies in wave activity form not along the path of extratropical wave packets, but in their wake. The out-of-phase anomalies in wave activity give rise to periodicity not only on hemispheric scales, but also on synoptic scales when the circulation is sampled along an eastward path between ~5 and 15 m s−1. It is argued that 1) periodicity in extratropical wave activity derives from two-way interactions between the heat fluxes and baroclinicity in the lower troposphere and 2) the unique longitude–time structure of the periodicity in upper-tropospheric wave activity derives from the contrasting eastward speeds of the source of the periodicity in the lower troposphere (~10 m s−1) and wave packets in the upper troposphere (~25 m s−1).

A New Perspective on Southern Hemisphere Storm Tracks

2005 ◽  
Vol 18 (20) ◽  
pp. 4108-4129 ◽  
Author(s):  
B. J. Hoskins ◽  
K. I. Hodges
Keyword(s):  
South America ◽  
Southern Hemisphere ◽  
High Latitude ◽  
Storm Track ◽  
Life Cycles ◽  
Storm Tracks ◽  
Lower Latitude ◽  
Upper Troposphere ◽  
The Andes ◽  
Subtropical Jet

Abstract A detailed view of Southern Hemisphere storm tracks is obtained based on the application of filtered variance and modern feature-tracking techniques to a wide range of 45-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) data. It has been checked that the conclusions drawn in this study are valid even if data from only the satellite era are used. The emphasis of the paper is on the winter season, but results for the four seasons are also discussed. Both upper- and lower-tropospheric fields are used. The tracking analysis focuses on systems that last longer than 2 days and are mobile (move more than 1000 km). Many of the results support previous ideas about the storm tracks, but some new insights are also obtained. In the summer there is a rather circular, strong, deep high-latitude storm track. In winter the high-latitude storm track is more asymmetric with a spiral from the Atlantic and Indian Oceans in toward Antarctica and a subtropical jet–related lower-latitude storm track over the Pacific, again tending to spiral poleward. At all times of the year, maximum storm activity in the higher-latitude storm track is in the Atlantic and Indian Ocean regions. In the winter upper troposphere, the relative importance of, and interplay between, the subtropical and subpolar storm tracks is discussed. The genesis, lysis, and growth rate of lower-tropospheric winter cyclones together lead to a vivid picture of their behavior that is summarized as a set of overlapping plates, each composed of cyclone life cycles. Systems in each plate appear to feed the genesis in the next plate through downstream development in the upper-troposphere spiral storm track. In the lee of the Andes in South America, there is cyclogenesis associated with the subtropical jet and also, poleward of this, cyclogenesis largely associated with system decay on the upslope and regeneration on the downslope. The genesis and lysis of cyclones and anticyclones have a definite spatial relationship with each other and with the Andes. At 500 hPa, their relative longitudinal positions are consistent with vortex-stretching ideas for simple flow over a large-scale mountain. Cyclonic systems near Antarctica have generally spiraled in from lower latitudes. However, cyclogenesis associated with mobile cyclones occurs around the Antarctic coast with an interesting genesis maximum over the sea ice near 150°E. The South Pacific storm track emerges clearly from the tracking as a coherent deep feature spiraling from Australia to southern South America. A feature of the summer season is the genesis of eastward-moving cyclonic systems near the tropic of Capricorn off Brazil, in the central Pacific and, to a lesser extent, off Madagascar, followed by movement along the southwest flanks of the subtropical anticyclones and contribution to the “convergence zone” cloud bands seen in these regions.

Recurrent Rossby wave packets and persistent extreme weather

2021 ◽  
Author(s):  
S. Mubashshir Ali ◽  
Olivia Martius ◽  
Matthias Röthlisberger
Keyword(s):  
Southern Hemisphere ◽  
Spatial Patterns ◽  
Rossby Wave ◽  
Wave Packets ◽  
Reanalysis Data ◽  
Synoptic Scale ◽  
Background Flow ◽  
Dry Spell ◽  
Upper Level ◽  
Wet Spells

<p>Upper-level synoptic-scale Rossby wave packets are well-known to affect surface weather. When these Rossby wave packets occur repeatedly in the same phase at a specific location, they can result in persistent hot, cold, dry, and wet conditions. The repeated and in-phase occurrence of Rossby wave packets is termed as recurrent synoptic-scale Rossby wave packets (RRWPs). RRWPs result from multiple transient synoptic-scale wave packets amplifying in the same geographical region over several weeks.</p><p>Our climatological analyses using reanalysis data have shown that RRWPs can significantly modulate the persistence of hot, cold, dry, and wet spells in several regions in the Northern and the Southern Hemisphere.  RRWPs can both shorten or extend hot, cold, and dry spell durations. The spatial patterns of statistically significant links between RRWPs and spell durations are distinct for the type of the spell (hot, cold, dry, or wet) and the season (MJJASO or NDJFMA). In the Northern Hemisphere, the spatial patterns where RRWPs either extend or shorten the spell durations are wave-like. In the Southern Hemisphere, the spatial patterns are either wave-like (hot and cold spells) or latitudinally banded (dry and wet spells).</p><p>Furthermore, we explore the atmospheric drivers behind RRWP events. This includes both the background flow and potential wave-triggers such as the Madden Julian Oscillation or blocking. For 100 events of intense Rossby wave recurrence in the Atlantic, the background flow, the intensity of tropical convection, and the occurrence of blocking are studied using flow composites.</p>

Are Recurrent Rossby wave packets linked to persistent extreme weather events in the Southern Hemisphere?

2020 ◽  
Author(s):  
Syed Mubashshir Ali ◽  
Olivia Martius ◽  
Matthias Röthlisberger
Keyword(s):  
Southern Hemisphere ◽  
Rossby Wave ◽  
Wave Packets ◽  
Extreme Weather Events ◽  
Synoptic Scale ◽  
Spatial And Seasonal Variation ◽  
Weather Events ◽  
Surface Weather ◽  
Winter Cold ◽  
Hot Spells

<p>Synoptic-scale Rossby wave-packets have a recurrent pattern during several episodes of persistent surface weather which is termed as 'recurrent Rossby wave-packets' (RRWP). They result in a statistically significant increase in winter cold and summer hot spells over large areas of the Northern Hemisphere mid-latitudes.</p><p>We present a global climatology of the RRWPs to study its spatial and seasonal variation. We also investigate the link of RRWPs to persistent surface extremes in the Southern Hemisphere (SH).  We find that RRWPs result in a statistically significant increase in winter cold and summer hot spells over broad areas in Australia and South America. Furthermore, we discuss the effects of climatological oscillations (Madden Julian Oscillation, ENSO, etc) on influencing the RRWPs.</p>

Mars: Detection of Atmospheric Water Vapor during the Southern Hemisphere Spring and Summer Season

Science ◽  
1970 ◽  
Vol 170 (3964) ◽  
pp. 1308-1310 ◽  
Author(s):  
E. S. Barker ◽  
R. A. Schorn ◽  
A. Woszczyk ◽  
R. G. Tull ◽  
S. J. Little
Keyword(s):  
Water Vapor ◽  
Southern Hemisphere ◽  
Summer Season ◽  
Atmospheric Water Vapor ◽  
Atmospheric Water

scholarly journals A Major Stratospheric Sudden Warming Event in January 2009

2010 ◽  
Vol 67 (6) ◽  
pp. 2052-2069 ◽  
Author(s):  
Yayoi Harada ◽  
Atsushi Goto ◽  
Hiroshi Hasegawa ◽  
Norihisa Fujikawa ◽  
Hiroaki Naoe ◽  
...  
Keyword(s):  
Wave Packets ◽  
Development Stage ◽  
Japan Meteorological Agency ◽  
Eastern Siberia ◽  
Climate Data ◽  
Stratospheric Sudden Warming ◽  
Upper Troposphere ◽  
Planetary Scale ◽  
The North ◽  
Zonal Wavenumber

Abstract The major stratospheric sudden warming (SSW) event of January 2009 is analyzed using the Japan Meteorological Agency (JMA) Climate Data Assimilation System (JCDAS). This SSW event is characterized by the extraordinary predominance of the planetary-scale wave of zonal wavenumber 2 (wave 2). The total amount of the upward Eliassen–Palm (EP) flux for wave 2 was the strongest since the winter of 1978/79. It is found that the remarkable development of the upper troposphere ridge over Alaska played important roles in the SSW in January 2009. During the first development stage, the ridge excited wave packets upward as well as eastward over around Alaska. The eastward-propagating packets intensified a trough over eastern Siberia, which led to the development of the planetary wave over eastern Siberia during the second development stage. The results of this study indicate that the pronounced wave-2 pattern observed in the stratosphere was brought about by accumulative effects of rather localized propagation of wave packets from the troposphere during the course of this SSW event rather than by the ubiquitous propagation of planetary-scale disturbances in the troposphere. The features of the SSW in January 2009 are quite similar to those during the major stratospheric warming event in February 1989: both SSWs are characterized by the predominance of wave 2, the remarkable development of the upper troposphere ridge over around Alaska, and positive SSTs in the eastern part of the North Pacific corresponding to a La Niña condition.

scholarly journals Stratosphere–Troposphere Exchange and O3 Decline in the Lower Stratosphere over Irene SHADOZ Site, South Africa

2020 ◽  
Author(s):  
Thumeka Mkololo ◽  
Nkanyiso Mbatha ◽  
Sivakumar Venkataraman ◽  
Nelson Begue ◽  
Gerrie Coetzee ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Potential Vorticity ◽  
Lower Stratosphere ◽  
Polar Vortex ◽  
Air Masses ◽  
Upper Troposphere ◽  
Average Decrease ◽  
Ozone Trends ◽  
K 12 ◽  
Troposphere Ozone

This study aims to investigate the Stratosphere-Troposphere Exchange (STE) events and ozone trends over Irene (25.5°S, 28.1°E). Twelve years of ozonesondes data (2000–2007, 2012–2015) from Irene station operating in the framework of the Southern Hemisphere Additional Ozonesodes (SHADOZ) was used to study the troposphere (0–16 km) and stratosphere (17– 28 km) ozone (O3) vertical profiles. Ozone profiles were grouped into three categories (2000–2003, 2004–2007 and 2012–2015) and average composites were calculated for each category. Fifteen O3 enhancement events were identified over the study period. These events were observed in all seasons (one event in summer, four events in autumn, five events in winter and five events in spring), however, they predominantly occur in winter and spring. The STE events presented here are observed to be influenced by the Southern Hemisphere polar vortex. During the STE events, the advected potential vorticity maps assimilated using Modélisation Isentrope du transport Méso–échelle de l’Ozone Stratosphérique par Advection (MIMOSA) model for the 350 K (~12–13 km) isentropic level indicated a transport of high latitude air masses which seems to be responsible for the reduction of the O3 mole fractions at the lower stratosphere over Irene which takes place at the same time with the enhancement of ozone in the upper troposphere. In general, the stratosphere is dominated by higher Modern Retrospective Analysis for Research Application (MERRA-2) potential vorticity (PV) values compared to the troposphere. However, during the STE events, higher PV values from the stratosphere were observed to intrude the troposphere. Ozone decline was observed from 12 km to 24 km with highest decline occurring from 14 km to 18 km. An average decrease of 6.0 and 9.1% was calculated from 12 to 24 km in 2004–2007 and 2012–2015 respectively. The observed decline occurred in the upper troposphere and lower stratosphere with winter and spring showing more decline compared with summer and autumn.

scholarly journals Hydrogen cyanide in the upper troposphere: GEM-AQ simulation and comparison with ACE-FTS observations

2009 ◽  
Vol 9 (1) ◽  
pp. 2165-2194 ◽  
Author(s):  
A. Lupu ◽  
J. W. Kaminski ◽  
L. Neary ◽  
J. C. McConnell ◽  
K. Toyota ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Atmospheric Chemistry ◽  
Hydrogen Cyanide ◽  
Weather Forecasting ◽  
Boreal Summer ◽  
Air Quality Model ◽  
Quality Model ◽  
Upper Troposphere ◽  
Mixing Ratios ◽  
The Tropics

Abstract. We investigate the spatial and temporal distribution of hydrogen cyanide (HCN) in the upper troposphere through numerical simulations and comparison with observations from a space-based instrument. To perform the simulations, we used the Global Environmental Multiscale Air Quality model (GEM-AQ), which is based on the three-dimensional global multiscale model developed by the Meteorological Service of Canada for operational weather forecasting. The model was run for the period 2004–2006 on a 1.5°×1.5° global grid with 28 hybrid vertical levels from the surface up to 10 hPa. Objective analysis data from the Canadian Meteorological Centre were used to update the meteorological fields every 24 h. Fire emission fluxes of gas species were generated by using year-specific inventories of carbon emissions with 8-day temporal resolution from the Global Fire Emission Database (GFED) version 2. The model output is compared with HCN profiles measured by the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) instrument onboard the Canadian SCISAT-1 satellite. High values of up to a few ppbv are observed in the tropics in the Southern Hemisphere; the enhancement in HCN volume mixing ratios in the upper troposphere is most prominent in October. Low upper-tropospheric mixing ratios of less than 100 pptv are mostly recorded at middle and high latitudes in the Southern Hemisphere in May–July. Mixing ratios in Northern Hemisphere peak in the boreal summer. The amplitude of the seasonal variation is less pronounced than in the Southern Hemisphere. Our model results show that in the upper troposphere GEM-AQ performs well globally for all seasons, except at Northern high and middle latitudes in summer, where the model has a large negative bias, and in the tropics in winter and spring, where it exhibits large positive bias. This may reflect inaccurate emissions or possible inaccuracies in the emission profile. The model is able to explain most of the observed variability in the upper troposphere HCN field, including the interannual variations in the observed mixing ratio. The estimated average global emission equals 1.3 Tg N yr−1. The average atmospheric burden is 0.53 Tg N, and the corresponding lifetime is 4.9 months.

Sign in / Sign up

Export Citation Format

Share Document