scholarly journals Gravity wave activity during stratospheric sudden warmings in the 2007–2008 Northern Hemisphere winter

2009 ◽  
Vol 114 (D18) ◽  
Author(s):  
Ling Wang ◽  
M. Joan Alexander
Keyword(s):  
Gravity Wave ◽  
Northern Hemisphere ◽  
Wave Activity ◽  
Stratospheric Sudden Warmings ◽  
Hemisphere Winter ◽  
Northern Hemisphere Winter

Observations of gravity wave activity during stratospheric sudden warmings in the Northern Hemisphere

2015 ◽  
Vol 58 (6) ◽  
pp. 951-960 ◽  
Author(s):  
Yue Jia ◽  
ShaoDong Zhang ◽  
Fan Yi ◽  
ChunMing Huang ◽  
KaiMing Huang ◽  
...  
Keyword(s):  
Gravity Wave ◽  
Northern Hemisphere ◽  
Wave Activity ◽  
Stratospheric Sudden Warmings

The Impact of Stratospheric Model Configuration on Planetary-Scale Waves in Northern Hemisphere Winter

2010 ◽  
Vol 23 (12) ◽  
pp. 3369-3389 ◽  
Author(s):  
Tiffany A. Shaw ◽  
Judith Perlwitz
Keyword(s):  
Gravity Wave ◽  
Northern Hemisphere ◽  
Momentum Flux ◽  
Planetary Scale ◽  
Model Configuration ◽  
Type Coupling ◽  
Hemisphere Winter ◽  
The Impact ◽  
Northern Hemisphere Winter ◽  
Wave Momentum

Abstract The impact of stratospheric model configuration on modeled planetary-scale waves in Northern Hemisphere winter is examined using the Canadian Middle Atmosphere Model (CMAM). The CMAM configurations include a high-lid (0.001 hPa) and a low-lid (10 hPa) configuration, which were each run with and without conservation of parameterized gravity wave momentum flux. The planetary wave structure, vertical propagation, and the basic state are found to be in good agreement with reanalysis data for the high-lid conservative configuration with the exception of the downward-propagating wave 1 signal. When the lid is lowered and momentum is conserved, the wave characteristics and basic state are not significantly altered, with the exception of the downward-propagating wave 1 signal, which is damped by the act of conservation. When momentum is not conserved, however, the wave amplitude increases significantly near the lid, and there is a large increase in both the upward- and downward-propagating wave 1 signals and a significant increase in the strength of the basic state. The impact of conserving parameterized gravity wave momentum flux is found to be much larger than that of the model lid height. The changes to the planetary waves and basic state significantly impact the stratosphere–troposphere coupling in the different configurations. In the low-lid configuration, there is an increase in wave-reflection-type coupling over zonal-mean-type coupling, a reduction in stratospheric sudden warming events, and an increase in the northern annular mode time scale. Conserving gravity wave momentum flux in the low-lid configuration significantly reduces these biases.

scholarly journals Solar and QBO Influences on the Timing of Stratospheric Sudden Warmings

2004 ◽  
Vol 61 (23) ◽  
pp. 2777-2796 ◽  
Author(s):  
Lesley J. Gray ◽  
Simon Crooks ◽  
Charlotte Pascoe ◽  
Sarah Sparrow ◽  
Michael Palmer
Keyword(s):  
Northern Hemisphere ◽  
Zonal Wind ◽  
Polar Vortex ◽  
Quasi Biennial Oscillation ◽  
Model Experiments ◽  
Zonal Winds ◽  
Stratospheric Sudden Warmings ◽  
Hemisphere Winter ◽  
Biennial Oscillation ◽  
Northern Hemisphere Winter

Abstract The interaction of the 11-yr solar cycle (SC) and the quasi-biennial oscillation (QBO) and their influence on the Northern Hemisphere (NH) polar vortex are studied using idealized model experiments and ECMWF Re-Analysis (ERA-40). In the model experiments, the sensitivity of the NH polar vortex to imposed easterlies at equatorial/subtropical latitudes over various height ranges is tested to explore the possible influence from zonal wind anomalies associated with the QBO and the 11-yr SC in those regions. The experiments show that the timing of the modeled stratospheric sudden warmings (SSWs) is sensitive to the imposed easterlies at the equator/subtropics. When easterlies are imposed in the equatorial or subtropical upper stratosphere, the onset of the SSWs is earlier. A mechanism is proposed in which zonal wind anomalies in the equatorial/subtropical upper stratosphere associated with the QBO and 11-yr SC either reinforce each other or cancel each other out. When they reinforce, as in Smin–QBO-east (Smin/E) and Smax–QBO-west (Smax/W), it is suggested that the resulting anomaly is large enough to influence the development of the Aleutian high and hence the time of onset of the SSWs. Although highly speculative, this mechanism may help to understand the puzzling observations that major warmings often occur in Smax/W years even though there is no strong waveguide provided by the QBO winds in the lower equatorial stratosphere. The ERA-40 data are used to investigate the QBO and solar signals and to determine whether the observations support the proposed mechanism. Composites of ERA-40 zonally averaged zonal winds based on the QBO (E/W), the SC (min/max), and both (Smin/E, Smin/W, Smax/E, Smax/W) are examined, with emphasis on the Northern Hemisphere winter vortex evolution. The major findings are that QBO/E years are more disturbed than QBO/W years, primarily during early winter. Sudden warmings in Smax years tend to occur later than in Smin years. Midwinter warmings are more likely during Smin/E and Smax/W years, although the latter result is only barely statistically significant at the 75% level. The data show some support for the proposed mechanism, but many more years are required before it can be fully tested.

scholarly journals Predictability Changes of Stratospheric Circulations in Northern Hemisphere Winter

2016 ◽  
Vol 94 (1) ◽  
pp. 7-24 ◽  
Author(s):  
Tomoko ICHIMARU ◽  
Shunsuke NOGUCHI ◽  
Toshihiko HIROOKA ◽  
Hitoshi MUKOUGAWA
Keyword(s):  
Northern Hemisphere ◽  
Hemisphere Winter ◽  
Northern Hemisphere Winter

scholarly journals Polar stratospheric cloud observations by MIPAS on ENVISAT: detection method, validation and analysis of the northern hemisphere winter 2002/2003

2005 ◽  
Vol 5 (3) ◽  
pp. 679-692 ◽  
Author(s):  
R. Spang ◽  
J. J. Remedios ◽  
L. J. Kramer ◽  
L. R. Poole ◽  
M. D. Fromm ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Detection Method ◽  
Michelson Interferometer ◽  
The Arctic ◽  
Spectral Signature ◽  
Winter Period ◽  
Second Phase ◽  
Good Correspondence ◽  
Hemisphere Winter ◽  
Northern Hemisphere Winter

Abstract. The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on ENVISAT has made extensive measurements of polar stratospheric clouds (PSCs) in the northern hemisphere winter 2002/2003. A PSC detection method based on a ratio of radiances (the cloud index) has been implemented for MIPAS and is validated in this study with respect to ground-based lidar and space borne occultation measurements. A very good correspondence in PSC sighting and cloud altitude between MIPAS detections and those of other instruments is found for cloud index values of less than four. Comparisons with data from the Stratospheric Aerosol and Gas Experiment (SAGE) III are used to further show that the sensitivity of the MIPAS detection method for this threshold value of cloud index is approximately equivalent to an extinction limit of 10-3km-1 at 1022nm, a wavelength used by solar occultation experiments. The MIPAS cloud index data are subsequently used to examine, for the first time with any technique, the evolution of PSCs throughout the Arctic polar vortex up to a latitude close to 90° north on a near-daily basis. We find that the winter of 2002/2003 is characterised by three phases of very different PSC activity. First, an unusual, extremely cold phase in the first three weeks of December resulted in high PSC occurrence rates. This was followed by a second phase of only moderate PSC activity from 5-13 January, separated from the first phase by a minor warming event. Finally there was a third phase from February to the end of March where only sporadic and mostly weak PSC events took place. The composition of PSCs during the winter period has also been examined, exploiting in particular an infra-red spectral signature which is probably characteristic of NAT. The MIPAS observations show the presence of these particles on a number of occasions in December but very rarely in January. The PSC type differentiation from MIPAS indicates that future comparisons of PSC observations with microphysical and denitrification models might be revealing about aspects of solid particle existence and location.

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