What is the true definition of meaning for the term “polar vortex”? It is hard to define something when its features cannot be fully described as an independent entity, or phenomenon, which has long been the case behind the shadowy nature of what is regularly tabbed the polar vortex. Last week the European Space Agency published a report about recent findings, based on actual measurement data, that are of great help in pinning down the true nature of this beast. The agency’s PR report is easily the sharpest and most understandable description of this singular natural phenomenon yet produced, well worth a good look: https://phys.org/news/2021-02-aeolus-polar-vortex.html.
One of the main defining characteristics of the vortex and its activities is that the home occupied by the phenomenon constitutes a separate wind system, based on a separate configuration of air pressures. All of these things appear to be confined within the layer we call the stratosphere, and also most likely limited regionally to the mid to upper latitudes capping each of the polar zones. This perception should readily remind one of the transition from one wind system to another, which I frequently write about, that takes place within the troposphere of each hemisphere at the lower level where jetstream activity begins. What we see this time looks like the same kind of step-change taking effect, but at a different altitude, with its own unique manner of activity. As a speculation, I think the observed temperature changes could involve rapid movements of precipitable water (PW) values that would read out in single-digit units of grams if they could be measured.
Since the vortex activity involves changes in air pressure, those differences must inevitably be further expressed in air pressure changes lower down. Air pressure is at all times determined by the weight of all the molecules in a column of air extending from any given level to the outermost edges of the total atmosphere. The map of high-altitude air pressure configuration (HAPC) that we frequently refer to (maybe it’s not really all that high) is affected by the balancing of up-and-down pressures that place it directly in the line of fire. Here the pressure changes emanating from the vortex are coming down from above. Most of the time we only think of changes derived from the expansion and contraction of air bodies near the surface as they become warmer or cooler, but that is clearly not the whole story. Let’s take a quick peak at today’s HAPC map, looking for any fresh signs of disturbance from above:
The disturbances previously recognized just seem to keep growing. What I am also seeing bears a close resemblance to some of the imagery in the above ESA report. Comparisons can also be generated going back a number of weeks, or ever since strong vortex developments were first announced.in early January. The HAPC map gives us a number of indicators about how weather effects at Earth’s surface can be transmitted from vortex activity, through having knowledge of the way jetstream formation is constantly governed by the current status of the HAPC. Jetstream wind velocities need not be getting any stronger in this situation but there are more winds blowing, covering more total mileage than usual, and some are roaming beyond usual geographical limits. The high-altitude streams of PW that carry powerful greenhouse effects are, as a consequence, sometimes granted more freedom of movement than normal and at other times less. The anomalies that result can be simultaneously extreme in both directions, and surprisingly close together, as we see in today’s anomaly map covering the Northern Hemisphere. (The SH is as bland as it can be in that respect.)
Carl