Something interesting, and a bit unusual, is going on today in the deep heart of the Arctic polar region. The remnants of at least five atmospheric rivers (ARs), originating in three different oceans, have all converged into one ensemble as they head toward the pole, causing the formation of a massive warm anomaly. This event is worth recording, and I hope most readers will give it some time spent in closeup study. It certainly demonstrates the power of precipitable water (PW) as a major provider of greenhouse energy. We’ll start with a global view of the ARs that are responsible for distributing PW across the upper latitudes of the planet on a daily basis, with a uniquely different pattern of results each and every day:
I see the one from the Pacific sending no more than a small volume of its remnants across North America and the North Atlantic, whereupon they unite with some of the remnants from the more northern of the Atlantic rivers. The two Atlantic ARs drop off much of their material into a single, well-constructed river that heads toward the UK, while other material splits off and spreads out and passes mainly over North Africa before turning north. A third, and rather stunted, Atlantic river can be seen crossing Central Africa, then combing with parts of perhaps three separate rivers, all quite small, emerging from the Indian Ocean. Another relatively weak river arises out of the West Pacific, near Japan, and follows the desert region on a westerly course before circling to the north. Here is how it looks, with more detail, when the remnants all come together in the Arctic seas north of Siberia:
The next map shows what happens to surface temperatures when so much vapor gets stacked up in the skies overhead. In this part of the far north it doesn’t take much greenhouse energy to produce temperature increases of ten or twenty degrees and more. Notice how the warm area is surrounded on three sides by a cup-shaped region that has not shared any of this approaching PW movement and remains bitterly cold:
This spectacle is spelled out through a different perspective, in an even more vivid way, with a look at today’s anomaly map. When the PW content is rich the anomalies run as high as +20C, while places farther to the east that are receiving less-than-average amounts of PW on this day are as much as 20C below normal in several spots. The large cold anomaly to the south, also running short of a normal dose of daily PW input, would usually be much, much warmer than the region at the center of the polar zone:
ARs are regularly established in either of two distinct categories of space and mode of transportation. Some are carried along by a variety of winds at the jetstream level, others by consistently strong surface-type winds at a lower altitude. Today’s event is the result of a mixture of both kinds, with most of the lower level activity occurring in the skies above the Asian continent. You can pick out such winds and see them converge on this map:
This particularly dramatic showing can only happen when the pressure gradients at the lower level are set up in a way that facilitates consistency for long distance travel by surface-type winds. Today is one of those days, making possible so much extra strength as well as breadth in the temperature anomaly:
Carl