Yesterday’s letter offered some details of a possible relationship between high-latitude surface air temperatures in the Northern Hemisphere and the positioning of an important pathway bearing jetstream winds at an altitude which could only begin at not less than about three miles above the surface. There is a way to explain this unusual relationship by invoking a physical process. The process involves a means of transformation from one configuration of air pressure differentials into another, ending up with a considerable difference between the two. The configuration at the surface is keyed to one set of factors and results in a pattern of winds that have familiar characteristics. A much different configuration is established in the upper part of the troposphere, resulting in a whole new wind system, which notably includes a unique assortment of pathways bearing the winds of very high velocities that we call jetstreams.
The transformation of one configuration to the other is to all appearances strongly influenced by the overall pattern of air temperatures on the surface, which range from very hot in the tropics to very cold in the two polar zones. Zonal temperatures outside of the tropics go through regular seasonal changes which can thus have a direct effect on the outcome for upper-level configuration. A physical mechanism can be described which reasonably explains the steps that enable the transformation to occur. Basically, air temperature always has a close by effect on air pressure, and this effect can apparently be transmitted over a considerable distance, far enough to affect the outcome for pressure differentials in the new upper-level configuration. Air temperatures at the higher level are generally colder than those below, but their effect on the outcome, if any, is unclear.
Today I am going to reiterate the basic ideas expressed yesterday, using the same three images, plus one more, this time with coverage of the Antarctic polar zone. This region is quite different from the Arctic because so much of it stays icy cold all year long. The blue zone of air pressure, unlike the one we studied yesterday, therefore has no chance of disappearing in the summer season, and hardly even weakens. Nearby jetstream winds can thus stay near top strength, tightly enveloping the polar zone all year long. Here is today’s temperature map, which notably has readings in spots that already go off the scale at -60C, and it’s not even winter yet:
Now for the local air pressure configuration. See how large the area of blue zone is, and how regular its shape. Its border can be seen to mostly extend for about two degrees past the zero temperature line, for perhaps a little warmer coverage than the blue zone in the north. Also notice how narrow the green zone is, and how tightly wrapped around the blue zone. This kind of pathway proximity will always give a real boost to jet wind velocity.
As we see in the next image, the current jetstream winds closely tied to the deep polar zone are indeed powerful, more so today than they ever are in the north. Any precipitable water concentrations at this altitude seeking access to the zone are thus certain to have a tough time passing through. Ice surrounding the continent, if exposed to ocean water, can and does melt from its underside, but surface melting for now is well-protected from admission of any unusual amount of greenhouse energy like we see in the Arctic.
I need to show one more image, of air pressure at sea level for this region, after noticing what a perfect fit the full 990hPa outline has with the outline of the blue zone in the second image. This is an altogether different situation from the everyday relationship of these two in the north. In fact, upon full comparison, the entire configuration of air pressure at the Antarctic surface has a great deal of similarity with the one higher up. There must be some implications here that are worth thinking about, but as of now remain unclear.
Carl