Art Rangno – Page 77

Bad things happen to good models

I got pretty worked up yesterday about the best weather maps I have ever seen for Arizona, ones produced by our best numerical forecast model, the WRF-GFS, one that had so much rain here at the end of the month, based on billions and billions of calculations. The rain in that model was due to a former hurricane (one that has not yet formed, but like me, is still merely a depressed area–in the eastern Pacific). It subsequently develops in the model into a strong tropical storm and its remains were forecast to track right into Catalina and SE Arizona and produce as much as 1.5 to 2 inches of rain in 12 h. I loved that forecast map so much! Thinking about having it framed.

And, rain in various amounts, was forecast here for a couple of model runs, not just one, before going away lately.

This is what weatherfolk deal with all the time, these model vagaries in the longer forecast range of 7-15 days. In the two maps below, one from yesterday’s blog, and the one to the right of that, the model run rain map from last night’s run for the SAME time and day, the afternoon of Friday, September 28th:

Well, that “solution” is gone now (see map at right), the one having no rain at all in AZ for the same time as the flood shown in the map at left. That remnant of a tropical storm off Baja shown on the right, just sits, spins lethargically, and dies, its moisture staying to the south of AZ now. I guess Wildcat fans will be happy that the football game on the 29th here won’t be played in the mud with some leftover rain falling.

This rain disappearance was not surprising, I guess, when “we” looked at the NOAA spaghetti plots and saw that the confidence level had to be low because of all the vagaries produced by “perturbing” the model with a little bad data at the outset of its run.

If I was a weather presenter, my 15th day would be stacked with the different forecasts produced by the model for that same day as it got closer in real time. This would be the purpose of demonstrating to my TEEVEE watchers that the forecasts for the SAME day, such as September 28th, are changing drastically: “Sunny!” “Rainy, 2 inches!” “Partly cloudy!” “Rainy, a quarter of an inch! “Sunny!” “I don’t have a clue!”–the correct answer for display.

Don’t give up all hope for rain here, though, in the coming two weeks.

First, the unpredictablility of our current situation means that the models could calculate a rainy “solution” for us at the end of the month yet. Second, another hurricane/topical storm comes marching up the coast of Baja at the end of the first week in October, heading in the direction of AZ. So, all the rain potential here in our Arizona fall is not lost yet.

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BTW, the uncertainty here was NOT the case for the weather back East in the spaghetti plots, where a cold regime has been solidly predicted there with considerable confidence in the 7-15 day range (forecast contours lines were pretty bunched up in that region AFTER the errors were introduced). Low temperature records are already falling in a few locations, and more will fall over the next two weeks.

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Clouds?

Nice pancake clouds yesterday, Stratocumulus clouds resulting from the spreading out of shallow Cumulus clouds. Here’s an example over the Cat Mountains. Tops ran about -10 C, maybe -11 C. Thought I saw a very, very fine ice veil between some clouds coming off the mountains, but, it could have been an aerosol haze. Concentrations of ice would have been VERY low, anyway, less than 1 per liter of air, in this marginal for ice-formation day.

This morning’s TUS sounding indicates a cooling at cloud top to -14 C or so. This will mean that you should see some virga around today in somewhat fatter clouds. Yay! Virga. Egad! I just looked out the window here at first light (5:50 AM), and there it is, that virga! There’ll be a real pretty sunrise as a result

The End.

“Unlikely” rain still in models for end of month, except there’s more of it now

Just yesterday I pooh-poohed the chance of rain toward the end of the month based on spaghetti, the NOAA spaghetti. In fact, I was afraid to be too happy yesterday when I saw that rain was foretold here after the long dry spell we are now in. So I looked around for some reasons to mash down my happiness, happiness that might well be mashed anyway by reality when the end of the month got here. Maybe, in the event of getting too happy about foretold rain that didn’t materialize again, and then being let down one more time, I wouldn’t feel like blogging anymore, and both of you might disappointed in that turn of events.

But this morning I looked again at the rain prediction map for the end of the month, based on our best model, the US WRF-GFS. As if to personally humiliate me, there was even MORE rain for AZ, and the very epicenter of that rain was forecast to fall on my house on the 28th of September! That model KNEW I had said rain here was unlikely (though not impossible).

Take a look at the small purple blob in the map below from the WRF-GFS model indicating 1.50 to 2 inches on top of Catalina that day! Imagine! What a wonderful rain that would be! The whole wonderful sequence is here. And below the rain map is the map for the winds and contours the day before the storm hits. This is the BEST weather map I have ever seen for AZ! Look at that tropical storm center over Hermosillo. Its incredible, still amost a hurricane at the 500 mb level (around 18,000 feet). Never seen one like this before, and it couldn’t be a better map if I drew it myself!

OK, so we got us a possible great storm in the works.

But, if you’re like me, you should keep your rainy hopes in control. Its still an unlikely event, even with the global data taken last evening at 5 PM AST, crunched into millions/billions of calculations, has come out with this “solution.” It won’t take much for this to disappear entirely with the vagaries in solutions shown in yesterday’s spaghetti plot.

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In addition to all of this excitement, yesterday’s sunset, featuring Altocumulus clouds with no ice virga. They were likely less than 500 feet thick. Tops were about -9 C (18 F) at 17,000 feet MSL, bases about -7 C (21 F). Such thin clouds, and those in a hazy layer like yesterday’s, have higher concentrations of cloud drops in them, causing them to be quite small, and in that attribute, resistant to freezing. The larger the drops in the clouds, the higher the temperatures in which ice forms, as a rule.

Also, at high levels, there is likely to be a dearth of those special aerosol particles we call ice nuclei. The most active natural ones come from soil particles. So the higher a cloud, the less likely will be a soil particle. There is some evidence that desert dust is an especially good ice nuclei.

So, it is not unusual to see Altocumulus layer clouds sit at low temperatures (-10 to -20 C) and not produce ice (which you would see as virga trailing down from them). There was a bit of virga visible in a spot or two in this morning’s Altocumulus clouds, ones that were a tad colder at top, at -10 to -11 C.

Will be polishing raingage surfaces every day now so I will be ready.

The End.

Looking for rain in all the model places

The scattered showers foretold for late Sunday and Monday have evaporated from the model runs now, and so have been looking around for a computer model run SOMEWHERE that had rain foretold for us. Once again, I could find a rain prediction for us near the end of a 15 day model prediction period. If we got all the rain the models predict for us in the 10-15 day period, year after year as they seemingly do, we’d all be growing bananas and coffee.

Below is a model prediction that was, in a sense, painful to see, and then de-construct, in a manner of speaking. A tropical storm/hurricane forms in the model, one that hasn’t even formed in real life yet (that’s how great our models are)! Eventually it races up the Baja California coast then turns toward Tucson, even strengthening that bit as it moves over the Sea of Cortez/Gulf of California. The map below is valid for 5 PM AST, Sept. 29th.

But the planets of the upper level steering flow are not aligned correctly; that storm takes a sudden right turn into Hermosillo and never makes it to AZ. Dud number one last night’s in the model run, except maybe they need some rain around Hermosillo so its not a dud for them. You can see this sequence here.

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Then, right after this missed tropical storm, a trough from the lower latitudes, rich with moisture, comes barreling across the Southwest with major rains indicated in AZ two days later, in early October. Great!

Except that this situation must be de-constructed by checking out the NOAA spaghetti factory outputs to see if the indication of a trough here in early October is a likely dud as well. I really hate checking, though, when the model run shows something I want to have happen.

The first map below shows the postiion of an upper level trough at 500 millibars as it was projected for October 2nd at 5 PM AST. Looks great over AZ doesn’t? Below this map is the map of the rain in the 12 hour period prior to the same time as the upper air map, denoted by the green area (of course). Bring it on, baby!

Now, let’s check….as we must do as scientists and junior cloud mavens. We can’t just take things at face value that far in advance, as you already know.

Below that rain map is the “spaghetti” plot resulting from some bad starting data which is deliberately input into the model as it begins its calculations. The model is run again and again with different bad data points at the outset several times over. These bad data points produce slightly different forecasts over time, forecasts of jet streams and such that get more different as time marches on in the model run. Often though, a weather system is so strong, so powerful, that these slight errors that are put into the model make little difference, even 10-15 days out. Other times, slight errors make huge differences.

Instead of, “garbage in, garbage out”, we get some incredibly important information about our model runs doing this, though it seems counterintuitive. Where the many lines from each model run are in chaos, that is, all over the place, forget whatever was predicted for that region; its very uncertain, “garbagy.”

But if those lines cluster your area, you’re real forecast, the single run produced by the model from, say, as in this case, from last night’s data for October 2nd, is much more likely to happen.

With these thoughts in mind, I then looked at the NOAA NWS spaghetti plots that tell us whether the ACTUAL model run showing a nice trough right over AZ is an outlier (read, is a “phony”). When I looked at the spaghetti plot, the wild display of blue contour lines in the eastern Pacfic and western US told me that last night’s run, with that great trough was a “phony”, an outlier model run, and that outlier run is indicated by the yellow line. You can see how that yellow line, dipping into AZ, is NOT accompanied by a bunch of blue lines also dipping to the south in this direction. Instead, they’re all over the eastern Pac and West Coast. So, no strong signal for a good rain on October 2nd, dang.

After this great explanation (hah!) you, too, will instantly see that the two maps produced from last night’s model run and shown here are not very likely to be observed, but then’s there’s probably going to be a college football game on TEEVEE somewhere anyway, so who care’s?! :}

What can you do with this information? Let’s say you’re watching TEEVEE again, and your favorite weather presenter comes on with his long range forecast and has rain for October 2nd. You can then turn to your TEEVEE viewing mates and inform them, with great confidence, “That’s not gonna happen!” They’ll be quite amazed that YOU could critique an honest-to-goodness, highly paid weather presenter, one that has fun everyday predicting weather and gets a huge salary for having that fun while I have fun but get nothing. Your friends might ask how you know that rain won’t happen. You answer, “I checked the spaghetti plots. It ain’t gonna happen. Let’s watch some fubball.”

Of course, that rain prediction could STILL happen, but the chances are very small.

The sad end.

¹though the blue lines are not exactly the same contour height level)

What being taller and darker can do for Cumulus cloud formation

Yesterday we had a great example of what that Mexican Cumulus cloud factory, the Pinacate Reserve north of Puerto Penasco (Rocky Point) can do. This darkened spot on the earth, mountainous with volcanic craters and lava fields to as high as 3,900 feet, is easily visible in satellite images. It often launches its own Cumulus field, as it did spectacularly yesterday. This darkened spot is likely much warmer than the surrounding desert.

Some of the Cumulus reached the Cumulonimbus stage, producing rain in that area and a bit downwind. There were no other Cumulonimbus clouds in the vicinity, at least when the Reserve ones first formed, so this cloud factory really stood out in the satellite imagery. I was thinking it might be a place you’d like to visit when on a cloud vacation, never mind all the strange and interesting critters, craters, and lava rocks there. (Hey, its so moonlike there NASA sent astronuts there to be trained for moon landings in 1965-1970!)

Here’s what the Pinacate Reserve looks like in a “close up” from the Landsat satellite:

Below the nice Landsat image is what it did to the cloud field yesterday in a sequence of satellite images from yesterday afternoon from the U of AZ.

annotated 1945 Sept 17th — 12:45 PM. A cluster of Cumulus clouds has already formed over the dark Pinacate Reserve (arrow).

2100 sept 17th — 2:00 PM. A large anvil cloud from a Cumulonimbus is clearly present, extending eastward from the Reserve.

2245 sept 17th — 3:45 PM. Still puffin’. Wonder if you can live there?

2315 sept 17th — 4:15 PM. Showing signs of decay, but is still “trying.”

The End.

Return of the “green pixies”

Been kind of sad since the “cold turkey” end of the summer rain season about a week ago, grasses browning now, pig weed wilting.

SONY DSC — 8:24 AM Saturday, Sept 15th, fubball day, near the back gate of Cat State Park.

Trying to “man up” today. Got happier just now when I saw that the “WRF-‘GOOFUS'” model returned “green pixies” (aka, green pixels indicating areas of rain) to Arizona beginning next Sunday. They stay around for a couple of days, too.

Now, in a disclosure of some kind, I have to tell you that this run from last night’s global data taken at 11 PM, is one of the wetter model indications from the past few days for rain in AZ, Sunday through Tuesday. Some horrible model runs have had NO RAIN whatsoever around these parts.

Here is last night’s model run as rendered by IPS MeteoStar, valid for 11 AM Tuesday. That green area below is for the rain the model thinks has fallen in the prior 12 h (from 11 PM Monday night, AST).

Seeing green in Arizona! Think GREEN!

Yesterday’s strange brew; partly cloudy, a few light morning rain showers, and, uh, oh, yeah, chance of a tornado

This is NOT about Cream, the Eric Clapton-led group who did the song, Strange Brew which I allude to in the title, though I did like that song at the time. (The link is hilarious. What were people thinking, dressing like that? And that hair on the expressionless Clapton!)

Yesterday was an interesting day with some gorgeous clouds, some light rainshowers and a tornado–well, not quite–but almost. A long funnel cloud appeared and re-appeared three times in succession over there by the Tortolita Mountains. Since this is the internet and you might not believe me, here is the proof in these photos taken in mid-morning:

Less sensational, erudite part of today’s yesterday’s rehash

Yesterday we had clouds developing rain by the “warm rain process”; light rain showers that fell from clouds with no ice, except maybe for one maybe that did appear to get a little ice in its top.

The formation of “warm rain”, something that occurs, say, in Hawaii all the time, and along the coasts of the continents, RARELY occurs in Arizona. Cloud bases have to be particularly warm (“check”, 15-17 C, around 60 F) in the morning hours yesterday), the air relatively “clean”, that is, free of much air pollution (“check”, due to rain lately), and perhaps even more importantly, updrafts that at the bottom of the cloud that relatively sluggish (check, weak updrafts only activate the biggest, best cloud condensation nuclei, insuring few and larger drops. I think that was a real contributor yesterday morning). Rarely are our high Cumulus cloud bases warmer than 10 C (49 F).

The last two factors, clean air, weak updrafts at cloud base, mean that the droplet concentrations in the clouds will be low. Low droplet concentrations mean that each itty bitty cloud droplet will carry more water, be larger in size than a cloud with high droplet concentrations in which the condensed water spread on many, many more drops that HAVE to be smaller.

“So whut?”, you say.

Well, when cloud droplets reach sizes between 30-40 microns in diameter, HUGE for drops formed by condensation alone, something rare here, they can bump into each other without bouncing off one another like ping pong balls, but can collide and stay together as one much larger drop (remember Hocking 1959? The reprise, Hocking and Jonas 1970?). Remember, too, that cloud droplets smaller than 30 or so microns have hardly any fall speeds and so those drops just hang around up there not doing anything but trying not to evaporate (“die”).

That larger drop that results from coalescence, then falls much faster, bumps into more of those larger in much more violent collisions, cloud drops and soon is a billion times bigger than a cloud drop. Drizzle, fine drops of thick, misty rain that almost floats in the air, but drifts toward the ground at 1-2 meters per second , about like a walking speed, from Stratus or Stratocumulus clouds is always formed by this process. This in turn tells you something about the drops in the clouds overhead. Tell your friends.

Remember that rain CANNOT form through condensation of water on nuclei alone! Your local weather presenter might assert this unless he/she is quite good and really knows stuff. There HAS to be ice, OR, collisions with coalescence. Sometimes ice AND collisions with coalescence are happening in the same cloud, ones with warm bases but also having high tops, ones above the -5 C, 23 F) level in the atmosphere.

Yesterday, nearly all of our clouds that sprinkled in the morning (a trace here) a bit did not reach above the ice-forming level of -5 C, and certainly, in the opinion-assessment of this eyeball, did not reach the -10 C (14 F) level.

Here is the one top that appeared to have ice in it. Can you find it without an arrow? That would be great, quite an advance for you, since it is pretty hard to see. First the pretty sky with two main clouds, then a close up:

Extra credit question (answer upside down at bottom of page. Note: it won’t make any difference):

Next, if that was ice in that cloud top, and it was indeed warmer than -10 C, 23 F) what would the ice crystals look like?

Congratulations! If you said “rod-like”, or specifically, “needles” and “sheaths” you have won a copy of the Magono and Lee 1966 classic booklet naming ice crystals!

upside down 06022225_73 — Rimed needles and/or sheaths (the latter, tube-like crystals, hollow inside) ones that collected water drops on the way down that then froze on them) . These are the ones that make it to the ground because after awhile, they become “graupel” or soft hail, roundish little snowballs in Cumulus and Cumulonimbus clouds.Today?

Today?

AZ mod here has a surprising chance of showers late in the afternoon here. Did not expect that. Fingers crossed for ONE MORE DAY!

The End.

Saying goodbye to green

Might get a shower today, likely our last day for a summer one, one spawned by all that residual tropical humidity we still have today in our lowest layers. Don’t really have a great chance for rain today, and the whole rest of the month looks dry, but you might see a shaft somewhere off in the distance. That would be nice.

Then it gradually dries out more and more in the days ahead, and, without the high humidities we’ve been immersed in for some months now, we’ll have to suffer through cooler nights, even a cool daytime snap is foretold in the models around the 20th.

Kind of sad when you think about it, because all that green we have been enjoying with our bountiful summer rains (8.91 inches here since July 1st), will be turning brown. Makes me think of that California song that was so popular some decades ago, “All the leaves are gray, and the sky is brown, I went walking for awhile on a winter’s day…”, etc. etc., the song referring to the gray coating of smog on the leaves that fall off trees there.

Here is the radar-derived rain report for the nation for the past 90 days, pretty much mid-June through mid-September (June 11 to September 11). Except where blocked by mountains, radar-derived rainfall amounts are really quite good. Check out those 8-15 inches blobs in southeast Arizona, and along the Mogollon Rim! Cool. What’s best about this period is that it took a huge bite out of some of the nation’s worst droughty areas during this spell, here in AZ, mountains of CO, KS, the Southeast. You can go here to create your own maps of rain. Below that is the AZ radar rain map from Intellicast for just the past WEEK. Its amazing. Check out those 4-8 inches (!) blobs in the south part of the State.

I think I will go walking in the desert this week and say goodbye to all that green because in a couple of weeks a lot of it, our grasses and remaining wildflowers, will be as dry and dead as Mars.

In the meantime, a reprise of yesterday’s clouds in the usual “cloud diary”; the light rain that produced 0.15 inches, somewhat disappointing. No thunder, either. Here are some of the best scenes, to me, anyway:

Will be hanging clothes up to dry in the house for extra humidity until July 2013 I suppose.

The End.

Day of early and late storms

First, the rain report: 1.73 inches on Samaniego Ridge in the 24 h ending at 3 AM this morning; 0.42 inches here! Fantastic. We’ll keep those watery, glistening rocks on the sides of the Catalinas for a few more days. How nice is that for mid-September? Some rain 24 h totals til 3 AM, catches the early yesterday storm period from some of the Pima County ALERT rain gages (a bit chopped up, sorry):

Today? Lots of incoming stuff, should be another day of major rains! (Maybe our last of the summer season. Enjoy.)

Reviewing yesterday…..

Looks like afternoon but its not; yesterday morning just after dawn:

Later that afternoon, after the morning Altocumulus clouds thinned and skies became sunny, there was explosive cloud growth over the Catalinas as the temperature recovered from our pre-dawn rains and clouds. Below, a few shots, the first three showing the transition from Cumulus congestus clouds lacking in ?????? (Answer: ice), to ones just starting to show ice in their tops (which means snow and then rain formation).

Now I am going to transition to tiny thumbnails, so you’ll have to work harder to see what I am talking about. But if you work hard, you might remember it better. Also, to help you, I have added an arrow in one shot, really going that extra mile for you today since usually I am too lazy to do that.

The Cumulus congestus clouds you see in the first couple of photos, though quite pretty, are oriented ALONG the Catalinas, not trailing over us from Mt. Ms. Lemmon. This tells you that should rain develop in these clouds over the Catalinas later on will stay ALONG the Catalinas, and not dribble over this way as it often does. That means incoming storms for us here in Catalina will be to the south, toward Pusch Ridge. Still pretty much the same today, except a bit more toward the right of Pusch Ridge, and toward Twin Peaks.

Below, another example of a cloud photo diary, pretty much like the one you should be keeping:

Loudness

This is not a tome about Spinal Tap….(clips here in case you forgot) that legendary, well, mythical, really, band described as “one of England’s loudest.”

If you thought the thunder was exceptionally loud yesterday morning during our “thunderrain”, even for strikes as far as a mile or two so away, as the writer did, it probably was. Sound travels best and away when the atmosphere drops in temperature rapidly as you go up, as it normally does on an Arizona afternoon.

But in yesterday morning’s very-unusual- for-us thunder before 8 AM LST, the temperature did NOT drop very rapidly as one climbed higher above the ground for the first couple of thousand feet. See arrow showing this layer above the ground in the sounding shown below. Under these conditions, the explosions produced by cloud-to-ground lightning, do not travel upward and away so well as they would with a sharp drop in temperature with height, as we have in the afternoons, and so what we hear is incredibly LOUD thunder under these conditions. Yesterday morning’s thunderstorm, no doubt to the glee of remaining Spinal Tap band members, was one of Arizona’s loudest it seemed to me.

This morning we have had another thunderstorm THIS MORNING, astonishingly unusual to have two morning thunderrains in a row, and strikes were again loud. The Tucson sounding this morning is very similar to yesterday’s; this time with an isothermal layer (temperature stays the same as you go up), something that would help trap the sound even better. However, it is not quite as deep, and that, too, would play a role.

Note: lived a couple of miles from I-5 in Seattle. That freeway was “closer” on morning’s with an inversion (say, after a clear sky night, quite unusual in Seattle, of course) and “farther away” without one, say when it was cloudy all night, and no inversion formed.

From the U of WY Cowboys, yesterday’s 5 AM Tucson sounding, followed by this morning’s:

The rain and cloud report: 0.45 inches here in the past 24 h! Excellent! Fell from these kinds of clouds::::: (I’ve got too many colons already; may as well add a few more for emphasis that there is supposed to be a pause for some kind of surprise or something, anyway that comes next. Besides, as many (“many”, hah!) of you have probably noted, I am a cloud maven, not a language maven.

Here is the surprise, one that I did not even know about until I uploaded the photo below::::::

Today?

Just eye-balling the maps and clouds, SOP forecast, looks like more thunderrain is in the bag today. Great!

Check with Bob and the NWS for a real good forecast… I have to go out and VIEW clouds now!

The End

So big, so little; in potential to realization

The U of AZ models got pretty excited about yesterday’s rain potential, even the WRF-GFS run AFTER the one I looked at and got me excited about yesterday’s rain potential. The model one that followed the one I saw when posting yesterday’s blog, one that comes out around mid-morning based on 5 AM data, also had a big rain day in these parts. (Sometimes the two runs don’t agree so well, so when they did, it seemed like a “done deal.”) Take a look, for example, at the total rain predicted in that later model run that came out yesterday morning, and take a look at what it thought Mt. Lemmon, would receive in the 24 h ending at midnight last night in this pdf:

U of AZ WRF Precip

Yep, 3-4 inches (!) was to have fallen from the skies on Ms. Lemmon in the 24 h ending at midnight last night. You can also see that we here in Catalina were supposed to see at least half an inch (that greenish area to the west of the orangy area). We got 0.14 inches. Better than zero, though.

Pima County ALERT rain amounts?

Catalina mountains max: 0.55 inches, at White Tail, near Palisades Ranger Station (on the highway to Mt. Lemmon).

Probably as much as half an inch fell “over there” under this sudden late afternoon thunderstorm by Samaniego Ridge shown in the photos below.

Two places, though, one in the Rincons, and once again over in Avra Valley, did get drenched with more than 2 inches yesterday, so large amounts did fall in some areas. Very appropriate for the really warm cloud bases and humidity we have these days.

Today?

That late night model run (based on 11 PM data) has another active day today, though not as active as yesterday. The model thinks showers will roll off the Cat Mountains this morning. Not so sure about that, but surely, there will be some giant clouds around and some tremendous falls of rain here and there with the humidity we have. 69 F dewpoint here now (5 AM) in Catalina. Enjoy, as we know these spectacular rain days are numbered, and sooner or later, the westerlies will creep down here and wash all this humidity away with dry Pacific air, and we’ll start to feel those cooler mornings associated with drier air overhead, that dry air that lets all that night warmth escape into space.

GW moisture factoid

One possible cause about why global warming has pretty much halted over the past 10-15 years (well, up to 2010, anyway, when this paper I am going to mention was published), was that the moisture in the stratosphere (the layer above where clouds and precip form) had declined over the period when the temperature stopped rising. With less moisture up in the stratosphere, more heat was escaping into space from the earth since water vapor is the biggest greenhouse gas of all, and when it changes a little, a lot happens to the radiation characteristics of the earth. This decrease in water vapor “topside” since the late 1990s was enough, it was calculated, to offset the effects of increasing anthropogenic greenhouse gases since then. Whether such a drying will continue, or why it happened, is not known.

This finding was from Susan Solomon’s group, work that appeared in the illustrious journal, Science. Solomon is the scientist that did so much work on explaining the ozone hole in the 1980s.