Solar cycle changes to planetary wave propagation and their influence on the middle atmosphere circulation

Abstract. Recent observations suggest that there may be a causal relationship between solar activity and the strength of the winter Northern Hemisphere circulation in the stratosphere. A three-dimensional model of the atmosphere between 10–140 km was developed to assess the influence of solar minimum and solar maximum conditions on the propagation of planetary waves and the subsequent changes to the circulation of the stratosphere. Ultraviolet heating in the middle atmosphere was kept constant in order to emphasise the importance of non-linear dynamical coupling. A realistic thermosphere was achieved by relaxing the upper layers to the MSIS-90 empirical temperature model. In the summer hemisphere, strong radiative damping prevents significant dynamical coupling from taking place. Within the dynamically controlled winter hemisphere, small perturbations are reinforced over long periods of time, resulting in systematic changes to the stratospheric circulation. The winter vortex was significantly weakened during solar maximum and western phase of the quasi-biennial oscillation, in accordance with reported 30 mb geopotential height and total ozone measurements.Key words. Meteorology and Atmospheric Dynamics (Climatology; Middle atmosphere dynamics; waves and tides)

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The Seasonal Cycle of Gravity Wave Drag in the Middle Atmosphere

Journal of Climate ◽

10.1175/2008jcli2006.1 ◽

2008 ◽

Vol 21 (18) ◽

pp. 4664-4679 ◽

Cited By ~ 20

Author(s):

Manuel Pulido ◽

John Thuburn

Keyword(s):

Gravity Wave ◽

Seasonal Cycle ◽

Middle Atmosphere ◽

Three Dimensional ◽

Wave Drag ◽

Smooth Transition ◽

Quasi Biennial Oscillation ◽

Summer Hemisphere ◽

Jet Streaks ◽

Biennial Oscillation

Abstract Using a variational technique, middle atmosphere gravity wave drag (GWD) is estimated from Met Office middle atmosphere analyses for the year 2002. The technique employs an adjoint model of a middle atmosphere dynamical model to minimize a cost function that measures the differences between the model state and observations. The control variables are solely the horizontal components of GWD; therefore, the minimization determines the optimal estimate of the drag. For each month, Met Office analyses are taken as the initial condition for the first day of the month, and also as observations for each successive day. In this way a three-dimensional GWD field is obtained for the entire year with a temporal resolution of 1 day. GWD shows a pronounced seasonal cycle. During solstices, there are deceleration regions of the polar jet centered at about 63° latitude in the winter hemisphere, with a peak of 49 m s−1 day−1 at 0.24 hPa in the Southern Hemisphere; the summer hemisphere also shows a deceleration region but much weaker, with a peak of 24 m s−1 day−1 centered at 45° latitude and 0.6 hPa. During equinoxes GWD is weak and exhibits a smooth transition between the winter and summer situation. The height and latitude of the deceleration center in both winter and summer hemispheres appear to be constant. Important longitudinal dependencies in GWD are found that are related to planetary wave activity; GWD intensifies in the exit region of jet streaks. In the lower tropical stratosphere, the estimated GWD shows a westward GWD descending together with the westward phase of the quasi-biennial oscillation. Above, GWD exhibits a semiannual pattern that is approximately out of phase with the semiannual oscillation in the zonal wind. Furthermore, a descending GWD pattern is found at those heights, similar in magnitude and sign to that in the lower stratosphere.

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Two-dimensional and three-dimensional model simulations, measurements, and interpretation of the influence of the October 1989 solar proton events on the middle atmosphere

Journal of Geophysical Research Atmospheres ◽

10.1029/95jd00369 ◽

1995 ◽

Vol 100 (D6) ◽

pp. 11641 ◽

Cited By ~ 55

Author(s):

Charles H. Jackman ◽

Mark C. Cerniglia ◽

J. Eric Nielsen ◽

Dale J. Allen ◽

Joseph M. Zawodny ◽

...

Keyword(s):

Middle Atmosphere ◽

Three Dimensional ◽

Solar Proton ◽

Two Dimensional ◽

Dimensional Model ◽

Three Dimensional Model ◽

Model Simulations ◽

Solar Proton Events

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Stratospheric ozone depletion during the 1995–1996 Arctic winter: 3-D simulations on the potential role of different PSC types

Annales Geophysicae ◽

10.5194/angeo-19-1163-2001 ◽

2001 ◽

Vol 19 (9) ◽

pp. 1163-1181 ◽

Cited By ~ 2

Author(s):

J. Hendricks ◽

F. Baier ◽

G. Günther ◽

B. C. Krüger ◽

A. Ebel

Keyword(s):

Ozone Depletion ◽

Middle Atmosphere ◽

Spatial Scales ◽

Stratospheric Ozone ◽

Three Dimensional ◽

Particle Growth ◽

Atmospheric Composition ◽

Formation Mechanisms ◽

Three Dimensional Model ◽

Type Ia

Abstract. The sensitivity of modelled ozone depletion in the winter Arctic stratosphere to different assumptions of prevalent PSC types and PSC formation mechanisms is investigated. Three-dimensional simulations of the winter 1995/96 are performed with the COlogne Model of the Middle Atmosphere (COMMA) by applying different PSC microphysical schemes. Model runs are carried out considering either liquid or solid PSC particles or a combined microphysical scheme. These simulations are then compared to a model run which only takes into account binary sulfate aerosols. The results obtained with the three-dimensional model agree with trajectory-box simulations performed in previous studies. The simulations suggest that conditions appropriate for type Ia PSC existence (T < TNAT ) occur over longer periods and cover larger areas when compared to conditions of potential type Ib PSC existence. Significant differences in chlorine activation and ozone depletion occur between the simulations including only either liquid or solid PSC particles. The largest differences, occurring over large spatial scales and during prolonged time periods, are modelled first, when the stratospheric temperatures stay below TNAT , but above the threshold of effective liquid particle growth and second, in the case of the stratospheric temperatures remaining below this threshold, but not falling below the ice frost point. It can be generally concluded from the present study that differences in PSC microphysical schemes can cause significant fluctuations in ozone depletion modelled for the winter Arctic stratosphere.Key words. Atmospheric composition and structure (aerosols and particles; cloud physics and chemistry; middle atmosphere composition and chemistry)

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