Today I will provide one more illustration of the fact that precipitable water (PW) has a powerful greenhouse energy effect. Every day there are a number of situations going on around the globe that provide the clearest possible evidence behind this claim, all of which are illustrated in imagery provided by Today’s Weather Maps at https://climatereanalyzer.org/wx/DailySummary/#t2. The best illustrations take advantage of the fact that “atmospheric rivers” (ARs), the very same upper atmospheric phenomena that provide the continents with precipitation in the form of rain and snow, and a few other related things, are composed of nothing but extraordinary concentrations of PW. These concentrations, which occur in discrete formations that are constantly in motion, are individually measurable by molecular weight. All concentrations are 100% effective in the production of greenhouse effects, which have a regular impact on surface temperatures at locations directly below the passage of each and every AR, whether or not the AR is producing precipitation at the same time. Today we will be studying an example in western Europe, where an incoming AR is meeting resistance—caused by a jetstream wind that is blocking its path at the same altitude—as it moves northward:
In the upper right part of the map, focus your attention on the brown bulb shape that appears to be caught between a pair of connected dark black eyeglass lenses. The brown represents an AR, all of which is composed of a high concentration of PW. This high-altitude PW contributes the bulk of a total reading of around 15kg per square meter for that location. The two dark lenses have comparable readings of only about 5kg, almost entirely based on ambient amounts of water vapor in the lower atmosphere. Let’s see what difference—if any—in surface temperatures may be occurring at these locations as a consequence of the different PW readings:
I see readings of +3-5C in the green area as an average for the day. In the blue area -10C is quickly reached and -15 is not far off, for totals that go all the way up to 20C in not many miles of distance. Let’s see how this looks on the anomaly map:
I would call it +4 to +7C in the warm area and -4 to -8C, and then colder yet, in the two cold zones. The cold zones are a bit farther north, which should account for part of the difference, and also may have more snow cover, as we can see on the next map. This map also indicates a lack of any significant difference in elevation over this entire region, making it a non-factor in the comparison.
To summarizes, what we see here is clear evidence of the overhead PW concentration having a significant warming impact on the surface below, with differences reaching about 15C (27F) at relatively nearby distances. The PW comparison that we saw on the first map, 15kg v. 5kg, must be interpreted logarithmically, which is standard for greenhouse energy effects. This means the warm area is receiving about 1.5 times as much incoming radiation energy as the nearby colder areas from this one source of input. How strong is the PW greenhouse effect in this situation? Based on many observations similar to this one, my general conclusion is that, if all else is equal, any doubling of total PW value in the overhead atmosphere will add about 10C, with a +/- 2C margin of error, to the surface temperature of a given location. The same rule can be applied to highly comparable locations on the same day, if all else is nearly equal, but with a somewhat greater margin for error. This situation is in close conformity with the general rule.
Carl