The diagram above serves as a reference frame. The middle stratosphere at 30 hPa has been off the scale cold since the end of November as the Arctic began to experience Polar night.
The great bulk of the northern landmasses are experiencing sub zero temperatures. The winds streaming out of the Arctic are warm by comparison with the air near Lake Baikal and the interior of Iceland. Reputedly China is experiencing its coldest winter for thirty years. The diagram below shows the circulation of the air and its temperature at 10hPa or 30 km in elevation.
The cold is due to the descent of mesospheric air in the circulation at left centred over Russia and spiralling in to the surface in the proximity of Lake Baikal. The warm ascending circulation on the right that is centred on the north Pacific is due to the persistent presence of high concentrations of ozone that gives rise to low surface pressure. By contrast, the Siberian high pressure zone centred on lake Baikal has an elevated surface pressure as seen below.
The diagrams below show the evolution of temperature at elevations between 10hPa (30 km) and 70 hPa (17 km) in the area of the polar cap that takes in only that part north of 65° north, where the polar night prevails. It is important to realize that Lake Baikal, where the descent of very cold air is centred is at latitude 53° north. We are in fact sampling the temperature of the air outside the zone where the cold air originates.
A sudden stratospheric warming affecting the lower stratosphere has materialized in the last few days.
The warming is more apparent at 30 hPa than at 70 hPa.
Just a few days ago on the 24 th January we had this distribution of ozone at 10 hPa. Notice that there is an increasing deficit in ozone from the equator towards the pole at this elevation with up to 20 ppm on the perimeter and down to 6 ppm in the core. This reflects the fact that the air that is descending is low in its ozone content and high in NOx, compounds based on nitrogen that destroy ozone. There is an ascending circulation located over the ozone rich north Pacific that was apparent above. That ascending circulation drags in air from the core and the entire ozone rich mass of air rotates about the core in a clockwise ascending spiral.
Observe the bulking up of the ozone driven circulation over the last three days. By the 28th there is an increase in the volume of ozone deficient air from the core inside the dashed oval that serves as a marking of the zone of ascent.
Latest available data is for the 28th January.
It is of the greatest importance that you understand that the inflow of NOX modulates the ozone content of the wider stratosphere. Just because climate science as embodied in the works of the IPCC is ignorant in this respect (wilfully so, I imagine, because they can’t be that unobservant). So, I will run down through the atmosphere to show you the process in detail.
At 20hPa background levels of ozone in low latitudes are distinctly lower than at 10hPa so there is less contrast between the ozone rich ascending circulation over the north Pacific and the background. We observe an extensive lateral mixing process in action. We have no means of judging the extent of vertical mixing in a diagram of this sort. There is a secondary exchange region, much smaller in scope at about 2 o’clock over the Middle East. The ozone deficient core is centred on Siberia and elongated towards Greenland. The ozone deficient core is weaker and less extensive than it is at 10hPa.
Below, the zone where ozone accumulation drives the ascending circulation is evident at 30hPa, an elevation of 23 kilometres.
At 30hPa ozone peaks over the North Pacific at 10ppm. On the periphery we have as low as 5ppm and in the core as low as 3ppm.
At 40 hPa the contrast between the ozone rich north Pacific at 9 ppm and the background at 3 ppm is still marked but the core is much reduced in area. There is less lateral mixing implying a steeper rate of vertical ascent in the ozone enhanced zone.
At 50hpa core ozone values in the north Pacific zone are in the region of 9ppm but ozone values fall away strongly towards lower latitudes implying fast ascent over the north Pacific. Notice the extent of the penetration of the Arctic circle by ozone rich air. The temperature of the air at 60-90° north reflects the varying penetration of the night zone by ozone rich air that circulates on its periphery. ‘Planetary waves’ reflect the pattern of ozone variability in the atmosphere that drives surface pressure. Cold core polar cyclones are warm core aloft. Without a warm core there can be no ascent.
At 70 hPa the descent of cold vortex air is the dominant feature of the atmospheric circulation. This air has changed very little in its temperature in its descent from 10 hPa at 30 km to the 70 hPa level at 17 km and nor would we expect it to. Although it may have run a perimeter course and suffered some admixture of ozone rich air in the process it has moved only 13 km in the vertical and it has essentially retained the character that it did at source. We don’t have any indication of the vertical vector in this plot but common sense dictates that the air can not pass through an ozone rich zone without having its temperature altered considerably. The implication is that the vertical vector at 9 0’clock is probably more important than the horizontal vector. The question is, How far does this mesospheric air descend and what is its effect on the circulation of the lower atmosphere.
The last observation of the temperature of the stratosphere that is available is at 100hPa.
In low latitudes through to about 30hPa there is no ozone. The uplift of tropospheric air containing NOx destroys ozone at the 100hPa level. The north Pacific still rejoices in up to 4ppm ozone while vortex air at 1.5 to 2.ppm ozone occupies an extensive zone from 30° of latitude northwards.
At 250hPa (9km) very cold mesospheric air is being mixed with warmer stratospheric air. Areas of low surface pressure on the periphery give rise to cyclones( cold below, warm at 250hPa). The Jet stream manifests at the edge of the circulation as a wave like formation.
Globally, we see that polar cyclones are warm core circulations aloft, especially evident in the southern hemisphere at this time of the year.
Some take home messages:
- Surface temperature in the winter is driven by a dramatic change in the source of the air, being driven from aloft. Notice the very cold air at 250 hPa over Lake Baikal.
- According to the rate of delivery of mesospheric air into the polar atmosphere the ozone content of the air will change and with it surface pressure polewards of about 50° of latitude. This pattern of surface pressure change shifts atmospheric mass between high and low latitudes as the ozone content of the air increases driving surface pressure ever lower. This (unknown t the IPCC) is the origin of the annular mode phenomenon.
- The winter polar circulation is highly energetic and is subject to ascent and descent. It is not stratified.
- According to the ozone content of the air and the contrast in density that arises polar cyclones are generated on the margins of descending mesospheric air.
- Planetary waves reflect the ozone content of the air.
- Polar temperatures aloft reflect the pattern of distribution of warm and cold air. There is nothing mysterious about sudden stratospheric warmings.
Last but not least lets see this:
Between the 8th and the 28th of January the ratios have changed implying that ozone has built up in the Pacific sector and is there is more ozone in the core than there was, perhaps via an exchange between the two. Or perhaps it represents a reduction of the inflow of mesospheric air heralding a major warming of which the one that we are seeing today is just a precursor?