In January 2017 an essay appeared with the title:
WHAT IS THE POLAR VORTEX AND HOW DOES IT INFLUENCE WEATHER?
Authors are Darryn W. Waugh, Adam H. Sobel, and Lorenzo M. Polvani
The essay can be found here: http://journals.ametsoc.org/doi/pdf/10.1175/BAMS-D-15-00212.1
Unfortunately this essay does nothing to advance our knowledge of the role of the polar atmosphere in determining climate dynamics. It represents the contrived views of established climate science practitioners of the alarmist persuasion.
There is a relationship between the ozone content of the air and surface pressure that was discovered prior to 1900 that was well documented by Dobson in the 1920s. In mid and high latitudes low surface pressure is associated with superior total column ozone. Ozone is a warming, rarefying influence because it is a greenhouse gas mobilising infrared energy from the Earth itself, even within the region of the polar night. To materially change surface pressure ozone must be present through the bulk of the atmospheric column. Half of the atmospheric column is found below the 500 hPa pressure level and half above. More than half of the column is affected. It follows that the tropopause is not found at the same pressure level in high latitudes as it is in low latitudes. This is important because the tropopause marks the boundary between the troposphere and the stratosphere.
Let me begin by taking issue with this following statement from the Waugh, Sobel and Polvani paper: The strong circumpolar westerlies that define the stratospheric polar vortex maximize at around 60° latitude, from just above the tropopause (~100 hPa) into the mesosphere (above 1 hPa; see Fig. 2).
The ’tropopause’, by definition, is found at the elevation where air temperature ceases to decline with altitude. Wikipedia puts it this way: ‘Going upward from the surface, it is the point where air ceases to cool with height, and becomes almost completely dry.’
The reversal of temperature decline at ‘the tropopause’ is due to the presence of ozone that absorbs energy from Earths long wave radiation in the infrared spectrum. The ‘tropopause’ marks the start of the stratosphere where the air is dry and it warms or at least maintains its temperature with increasing elevation.
The atmosphere in the mid latitudes between 400 hPa and 50 hPa moves from west to east and pole-wards. The strongest winds on the planet are the north westerlies of the southern hemisphere. Even in the northern hemisphere air masses move gradually southwards towards the Antarctic polar front where surface air pressure achieves a planetary minimum that is sustained across all months of the year.
In regions of low surface pressure, commonly centred at about 60° of latitude, the decline in temperature with increasing altitude ceases at a lower elevation (400hPa) than in zones of high surface pressure. Between 400 hPa and 50 hPa air masses with a very different composition in terms of ozone, temperature and density occupy the same horizontal domain. Here, instability is the rule. Ozone rich air is displaced upwards and polar cyclones are initiated. Polar cyclones propagate from the interaction layer down to the surface and they initiate the flow that manifests as the vortex in the stratosphere.
Over the polar cap the temperature of the air falls all the way between the surface and the upper stratosphere. Patently, there is no tropopause to be found inside the vortex. Here the air contains little ozone.
Lets re-iterate this point: Polar cyclones are generated at the front between air of polar and extra-tropical origin the latter being rich in ozone, warmer, less dense and manifesting at a lower altitude. The ‘polar front’ is where two air streams of different character converge. The difference in air density is most extreme in winter due to the descent of ozone starved mesospheric air inside the vortex and the increase in the ozone content of the air outside the vortex in the winter season. But, summer or winter, it is the ozone content of the air, and its latitudinal origin that is a major influence on air density. If air travels pole-wards it is less dense because it comes from a warmer place and in addition it is continually warmed because it is ozone rich. As such it derives energy from the Earths itself.
Polar cyclones propagate downwards from the domain where marked differences in the ozone content of the air manifest. This domain lies between the 400 hPa and 50 hPa pressure levels. This domain can not be described as either troposphere or stratosphere and the term ‘tropopause’ has no place in the description of the properties of this domain. Arguably, in winter, the atmosphere directly over the poles is entirely stratospheric and mesospheric in origin. It is extremely dry and very cold. Air that enters the circulation from the mid latitudes is warm and rich in ozone. It is stratospheric in its composition at 400 hPa.
A chain of Polar Cyclones constitutes THE POLAR VORTEX. The strongest winds are located between 400 hPa and 50 hPa and again in the upper stratosphere at 10 hPa.
Given the relationship between the ozone content of the air and its density and also the highly variable increase in the ozone content of the air in winter from one winter to the next and also across the decades, the rate of transfer of energy from the equator to polar regions via atmospheric movement is inconstant. The temperature of the air at a particular location is a function of the strength of the polar vortex. Enhanced north westerly winds in the southern hemisphere are consistent with enhanced flows of warm, moist air of tropical origin to high latitudes. On the other hand, displacement of the polar cyclones towards the equator brings cold polar air to the mid latitudes. Lower surface pressure in high latitudes results in higher surface pressure in the mid latitudes affecting cloud cover, rainfall, and air flows.
The decline in surface pressure at all latitudes south of 50° south over the last seventy years is well documented. This decline in surface pressure relates to an increase in the ozone content of the air outside the vortex. It constitutes climate change in action.
RE The stratospheric polar vortex appears each winter as a consequence of the large-scale temperature gradients between the midlatitudes and the pole.
Emphatically no, the vortex is a product of variations in air density at the same elevation, not the gradient in temperature between the equator and the pole. In winter ascent occurs outside the vortex proceeding to the limits of the stratosphere while descent of cold air prevails inside the vortex. Descent also occurs in the mid latitudes of the winter hemisphere where high pressure cells prevail. Over the polar cap in winter descent is reinforced by high surface pressure. In summer a gently ascending circulation of low density ozone rich air occurs in the stratosphere across the entire polar cap. For this reason and the slight warming due to summer insolation and despite the shift in the atmosphere from mid latitudes to the poles as surface pressures rise due to reduced polar cyclone activity, polar surface pressure is lower in summer than in winter.
Differences between the hemispheres
There is a fundamental difference between the hemispheres in the nature of the polar vortex. It is more vigorous and longer sustained in its winter form in the southern hemisphere than in the northern hemisphere. This is due to sustained contrasts in air density in the 400 hPa to 50 hPa domain on the margins of Antarctica. The geography of the distribution of land and sea between the hemispheres is responsible for this difference. In the upshot strong flows of mesospheric air inside the vortex dilute the ozone content of the air in the entire southern hemisphere while an absence of this flow in the northern hemisphere allows ozone partial pressure to build.
The Ozone Hole over Antarctica in Spring
This phenomenon is entirely natural. It is a consequence of the change in the circulation of the air during the final warming that brings ozone deficient tropospheric air of mid latitude origin flooding across the polar cap and into the 400 hPa to 50 hPa domain.
Rossby Waves and sudden stratospheric warmings.
re this statement
“Rossby waves excited in the troposphere propagate up into the stratosphere and perturb the vortex away from radiative equilibrium, weakening it and distorting its shape away from circular symmetry about the pole.”
The more rational explanation is that localised centres of tropospheric descent and stratospheric ascent that form up in the mid latitudes over the oceans are periodically invigorated as ozone accumulates above 50 hPa. Episodically, these centres of ozone accumulation expand in diameter and invade the polar domain assisting the lowering of surface pressure in high latitudes as they do so. Centres of ozone accumulation are represented on diagrams of the upper atmosphere as regions of elevated geopotential height. The phenomenon of sudden stratospheric warmings in winter are no different in nature to that of the final stratospheric warming in late spring. Both involve a takeover of the polar cap by ozone rich air that circulates anticlockwise on the outer margins of the polar vortex. Hence, in summer, and during a stratospheric warming over the pole, easterlies replace westerly winds at the 10 hPa pressure elevation. The takeover in winter begins and has its greatest impact at the highest elevations.
All movements in the atmosphere are driven in the first instance by surface pressure relationships. Secondly, differences in air density in the horizontal domain result in uplift whatever the elevation that they occur at. Thirdly, in view of the fact that the atmosphere rotates in the same direction as the Earth, but faster, there is very likely an electromagnetic driver that is most energetic at the highest elevations where the atmosphere carries particles with an electric charge. Gravity ensures that what goes up must come down. Areas of descent tend to form over the cooler oceans especially in the winter hemisphere. In the upper stratosphere these areas of tropospheric descent are ozone rich and give rise to ascent and spreading as ozone accumulates.
Inside the polar vortex there is mixing of stratospheric and mesospheric air, that remains relatively ozone poor.
Conclusion: Climate science as presently constituted fails to get to grips with the natural and enduring dynamics of the atmosphere that are manifestly responsible for climate change. Unfortunately establishment climate science is wedded to the philosophy that demonises carbon dioxide, an essential ingredient for photosynthesis on land and in the oceans. Carbon dioxide is at the base of the food chain. Human welfare is tied to its proliferation.
The establishment has it ‘arse about’ and are hell bent on ruination.