My previous effort in relation to this chapter attracted very few readers. So, here I re-state the argument, hopefully in a more accessible form. I do so because the subject matter is critical. A great deal depends upon an appreciation of the matters described below. If there are queries and disagreements lets have them up front in the comments:
The description of the nature of the stratosphere given below differs from accounts that you will see in the literature in important respects, and for good reason. The stratosphere is a complex entity, much more complex and interesting than the troposphere. By virtue of its effect on atmospheric pressure in high latitudes (directly responsible for Polar Cyclones and the Jet Streams) the stratosphere drives weather and climate, the planetary winds and surface temperature on all time scales. This realization is new, a product of investigation into what is known as the Annular Modes (ring like modes) of variation in surface pressure over just the last couple of decades and insights into the origin of polar cyclones together with the observations of the early French balloonist De Bort, Gordon Dobson and others that ozone maps surface pressure. It has long been known that there is enhanced total ozone in cyclones of ascending air (called cold core cyclones) but the significance of this observation has been unrealized. Ozone heating of the upper part of the atmospheric column is responsible for these cyclones.They are so pervasive in high latitudes that the formation of more cyclones and the intensification of existing cyclones changes surface pressure in high latitudes shifting atmospheric to or from high latitudes in the process.
It is the difference in atmospheric pressure at the surface of the planet that determines the planetary winds, patterns of precipitation and surface temperature so we must get a grip on the nature of Polar Cyclones if we are to understand surface climate.
There are three modes of heating of the air, heating by a warm surface, heating within the atmosphere due to the release of latent heat and heating within the atmosphere by absorption of long wave radiation from the surface of the Earth. Notably, it is the heating of the air due to the presence of the greenhouse gas ozone that accounts for the warmth of the stratosphere and the generation of polar cyclones that are the manifestation of the strongest modes of atmospheric heating on the planet, albeit hitherto overlooked.
In this account I focus exclusively on the southern stratosphere because it is simpler, being relatively unaffected by north south intrusions by land masses, except in the notable instance of South America. In the southern hemisphere a strong accent is given to polar processes due to the presence of the Antarctic continent almost symmetrically distributed about the pole. In southern winter the massive and relatively invariable heating of the entire northern hemisphere adds to surface pressure in high southern latitudes. In fact this seasonal shift of atmospheric mass to the southern hemisphere creates a planetary high in surface pressure over Antarctica. The atmospheric dynamics resulting from the donut shaped peak in ozone partial pressure at 60°-70° south latitude result in an ‘ozone hole’ over the polar cap. The chemical composition of the space inside the donut of ozone rich air, and the manner of its escape into the wider atmosphere has profound implications for the evolution of the ozonosphere and the extent of cloud cover globally.
FACTORS AFFECTING THE TEMPERATURE PROFILE OF THE SOUTHERN STRATOSPHERE LATERALLY AT 10hPa.
All the remarks under this head address what can be observed in the diagram immediately below. Please give it your closest inspection.
The temperature profile at 10 hPa that is mapped above exhibits differences in the evolution of temperature between the hemispheres. This has nothing to do with the sun or short wave solar radiation. Air temperature varies with the place that the air comes from and the upper atmosphere is an active rather than a passive medium. Cooling in high latitudes in winter represents a regime of supercooling that is completely unrelated to the progress of the temperature at the surface. This supercooling is the thermal consequence of the penetration of the polar stratosphere by very cold, ozone deficient air that originates in the mesosphere. When mesospheric air is present, temperature plummets and when it is not present the space hitherto temporarily occupied is taken by warmer, ozone rich air that is immediately adjacent. That pattern of arrival and departure is mapped in shades of blue and green above. By virtue of the erosive effect of NOx compounds present in mesospheric air the ozone content of the wider atmosphere is much affected as mesospheric air is inevitably mixed into the wider atmosphere. It is obvious from the diagram above that this has knock on consequences over a very wide latitude band. Mixing processes speedily impact the evolution of ozone partial pressure and temperature at lower latitudes and especially so in the northern hemisphere where a prevailingly slight presence of mesospheric air enables a regime of high ozone partial pressure and elevated temperature to prevail. In this regime, small additions of mesospheric air to the melting pot result in widespread change.
The temperature of the stratosphere is a function of the extent of the heating by short wave radiation from above, long wave infra-red from the Earth itself and the dynamics of the movement of the atmosphere affecting the extent of the presence of mesospheric air. Atmospheric dynamics vary strongly with latitude.
The chief absorbers of outgoing infra-red radiation from the Earth are water vapour, of which there is little in the stratosphere, carbon dioxide, that is uniformly distributed and therefore of little account as far as surface pressure is concerned and ozone that is much affected in its concentration by the impact of photolysis. In addition the presence of NOx that catalyses the destruction of ozone affects ozone partial pressure as NOx is rapidly spread across the stratosphere.
Heating by short wave incoming radiation is the dominant influence on the temperature of the stratosphere above 10 hPa affecting the most elevated 1% of the atmospheric column by weight. Long wave infra-red radiation from the Earth drives the warming of the stratosphere very broadly between about 300 hPa and 10 hPa, although the lower fuzzy margin is higher at the equator and lower in high latitudes. The lower fuzzy margin corresponds with the tropopause near the equator but nowhere else. Outside near equatorial latitudes, as the air increasingly dries, the forces responsible for the cold point at the tropical tropopause wither away and the descent of cold mesospheric air at the pole in winter moves the cold point upwards towards 10 hPa. This divorces the cold point from any association with ozone distribution or the distribution of water vapour and the notion of a ‘tropopause’ that happens to be conjunction-al with the cold point and the presence of very dry air in low latitudes. It is only conjunction-al in low latitudes because massive continuing uplift keeps ozone aloft. The notion of a tropopause has no meaning, and is therefore un-locatable in mid or high latitudes.
Marked differences in ozone partial pressure give rise to a very different stratosphere between winter and summer. This reflects the presence of mesospheric air and enhanced O3 in high latitudes in winter.
The pressure of photolysis on ozone diminishes as the path through the atmosphere lengthens accounting for a natural increase in ozone partial pressure with latitude and more so in winter. This sets the background level of ozone according to latitude, less at the equator and more ozone closer to the poles. But it is over the polar caps that mesospheric air establishes its presence interfering with the aforesaid pattern and via its interaction eroding ozone partial pressure throughout the stratosphere.
To reiterate and expand: The impact of NOx from the mesosphere occurs via a tongue of mesospheric air that enters the stratosphere in winter. Entry is facilitated via an increase in the velocity and mass involved in the overturning circulation driven by ozone in high latitudes (forming Polar Cyclones). Descent that represents the return arm of this circulation occurs at the pole and in the mid latitudes. Ascent involving that part of the column containing ozone occurs in an ‘annular ring’ that is most intense at 60-70° of latitude and descent is apparent at 20-40° of latitude especially over cold waters on the Eastern side of the major oceans. The latter constitutes the corresponding ring like mode of descent in the mid latitudes. Because the circumference of the Earth is so much greater in the mid latitudes than it is over the polar cap the overturning circulation heads in this direction, the line of least resistance, rather than towards the polar cap. Descent over the polar cap is by comparison almost a stalled circulation in the sense that the rate of descent is very slow. If it were fast and continuous we would have much less ozone in the southern hemisphere than we do currently. The southern hemisphere would become almost uninhabitable. Fortunately for the inhabitants of the Southern Hemisphere NOx rich air from the mesosphere enters the wider stratosphere at a much slower and intermittent rate across the leaky polar vortex and is replaced from above. However there is one part of the southern hemisphere where the mesospheric air tends to lean northwards and that is towards the continent of south America. In the high Andes where elevation enhances exposure to UV light, the suicide rate peaks in spring.
The rate of descent of mesospheric air, the surface area of the interaction zone, its depth of penetration and impact on the wider stratosphere across the entire globe is surface pressure dependent. The landmass of south America interrupts the formation of polar cyclones. Zones of very high surface pressure form to the East and west of the continent in the mid and high latitudes associated with the presence of very cold oceans. The tongue of mesospheric air expands in its volume as surface pressure increases over the polar cap. Surface atmospheric pressure at the pole is to some extent just a proxy for the rate of overturning of the ozone driven circulation in high latitudes and to the remaining extent a proxy for the tendency of the atmosphere to be shifted equator-wards under the impact of geomagnetic pressure wrought by the solar wind. In the long term the latter determines the issue driving ozone partial pressure one way or the other and with it surface pressure over the polar cap and in the mid altitudes. Hence the relentless loss of mass since 1948.
It is important to realize that infrared emission from the Earth is never limiting, even at the highest latitudes. That stream of energy that is available both day and night and at all levels of the atmosphere. Ozone absorbs at 9-10 µm in the peak of the energy spectrum emitted by the Earth. Ozone is most enhanced between 30 hPa and 10 hPa shading away in concentration to the limits of the mesosphere on the one hand and downwards into the lower atmosphere to an altitude that varies with latitude on the other. Because the energy flow from the Earth is inexhaustible in terms of the amount intercepted by ozone there is little difference in the temperature of the stratosphere between day and night. This is a very different situation to that at the surface where short wave energy from the sun heats only during the daylight hours and wide diurnal fluctuations in temperature are the rule. If you read that the temperature of the stratosphere is the result of the interception of of short wave radiation by the atmosphere check the credentials of the author of that statement, even though he is a co-author or even a chairman of the committees responsible for UNIPCC reports. That author is not getting to grips with the nature of the ozonosphere.
As already mentioned geography ensures that the cooling in the stratosphere over the Antarctic during the polar night is much enhanced by comparison with the Arctic. The Antarctic at 1 hPa is slightly warmer in summer due to orbital influences. The massive annual range of temperature over Antarctica due to the depression of the winter minimum is anomalous because, at the surface, it is the northern hemisphere that exhibits the greatest swing between summer and winter. This enhanced range is mainly the result of the presence of very cold mesospheric air over the Antarctic pole in winter and its relative exclusion between December and March.
The relative absence of cold mesospheric air in southern spring of recent times has resulted in a marked increase in the temperature of the polar cap and the intensification of the southern circulation. This trend is related to the 15 hPa fall in surface pressure over Antarctica since 1948. The decline very likely began at the turn of the nineteenth century. The process of withdrawal of mesospheric air was already well under-way in the 1940’s. To some extent the warming of the polar cap between 65-90° of latitude is due to a narrowing of the tongue of mesospheric air due in turn to enhanced uplift closer to the margins of Antarctica as the air that is external to the vortex becomes warmer in late winter and spring, reflecting its increased ozone content. In this way atmospheric dynamics drive ozone content and the extent of the ‘ozone hole’ over Antarctica. That hole was present at the time of the earliest measurements of total column ozone by Dobson’s colleagues at the British Antarctic base situated in Halley Bay in 1956, astounding Dobson and leading him to question the validity of the measurement. It was not what was expected given the pattern that he had observed in the Northern Hemisphere. The Antarctic ‘hole’ disappeared in November at that time as it does today. Measurements of total column ozone in the following year confirmed that it was the stratosphere and not the instrument that was responsible for the difference. Students of history will remember that the use of Freon in air conditioning and domestic refrigeration only really got going in the post WW2 era.
The anomalous warming of the Antarctic stratosphere that shows up between October and December in the data for 2014 in the diagram above is a function of the sustained ozone content of the air after the period of the polar night and despite the growing impact of photolyzing solar radiation as the sun rises higher into the sky and the atmospheric path shortens. Plainly it is the rate and the extent of the descent of mesospheric air that rules the temperature regime over the Antarctic polar cap rather than the angle of the sun.
By comparison the descent of mesospheric air in the Arctic comes in fits and starts allowing the northern hemisphere to maintain a much enhanced level of ozone in the stratosphere.
Again, looking at the diagram above, the temperature of the entire stratosphere is much affected by short term dynamical processes that manifest in the Arctic in winter. The descent of mesospheric air over the Arctic polar cap has knock on effects across a very wide band of latitudes. In terms of timing, the plethora of warming events in the Arctic has a life that is independent of the march of the sun. Again, it is the dynamics within the atmosphere that determine the pattern of evolution of temperature in the Arctic.
THE VERTICAL PROFILE IN THE TEMPERATURE OF THE ATMOSPHERE
Gordon Dobson who invented and built a spectrophotometer to measure the quantity of ozone in the atmospheric column according to the attenuation in the energy at the wave length that destroys it (and is partially used up in the process) observed that ozone affects the upper troposphere:
The chief result of these measurements at Arosa (1932 Swizerland 46.78° N) was to show with certainty that the average height of the ozone in the atmosphere was about 22 km and not about 40-50 km as had been thought before. They also gave a fair idea of the vertical distribution, showing that the main changes took place at heights between 10 km and 25 km. This made it much easier to understand why changes in the total amount of ozone should be so closely correlated with conditions in the upper troposphere and lower stratosphere.
We may think it strange that Dobson writes about the presence of ozone affecting the upper troposphere because it is often (always) assumed that the quantity involved is immaterial. But, in fact the issue as to whether ozone is present at 10 km in the mid latitudes or not, and of significance to weather and climate, is worthy of close examination. Is the boundary between the ozonosphere and the lower atmosphere actually fuzzy?
The French balloonist deBort had actually settled the issue at the turn of the 19th century when he observed that the ‘isothermal layer’ as he called it was encountered at 9-10km when surface pressure was low and at 12.5 km when it was high but let us not take too much account of that. He is French and we are British….and the message got awfully rusty in the effluxion of time…or did we simply regard him as a crank.
A simple method of ascertaining where ozone begins to affect the temperature of the atmosphere is to inspect the rate at which temperature falls with elevation. The rate of change of temperature with elevation is affected by the release of latent heat (predominantly a near surface phenomenon) and the presence of ozone (an upper air phenomenon), both reducing the lapse rate. In parts unaffected by precipitation or ozone heating the decline of temperature with elevation should be the dry adiabatic lapse rate of about 10°C per 1000 metres. As ozone begins to affect the temperature of the air the lapse rate should immediately fall below the dry adiabatic lapse rate…..or whatever the rate has been to that point of elevation.
At any concentration above zero ozone has the ability to raise the temperature of the air via absorption of long wave energy from the Earth and the instantaneous transfer of this energy to surrounding molecules. At 30 hPa where the ratio between ozone and other atmospheric constituents is greatest the actual ozone content is only about 30 parts per million, well below the concentration of CO2 at 400 parts per million. But, by virtue of its uneven distribution it is responsible for the stratosphere. Strangely, when we inspect the curves there is no evidence that down radiation from an ozone rich layer causes an increase in the temperature of the air below…..but that is an entirely different type of investigation that should not distract you or me at the moment.
In an effort to locate the effective starting elevation of the stratosphere the thermal profile of the atmosphere will be mapped in 10° latitude bands between the inter-tropical convergence zone just north of the equator and the southern pole. The data is for the year 2014 available in the database that can be accessed at: http://www.esrl.noaa.gov/psd/cgi-bin/data/timeseries/timeseries1.pl We can delve into the distant past later on.
The inter-tropical convergence
Here the South East Trades meet the North East Trades and a line of tropical thunderstorms rings the globe, especially in the afternoon.
Because the horizontal scale is in pressure levels rather than metres the intervals on the horizontal axis are not constant. However the blue line indicates a lapse rate of 6.44°C per 1000 metres that is a true reflection of the lapse rate between the surface and 600 hPa a distance of 3500 metres with the temperature falling 22.54°C over that interval. The red line represents a lapse rate of 6.86°C per 1000 metres that is a true reflection of that particular lapse rate between 300 hPa and 100 hPa where the temperature falls 48°C over 7000 metres. The dry rate of 10°C per 1000 metres can only be attained if there is a lack of warming from any source. The degree of uplift at the ITC and the presence of appreciable moisture can be assumed to reduce ozone to near zero levels below 100 hPa. Away from the ITC both uplift and moisture levels do fall away allowing ozone to penetrate below the 100 hPa pressure level and down to less than 10,000 metres in low pressure cells. Let us assume however that ozone is not present unless the lapse rate falls below 6.86°c per 1000 metres, the slope of the red line. That is the conservative approach.
Both the blue and the red lines have the same slope in all diagrams that follow. All the diagrams have a common vertical and horizontal scale so that the slope of the blue and red lines is invariable.
There is a cold trap (about -80°C) at 100 hPa that is said to promote a dry atmosphere above this pressure level. In practice clouds do manifest in the lower stratosphere, particularly in the region of the south East Asian warm pool. A high rate of uplift results in he sudden appearance of ozone above 100 hPa and a steep increase in temperature above that pressure level. At 100 hPa only 10% of the atmosphere by weight lies above while 90% is below. In terms of distance there is 15 km of atmosphere below and another 15 km to get to the 10 hPa pressure level so the graph exaggerates the rate of increase in temperature with altitude above the tropopause.
At no other latitude do we see as steep an increase in temperature in the stratosphere. At no other latitude is the stratosphere as elevated at its inception.
At the poles in winter the temperature of the air falls to minus 85°C. Convection over the inter-tropical convergence keeps ozone so much at bay as to produce exactly the same temperature, -85°C at 15 km in elevation.
Notice that the month to month variation in the temperature of the stratosphere over the I.T.C. at 100 hPa and higher is greater than is seen in the troposphere below. At 100 hPa temperature is depressed in December and elevated in August when ozone partial pressure increases strongly outside the margins of the Antarctic polar vortex. This testifies to the vigour of mixing processes in the stratosphere.
Equator to 10° south
Between the equator and 10° south latitude the thermal structure of the atmosphere is very similar to that at the inter-tropical convergence.
At 10-20° south latitude a slight reduction in the lapse rate above 300 hPa indicates the presence of ozone in the atmospheric profile.
A temperature of about minus 30°C at 300 hPa is common to latitudes below 20°.
At 100 hPa temperature is warmer by a few degrees than at the I.T.C. The black dotted line has a common length in all diagrams. The minimum or ‘cold point’ warms as latitude increases reflecting an increase in the ozone content of the air with increasing latitude.
At 20-30° south latitude where high surface pressure is the rule, the presence of ozone appreciably reduces the lapse rate above 300 hPa. At 300 hPa the atmosphere is slightly cooler than it is in the tropics.
The temperature at 100 hPa is warmer than in the tropics indicating more ozone in the air at 100 hPa.
Between the months of August and November in late winter and spring, the ‘cold trap’ and the stratosphere in general is warmer than it is in summer indicating enhanced descent of ozone in high pressure cells at the particular time of the year when ozone partial pressure peaks outside the margins of the Antarctic polar vortex driving a shift of atmospheric mass away from the poles and towards these latitudes. An enhanced rate of descent from the stratosphere brings ozone into what has been hitherto regarded as the ‘troposphere’. If the word troposphere is intended to indicate the absence of ozone to the point where the lapse rate is unaffected then plainly we have a dilemma. The terminology is no longer appropriate to circumstances at this latitude and even less so in higher latitudes. This dilemma can be avoided if the term ‘troposphere’ is used in reference to truly tropical latitudes and the word ozonosphere is used to indicate air that is warmed by ozone, at this latitude well below the cold point from about 300 hPa or eight kilometres in elevation, less again in zones of low surface pressure. What we have here is data for the average of high and low pressure cells at this latitude.
By virtue of its effect on cloud cover the relatively amplified increase in temperature aloft drives temperature variations at the surface. The mechanism behind the relationship between increased surface pressure anomalous warming at the surface is described in terms of anomalous increases in geopotential height and surface temperature in chapter 3 entitled ‘How the Earth warms and cools naturally’.
At 30-40° south latitude the presence of ozone markedly reduces the lapse rate of temperature with elevation above the 300 hPa pressure level.
At 40-50° south latitude the temperature of the ozonosphere at 100 hPa is considerably warmer than at lower latitudes and particularly so in winter.
The temperature at 300 hPa is very little different between 40-50° of latitude and 70-80° of latitude despite cooling at surface with increasing latitude indicating that this is indeed part of the ozonosphere. This warming occurs in the absence of mesospheric air in the summer season and more so in winter when cold mesospheric air is present. However there is obvious cooling of the ozonosphere above 100 hPa due to the influence of mesospheric air in winter the depression of air temperature increasing with elevation. Looking back we see that this trend emerged at 30-40° south latitude. The mechanism by which mesospheric air reduces the temperature of the ozonosphere beyond the margins of the polar vortex that is traditionally seen as containing it (cannot get out), involves both mixing and the chemical erosion of ozone by NOx. This process is fundamental to the long term evolution of ozone partial pressure in the ozonosphere and the temperature at the surface of the planet because it affects the Earth’s cloud albedo. It is the diminution of the flow of mesospheric air over time that has allowed ozone partial pressure to build in high southern latitudes and with it surface temperature and the volume of energy stored in the global oceans. The build in ozone partial pressure has produced a dramatic fall in surface pressure in high latitudes and a less dramatic but highly influential increase in surface pressure and energy gain in the mid latitudes.
The containment of mesospheric air within the polar vortex is an essential requirement if the Earth system is to be entirely self contained and free of influences from our highly variable local star….the sun. Certain people who wish to drive a political agenda will hang on to that notion like a dog with a bone. These people will not want to know about stratospheric processes.
At 40-50° south ozone drives a halving of the lapse rate above 300 hPa and a 10° C increase in the temperature of the cold point by comparison with latitudes only 10° closer to the equator. The lapse rate is particularly curtailed and the temperature of the cold point is particularly affected in the winter/spring period. Temperature above 300 hPa plainly relates more to polar atmospheric processes than surface temperature at this latitude.
So far as the use of the term ‘tropopause’ is concerned we must note that the ‘cold trap’ is unequivocally located in the stratosphere and is further elevated in late winter–spring (reduced descent of mesospheric air). It is warmer in winter than in summer. It is no indication of a ‘boundary’ between spheres of interest climatically. That ‘boundary’ is now to practical intents and purposes at 300 hPa and the cold point will be lower when surface pressure is lower, as observed by the French balloonist Debort who discovered ‘the stratosphere’ in the 1890’s. The notion of a ‘tropopause’ is devoid of content in defining the character of the atmosphere in mid latitudes and should be abandoned. The use of the term is rooted in a failure to observe the dynamics that determine the thermal structure of the atmosphere and the origins of the surface pressure regime. We abandoned the use of the term ‘isothermal layer’ as a description of the stratosphere when we found that it is by no means equal and we should abandon the use of the term tropopause and troposphere when we refer the atmosphere outside the tropics. These terms mislead and result in sloppy thinking.
At 40-50° south latitude the marked variation in the temperature of the stratosphere at 10 hPa across the year reflects the impact of the pulse in ozone partial pressure outside the polar vortex where 10 hPa temperature rises quickly to be very close to its annual peak and surface pressure falls to its annual minimum in September-October.
Seventy percent of the depth of the atmospheric column lies above the 300 hPa level at this latitude. It stretches between 8 and 30 km in elevation.
Warmer temperature in the lower stratosphere between June and October is the product of the increase in ozone partial pressure across mid and high southern latitudes in late winter-spring. Mass transfer from the summer hemisphere and the high latitudes enhances surface pressure in the mid latitudes of the southern hemisphere in winter. The transfer of mass from high latitudes involves enhanced uplift due to ozone heating affecting the entire atmospheric column. That which ascends must descend and it does so in the mid latitudes. The rate of descent and the surface area of descending air is simply a function of the dynamics of ascent in the near polar atmosphere. Again we see a dynamic affecting the Earth’s albedo, stronger at this latitude than at 30-40° south latitude.
At 50-60° south we enter the domain of the ozonosphere proper. The lapse rate is diminished above 500 hPa due to appreciable ozone in the upper half of the atmospheric column. Regional density differences in the stratosphere promote strong uplift. This is the domain of the Polar cyclone that is generated between 50 and 70° south. The ozonosphere drives cyclogenesis, the distribution of atmospheric mass, short and long term weather variations and the evolution of the planetary winds. The notion that the ‘troposphere’ is the ‘weather-sphere’ at these latitudes is silly. None of the circumstances that give this term relevance in the tropics apply at 50-60° south. The surface itself is very cold. The near surface atmosphere is cold and dry. Cloud is associated with uplift at the junction of warm wet and cold dry air masses. Convection originates in the ozonosphere by virtue of the behaviour of ozone as a greenhouse gas. Heating is then assisted by the release of latent heat associated with frontal activity. Cyclones move equator-wards tending to maintain the distinctive differences that maintain their vorticity until they run out of ozone aloft and moisture below.
The ‘cold point’ that is named the ‘tropopause’ in low latitudes is located within the stratosphere in all months. In June it is found above 10 hPa. As an indicator of the ceiling for convection due to the release of latent heat of condensation it is irrelevant. Wet air never reaches this altitude. The cold point is much warmer than it is in the tropics. The air is very much drier in high latitudes and precipitation is consequently light. But the elevation of the cold point materially assists the process of convection whereby lower density air is squeezed upwards. Convection affects the entire atmospheric column rather than being confined to the atmosphere near the surface. At latitudes pole-wards of 50° south we find the true weather-sphere,. This is the domain of the roaring forties the furious fifties and the screaming sixties. The enormous forces operating aloft are muted at the surface but still rock us back on our heels.
Polar cyclones owe their origin to heating of the atmospheric column by ozone. Heating occurs at all elevations where ozone is found, both above and below the cold point. This heating is driven by long wave infra-red emissions by the Earth itself varying little between day and night, and via energy redistributed polewards by the oceans and the atmosphere so that outgoing radiation has a pattern of annual variation much less extreme than the variation in the energy supplied in the form of short wave radiation from the sun.
In mid and high latitudes the Earth starts to act like a battery for energy storage and energy supply to the atmosphere at a relatively invariable rate. This energy performs work via the agency of ozone. That work is weather change if we are talking of short term effects and ‘climate change’ in the longer term. The stratosphere is now the ‘weather sphere’ because this is where weather is generated. The partial pressure of ozone evolves on very long time scales.
In climatology as presently taught, what happens in the lower half drives the upper half. Motions in the lower atmosphere condition the distribution of ozone in the stratosphere. This doctrine is absurd. People refer to a coupling process between the troposphere and the stratosphere. What troposphere would that be?
At 60-70° south latitude, the lapse rate is reduced below and above 500 hPa and we have a very warm cold point in summer and a cold point in winter that approaches the temperature of the mesosphere to which it is proximate. The temperature of the ozonosphere declines in winter due to the influence of mesospheric air that descends inside the polar vortex over the Antarctic continent. Ozone partial pressure increases strongly outside the margins of the polar vortex but the temperature of the air still falls away at 60-70° of latitude in winter. The nature of the mesospheric air, the variation in the exposed surface of this tongue of air and the interaction of this air with that in the ozone rich stratosphere determines the evolution of ozone partial pressure in the wider stratosphere in a process unrecognised in ‘climate science’. The tongue of mesospheric air is continually being abraded by a Jet Stream at the polar vortex and large portions escape beyond the margins of the vortex to be gradually absorbed into the ozone rich surrounding atmosphere. Jet streams are wavy discontinuous phenomena and the notion that this air is confined behind some sort of wall is …., not to put too fine a point on it, akin to a fairy tale.
The temperature at 10 hPa rises quickly from July to be very close to its annual peak by October-November, well before midsummer. Ozone partial pressure outside the polar vortex peaks in October as the tongue of mesospheric air retracts in Spring. This is in part a function of change in surface pressure as atmospheric mass swings back to the now swiftly cooling northern hemisphere. The resulting very late accumulation of ozone despite the fact that the pole is now in full sunlight brings the temperature peak forward in time so that it is only loosely related to the angle of incidence of the sun. See the diagram below for the annual evolution of 10 hPa temperature according to latitude. This diagram represents a 1948-2014 average and conceals change that has brought the temperature peak forward over time, the subject of later chapters.
The accumulation of ozone in the atmosphere outside the polar vortex from mid winter through till the spring equinox relates to a diminishing influence of the tongue of mesospheric air over the pole at this time of year and the consequent enhancement of ozone partial pressure outside the vortex. As ozone partial pressure peaks the vorticity of the overturning circulation brings raw mesospheric air deeply into the lower stratosphere and an ozone hole manifests, in truth it has been growing in size since March but at this time of the year it is squeezed into a narrower profile. This is veritably the hole in the donut. Those who talk ‘hole’ seem to be blind to the substantial donut that surrounds it. They have little appreciation of atmospheric dynamics in high latitudes. Chemists need training in atmospheric dynamics if they are to be relevant and helpful so that they avoid the unpleasantness involved in offering themselves as unwitting shills to environmental activists.
Heating of the atmospheric column by ozone results in a planetary low in surface pressure at 60-70°south latitude that is present in all months but most extreme in September/October (see below). There is no counterpart to this in the northern hemisphere, just patches of low surface pressure over bodies of water over a broad range of latitudes. Observe that all the surface heating and the release of latent heat in near equatorial latitudes is incapable of driving surface pressure to the lows seen in the high latitudes of the northern hemisphere, let alone the extreme pressure deficit seen on the margins of Antarctica. It is not the Hadley cell that drives the atmospheric circulation, it is not the heating and uplift in the tropics, it is heating by ozone in high southern latitudes. Hadley cell dynamics are determined according to the extent of atmospheric shifts from high latitudes because the Hadley cell expands with surface pressure. The ring like modes that characterise atmospheric shifts are a response to the distribution of ozone in high latitudes. The mechanics of the global circulation is driven not from the equator but from the poles and the Antarctic pole in particular. This is the reason why this chapter focusses on the southern hemisphere.
As noted repeatedly, the depression of the temperature of the ozonosphere over the pole in winter is due to the descent of very cold, relatively ozone deficient air from the mesosphere. This air is mixed into the mid latitude flow on the margins of the polar vortex by what is referred to as the Jet Stream that pares away at the margins of the tongue of mesospheric air. There is a knock on effect via chemical erosion of ozone by NOx species (NO, NO2) from the mesosphere. It is at 60-70° south latitude that the interaction primarily occurs. That interaction is the engine room of climate change.
At 70-80° of latitude the near surface air is warmer than the surface itself. Its warmth is due to transport from warmer latitudes by the westerlies and the presence of ozone throughout the profile. Slow descent is the order of movement within the atmospheric column enhanced in the winter, when surface pressure is high and retarded or stalled completely when it is low. The lapse rate above 850 hPa is considerably flattened and in this cold desert with sparse precipitation there is little release of latent heat to contribute to that flattening. Ozone is present throughout the profile.
Practically speaking the entire profile is part of the ‘ozonosphere’ that continues into the mesosphere. Atmospheric dynamics are not related to the coupling of something that exist with a mental construct that is locally irrelevant.
It is sometimes remarked that we do not understand the coupling of the troposphere and the stratosphere in high latitudes. I have a large dam on my property in which I swim. I have looked intensively for a Bunyip without success. We can give up looking for a tropopause in high latitudes. It’s not a favourable environment for that beast. Its far too cold and dry.
Winter air temperatures are markedly affected by the descent of very cold air from the mesosphere that operates to a schedule unrelated to the march of the sun or the duration of the polar night that runs from March 21st through to September 21st. The schedule is much affected by the overturning of the atmospheric column at and beyond the polar vortex. This phenomenon is driven by the ozone content of the air.
The cooling due to the descent of mesospheric air is episodic as is evident in the diagram below. The flip side of that coin is called a sudden stratospheric warming. A warming occurs when surface pressure falls away, the tongue of mesospheric air retracts and the space that it formerly occupied is taken by ozone rich air. The polar vortex and the jet stream contract towards the pole, the westerlies stream further polewards and high latitudes warm accordingly. This is the ‘Arctic Oscillation/ Northern Annular Mode/Atlantic Oscillation or the SAM’ in action. Meteorologists however, with their noses very close to their weather maps, converse together talking about the waviness of the jet stream, the incidence of so called blocking events and Arctic outbreaks.
At 80-90° south the main dynamic affecting the temperature of the atmospheric column is the variable presence of very cold, ozone deficient air descending from the mesosphere. At this latitude it is the interaction between the mesosphere and the stratosphere and whether the air is descending or ascending that determines the temperature profile from the surface upwards. December is the warmest month at 10 hPa due to relatively enhanced ozone in high latitudes, a near static atmospheric column gently ascending and the relative proximity of the sun bringing a 6% increase in solar irradiance by comparison with July. There is a reversal of the circulation at 10 hPa in late December as the descent of mesospheric air finally stalls. The cessation of a regime of vigorous interaction with mesospheric air results in a relatively invariable temperature regime from 100 hPa through to 10 hPa. In November, very regularly from one year to the next, as the Antarctic closes up shop, the action centre shifts to the Arctic.
Enhanced descent of the atmospheric column containing ozone warms at the 600 hPa pressure level, particularly in winter/spring the cycle in temperature at this level influenced by descent rates, penetration ratios and the flux in ozone partial pressure.
At 300 hPa the Antarctic stratosphere is warmest in February reflecting enhanced long wave radiation and the temporary absence of mesospheric air from the circulation until it enters again, in March. Accordingly, the range of temperature is minimal at all levels above 300 hPa between February and March (see below).
At 850 hPa the temperature peak is in January driven by the march of the sun.
It is plain that other than quite close to the surface, the forces responsible for temperature and ozone content of the upper and lower portions of the atmosphere are very different.
Back in the 1940s the Antarctic ozonosphere used to be conditioned by the presence of a tongue of mesospheric air throughout the year. At that time 10 hPa temperature was very much cooler than it is today.
Inspecting the three diagrams above, we can infer that variability increases the closer one gets to the mesosphere. It is mesospheric air that is the source of that variability and it dances to the tune of surface pressure variation, a good indicator of the vorticity of the overturning, ozone driven circulation.
Change in the rate of uplift in the stratosphere (and descent from the mesosphere) associated with ozone heating outside the margins of the polar vortex occurs on all time scales but is most active in the month of July and August as is apparent above. It is at this time of the year that the interaction between the stratosphere and mesosphere over the Antarctic pole is most variable. The decline in the temperature of the Antarctic stratosphere at 10 hPa since 1998 indicates that mesospheric air is driving down the ozone content and the temperature of the ozonosphere at 10 hPa over time. This heralds cooling. An Earth system that is already on the cool side will become colder. Fortunately, mankind has many tools at his disposal to survive and prosper in adverse circumstances. Clothing helps. Warm slippers and thick socks keep the toes warm and we have a good supply of cheap fuel to keep interior of our shelters warm. In the absence of viable battery storage storable fuel needs to be available both day and night, when the sun does not shine and the wind does not blow. There is no need to fast track so called renewable energy technologies with massive subsidies at the taxpayers expense. There is no ‘carbon pollution’ problem. We are in a regime of carbon enrichment that will serve all species well, including the polar bears that will find more to eat in summer but will unfortunately have to go hungry for a longer period in winter.
A note for theorists: The temperature of the stratosphere at 10 hPa cannot vary on the time schedule and in the manner seen in the last graph according to internally generated ‘planetary waves’. That is a logical absurdity. Yes, waves there are, but in terms of modes of causation for the temperature of the stratosphere, look elsewhere. Bottom up thinking represents a failure to grasp the reality of ozone flux over time and its relationship with surface pressure, an inability to appreciate the factors responsible for the increase in ozone partial pressure in winter and factors responsible for the variability in incursions of mesospheric air. It represents an inability to grasp the importance of NOx in mesospheric air, the dynamics behind the jet stream and the origins of the ‘ozone hole’. Bottom up thinking makes it absolutely impossible to grasp the cause of the ‘annular mode’ phenomenon. It makes it impossible to appreciate the fact that the planetary winds evolve on all time scales changing the basic parameters of the climate system. Above all, bottom up thinking makes it impossible to model the atmosphere numerically. It dooms us to failure. It opens us up to superstition and exploitation. In general, it’s a disaster. Climate change is manifestly ‘top down’.
2014 is not a typical year. Every year is different. The geography of the stratosphere evolves over time. As we will see the influence of the stratosphere is indelibly imprinted on the surface temperature record.