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:
- Heating at the surface.
- Heat released to the atmosphere via condensation of water vapour.
- 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.
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.