Note: Unfortunately, the first two maps in this letter do not represent the original image inputs and must be disregarded. An unknown computer glitch is causing these images to be updated each day, something I now have no way to correct. Parts of the letter should still have value for broader application. Very sorry about this.
Today we will keep things simple and just look at some everyday evidence of the close relationship between total atmospheric precipitable water (PW) values and surface air temperatures on continental land, outside of the tropical belt. There is no better place to do this exercise than northern Asia, Siberia in particular. Siberia is a very long way away from the principal sources of PW, tropical ocean waters, which have some chance of being added in fairly significant parts to the local sources when they travel that far. The latter are not very robust at this time of year, which is still quite wintry, with temperatures all below freezing and snow on the ground everywhere. It seems that any little extra bit of PW in the sky will have lots of leverage when it comes to greenhouse energy effects.
You should keep in mind a basic fact about all of the different kinds of airborne matter that generate greenhouse effects: when concentrations are at their lowest the effect on temperature is strongest, per molecule, from a purely molecular standpoint. When concentrations grow the effect per molecule diminishes, logarithmically. That is, each double produces only half the effect on temperatures as the one preceding. Also keep in mind, with respect to greenhouse gases, that most of them are not very powerful, per molecule, to begin with. This is because of the relatively minor positions held all to themselves on the solar radiation spectrum. CO2 has a relatively strong position. It can add about a whole degree (all by itself with no feedbacks) to global temperatures by doubling, and its level is growing too fast for comfort. Methane, growing at about the same rate but with a less strong position on the spectrum, adds a little less than half a degree with every double. Fortunately, in one sense, both of these gases are growing at rates well under 1% per year, and can be controlled by human action if there is a will to do so.
PW, composed of varying amounts of H2O in several states, is a real oddity. It is mostly in a gaseous state, water vapor, and behaves much like a gas. It differs from the gases mainly because of its tremendous variation in concentrations, which are everywhere in a constant state of change, which can at times be dramatic in terms of both doubling and halving, and multiples thereof. And oh, it has unparalleled strength on the spectrum—each double is worth about 10C in surface temperature, always localized and never permanent, fortunately. Differences in the composition of PW materials, from gas to icy things, does not seem to matter very much. I find this all quite interesting, and wonder why similar observations are not well-publicized in educational circles.
Now for some sampling of PW at work today in Siberia, as promised. The anomaly map is intriguing because of the big blue anchor shape that is seen. We will want to see if the PW map will have any imagery in that same position with a similar unique shape. Note that the anchor handle contains a cold spot that has an anomaly reading all the way down to -21C:
The anchor image on the PW map does not stand out as clearly as the other, but certainly has the right shape. If you magnify the image you will be better able to pick out the low readings, mostly at the level of 2-3kg. The coldest spot of all is associated with a PW reading of less than 1kg, indicating a probable actual temperature of -38C. That temperature places the true PW value at about 750 grams. A short distance to the south, where a warm anomaly shows up, the shading indicates an actual temperature of about -8C, for a 30-degree difference. I can see a PW value of 6-7kg in that area., representing about three doubles when compared with the coldest place.
Here is a map of actual temperatures to use for reference. You are invited to look for similar connections in other parts of the Arctic region, such as the areas around Scandinavia, or the Kamchatka Peninsula, and many more.
Carl