Carl's Climate Letters

Why the study of precipitable water is a matter of critical importance.

The short answer is because it may have a significant bearing on the way climate forecasting is done.  We all have a deep interest in that subject, and there are unanswered questions about the recent acceleration of global temperatures. (See, for example, this recent post from James Hansen: http://www.columbia.edu/~jeh1/mailings/2020/20201214_GlobalWarmingAcceleration.pdf.)  Other potential explanations should not be ruled out simply because they are novel. Current forecasters and their models have rarely, if ever, had anything at all to say about precipitable water (PW) as a possibility.  PW is never listed as a forcing.  It is not even listed as one of the feedbacks, like water vapor, cloud cover, sea ice and so on.  The whole idea of studying PW as a possible factor in climate change is simply not entertained, so it doesn’t happen.  That needs to change, and I will present some reasons why:

Reason #1:  The Clausius-Clapeyron equation does not set an absolute limit on the amount of PW the atmosphere can hold.  The equation and its underlying principles are firmly given credit for setting such a limit on water vapor, in that water vapor is a condensable gas, deemed subject to temperature increases.  PW is a gas-like material containing substances that have already condensed and is thus not fully governed by the C-C equation.

Reason #2: PW virtually always exists wherever water vapor exists, which means its non-gas substances in their entirety must have an abundance of properties of a gas-like nature. Should PW be found to have greenhouse energy supplying powers of its own, aside from its vapor content, it is clearly in a position suitable for exercising them.

Reason #3.  Instruments have been created that can accurately measure the total weight of all the molecules of PW within any vertical column of air from the surface to the top of the atmosphere.  These instruments are currently in operation, taking measurements several times a day over virtually every bit of the entire surface, with results made available to the public.  The results are notably incapable of showing anything other than total vertical weight, with horizontal distribution separately added.  There is no breakdown of PW content mix, or the vertical distribution of total content, known to be available from any other source. Total weight by itself, even if it does not seem promising, can still be tested for possible value.

Reason #4. Some of the non-vapor material contained by PW, while not gaseous, is known to have greenhouse energy effects not unlike those produced by water vapor and the other “greenhouse” gases. There are many references to these effects in scientific literature, in particular with respect to different kinds of clouds, but no definitive measurements have been reported. There are no other reports (that I know of) of any other non-gaseous material, of any type or source, known to be producing meaningful greenhouse energy effects on Earth’s surface. Nor is there much explanation given about the physics involved in the specific manner of their actual production by cloud bodies.

Reason #5. Data produced by PW weight measurements for any one location on any one day can easily be compared with similar data for the same location on any other single day, or different locations on the same day, or with daily averages if such were to be made available. These comparisons can be matched up with similar data relevant to surface air temperatures, also accomplished without difficulty but on no more than a moderate level of exactitude. I have done this experimentally many hundreds of times, and reported well-illustrated results in these letters—serving as a journal—dozens of times. The results indicate that PW, as a singular entity and no matter how composed, has an immediate and often extraordinarily powerful effect on temperatures, both up and down, whenever it changes. Effects and daily changes are observed in all locations outside of Earth’s tropical belt.

Reason #6.  A preliminary evaluation of the PW effect on surface temperatures, outside of the tropical belt and apart from other known sources of daily temperature effects, suggest that any one double of atmospheric PW content, from no matter what level, has the power to raise the corresponding surface air temperature by about 10C degrees.  Fractions and multiples are readily applicable, always logarithmic and reversible. Multiple events greater than 10C due to PW changes can be uncovered daily. The extraordinary Arctic heat waves of last summer and in recent months are largely explainable by PW phenomena, some of which are recorded in older letters.

Carl

Precipitable water (PW)—is it a greenhouse “gas”? This complex material is in large part a true gas, but the remainder, condensed from pure vapor, is not. Still, the remainder has certain features that have much in common with water vapor. For one thing, almost every bit of it is composed from the exact same H2O molecules. The only exception would be the tiny foreign particles around which water droplets are formed via vapor condensation. Their weight is not a significant part of the whole but they are a real part of PW and should at least be kept in mind, were it somehow to matter.

PW in its entirety has two important features in particular that cannot be distinguished from those of water vapor and every other greenhouse gas. One is simply the fact that, by definition, it all exists as part of the atmosphere, floating around above Earth’s surface. That’s what makes every bit of it precipitable at some point in its lifetime, and in fact it all soon drops back down to the surface. By virtue of being part of the atmosphere all PW material is in a perfect position to capture longwave photons of energy that have radiated away from Earth’s surface and are headed toward outer space. By common understanding, any such capture will be reversed via re-radiation, ultimately causing what we call the greenhouse effect.

All greenhouse gases, by definition, have this power of re-radiation, but only to a limited extent, specific to each gas. Water vapor happens to exceed all of the others in this respect, giving it extra “muscle power.” Ultimately, the effective greenhouse power of each gas also depends on its volume of concentration in the atmosphere as well as its wavelength band coverage. Here again water vapor is unusual, due to the fact that variations in its volume of concentration in different locations range from one extreme to the other. Concentrations are further subject to a continual amount of shifting up and down in each location. All other greenhouse gases are functionally just the opposite, with concentrations that are nearly the same in all locations and slow to change over time.

So much for water vapor. What about the remainder of materials that constitute PW? Do they or do they not add to the considerable strength of vapor alone? There are two principal considerations. One concerns the nature of any such possible greenhouse effect they might have, which should differ from the characteristics of gaseous molecules due to their large-body type of composition. These materials also have a different kind of distribution from that of the water vapor, and in addition the overall nature of the mixture is quite variable in a number of ways. For illustration, just think of the difference between a sky that is clear and one full of heavy clouds and maybe even rain. The potential for effective variability of greenhouse power between vapor and the other PW materials would appear to be endless.

What does science really know about the greenhouse power of these other materials? To the best of my knowledge, the answer is “not much.” There are plenty of references to observations that clouds do have a greenhouse effect of their own, extremely difficult to measure. Estimates suggest that the grand total of this effect, globally, is roughly offset by the total albedo effect of cloud tops as they reflect incoming solar rays. Not exactly, of course, but it would not be something to worry about apart from an adverse change in their relationship, which some say is a possibility.

Sorry to be rambling on so long, but I need to finish this train of thought by taking a different view of the non-vapor greenhouse power.  Let’s just assume that all non-vapor material, like clouds, does have greenhouse power that cannot be directly and separately measured by any acceptable means.  Does that matter?  Maybe not.  What I believe we can measure, in an indirect way, is the greenhouse effect of PW in its entirety.  We know almost exactly what that entirety means in terms of overall weight—at practically any location, on every day of the year.  And we know almost exactly how temperatures differ from average at each of those locations on each day of the year.  We also have a pretty good understanding of those many other different things, aside from the total greenhouse effect of PW alone, that might have a bearing on the temperature differences. If we simply subtract the net effect of all these things whatever is left of the anomaly could then presumably be attributed to the overall greenhouse effect of PW, vapor and all, in combination..  

This is basically what I have been doing, in an admittedly primitive way, mainly using the Weather Maps. As often reported, I keep getting results that have extraordinary regularity. This outcome suggests a conclusion that it does not much matter what the mix may be for the entire PW component, just the weight. In other words, all the other-than-vapor H2O material, by weight, may realistically have effective greenhouse power similar to that of water vapor alone. This unexpected finding will need to be tested and validated by more rigorous methods. If confirmed, the knowledge gained would almost certainly have many useful applications.

Carl

For purposes of evaluating global air temperatures, should ‘precipitable water’ (PW), a complex substance, be treated as if it were a single greenhouse gas, one having the same power as water vapor, thereby encouraging applications of the substance as a substitute for water vapor?  Regular readers of these letters will have have noticed that I have been heading in this direction lately when analyzing daily temperature anomalies.  I have been making a conscious effort to avoid talking about water vapor when doing these analyses, based on the realization that I had all kinds of valid data available for measuring volumes of PW by weight and nothing of the sort for water vapor.  Previously, when making use of PW measurements, I would talk about them in terms of water vapor measurements.  That didn’t seem right, even though the answers arrived at generally seemed to make sense.  Now I am doing the same calculations, focused as before on examining the temperature effects of rapid changes in greenhouse energy inputs, and getting the usual answers.  The only difference is that now the greenhouse effects are attributed exclusively to changes in PW measurements that are either known or subject to reasonably good estimates.

Now back to the original question, which is actually addressed to the science community at large, in very specific terms.  Is it even a legitimate question, or worthy of consideration?  If so, after taking a big leap forward, what if the best answer turns out to be ‘yes’?  What if PW, molecule for molecule, or weight for weight, really does exert greenhouse energy effects quite similar to those of water vapor alone?  The comparison does not need to be perfect, nor should this be expected, but what if it is so close, for practical purposes, that climate models would need to be adjusted in order to account for it?  To wit, PW quantities are not the same as water vapor quantities, and the factors that have control over the quantities of each are not the same. The implied changes from substitution would therefore be considerable, perhaps revolutionary, on a scale the dimensions of which are not yet knowable, yet these would be changes of a type that had to be dealt with for the same reasons that cloud cover particulars are currently being evaluated.

I am not ready to make any claims about how this effort would will turn out, but I do have a strong feeling that the question is important and should not be ignored. Do I have any evidence to back up this idea? Sure. I have been serving up illustrations in these letters almost every day since last April, and could show more of the same today. Do I have any standing for making such a request? Well—who else is out there doing analysis of the causation of almost every kind of air temperature anomaly that can be found on the daily maps? I am fascinated by this work, and can only wonder why other people are not doing it, or at least not saying anything if they are doing it. Why are there no trained climate scientists following this trail? Why just one old man, self-trained, using nothing more than a home computer?

Daily temperature anomalies are genuine natural phenomena.  Some are truly spectacular in scale.  On the upside, for example, there are a few every day that reach +20C and more.  Today I can see a few cold ones only a few degrees short of -20C. Every one of these, and everything in between, is in fact (I believe) determined by a specific set of positive and/or negative causation factors.  Those factors can all be found and evaluated, if one will take the time to root around and look for them.  Common stocks get analyzed every day for investment purposes in exactly the same open-ended way. What I have found when studying temperatures is that a measurable change in PW is involved as a cause of practically every anomaly, usually the dominating cause in cases of major anomalies.  I have even learned how to explain how it’s done, in ways that gain credibility by virtue of their extraordinary consistency.  These explanations are still evolving. They include mechanical features that have revolutionary implications of their own, relevant to how the fundamentals of climate science can be taught.  Climate forecasting might even benefit from future work aimed at acquiring a deeper understanding of how these features work and interact as circumstances change.

Carl

The images in today’s letter are all one day old. I saved them yesterday because the story they tell is so strangely interesting, knowing that by today it will have changed in some ways. The primary focus is on the truly peculiar shape of the jetstream-level air pressure configuration in the Northern Hemisphere, as mapped at the 500hPa level. This pattern of air pressure changes is considerably different from the pattern of high and low pressure changes at sea level, as commonly found elsewhere. The changeover is always completed at an altitude of less than 5000 to 6000 meters, or 3 to 3 1/2 miles—probably not very much less since I don’t recall ever hearing about jetstream winds being found at less than three miles high. Anyway, except for the zone of the tropical belt, the airspace above this level has a demonstrably different wind system from the space below and everything contained in that space (including airplanes) will be influenced accordingly. Keeping in mind the principle that every pattern of configuration completely governs the strength and location of all jetstream wind pathways, this peculiar pattern should pose no exception. Those winds, in turn, always have a profound influence on the behavior of any bodies of precipitable water (PW) that may have entered the airspace, which then respond by the way they influence the temperature of air at the surface below by virtue of their greenhouse effect, which can be considerable.

Jetstream winds always move counter-clockwise in the NH.  One major pathway always follows the outer fringe of the “green zone” of air pressure, as depicted, while a separate pathway follows the light blue line that fringes the blue zone.  Yesterday’s odd setup will obviously create some complications of a type we don’t usually see.  Let’s have a look, this time with a focus on the deep and narrow penetration of the green zone as it pokes its way past Alaska and the wider, block-shaped penetration that reaches over Greenland :

You can always figure out the location of green zone jet wind pathways just by looking at their isobars. In these two situations wind strength is getting all messed up, literally disappearing in the “outcrop” approaching Greenland. How should this picture affect the behavior of major PW concentrations that are actively engaged in both situations? One large stream has risen from Pacific waters, the other from waters in the Caribbean area of the Atlantic.  Considerable amounts of PW from both streams, after first being carried off by larger jetstream winds of a more regular type, have eventually found their way into these deviant sidetrack movements, as we see in this image: 

One of these heads straight north along the North American coast line, carried by a weakly-constructed jet. When that jet makes a sharp bend and heads south again practically all of the PW it has been carrying is ejected, right into the heart of the polar zone. Nothing unusual about that development. On the Atlantic side a substantial amount of PW has also escaped its jet carrier at a bending point and freely dispersed into a wide open space in the direction or Greenland. The only thing holding it back from still further progress is the square-shaped pathway holding a moderately strong jet on the fringe of the blue zone. This is how things can happen up there, and nobody would know about it without the amazing instruments we have invented. The resulting effect on surface air temperatures is just what one should expect under a proper understanding of greenhouse energy theory:

The warm track that is visible along the Pacific coastline, being over water, is not very prominent, but as soon as the PW remnants journeyed over naturally very dry land or ice their strength became amplified.  We then can see how the jet wind on its return journey south, once stripped of its cargo, left a trail of cold anomalies.  Curiously, as we see on the last chart, this trail is also marked by a virtually cloudless sky, putting an exclamation point on the lack of PW being carried.  On the Greenland side, a fairly heavy input of PW has certainly had considerable leverage over the normally very dry surface air, producing a major warm anomaly with readings of +20C or better in places.

Carl

Continental Asia has a great assortment of anomalies to work with today. We’re going to investigate the value of the more interesting ones by focusing on just three variables, each of which can create large differences at this time of year. Sometimes they add up and sometimes cancel each other out. The three are total precipitable water (TPW), snow cover and sea ice, all of them mapped in their current state. I have added a map of snow depth because sometimes it will add important clarity to otherwise ambiguous images of snow cover alone. All we are missing is accurate information about relevant baseline averages for these factors, but they can all be reasonably well estimated. (Thankfully, this is a matter of no concern when it comes to temperature anomalies.) Cloud cover and precipitation are not included on this list of factors because I think the albedo effect of cloud cover does not make much difference this far north at this time of year. I’ll mainly be showing the map images with only a few basic comments, and urge you to spend some time on your own making comparisons.

On this map we are seeing two large hotspots in the Arctic Ocean that require special attention, another in the area where southeast Siberia meets northeast China, and the one in the Himalaya mountain area north of India.  The very large region of cold anomalies can only have one explanation, a widespread relative shortage of TPW.  Such an assumption will be easy to accept when you see all the gray shading on this next map.  Remember that gray shading, maybe even on the dark side, is always just plain normal at this time of year for adjoining elevated locations and for the entire region farther to the north.

Now we’ll look at the Sea Ice/Snow Cover map. The absence of sea ice is a major factor for temperatures in several spots that are not especially large in size. A shortage or absence of snow cover is a factor applicable to an area of unusual size this year, possibly greater than the total area where snow has fallen and stayed in place. I think a normal year from a few decades back would have snow fully covering almost all of the ground that is presently dotted with little more than a few random freckles. Snow is an effective insulator, and holding back an extra 5C or so from radiation that could come out of the ground should not be surprising. Almost the entire Himalayan range may be affected in this way plus many parts of a wide swath from the mountains up to and including the southeastern corner of Siberia. Many of the warm anomalies in that region cannot be attributed to anything else when TPW readings are as low as what we’re seeing.

The Snow Depth map is especially useful for highlighting reasons for some of the smaller and relatively isolated warm anomalies that appear in numerous locations. Also, this map will always help in making judgments about relative importance whenever snow cover images of the thinner sort are showing.

The two major anomalies in the Arctic Ocean both display sea ice shortages plus high relative values of TPW. You may want to use magnification to pick out all the details of shapes and shadings. The eastern anomaly has a TPW reading no higher than 3kg, which is quite sufficient for additional warming of around 20C over normal. The actual temperature for this spot today on the Windy site is -16C, while a comparable area not far away is reporting -42C and lower. That area has a TPW reading of less than 1kg, probably closer to 500 grams. Both oceanic anomalies reflect the tail ends of high-altitude PW streams that have traveled thousands of miles from their sources, just like the many others we have watched in recent months but not quite as potent.

Carl

There is a major warm anomaly in the center of northern Africa that has been there for a number of days. We should take a close look at it and see what we can learn from the maps. These same maps will also have some other interesting things to report:

This anomaly, like the one we studied yesterday, can easily be attributed to the presence of an extraordinary amount of precipitable water (PW) in the atmosphere above.  The anomaly of 8 to 9C is large enough to imply close to a double in the region’s usual amount of total PW.  We have strong visualization to work with, and can quickly see that the difference between the brownish streak and nearby gray-tone areas will fit that requirement, e.g., about 16-17kg v. 7-9kg.  Today we are going to dig deeper into the origin of this PW display and look for detailed information about the pathway it is taking:

This is a generally hot and dry part of the world without many local sources of evaporation. Everything points to a part of the Atlantic that sits directly to the west. Also, the shape of the imagery on the PW map suggests the formation of a concentrated stream following evaporation, with particles traveling from west to east as they move far inland. We cannot really confirm any of this without consulting the animated TPW website, where details of every such stream are depicted in a continuous way over 5-day time periods—time enough to fully cover most of their lifespans. This review, at http://tropic.ssec.wisc.edu/real-time/mtpw2/product.php, needs to be done without any delay, and is not recordable in any way that I know of. One other thing we can do is to look at maps that can tell us whether conditions in the Atlantic are suitable for creating large amounts of evaporation and propelling it over the prescribed course. One such map, shown here, is useful because it reveals a well-placed area of clear sky not far from the equator where the water is very warm (not shown, but indicated on another map) and well-suited for an unobstructed sendoff:

Once the vapors have evaporated we need to know more about potential travel factors that can carry them for such a long distance over land.  Why this particular route?  Were there any travel aids available?  There is a good answer, and we’ll go directly to it.  This particular vapor, which may have originally headed more toward the north, is in all likelihood being quickly and completely swept up in the underbelly of a fairly swift jetstream wind that is moving straight across Africa, which we see on this map:

By studying these maps in combination it is possible to determine that the stream containing vapor—and/or any products of condensation—remains tied to this same jetstream wind over quite a long distance, probably across not just Africa but Arabia, India and beyond. Some amounts keep breaking off on sidetracks, but whatever remains continues to produce a trail of warm anomalies. One can even surmise that the mountains north of India have gotten a taste of it. What is otherwise interesting about the maps is that practically the entire parade continues with barely a trace of clouding and precipitation in the sky. How and when does the original vapor start condensing, and does it ever precipitate? It almost has to surrender in some way at some point, but any evidence is lost.

These same maps have another story to tell, one having a great deal of contrast, concerning the gigantic PW stream seen moving out of the central Atlantic in the direction of Europe.  This stream has also been picked up and carried off by a jetstream wind, this one more speedy than the other.  Clouding is plentiful and precipitation never stops, but the jetstream itself comes to an abrupt stop after making a sharp bend.  At that point all of the remaining PW spills out, scatters, and heads off in a number of different directions.  I think some of it drops down over North Africa and makes a contribution to the large anomaly we’ve been studying.  The rest mostly heads northward, continuing shows of rain, while maintaining a capability to produce warm anomalies of moderate strength in a number of places.  The polar zone looks like one destination.

Carl

I want to revisit the big North American anomaly today because it offers such a great illustration of the connection between Total Precipitable Water (TPW) and surface air temperature. This time I won’t even bother to do an analysis of where the TPW is coming from, or how quantities can be broken down into two uniquely separated strata. We’re just interested in the effect generated by the combined total. Surface air doesn’t appear to care at all about any of the nuances, but rather just the total, so why can’t we? Let’s assume for now the total is all that matters , but still save time for further investigation of those nuances in the future. So TPW will be treated monolithically as if it had all of the very same kinds of properties as any well-known greenhouse gas, other than being a whole lot more irregular with respect to amounts of everyday presence in the atmosphere. Plus it’s a whole lot stronger. There will also be a little surprise at the end of the letter. Now for the anomaly map:

This map looks a lot like yesterday’s map except that everything has shifted eastward by around a hundred miles.  We know why this movement occurs because we can see the same sort of thing happening every day on a universal scale when we study the animated website portraying the behavior of TPW streams. (http://tropic.ssec.wisc.edu/real-time/mtpw2/product.php).  There is a special greenhouse effect that comes and goes each day which surface air will respond to in full, with no second thought about origin. Also, be sure to note on the map how a cool down has continued to develop over Arctic Ocean, something we can hope is unstoppable for awhile.  Now for the TPW update:

What I like most about doing this particular map comparison starts with the visualization of the strong brown feature tilted downward across the center of the 48 states, surrounded by all sorts of gray stuff.  The brown part jumps out at us with a message—look at this same area on the anomaly map for a strong reading of the warm type. We saw it yesterday and we see it again today, perfectly well-matched.  We can even get the value readings and start to do some calculating about relationships.  Now you might ask, what about all the equally warm anomalies to the north where nothing on the TPW map is brown, just shades of gray?  No problem at all, except that the sharp visualization factor is missing.  We can still get good readings for TPW everywhere, and we know that it takes less and less TPW  presence in the atmosphere to cause any additional amount of surface warming as you proceed toward the north—where natural surface conditions keep getting drier and drier.  This view may be unusual, but I am convinced that any double of TPW value for a given location on a given day of the year, no matter from what level, provides enough energy for an immediate extra 10C in surface air temperature.  The greenhouse effect of TPW is the only thing responsible, and it is inescapable.  Anyone who does the study should have no trouble seeing it, every day of the year, in all places outside of the tropical belt.

Now for the little surprise.  On the above map of air temperature anomaly, out in the Atlantic Ocean and off the coast of Newfoundland, you can see a rather large blob of warm anomaly that looks like it runs as high as 6 or 7C in the central part.  This is a most uncommon phenomenon for air over a mid-ocean region, and it has nothing to do with TPW readings.  This one is all about water temperature.  As a general rule, surface air temperatures are closely tied to corresponding surface water temperatures, with the latter being dominant, and having its own set of reasons. This holds true for anomalies as well as everything else.  On this next map of sea surface anomalies you can see where the effect is coming from—water temperature anomalies that range in spots all the way up to the top of the scale, which is 6C.  It is a reality, it’s extreme, and it’s probably not a good thing.  That’s all I can say.

Carl

The longstanding anomaly in the Arctic Ocean is finally shutting down, following a steady streak of high daily numbers that began on September 24.  My take is that the streak was created by constant inputs of relatively high volumes of high-altitude precipitable water (HAPW) that were entering the polar zone via concentrated streams. The streams would have originated as evaporation from various warm ocean waters on the northern margin of Earth’s tropical belt.  My letters have preserved a modest record of how many these streams functioned from start to finish, with everything in a constant state of change.  Remnant parts of each stream would find an entry point into the zone, ending with dispersal and total disintegration in just a day or two.  What makes the situation so interesting is that for every stream that died a new one was able to move in through its own entry point and replace the warming effect of the other.  What has changed is that new streams are no longer getting that opportunity because of the seasonal strengthening of jetstream winds that are able to block their movement.  The effectiveness of these winds has been late to develop this year.

The streams that carry HAPW still exist, and are still generally heading northward, but they just don”t travel as far before being blocked off. They still provide the same high volumes of sources of greenhouse-type energy, ending with the same kind of dispersal, and are causing surfaces below to become warmer. One primary thing that has changed, for now anyway, is the location of the warm anomalies. The Northern Hemisphere as a whole has warmed up over the baseline average today by a reported 1.3C degrees, which is entirely the same as it has been in recent weeks. One particular continent, North America, is getting more than its customary share of this warming power, as we can see on this map. The map also reveals the extensive temperature reduction inside the Arctic circle as a whole, as well as across much of its ocean water:

The entire north-center of the continent is feeling the brunt of this shift of warming power, with wide-ranging anomalies in the 10C area. Northern Manitoba is the standout with a solid +20 and probably a little more in spots. We now need to open the TPW map to see if it reveals how the bulk of this warming is being produced. I am changing the angle of perspective in order to provide the best overall showing of the selected stream flows:

The strongest stream is clearly the one that evaporated from waters west of Hawaii and headed straight for the Pacific Northwest.  It appears to be staying quite intact until reaching its most northern extent in the Manitoba area, where it finally disperses.  Manitoba does not experience any such kind of event very often, hence the large anomaly.  The TPW reading of about 13kg that you can see in this location would probably be no more than 3kg on a normal day at this time of year.  Getting two doubles is a rare honor, and the reward of +20C (36F) or more for a day or two is surely being locally welcomed.  Personally, I welcome the fact that I know how to explain where all that heat is coming from in a reasonable way, and I would be glad to welcome everyone else, including climate science professionals, into the learning of these same well-kept secrets. So—when are you science folks going to get interested? When you do get interested I hope you will quickly send a notice to the University of Maine requesting them to create a map that displays either average TPW readings for each day of the year, tied to an accessible and appropriate baseline period, or else actual TPW anomalies from those averages to each current day.  Either one of these would remove a lot of time wasted on improvisation and low-quality guesswork.  Would the result be of benefit to science?  Who wants to say no?  In any case, there is an easy way to find out. 

I should mention that there are two more HAPW streams currently affecting North American temperatures, both having sources in waters of the Pacific, which are one to each side of the large major. Their impacts are diversified and real, but less strong, less dramatic. One further note—I have checked for cloud cover and snow cover in Manitoba, using the regular map sources, and found them both to be on the heavy side, with more snow coming down. Neither of these factors could be adding anything to the observed warm anomaly.

Carl

I am opening three maps today with two purposes in mind. Two of the maps provide a countless number of illustrations about the close relationship between (Total) Precipitable Water (TPW) and air temperature anomalies on this one day. I have added the third map because it contains a striking illustration related to two other points of interest that can both use some clarification. Cloud cover is a key part of both points. For one, any combination of cloud cover and sunshine is known to have a cooling effect at the surface, simply because a portion of the incoming solar energy will be reflected back to space before it ever reaches the surface. This effect has peaks and valleys, depending on numerous factors including the angle of sunlight and its hours of duration. The illustration I have today suggests that at this time of year, even in the mid-latitudes, the realized amount of cooling from this effect may tend to be of little significance. To that end, focus your attention on the shape of the long and large band of relatively clear sky in the top half of this map:

Next, compare that shape and its position on the map with the shape and position of the long and large cold anomaly that stands out so clearly on this next map.  Then ask yourself, if clouds were to move into this region and start blocking off sunlight the temperature should just become colder yet, shouldn’t it?  Maybe so, if those clouds were only condensed from existing water vapor, but what if they moved in from the outside? Then everything changes. Or what if, to begin with, there was only a little water vapor on hand to make condensing feasible? Moreover, what about the many nearby regions on all sides that are well clouded over and even precipitating, yet showing up with rather significant warm anomalies—despite no help from the sun?  Take a look:

The best answer I can give is that maybe there is something else, in this kind of situation, that has a decisively more significant effect of temperature anomalies than any amount of cloud cover. Perhaps I can even present vivid imagery that helps to make the point.  Just look for the long and large area of relatively low level of TPW that coincides with the shape and position of the two clear-air and cold-anomaly images we’ve just viewed, best delineated on the western end but still complete via darker shading in the gray part:

The relative absence of PW certainly provides a good reason for the cold anomaly and also helps to explain why the skies are clear, assuming only that clouds have had no reason to form in this area. A reminder may be useful here that apparently low levels of TPW can become associated with warm air anomalies whenever the situation moves northward, as we see in abundance in these images. Less and less additional PW is needed to warm things up by a given amount when the normal amount of TPW over the surface keeps declining for entirely natural geographical reasons.

Clouds may or may not be present as part of a TPW product mix. Another point of interest I have been wondering about is whether this factor alone makes any difference in the greenhouse energy effect of a given weight of TPW above a given surface, all else being equal. It is impossible to get an exact answer without having an abundance of now-missing data, but it never hurts to look for a better understanding. The above two maps of TPW and anomalies provide many opportunities to prove how powerful the relative effect of TPW on temperature can be. Whenever you are checking out an example it is always a good idea to hop over to the third map to see what the cloud situation is for that area, and whether or not it may be making a difference in the result.

Carl

You may remember the bitter cold snap that struck North America just a short time ago.  Here is a quote from my letter on Oct. 27 (CL#1796):  “I can see anomalies of minus 20C (-36F) in six different states, from Texas to Minnesota.  For any piece of land in a temperature zone that number is practically unheard of, at any time of year.”  I showed an image of this very rare event, which unfortunately has not been preserved because of technical difficulties that are interfering.  (You can still see the right map, but only one that is constantly updated to the present day.)  In addition to that, I failed to do as much analysis as I could have, but vaguely do remember seeing total precipitable water (TPW) readings as low as 3kg for the coldest locations on that day.  I have vowed never to miss another chance to fully analyze an extreme cold situation like that one, especially one so far away from either polar region, were it to come about.  Well, today we’ve got one, at about the same latitude as Minnesota, though not quite as deeply cold.  You can see it on this map in Kazahkstan, best doing so by adding magnification.and getting the right angle of sight, where I am getting a reading from shades that look like -16C in spots:  

Now we’ll do the same thing with the (Total) Precipitable Water (TPW) map, where the readings that match the location of the cold anomaly are truly unusual lows, relative to the geography, of just 3 and 2kg. On the straight temperature chart (not shown) I can see a daily average reading of -22C, or -8F. This can be compared with a current average for the whole country, found elsewhere, which is close to 0C for this day. The area under scrutiny is not especially elevated, and the small amount of snow on the ground is probably near normal. The cloud map, interestingly enough, shows a clear sky over the coldest spots and light clouds close by where things are a bit warmer. (This map can be seen at the bottom of the letter.)

What would the average TPW reading for this area have been during a baseline period three decades old? Or, for that matter, even the current average would do just fine since the average temperature is only up a little more than one degree in that time span. There is no data available, but I think 5kg, maybe 6, would be a reasonable number, arrived at by making comparisons with other locations that are roughly similar in geography but have different current readings for both anomaly and TPW. Using the 10C per double rule, but now in reverse, a move from 5-6kg down to 2kg, or possibly even a bit less, is fully enough to impose a temperature difference of -16C. How many other ways—beside an absence of TPW—can you think of that would remove so much normal heating power from a sizeable area with just one swift kick? A few days from now all that heating energy could very well be back in place, and perhaps even more. I think all it would take would be a considerably larger dose of high-altitude PW cruising by in an overhead stream. This stuff is constantly shifting gears, higher and lower, day after day, everywhere in the mid to upper latitudes. You can watch it happen at the http://tropic.ssec.wisc.edu/real-time/mtpw2/product.php animated website.

What would 10kg of TPW do for Kazakhstan temperatures right now? The answer is surprisingly close. Looking at the map again, you will see an area immediately south of the cold anomaly, still in Kazakhstan, where a stream of PW has broken through and raised the local TPW to as much as 11kg in spots.  On the anomaly map, when you match things up, you can see temperature anomalies in the area ranging from zero to plus one.  I think the number could be even higher were it not for the fact that this spot has an overcast of clouds heavy enough to produce snowfall, implying a sharp dropoff in solar energy during daylight hours.  Here is the map that has the story:

Carl