In this post I want to go straight to the nature of the forces responsible for surface atmospheric pressure and surface temperature. Essentially pressure and temperature are a direct response to the nature of the stratosphere in the local domain. The local domain in the stratosphere changes dramatically according to latitude and season and also over time in response to change in the partial pressure of ozone in the upper atmosphere. Unfortunately, the role of ozone in determining surface pressure, temperature and wind is unrecognised in climate science. This will change.
THE BEHAVIOUR OF THE ATMOSPHERIC COLUMN
Gas molecules have weight. The greater the number of molecules in a column of air the greater will be the pressure measured at the surface.
Imagine you are ascending in a balloon and you have an instrument on board that measures atmospheric pressure. At the surface it indicates a pressure of 1000 hPa (or 1 Bar or 1000 millibars or 29.53 inches of mercury). You watch the needle falling as you ascend. At 500 hPa with half the atmosphere below and half above you ascertain that your elevation is 5600 metres. Each time you perform this exercise you get a different figure because the atmosphere is subject to warming that changes its density. If today’s height is 5600 metres and the average is 5500 meters you know the lower half is warmer than normal. The height of a pressure level measured in metres is called its geopotential height. Geopotential height is a proxy for air density below the point of measurement. It is also a proxy for surface pressure with pressure increasing as geopotential height increases.
Air density varies with temperature and moisture levels. The contribution of moisture is most important in low latitudes and close to the surface of the planet where humidity is high. It has little importance in the stratosphere where the air is very dry.
Imagine a column of gas contained within a cylinder that stretches from the surface of the Earth to well beyond the limits of the atmosphere. The gas inside is held in close embrace due to the gravitational attraction of the Earth. The cylinder is open at the top. When the air is heated it rises up in the cylinder but cannot spill over. In this situation surface pressure can never change.
The atmospheric column inside that cylinder could be heated at its base, in the middle or in the upper half. Let’s imagine that the energy could be retained in the zone where the heat was applied. If heating was applied in the bottom or the middle of the column the half way point would move upwards. If the heating was applied to just the upper half of the column then the geopotential height at 500 hPa should not change. Height would increase at all points above 500 hPa but not below. If we find that the 500 hPa level is elevated we can deduce that, despite our intention to heat only the upper half of the column, somehow, energy travelled downwards into the lower half.
If the glass cylinder was just high enough to contain the air prior to heating the column, some of the molecules would spill out of the top of the cylinder as heat was applied. It matters not where the heat is applied. Then, surface pressure as measured at the bottom of the cylinder would diminish. This is what happens in high latitudes where ozone causes heating of the upper part of the atmospheric column producing Polar Cyclones. The heating is substantial because to produce low surface pressure (let alone the planetary minimum that is actually achieved) it has to compensate for the fact that the lower part of the column is cold and almost as dense as it is possible to achieve on Earth, and then some. Atmospheric pressure at the surface can be driven down to 980 hPa. In the process, and because this phenomenon occurs over the entire latitude band 50-90° south a loss of atmospheric pressure in high latitudes represents a transfer of atmospheric mass to other latitudes. When air exits the cylinder, it finishes up somewhere else.
Cyclones that develop in the tropics are called warm core cyclones. Cyclones that develop under a warm stratosphere are mistakenly called cold core cyclones, referring to the temperature of the air at the surface. Some cyclones form in the stratosphere and do not penetrate into the troposphere. No cyclone can ever be born without a warm core somewhere. The uniqueness of the Polar cyclone is that its warmth is generated aloft. You can start an updraught in a chimney with a candle at any elevation.
The Polar Cyclone is a product of the presence of ozone throughout most of the atmospheric profile. This is especially so in winter and most intensely in the southern hemisphere in particular. The associated uplift in the lower atmosphere is a response to the intensity of the forces generated aloft. Essentially, the movement of the air is no different to the convergence of air at the surface that occurs in a tropical cyclone in response to the release of latent heat of condensation aloft, albeit, less aloft than in the polar atmosphere. That such cyclones can be generated in the polar atmosphere testifies to the energy that is transferred from the ozone molecule to the atmosphere at large. That energy comes from the Earth itself in the form of infra-red radiation.
A BLIND SPOT IN CLIMATE SCIENCE
Why is this phenomenon not recognized in climate science: Firstly, the ‘stratosphere’ is supposed to be ‘stratified and incapable of generating convection? Secondly, climate science takes little interest in the stratosphere and is obsessed with the notion that wind is driven by energy flows near the surface. Thirdly climate scientists have failed to notice that what they describe as a ‘troposphere’, a zone rich in moisture that has a cold trap that separates the troposphere from the stratosphere exists at the equator and nowhere else. The surface is much colder at higher latitudes. The air gets drier in high latitudes. The cold point ascends into the upper stratosphere in winter and no longer constitutes the boundary between one realm containing ozone and another that does not. If we want to discern a boundary between a realm that has no ozone and one that does, we need to look at some other metric, (for example the rate of temperature decline with increasing altitude) to work out where that fuzzy zone is located. The further from the equator the fuzzier it will be. These are mistakes born of over-generalization and a failure to closely observe reality. Fourthly, there is a predilection to consider that the Earth system is closed to external influences after a plethora of unsuccessful attempts over a long period of time to demonstrate otherwise. The notion is that only cranks suggest that the sun could be influential in driving climate. Fifthly, there is a strong tendency for recent generations of ‘climate scientists’ to avoid speculation as to cause and effect in favour of mathematical analysis that is taken to somehow ‘account for’ things. The discovery of connections and even ‘teleconnections’ between disparate phenomena is the apparent purpose. There appears to be a lack of realization that ‘correlation does not mean causation and the lack of correlation does not mean that a causal relationship can be ruled out.’. Maths rather than physics graduates enter this field. Sixthly, there is the failure to recognise ozone as a very unequally distributed greenhouse gas and that there is a clear signal in the surface temperature record that unequivocally implicates ozone as the generator of temperature variations at the surface of the Earth. But most critically and disappointingly there is the notion that ‘the science is settled’. That represents either complacency or a determination to force a particular viewpoint.
ENERGY SUPPLY TO HEAT OZONE
Ozone absorbs radiation from the Earth itself at a wave length of 9-10 um. One um is one millionth of a metre in length. This unit is called a ‘micron’ or a ‘micrometre’. Radiation from the earth is heavily concentrated around that wave length. The radiation from the sun arrives in a wide spread of wave lengths of which a small portion is in the infra-red spectrum. In the atmosphere outgoing radiation is closely focussed about the wave length that excites ozone. At the outer limits of the atmosphere we can detect how much ozone is in the air by measuring the attenuated energy that passes by at particular wave lengths. At 9-10 um t’s never entirely used up and is in effect inexhaustible given the tiny concentration of the gas that it excites.
THE STRUCTURE OF A HIGH PRESSURE CELL
In low latitudes the atmospheric column is warmer in the lower portion and colder aloft due to the relative deficiency in ozone. The increase in density aloft has to be substantial to compensate for the low density below so that surface pressure gets to be on average much higher. Accordingly there is much less ozone in the stratosphere above high pressure cells. The portion of the upper atmosphere containing ozone is smaller in vertical extent in high pressure cells (above 300 hPa) than low pressure cells (above 500 hPa) so that helps.
THE OVERTURNING STRATOSPHERE
A polar cyclone that is formed in the stratosphere in winter causes ascent throughout the atmospheric column. Air that rises must be balanced by air that descends. Ozone change in high latitudes is quickly propagated to lower latitudes where the change is muted due to the increasing radius of the Earth as one approaches the equator. In the mid latitudes enormous high pressure cells convey ozone into the lower atmosphere, raising its temperature, evaporating cloud as surface pressure increases. The increase in temperature is tied to the increase in pressure due to the shift in atmospheric mass from high altitudes, in turn due to episodic heating of the high latitude stratosphere tied in turn to a reduction in the rate of ingress of NOx from the mesosphere via the polar vortex.
The implications are: the stratosphere drives weather and climate on all time scales. We need to work out what drives the stratosphere.
Is anything not clear? Please tell me if its not……could be the result of a dyslexic impulse on my part.