Lots more images today. I want to do a refresher showing the key elements involved in the formation of a self-reinforcing feedback loop, this being one of a type that occurs with great regularity in the upper atmosphere. This particular type of loop is not referred to anywhere in the science literature but has been demonstrated and more fully explained many times in previous climate letters. The featured sequence of events was originally established as a driver of change in the behavior of precipitable water (PW) movement in that high-level venue. The creation of feedback loops adds a surprise ending to the story, with its own potential level of importance. The loops are effective in extending the duration of both warming and cooling anomalies, mostly for short periods of time but sometimes longer. The one I am showing today is of the cooling type and will be brief. For the first time my display will incorporate cloud cover as a noteworthy cooling factor. We’ll start the series with an image of a large isolated region of cool temperatures extending southward from the polar zone through central Russia:
These temperatures, at around 10 to 12C, were just cool enough to cause a thumb-like extension to the green-zone image of air pressure configuration in the upper atmosphere. It’s weaker than most other parts of the green zone but should still be strong enough to have some consequences while it lasts:
Will its strength be strong enough to establish normal isobar encirclement at its outer perimeter, creating a regular pathway for winds of jetstream strength to follow? Absolutely. Here it is, and the resulting wind velocity is certainly not too shabby:
Next question: is that wind going to be strong enough to hold back the movement of PW concentrations that might otherwise be passing through the area that is now inside the loop of the jetstream path? On this map you can see that current PW values are much stronger on both the left and right sides of the loop, and to some extent below as well. Values on the inside are kept all the way down to 10-12 kg, compared with 25-30 kg over broad stretches on either side:
With that much difference in PW values, should we not anticipate seeing considerable differences in surface temperature anomalies between the contained region and those on either side—probably on the order of 10C and more? Let’s take a look:
The difference in places is a lot more than 10C. We’ve lately been discussing how cloud top albedo, when clouds have formed, can be strong enough at this time of year to offset all or more of the greenhouse effect of whatever PW values were involved in the creation of those clouds. Is there any such confliction in play in this situation?
This is a surprise. The heaviest clouding may be that which shows up inside the area of cool enclosure, created by PW values that are only on the moderate side. This appears to be capable of having a hand in creating the area of deepest blue we see in the lower part of the cool anomaly, bringing the anomaly downward by an extra 5 degrees or so. This extra bit of cooling may not properly qualify as a regular part of a feedback loop, but it does contribute toward keeping this loop alive and running for possibly a few extra days. Summer heat buildup will soon knock this particular chain of events completely off the map.
Carl