Search Results

You are looking at 1 - 4 of 4 items for :

  • Author or Editor: Karin Labitzke x
  • Journal of the Atmospheric Sciences x
  • Refine by Access: All Content x
Clear All Modify Search
Karin Labitzke

Abstract

Rocketsonde and rocket grenade data show that stratosphere temperature changes in winter in both low and high latitudes are accompanied by simultaneous changes of opposite sign in the mesosphere, which indicates that the two layers interact.

Full access
Karin Labitzke

Abstract

The midwinter temperature changes of the mesosphere and stratosphere are described by means of Satellite Infrared Spectrometer and Selective Chopper Radiometer data, rocketsondes, and rocket grenade data, which show that the so-called stratospheric midwinter warmings extend at least into the upper mesosphere. Temperature changes of opposite sign take place at the same time at different levels, probably as a result of vertical motion. The event begins around a very high stratopause, ∼60 km, which descends 20 km within several days while the warming intensifies. At the same time the upper mesosphere and lower stratosphere cool. When the polar vortex breaks down, the warming reaches the lower stratosphere, the warm stratopause region is destroyed through cooling of the layer between 30 and 60 km, and the upper mesosphere warms.

The mean vertical temperature profiles suggest that the upper mesosphere is cold at high latitudes in early winter and again in late winter, and that the warm upper mesosphere observed in late January–early February is associated with the breakdown of the stratospheric polar vortex.

Full access
Kirstin Krüger, Barbara Naujokat, and Karin Labitzke

Abstract

A strong midwinter warming occurred in the Southern Hemisphere (SH) stratosphere in September 2002. Based on experiences from the Northern Hemisphere (NH), this event can be defined as a major warming with a breakdown of the polar vortex in midwinter, which has never been detected so far in the SH since observations began at the earliest in the 1940s. Minor midwinter warmings occasionally occurred in the SH, but a strong interannual variability, as is present in winter and spring in the NH, has been explicitly associated with the spring reversals.

A detailed analysis of this winter reveals the dominant role of eastward-traveling waves and their interaction with quasi-stationary planetary waves forced in the troposphere. Such wave forcing, finally leading to the sudden breakdown of the vortex, is a familiar feature of the northern winter stratosphere. Therefore, the unusual development of this Antarctic winter is described in the context of more than 50 Arctic winters, concentrating on winters with similar wave perturbations. The relevance of preconditioning of major warmings by traveling and quasi-stationary planetary waves is discussed for both hemispheres.

Full access
Paul R. Julian and Karin B. Labitzke

Abstract

The spectral energy equations for zonal and eddy kinetic and available potential energies are used to investigate the energetics of the lowest 30 km of the atmosphere during the months of January and February 1963. A major stratospheric warming, manifested in the reversal of the stratospheric meridional temperature gradient and destruction of the polar-night stratospheric vortex, began in mid-January.

Data for eight standard pressure levels, from 850 to 10 mb, for every fifth day were utilized. The horizontal wind field was estimated by using both the geostrophic approximation and a modified stream function. The vertical motion field (dp/dt) was estimated both by the adiabatic technique and by the solution of the omega equation.

The variation of the energy exchanges with height (pressure) indicates that the lower and middle troposphere and the middle stratosphere were baroclinically active regions before and during the warming. The principal path of energy flow in these regions was from zonal to eddy available potential energy, from there to eddy kinetic energy and thence to zonal kinetic energy. After the reversal of the meridional temperature gradient, however, the portion of the stratosphere studied rapidly lost eddy kinetic energy to other forms of energy. At all times eddy kinetic energy was supplied to the stratosphere by the upward flux of mechanical energy from the troposphere.

The upper troposphere and lower stratosphere appear, as a whole, to contribute little to the net energy changes both before and after the warming. Barotropic effects are suggested, however, since the principal energy exchange in this region is from zonal to eddy kinetic energy. The upward flux of energy from the troposphere to the stratosphere is large compared with the energy exchange processes occurring in the stratosphere and must be considered a significant item in the budget of the stratosphere.

A relationship between high-latitude blocking in the troposphere and the onset of the stratospheric warming is shown by comparing the variation of the 500-mb zonal wind with latitude and time with the average absolute vertical motion (dp/dt) for a mid-tropospheric and a mid-stratospheric level. Increased vigor of the vertical motion field accompanies both the onset of blocking in the troposphere and the warming in the stratosphere. Some speculation is offered concerning the interpretation of this relationship as it pertains to the cause of the stratospheric warmings.

Full access