Today’s Weather Maps offer a fine example of what atmospheric rivers (ARs) can do when they find a way to carry their content of concentrated precipitable water (PW) into the heart of the polar region. These images will show you exactly what I mean when I describe the extraordinary greenhouse energy powers of the PW that exists in the upper part of the troposphere. This is a perfect example of the kind of evidence I rely on, one of many that have had very similar outcomes. The evidence is obtained in a ridiculously simple and easy manner, by opening a number of different kinds of weather maps and focusing all of my attention on any one specific region that appears to be of significant interest. Today I selected a particular region after I first became interested in the massively large warm anomaly, averaging +3.8C for the day, that was showing up across the entire Arctic Circle. A quick survey called attention to one small area of particularly high anomaly, in the form of a small round shape surrounded by darker shades, located in the ocean just off the coast of Canada’s two most northwestern territories, next to Alaska. This anomaly turned out to be in the +14-16C category, which is a good four degrees higher than the very darkest shade reading on the scale at the side. (Best to view these things with some magnification, like 200%.) Here is the appropriate map—notice how the darkest shades (up to +10-12C) extend into places that reach all the way to the pole:
Next stop, the PW map. Here we see the cleat image of an undersized but well-defined AR that has branched off from a larger AR which originated farther to the south in the west-central part of the Pacific. The branch heads straight toward eastern Alaska, where it starts fragmenting and expanding. Notice how the fragmentary bits and pieces, while steadily being reduced in strength, remain visible, and thus measurable in their kg strength, all the way to the pole. The full track coincides neatly with the darker part of the above anomaly pattern, which I think is very meaningful because it is not the least bit unusual to see such a relationship:
This particular AR may be kind of a runt, but I still think it qualifies as the real thing. In case you were wondering, it even passes the precipitation test. Not just rain, but this one is dropping a little snow as well on the final leg of its approach to the North Pole:
One adjustment still had to be made. It never hurts to check out sea ice coverage in a situation like this, which I did. It turns out that the small area of very warmest anomaly exactly corresponds with a small patch of open water in the ocean, which most likely had been regularly frozen over at this time 30 years ago. The warm surface of that water could easily account for several degrees as part of the total anomaly we see, adding that amount to the warming produced by PW’s greenhouse energy. Looking at the full context of imagery, it is not hard to figure that the open water is in fact adding about four degrees to the total temperature at that spot:
A quick check of open temperatures is always relevant. On this map, the (salty) open water is registering a degree or two below freezing. It is more than likely surrounded by patches of broken or mushy ice that are only a few degrees colder. Moving on, when we get to the lightest blue shading we’re at -10C, which can now be more directly attributed to the influence of the PW fragments in the AR. Temperatures that have dropped to around -13C are visible on the PW track all the way to the pole. These are surrounded by off-track numbers that quickly move into the -20s and then the -30s in their closest to Greenland.
To wrap this up properly, we need to do some calculating, to see how well the main area of high temperature anomaly matches up with the incoming PW differential (after subtracting out the open water anomaly). For temperature, all those +10C areas, by my standards, should reflect actual PW kg readings that fully double the kg value of readings that only produce normal temperatures on this day at this location. What do we see here? Even though we do not have genuine baseline averages for PW, we can see how readings making up the inside of this river, running from 3kg to about 8kg, are probably averaging a full double over those that are currently producing much colder—yet still a little above normal—temperatures off to either side. This is not a solid proof, but the relationship is common, and can’t be too far off.
Carl