40 A WIND FROM THE SOUTH AND A WIND FROM THE NORTH

Ecclesiastes 1:6
The wind goeth toward the south, and turneth about unto the north; it whirleth about continually, and the wind returneth again according to his circuits.

This post revises key concepts that relate to the evolution of climate. Good teaching is about saying it again in slightly different ways until it sinks in. This caters for the students who can’t tune in at a particular time and many others whose perceptual frameworks are sort of ‘frozen’. Its also possible that the message can be delivered without the  necessary flair.

Knock-knock.  New idea. Fundamental to the nature of Earth is the difference between  the warmth of low latitudes and the cold of high latitudes.  Without the redistribution of energy by wind and water the extent of the habitable latitudes would be tiny. In the tropics there is little variation in the nature of the air from day to day. But in the mid and high latitudes change is the rule.  When the wind changes in a systematic fashion  to establish new states, we have climate change. The further we depart from the equator, the greater is the change that is experienced.

The air moves from zones of high to zones of low surface pressure. Pre-eminent in terms of low surface pressure is the Antarctic Circumpolar Trough. It is the zone coloured orange in figure 1.

Annual SLP
Figure 1

Kalnay et al’s reanalysis of 1996 to be found here. shows the evolution of surface pressure by latitude over time and is presented in a graphical format in figures 2 and 3.

July pressure
Figure 2.
January pressure
Figure 3

Plainly, the work that is done in redistributing energy across the latitudes is dependent on the evolution of surface pressure in the Antarctic Circumpolar trough and to a lesser extent the latitudes north of 50-60° north.

 

40-60-n-and-s-t-air
Figure 4

Figure 4 plots the temperature of the air as it evolved in the year 2015 at  500 hPa at 40-60° of latitude in the northern hemisphere at left and the southern at right. Plainly there is a north-west to south-east orientation in the movement of the air masses as  the atmosphere super-rotates about the Earth in the same direction that the Earth rotates, but faster. The speed of rotation increases in the southern hemisphere where the angle of attack is more aligned with the parallels of latitude. The air spirals from north to south at all latitudes.Warmer parcels will have an ascending  tendency while colder parcels will be descending.

THE IMPORTANCE OF POLAR CYCLONES

New Concept: It is polar cyclones that are responsible for the intensity and evolution of the circumpolar trough.

A core theme of this work is that Polar Cyclones are energised by warm, low density cores in that space where the troposphere overlaps with the stratosphere. Differences in the ozone content of the air gives rise to differences in air density. A chain of cyclones on the margins of Antarctica   give rise to a rapidly circulating polar vortex in the stratosphere. There are no limits to convection in the stratosphere.

In summer the air rises to the limits of the atmosphere directly over the continent of Antarctica but in winter there is descent. A rising cone of air surrounds the zone of descent. This cone is sometimes described as a polar vortex. The cone begins at 300 hPa over the circumpolar trough and widens to take in the mid latitudes at the highest levels.

The upper troposphere/Lower stratosphere in the region of the circumpolar trough is characterised by intense mixing of air from diverse origins, the troposphere, the stratosphere and the mesosphere.

Between October and March the cone of ascending air below 50 hPa tightens like a hangman’s noose bringing air from the troposphere to the pole, creating an ozone hole, the falling away of surface pressure at this time of the year associated with generalised ascent over the Antarctic continent and so excluding the flow of air from the mesosphere that descends throughout winter.

That the circumpolar trough is due to differences in the ozone content of the upper air should be non-controversial.

THE DENSITY OPACITY OF THE GREEN BLOB

The circumpolar trough is an unremarkable aspect of the atmosphere in the view of UNIPCC. The significance of its presence is  unappreciated. This is not an unusual state of affairs in the annals of humanity. In fact,  ‘Climate Science’ has not leaned a lot about atmospheric dynamics since the time of the pioneer Bjerknes who published a work on the near surface characteristics of polar cyclones in 1922.

Bjerknes

It is realised, at least in meteorological circles, that a trigger is required for the formation of low pressure cells of rotating air  in the region of the circumpolar trough. That trigger  is an upper level trough, a mass of warmer, low density ozone rich air.

In  1922 it was not apparent that the most vigorous winds are located in the overlap between the stratosphere and the troposphere. Neither was it apparent that cold ozone deficient air  from both the mesosphere and the tropical troposphere are drawn towards the circumpolar front in the space shared by the upper troposphere and the lower stratosphere.

In fact the concept of a ‘stratosphere’ was pretty new in 1922. In many respects we have not moved on from that position despite the passage of 100 years. Indeed much that was known prior to the 1970’s has since been forgotten in parallel with the increasing concern that man and the environment in which he lives are  incompatible entities. Educators went off in socially responsible directions. A fabulous gravy train  was created for scientists and space agencies and all those who aspire to gain their daily bread by looking after the environment, painstakingly monitoring the activities of a an every increasing panoply  of despoilers, at one end mighty global corporations and at the other the humble cow that provides the milk for your morning cereal irresponsibly farting in  its field of green. Such is the work of the modern missionary.

The intensification of polar cyclones in winter, and the consequent lower surface pressure at that time of the year is due to the proliferation of ozone. Gordon Dobson observed in the 1920’s that, in high and mid latitudes low surface pressure identifies areas with high total column ozone. Dobson measured wind velocity and discovered that the strongest winds were not at the surface but in the region of the tropopause. The tropopause is kilometres lower when surface pressure is low than when surface pressure is high. This circumstance may be described as an upper level ‘trough’, a zone of  reduced air density that shows up in elevated geopotential height contours. Had Bjerknes apprehended the structure of the upper air we would not now be worrying about carbon dioxide in the atmosphere. We would be aware that the source of long term climate change, the source of decadal variations, the source of inter-annual variations and indeed our daily weather lies in variations in the ozone content of the stratosphere. We would  be at peace with the notion that our ‘rather too cool for comfort’ planet gains and loses energy according to change in the extent of its cloud cover.

There is so much to learn.

 

In thanks to Stephen Wilde

To see the context refer to the post ‘Heresy and orthodoxy’ and the comments attached thereto: It’s here.

Just a bit of background first up. The sources of convection in the atmosphere are:

  1. Heating at the surface.
  2. Heat released to the atmosphere via condensation of water vapour.
  3. Heating due to the absorption of infra-red radiation in the 9-10 micrometre band by ozone.

Of these three, the most influential agent of convection is ozone but you won’t hear that in the annals of climate science so its not much good Googling the phenomenon.

Gordon Dobson who first measured ozone in the atmospheric column observed that low pressure cells had greater total column ozone than high pressure cells.

We are discussing the movements of the atmosphere and whether and to what extent the stratosphere is ‘stratified’, stable and to that extent unimportant in terms of weather and climate at the surface.

Dear Stephen,
Thanks for your comment. It takes guts to speak your mind and I respect that. You are always welcome here. You have impeccable manners.

Southern Hemisphere winter: There is a descent of very cold mesospheric air inside the polar vortex that reaches down to perhaps 300 hPa. The air is very cold throughout its profile and it gently descends. However, if we look at the temperature at 1 hPa in June 2015 it was -32°C and at 70 hPa -73°C . So, it is warmer at the top of the column than below and with that profile we would expect that it would be ascending.

Southern hemisphere summer: At this moment temperature at 1 hPa over the polar cap (65-90°C) is +6°C at 1 hPa, at 10 hPa it is -26°C , at 30 hPa it is -29°C, at 50 hPa it is -36°C and at 70 hPa it is -40°C. Directly over the pole, the air at 1 hPa is warmer than the average for the polar cap and warmer than the air over Australia or the Equator. The air is gently ascending with core ascent over the pole. Air from the mesosphere is excluded. It is in the state that some refer to as following a ‘final warming’ that happened in December. By March, this situation will revert to the winter pattern. Seventy years ago there was no final warming, no summer pattern.

Whether the air ascends or descends in the stratosphere over the pole is not a function of its temperature profile. It is a function of the strength of the ascent above 500 hPa outside the vortex where the presence of ozone is much enhanced in winter, strongly heating the atmosphere. It drives the density of the air above 500 hPa so low as to result in surface pressures down to 980 hPa in the entire band of latitude 60-70° south. It is the rate of ascent in this latitude band that forces descent over the polar cap and in the mid latitude high pressure cells. Ascent aloft forces ascent below 500 hPa all the way to the surface. The result is the constant presence of 5 or 6 Polar Cyclones of an intensity that equates to a regular tropical cyclone.

In winter the northern hemisphere heats very strongly driven by land masses that return heat to the atmosphere as fast as energy accrues at the surface. So, atmospheric mass shifts strongly to the southern hemisphere. As a result surface pressure over Antarctica reaches a resounding planetary maximum. Off the coast of Antarctica at 60-70° south ozone forces surface pressure to a resounding planetary minimum at exactly the same time. This shifts atmospheric mass from high southern latitudes to low southern latitudes dramatically increasing atmospheric pressure in zones that already experience high surface pressure.

But there is a big difference in how this circulation affects the ozone profile. What goes up must come down. Ozone that ascends into the upper stratosphere via a Polar Cyclone must come down somewhere. It is precluded from descending over the pole. That parking space is occupied by low ozone content, high NOx air from the mesosphere. So, it descends in the very broad high pressure cells that circulate between the equator and 40° of latitude at this time of the year where the body of air involved is so large that it much dilutes the the descending ozone. Nevertheless, ozone warms the entire stratosphere in these latitudes so that it is warmer in winter than it is in summer. That ozone descends into the troposphere affecting cloud cover.

So, just forget about ‘stratification’ in the stratosphere. The circulation throughout the entire atmosphere is driven by ozone that accumulates in the winter hemisphere. The base state of surface pressure is determined by the distribution of land and sea and the revolution of the Earth around the sun. The flux of ozone partial pressure driven by the highly variable interaction between mesospheric and stratospheric air at the winter pole works variations on that base state.

The accumulation of ozone outside the vortex, strongest on the margins of Antarctica,but occupying the latitude band 50-90° south has driven a 15 hPa loss of surface pressure over Antarctica in the last 70 years, in the process further opening the natural clear sky window over the Southern Oceans.

The good (or is it bad) news is that the process stalled about 1998 and is currently reversing. This is reflected in the gradual decline in the temperature of the stratosphere in high southern latitudes currently under way. Outgoing long wave radiation as measured at the top of the atmosphere peaked about 1998 and has been up and down since that time but nevertheless on a plateau. Tropical sea surface temperature is down over the last decade is down in eight of the 12 months of the year. These are the months where surface temperatures are most affects by the rate of entry of mesospheric air into the stratosphere in high latitudes.

What worries me is that the people who advise governments on climate related matters are not driven by observation and deduction but by ideology. We fear the followers of Allah but there are people equally determined, equally ruthless, in their demeanour the latter day descendants of Joseph Goebbels but without his swagger, and they occupy the high ground. These people will not be swayed by reason. They are social engineers with an objective in mind. To these people, the end justifies the means. There is no subtlety to them. They are brutes.

Stephen, thanks for the opportunity to make this comment. But for you I would have devoted the time to something else entirely and perhaps much less fun.