Midlatitude and high-latitude N2O distributions in the Northern Hemisphere in early and late Arctic polar vortex breakup years

Abstract. The influence of a CO2 doubling on the stratospheric potential vorticity (PV) is examined in two climate models. Subsequently, the influence of changes in the stratosphere on the tropospheric zonal wind response is investigated, by inverting the stratospheric PV. Radiative effects dominate the stratospheric response to CO2 doubling in the Southern Hemisphere. These lead to a stratospheric PV increase at the edge of the polar vortex, resulting in an increased westerly influence of the stratosphere on the tropospheric midlatitude winds in late winter. In the Northern Hemisphere, dynamical effects are also important. Both models show a reduced polar PV and an enhanced midlatitude PV in the Northern Hemisphere winter stratosphere. These PV changes are related to an enhanced wave forcing of the winter stratosphere, as measured by an increase in the 100 hPa eddy heat flux, and result in a reduced westerly influence of the stratosphere on the high latitude tropospheric winds. In one model, the high latitude PV decreases are, however, restricted to higher altitudes, and the tropospheric response due to the stratospheric changes is dominated by an increased westerly influence in the midlatitudes, related to the increase in midlatitude PV in the lower stratosphere. The tropospheric response in zonal wind due to the stratospheric PV changes is of the order of 0.5 to 1 m s−1. The total tropospheric response has a somewhat different spatial structure, but is of similar magnitude. This indicates that the stratospheric influence is of importance in modifying the tropospheric zonal wind response to CO2 doubling.

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The influence of the stratosphere on the tropospheric zonal wind response to CO<sub>2</sub> doubling

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-4915-2011 ◽

2011 ◽

Vol 11 (10) ◽

pp. 4915-4927 ◽

Cited By ~ 1

Author(s):

Y. B. L. Hinssen ◽

C. J. Bell ◽

P. C. Siegmund

Keyword(s):

Northern Hemisphere ◽

Zonal Wind ◽

High Latitude ◽

Climate Models ◽

Polar Vortex ◽

Late Winter ◽

Wave Forcing ◽

Eddy Heat Flux ◽

Wind Response ◽

Hemisphere Winter

Abstract. The influence of a CO2 doubling on the stratospheric potential vorticity (PV) is examined in two climate models. Subsequently, the influence of changes in the stratosphere on the tropospheric zonal wind response is investigated, by inverting the stratospheric PV. Radiative effects seem to dominate the stratospheric response to CO2 doubling in the Southern Hemisphere. These lead to a stratospheric PV increase at the edge of the polar vortex, resulting in an increased westerly influence of the stratosphere on the troposphere, increasing the midlatitude tropospheric westerlies in late winter. In the Northern Hemisphere, dynamical effects are also important. Both models show a reduced polar PV and an enhanced midlatitude PV in the Northern Hemisphere winter stratosphere. These PV changes are likely related to an enhanced wave forcing of the winter stratosphere, as measured by an increase in the 100 hPa eddy heat flux, and result in a reduced westerly influence of the stratosphere on the high latitude tropospheric winds. In one model, the high latitude PV decreases are, however, restricted to higher altitudes, and the tropospheric response due to the stratospheric changes is dominated by an increased westerly influence in the midlatitudes, related to the increase in midlatitude PV in the lower stratosphere. The tropospheric response in zonal wind due to the stratospheric PV changes is of the order of 0.5 to 1 m s−1. The total tropospheric response has a somewhat different spatial structure, but is of similar magnitude. This indicates that the stratospheric influence is of importance in modifying the tropospheric zonal wind response to CO2 doubling.

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The impact of volcanic aerosol on the Northern Hemisphere stratospheric polar vortex: mechanisms and sensitivity to forcing structure

Atmospheric Chemistry and Physics ◽

10.5194/acp-14-13063-2014 ◽

2014 ◽

Vol 14 (23) ◽

pp. 13063-13079 ◽

Cited By ~ 25

Author(s):

M. Toohey ◽

K. Krüger ◽

M. Bittner ◽

C. Timmreck ◽

H. Schmidt

Keyword(s):

Northern Hemisphere ◽

High Latitude ◽

Climate Model ◽

Polar Vortex ◽

Volcanic Aerosol ◽

Stratospheric Polar Vortex ◽

Model Simulations ◽

Aerosol Forcing ◽

Climate Model Simulations ◽

The Impact

Abstract. Observations and simple theoretical arguments suggest that the Northern Hemisphere (NH) stratospheric polar vortex is stronger in winters following major volcanic eruptions. However, recent studies show that climate models forced by prescribed volcanic aerosol fields fail to reproduce this effect. We investigate the impact of volcanic aerosol forcing on stratospheric dynamics, including the strength of the NH polar vortex, in ensemble simulations with the Max Planck Institute Earth System Model. The model is forced by four different prescribed forcing sets representing the radiative properties of stratospheric aerosol following the 1991 eruption of Mt. Pinatubo: two forcing sets are based on observations, and are commonly used in climate model simulations, and two forcing sets are constructed based on coupled aerosol–climate model simulations. For all forcings, we find that simulated temperature and zonal wind anomalies in the NH high latitudes are not directly impacted by anomalous volcanic aerosol heating. Instead, high-latitude effects result from enhancements in stratospheric residual circulation, which in turn result, at least in part, from enhanced stratospheric wave activity. High-latitude effects are therefore much less robust than would be expected if they were the direct result of aerosol heating. Both observation-based forcing sets result in insignificant changes in vortex strength. For the model-based forcing sets, the vortex response is found to be sensitive to the structure of the forcing, with one forcing set leading to significant strengthening of the polar vortex in rough agreement with observation-based expectations. Differences in the dynamical response to the forcing sets imply that reproducing the polar vortex responses to past eruptions, or predicting the response to future eruptions, depends on accurate representation of the space–time structure of the volcanic aerosol forcing.

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The Dynamics of Northern Hemisphere Stratospheric Final Warming Events

Journal of the Atmospheric Sciences ◽

10.1175/jas3981.1 ◽

2007 ◽

Vol 64 (8) ◽

pp. 2932-2946 ◽

Cited By ~ 48

Author(s):

Robert X. Black ◽

Brent A. McDaniel

Keyword(s):

Northern Hemisphere ◽

Zonal Wind ◽

Potential Vorticity ◽

High Latitude ◽

Dynamical Behavior ◽

Polar Vortex ◽

Stratospheric Polar Vortex ◽

Stratospheric Final Warming ◽

Concomitant Reduction ◽

Indirect Consequence

A lag composite analysis is performed of the zonal-mean structure and dynamics of Northern Hemisphere stratospheric final warming (SFW) events. SFW events are linked to distinct zonal wind deceleration signatures in the stratosphere and troposphere. The period of strongest stratospheric decelerations (SD) is marked by a concomitant reduction in the high-latitude tropospheric westerlies. However, a subsequent period of tropospheric decelerations (TD) occurs while the stratospheric circulation relaxes toward climatological conditions. During SFW onset, a wavenumber-1 disturbance at stratospheric altitudes evolves into a circumpolar anticyclonic circulation anomaly. Transformed Eulerian-mean dynamical diagnoses reveal that the SD period is characterized by an anomalous upward Eliassen–Palm (EP) signature at high latitudes extending from the surface to the middle stratosphere. The associated wave-driving pattern consists of zonal decelerations extending from the upper troposphere to the midstratosphere. Piecewise potential vorticity tendency analyses further indicate that zonal wind decelerations in the lower and middle troposphere result, at least in part, from the direct response to latitudinal redistributions of potential vorticity occurring in the lower stratosphere. The TD period exhibits a distinct dynamical behavior with anomalous downward EP fluxes in the high-latitude stratosphere as the zero zonal wind line descends toward the tropopause. This simultaneously allows the stratospheric polar vortex to radiatively recover while providing anomalous upper-tropospheric zonal decelerations (as tropospheric Rossby wave activity is vertically trapped in the high-latitude troposphere). The tropospheric decelerations that occur during the TD period are regarded as a subsequent indirect consequence of SFW events.

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Comparison of Key Characteristics of Remarkable SSW Events in the Southern and Northern Hemisphere

10.5194/egusphere-egu21-7702 ◽

2021 ◽

Author(s):

Michal Kozubek ◽

Peter Krizan

Keyword(s):

Northern Hemisphere ◽

Planetary Wave ◽

Polar Vortex ◽

Wave Number ◽

Strong Activity ◽

Key Characteristics ◽

Zonal Wave Number ◽

Show Difference ◽

Temperature Enhancement ◽

Stationary Planetary Wave

<p>An exceptionally strong sudden stratospheric warming (SSW) in the Southern Hemisphere (SH) during September 2019 was observed. Because SSW in the SH is very rare, comparison with the only recorded major SH SSW is done. According to World Meteorological Organization (WMO) definition, the SSW in 2019 has to be classified as minor. The cause of SSW in 2002 was very strong activity of stationary planetary wave with zonal wave-number (ZW) 2, which reached its maximum when the polar vortex split into two circulations with polar temperature enhancement by 30 K/week and it penetrated deeply to the lower stratosphere and upper troposphere. On the other hand, the minor SSW in 2019 involved an exceptionally strong wave-1 planetary wave and a large polar temperature enhancement by 50.8 K/week, but it affected mainly the middle and upper stratosphere. The strongest SSW in the Northern Hemisphere was observed in 2009. This study provides comparison of two strongest SSW in the SH and the strongest SSW in the NH to show difference between two hemispheres and possible impact to the lower or higher layers.</p>

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Turbulent kinetic energy spectra and cascades in the polar atmosphere of Saturn

10.5194/egusphere-egu21-14857 ◽

2021 ◽

Author(s):

Peter L. Read ◽

Arrate Antuñano ◽

Simon Cabanes ◽

Greg Colyer ◽

Teresa del Rio-Gaztelurrutia ◽

...

Keyword(s):

Kinetic Energy ◽

High Latitude ◽

Deep Convection ◽

Baroclinic Instability ◽

Polar Vortex ◽

Energy Spectra ◽

Horizontal Wind ◽

Polar Regions ◽

Zonal Wavenumber ◽

Cloud Tops

<p>The regions of Saturn&#8217;s cloud-covered atmosphere polewards of 60<sup>o</sup> latitude are dominated in each hemisphere near the cloud tops by an intense, cyclonic polar vortex surrounded by a strong, high latitude eastward zonal jet. In the north, this high latitude jet takes the form of a remarkably regular zonal wavenumber m=6 hexagonal pattern that has been present at least since the Voyager spacecraft encounters with Saturn in 1980-81, and probably much longer. The origin of this feature, and the absence of a similar feature in the south, has remained poorly understood since its discovery. In this work, we present some new analyses of horizontal wind measurements at Saturn&#8217;s cloud tops polewards of 60 degrees in both the northern and southern hemispheres, previously published by Antu&#241;ano et al. (2015) using images from the Cassini mission, in which we compute kinetic energy spectra and the transfer rates of kinetic energy (KE) and enstrophy between different scales. 2D KE spectra are consistent with a zonostrophic regime, with a steep&#160;(~n<sup>-5</sup>) spectrum for the mean zonal flow (n is the total wavenumber) and a shallower Kolmogorov-like KE spectrum (~n<sup>-5/3</sup>)&#160;for the residual (eddy) flow, much as previously found for Jupiter&#8217;s atmosphere (Galperin et al. 2014; Young & Read 2017). Three different methods are used to compute the energy and enstrophy transfers, (a) as latitude-dependent zonal spectral fluxes, (b) as latitude-dependent structure functions and (c) as spatially filtered energy fluxes. The results of all three methods are largely in agreement in indicating a direct (forward) enstrophy cascade across most scales, averaged across the whole domain, an inverse kinetic energy cascade to large scales and a weak direct KE cascade at the smallest scales. The pattern of transfers has a more complex dependence on latitude, however. But it is clear that the m=6 North Polar Hexagon (NPH) wave was transferring KE into its zonal jet at 78<sup>o</sup> N (planetographic) at a rate of &#8719;<sub>E</sub> &#8776; 1.8 x 10<sup>-4</sup> W kg<sup>-1</sup>&#160;at the time the Cassini images were acquired. This implies that the NPH was not maintained by a barotropic instability at this time, but may have been driven via a baroclinic instability or possibly from deep convection. Further implications of these results will be discussed.</p><p>&#160;</p><p>References</p><p>Antu&#241;ano, A., T. del R&#237;o-Gaztelurrutia, A. S&#225;nchez-Lavega, and R. Hueso (2015), Dynamics of Saturn&#8217;s polar regions, J. Geophys. Res. Planets, 120, 155&#8211;176, doi:10.1002/2014JE004709.</p><p>Galperin, B., R. M.B. Young, S. Sukoriansky, N. Dikovskaya, P. L. Read, A.&#160;J. Lancaster & D. Armstrong (2014) Cassini observations reveal a regime of zonostrophic macroturbulence on Jupiter, Icarus, 229, 295&#8211;320.doi: 10.1016/j.icarus.2013.08.030</p><p>Young, R. M. B. & Read, P. L. (2017) Forward and inverse kinetic energy cascades in Jupiter&#8217;s turbulent weather layer, Nature Phys., 13, 1135-1140. Doi:10.1038/NPHYS4227</p><div> <div> <div>&#160;</div> </div> <div> <div>&#160;</div> </div> <div> <div>&#160;</div> </div> <div> <div>&#160;</div> </div> </div>

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Strategies for high-latitude northern hemisphere CO2 sampling now and in the future

Deep Sea Research Part II Topical Studies in Oceanography ◽

10.1016/j.dsr2.2008.12.008 ◽

2009 ◽

Vol 56 (8-10) ◽

pp. 523-532 ◽

Cited By ~ 10

Author(s):

Andrew Lenton ◽

Laurent Bopp ◽

Richard J. Matear

Keyword(s):

Northern Hemisphere ◽

High Latitude ◽

The Future

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Intra-interglacial climate variability: model simulations of Marine Isotope Stages 1, 5, 11, 13, and 15

Climate of the Past ◽

10.5194/cp-12-677-2016 ◽

2016 ◽

Vol 12 (3) ◽

pp. 677-695 ◽

Cited By ~ 11

Author(s):

Rima Rachmayani ◽

Matthias Prange ◽

Michael Schulz

Keyword(s):

Climate Variability ◽

Surface Temperature ◽

Northern Hemisphere ◽

High Latitude ◽

West African ◽

Boreal Summer ◽

The West ◽

Temperature Anomalies ◽

Astronomical Forcing

Abstract. Using the Community Climate System Model version 3 (CCSM3) including a dynamic global vegetation model, a set of 13 time slice experiments was carried out to study global climate variability between and within the Quaternary interglacials of Marine Isotope Stages (MISs) 1, 5, 11, 13, and 15. The selection of interglacial time slices was based on different aspects of inter- and intra-interglacial variability and associated astronomical forcing. The different effects of obliquity, precession, and greenhouse gas (GHG) forcing on global surface temperature and precipitation fields are illuminated. In most regions seasonal surface temperature anomalies can largely be explained by local insolation anomalies induced by the astronomical forcing. Climate feedbacks, however, may modify the surface temperature response in specific regions, most pronounced in the monsoon domains and the polar oceans. GHG forcing may also play an important role for seasonal temperature anomalies, especially at high latitudes and early Brunhes interglacials (MIS 13 and 15) when GHG concentrations were much lower than during the later interglacials. High- versus low-obliquity climates are generally characterized by strong warming over the Northern Hemisphere extratropics and slight cooling in the tropics during boreal summer. During boreal winter, a moderate cooling over large portions of the Northern Hemisphere continents and a strong warming at high southern latitudes is found. Beside the well-known role of precession, a significant role of obliquity in forcing the West African monsoon is identified. Other regional monsoon systems are less sensitive or not sensitive at all to obliquity variations during interglacials. Moreover, based on two specific time slices (394 and 615 ka), it is explicitly shown that the West African and Indian monsoon systems do not always vary in concert, challenging the concept of a global monsoon system on astronomical timescales. High obliquity can also explain relatively warm Northern Hemisphere high-latitude summer temperatures despite maximum precession around 495 ka (MIS 13). It is hypothesized that this obliquity-induced high-latitude warming may have prevented a glacial inception at that time.

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