Picking up from where we left off yesterday, something really big is going on in the atmosphere of the Northern Hemisphere, and it is happening rather quickly. It seems that each day more of the effects become visible on one or another of the Weather Maps. The one effect that I find most fascinating right now, because it is so unfamiliar, and yet fundamentally kind of mind-boggling, concerns the changes we are seeing in upper level air pressure. I have been trying to think it through in three dimensions, hoping to get a complete picture of cause and effect, and have come up with a set of ideas that can be put into words that hopefully make sense.
With reference to the first image in yesterday’s letter, showing the full global view of the 500hPa pressure level, and taking note that there are very few differences between the hemispheres in the large area ranging from 30N to 30S, we would all like learn as much as possible explaining the strange behavior of the atmosphere in the north from 30N on up. The total mass of overhead air by weight can be assumed not to have changed, otherwise one might suppose we would already be noticing more changes in the average of pressures at the surface. That means spatial dimensions of volume must be changing, creating both thinner air and a sort of bubble, or blister effect, that stretches the entire air mass located north of 30N in an outward direction. The greatest amount of stretching is appearing right at the peak, diminishing from there all the way around the globe and all the way back down to the starting point at 30N. Such stretching would inevitably move the gravitational halfway point for a total column of air, as signified by 500 hPa, up with it, which is what we see happening.
Next, considering the evident fact that the slope of the stretching effect keeps growing at every latitude from 30N to the top, one must expect corresponding changes of some sort in the nature of the gradients that separate any one pressure level from the one next to it, possibly expanding and deepening on the way up. These are the very same gradients that are home to all kinds of wind currents, including those of the jet-producing type. We do in fact see remarkable changes in the structure of the inner two major jetstream pathways (the ones marked by thick deep green and thin light blue lines), enough to cause both of them to break up into small circular pieces, apparently losing strength along with singular continuity. This result is almost certainly a key factor favoring the expanded movement of precipitable water streams into the very heart of the high-altitude polar region, as recently described.
What is causing the pronounced expansion of this part of the global atmosphere in the first place? The only thing I can think of, and this is purely a guess, is that it must have something to do with heat. More specifically, heat created by increases in thermal activity generated by the presence of large quantities of material in the upper atmosphere that has a greenhouse effect—not all of which need be purely gaseous by nature. Such materials re-radiate energy in all directions, which I believe tends to warm the surrounding air in ways that should cause it to expand whenever the bulk quantity of such materials is increasing, at whatever altitude. There may be enough of an increase in this normally cold-air region to accomplish the big blister we are seeing.
Whether my ideas are right or wrong, some of the facts that have been described in these letters are pretty clear. Two of them, the change in 500 hPa levels high above, and the simultaneous rise in temperature anomaly at the surface below, are indisputable. The connection involving high-flying streams of precipitable water can and should be questioned. If correct, the possibility of an emerging positive feedback loop comes into view and is hard to reject. Lastly, look at the two images below. I invite you to make a good study of the differences, then return to both of them every day on your computer and look for frther changes that may be meaningful, particularly in the north. Not long ago there was very little difference in the structures of these two.
Carl