A Tropical Oddity

Guest Post by Willis Eschenbach

I wanted to bring you up to date on my current meanderings in the TAO buoy data that I investigated previously in a post called “Cloud Radiation Forcing in the TAO Dataset“. In my peripatetic inquiries into all things that are ooh, shiny, I ran across a curiosity. First, a very small bit of backstory.

Figure 1. Location of the buoy (red square) which recorded the data used in this study. Solid blue squares show which of all the buoys have the two-minute data. DATA SOURCE

The TAO buoys are strung out across the tropical Pacific, recording a variety of surface and subsurface data. The data I’m looking at now include the solar radiation. From the radiation, it’s possible to tell when the skies are clear and when they are overcast. I wanted to understand the effects of the clouds. So I needed to be able to identify the clear-sky observations, and reliably separate them from the observations made when the sky was overcast. I thought folks might be interested in how I went about doing that.

First, as usual, I eyeballed the data. Figure 2 shows a time slice of the entire dataset for downwelling solar radiation, which covers over 2,000 days at two-minute intervals, or about a million and a half observations. This particular time slice shows the downwelling radiation at local noon for each day of record. I looked at a bunch of the slices, from morning and evening, all times of day, so I could understand what’s going on.

tao buoy 0n165e downwelling solar vs timeFigure 2. Data taken at local noon over the period. The data exists in five separate chunks. However, this does not matter since I am analyzing daily averages.

The dark wavy line at the top of the data is the record of all of the clear days. The up and down wave reflects the variation in the strength of the sun at the equator. This variation is about 150 W m-2 in amplitude, and has two maxima and two minima per year. So the observations near and above that wavy black line are clear sky observations, while the rest of the observations below that dark wavy line are overcast observations. The question was, how to reliably separate them mathematically.

I started by establishing a breakline. To do that, I took the median of the upper quartile (top 25% of the data). I set the break line at 80% of that median, as shown in Figure 3.

tao buoy 0n165e downwelling solar vs time plus breakFigure 3. As in Figure 2, and including the breakline.

This left few enough data points in the upper section that I could use a gaussian average to reliably estimate the location of the center of the wavy black line. I used a 73-point gaussian filter, which gives the result shown in Figure 4

tao buoy 0n165e downwelling solar vs time plus gaussFigure 4. As in Figure 3, and including the Gaussian filter.

As you can see, the gaussian average does a very good job of determining the center of the black wavy line demarcating the clear day observations. (Note the differences in the two annual minima of the clear-sky line, due to the earth being closest to the sun in January and furthest away in August.) Finally, I created a new line at 92% of that gaussian average. This line, shown in Figure 5, was the line that I actually used to divide clear-sky observations from overcast observations.

tao buoy 0n165e downwelling solar vs time dual gaussFigure 5. As in Figure 4, and including the final line used to separate clear-sky observations from overcast sky observation.

OK, so that procedure let me reliably distinguish between the clear-sky and the overcast situations. (Note that I didn’t really have to go to that extent, because results don’t change much by just using my first breakline alone to make the cut … but I didn’t know that until I did the gaussian average, did I?. End of digression on methods …)

Now that I had collected and averaged my data, as a first cut in investigating the situation, I took the minute-by-minute average of all of the clear-sky observation, and of all of the overcast-sky observations. I also took the “All Sky” observations, which means the average of all of the observations for that minute of the day.

The results of these are graphed up in Figure 6.

tao buoy 0n165e insolation averageFigure 6. Downwelling solar radiation during daylight hours at the TAO buoy at 0N, 165E. Blue circles are clear sky, green are all sky, and gold are overcast sky. The light red circles show the percentage of sunlight making it through the clouds during just the overcast observations (not all observations). Values following the names are the 24-hour average for each variable.

Now, here is the oddity that I mentioned in the title of this post. The light red circles show, solely for overcast observations, the average amount of sunlight making it through the clouds, as a percentage of the total sunlight available at that time. The oddity is that it is nearly the same all day. That is to say that no matter what time of day the clouds form, on average they intercept about the 45% of the available sunlight, and that’s how it is.

I didn’t expect that. I kind of understand it, in that in my post called The Thermostat Hypothesis I used the point of view of the sun to show that on average it takes less than an hour for the tropical cirrus clouds to set in. Once that happened, there was little change in cloud density for the rest of the day. It appears that a fully developed bank of cirrus/cumulonimbus clouds intercepts about 45% of the sunlight, no matter what time of day it occurs.

Anyhow, that’s the oddity. Like I say, I ascribe it in part to “on/off” nature of the cirrus regime. Seems that either they are there or not there. Still, it doesn’t really explain why the same amount of sunlight would be intercepted on average during overcast periods at any time of day. I would have thought that merely the different angles of the sun hitting the clouds would cause a fairly large variation. The sun angle may be responsible for the slight decline in the afternoon around 4 PM, when the tall towers of the thunderstorms would intercept a larger amount of the slanting afternoon sunlight. Also, it may reflect the increasing thickness of the afternoon clouds.

Let me show one last result of my investigation. This is the average amount of solar energy reflected by the clouds, minute by minute. It is shown by the red circles in Figure 7.

TAO buoy 0N165E insolation plus cloud lossFigure 7. As in Figure 6, and including the amount of energy reflected (on average) by the clouds (red line). This is calculated as the clear sky insolation, minus the all sky insolation (i.e. potential insolation minus actual insolation). This difference is the amount reflected back to space by the clouds.

This result is further evidence supporting my thunderstorm thermostat hypothesis. It does so in two ways. The first way is that the forcing is inversely proportional to the temperature. More sunlight makes it through in the morning (when it is cooler) and less makes it through in the afternoon when it is warmer. The average energy lost to cloud reflection in the morning is 22 W m-2 less than in the afternoon. This warms the mornings, when it is naturally cool, and cools the afternoons, when it is naturally warm.

The second way that it supports my hypothesis is that the morning to afternoon difference in this analysis (22 W m-2) is of the same order of magnitude as that of my previous analysis done in the post “The Thermostat Hypothesis”. That data indicated a morning to afternoon difference (across the Pacific) of just over 40 W m-2. Since they are not measuring exactly the same thing, and my previous data was proxy-based and much cruder, I find that amount of agreement encouraging. Here is the figure showing the previous data:

Figure 8. Average of one year of GOES-West weather satellite images taken at satellite local noon. The Intertropical Convergence Zone is the bright band in the yellow rectangle. Local time on earth is shown by black lines on the image. Time values are shown at the bottom of the attached graph. Red line on graph is solar forcing anomaly (in watts per square meter) in the area outlined in yellow. Black line is albedo value in the area outlined in yellow.

I have no big conclusions out of this, other than to note that once again we see a strong thermostatic temperature governing mechanism in action. It is not simple feedback. It adds more energy to the surface in the morning when it is cool, and it reflects more energy to space in the afternoon when it is warm … just one of the many homeostatic mechanisms that keep the planet from overheating. It is a fairly powerful mechanism. As a measuring stick, 22 W m-2 is the expected change in forcing from CO2 increasing from its present value (~390 ppmv) to about 24,000 ppmv … just providing a sense of scale here …

In any case, that’s the news from my latest investigations. I was marveling today that I have that rare opportunity, with both the freedom to look into whatever might interest me at the moment, plus a host of wicked-smart folks to discuss my findings with. What more could a man want … except longer days. Somehow, it’s slipped past midnight again.

In between paroxysms of writing I frequently walk out to take the measure of the night. It’s crisp and cold this evening. The moon is up in the sky about 30°. I know because using a trick I learned doing celestial navigation with a sextant, I measured it using my hand at arm’s length with my thumb like this:

hand for 15°I know from experiment that from the top of my thumb knuckle to the bottom of my fist is 15° (for me, YMMV), which is a useful measurement because it is the distance that the sun or moon travels in the sky in one hour. I can measure up from the horizon and estimate how long it will be until sunset, one hand per hour. So I know the moon is about two hours above the horizon. That means it rose about 10:30.

Sunset these days is at 5:30. At full moon, the moon rises just as the sun sets, that’s why it is full, because it is exactly opposite the sun. (In fact, the full moon traces out the same path in the sky that the sun will take in six months … again because it is about directly opposite the sun. But I digress from my digression…)

Now, every day after the full moon, the moon rises after dark, and just under an hour later. So if it rose at 10:30 tonight that’s about five hours after dark, so we’re about five days past full … I check the moon tables to see how well I’ve done. Moonrise was 10:35 but that’s just luck to hit it that close, and we’re just starting the sixth day past full. Works for me …

The moon can also be used to determine the position of the sun. If you look at a half moon and you imagine it as a drawn bow, you’ll see it shoots its arrow directly at the sun … why do I bring this arcana up? Mostly to remind myself why I do this—because I love observing the oddities and iniquities of this most mysterious and enigmatic universe.

Tonight, Jupiter and Sirius the Dog Star frame the constellation of the hunter Orion in the southern sky. Jupiter’s a planet so it doesn’t twinkle, it’s a serene peaceful white, like a ship’s anchor light. Sirius is a star so it flashes and flickers, in shades of crimson. I take it as a channel marker for the course out of the harbor. Because it is red and I’m leaving harbor for the open sea, I’ll take it on the left, following of the “Red Right Returning” rule for channel markers …

… and in the distance, from my house I can see a tiny triangle of ocean glistening under the moon. And like the poet I long to go down to the sea again, but not to this cold green Northern sea that lies moon-bound in my night vision. The ebbing tide calls me much further afield, it’s angling on a long glance off of the horizon and out to a proper warm tropical sea of viridian and azure, with the sunlight far-reaching across the sparkling surface and lighting the color-drenched reef below, and my friends and I laughing and chaffing on our surfboards waiting for the next set … like the man said;

... The long day wanes:

                        the slow moon climbs:

                                               the deep

Moans round with many voices.

                               Come, my friends,

'Tis not too late to seek a newer world.

Push off, and sitting well in order smite

The sounding furrows;

                       for my purpose holds

To sail beyond the sunset, and the baths

Of all the western stars,

                           until I die. ...

I wish the best of that wildering road for all of you, the finest of that side-winding path half seen through that hidden door you occasionally redismember in your wainscoting. You know the one, that unacknowledged door into summer that beckons and tickles at your mind in the gloaming, calling for you to slip once more through that fugitive crack like when you were only three but you forgot, daring you to slide unseen through that opening into whatmight, beckoning you to make a spectacular of yourself and go a-yondering far and away beyond that boringly flat event horizon you resignedly contemplate through your quotidian expectacles …

I know that road calls for me, but I’m at anchor here for a while, as I am bound at this time by family obligation to stay where I am, and I will honor that obligation fully and joyously until it ends, but hey, let’s get real here. Someone should be taking my place in the ocean, investigating the mysteries of the thermal stratification and overturn of the warm tropical waters and their relationship with climate, suntans, and bikinis … so why not you now? I mean … who better, and what better time?

Hele on …


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February 1, 2013 12:33 pm

Maui beckons followed by Sydney and then Kangaroo Island. Sipping each as a quaff, light-headed and deliriously happy from its intoxicant, the clear night sky; first the Dipper and then the Southern Cross. Music for my journey from Crosby Stills & Nash’s Southern Cross I hear: “We got eighty feet of waterline/ Nicely making way.” What better investigation is there but the juncture of wind, water & ship.

February 1, 2013 12:33 pm

Interesting post. Apropos using the moon to find the sun- I’ve often thought there must have been at least one ancient civilisation that worked out that the sun didn’t circle the earth just by observing the slow-moving crescent of the moon.

P. Solar
February 1, 2013 1:19 pm

Facinating stuff (as usual) , Willis. Glad to see I’m not the only one who prefers gaussian to crappy running means when I need a filter. 😉
” (Note the differences in the two annual minima of the clear-sky line, due to the earth being closest to the sun in January and furthest away in August.)”
I understand the comment and I’d expect a six month cycle at the equator, but the comment does not seem to tie in with graph in figure 4.
The scale is a bit crude and there’s no grid, but it appears to me to be two year cycle of ‘M’-shaped patterns, not a two times six months.
Could you elaborate?

February 1, 2013 1:28 pm

Brilliant observations, as always, Willis…. Great way to end a post, as well.

February 1, 2013 1:39 pm

A scientist and a poet. Willis you are a Renaissance man.

February 1, 2013 2:32 pm

Willis you are a great writer,I’ve said this before.
I am not taking about your charts and data and
things like that,they’re good,but you begin WRITING
about things saw and did,it is beyond great.(gans besser)
Oh,maybe clouds can act as poloroid lens? [:{)

Rud Istvan
February 1, 2013 2:55 pm

Willis, beautiful. I learned but never practiced celestial navigation like you have. GPS launched, and took all the incentive away. Cocked thumb up. You provide more empirical evidence for Lindzen’s ‘adaptive iris’ hypothesis.
Two unbent thumbs up for that.
You might want to expend equal mental energy on the peak fossil fuels hypothesis advocated by many far more versed than myself. I reported in my books the factual results of a multidecadal debate. Plus additional calculations for the future. Unfortunately, unlike the climate skeptics until recently, peak fuels experts seem to have been ‘winning’ on data since 1970. Please provide alternative factual evidence, as is your eloquent wont. Rather than denigration in previous threads.

Denis Rushworth
February 1, 2013 3:12 pm

So Figure 6 seems to show that on any day, when there is enough moisture in the air to form low level clouds and sea surface temperature is in consonance, as the incident sunlight increases towards noon and recedes thereafter, the clouds increase as needed up to noon and recede thereafter to keep the radiation incident on the sea near constant throughout the day. Do I understand this? Seems like a perfect thermostat. If the sea surface temperature is too low, or one is on a land desert one gets a sunny day.

Gary Pearse
February 1, 2013 3:22 pm

“…the top of my thumb knuckle to the bottom of my fist is 15°..”
I use a similar measure that I had used mapping geology in the late 1950s in Northern Canada to have a quick idea how long I had to get back to the canoe from a compass traverse before dark. I turn my hand with my fingers at rt angles to the path of the sun and moon (horizontally at the horizon and at arm’s length). Also, each finger and the thumb are roughly 3 degrees this way – it can also be used for some rough surveying. Because of having a smaller hand, I had to curve my thumb tip outwards slightly to get the 15 degrees.

Philip Bradley
February 1, 2013 3:34 pm

Your reference to stars and twinkling, got me thinking (again) about why stars don’t twinkle here in Perth.
This from the Perth Observatory alludes to it without directly stating the fact.
We’ve all been brought up to expect that normal star behaviour is to twinkle, twinkle. In fact, stars don’t twinkle in any way that can readily be seen with the unaided eye. The twinkling and flashing and colour-changing that you can see in stars near the horizon is caused by the shimmer and the impurities in the atmosphere. The stars aren’t doing it. Look higher up and you’ll find that the higher stars are much steadier. Where the stars are steady, you’ll have a clear view.
The conventional explanation for stars twinkling is atmospheric turbulence, but we have fairly large diurnal range and should have more convective turbulence than most places.
We also have very bright sunlight. Only yesterday someone from the east commented how bright Perth sunshine is. Which makes me think the 2 phenomena are related and result from low levels of aerosols and aerosol seeded water droplets due to the fact the air over Perth normally comes across 7,000 kms of open ocean.
There aren’t any bouys at the latitude of the westerlies. Otherwise, I’d look into whether solar insolation increases from west to east over the oceans.

February 1, 2013 3:43 pm

I use my hand at arms length, fingers together, not using the thumb, at a ninety degree angle. Each finger equates to about fifteen minutes. Top of top finger at the bottom of the suns disc then work down to the horizon. Has been close for me.

February 1, 2013 3:45 pm

Terrific read as usual, thanx Willis.
Eyeballing the fig. 6, seems there is enough solar insolation to heat a black body to somewhere around 30 – 35 DegC.
No ‘backradiation’ required to keep sea water liquid?

February 1, 2013 3:52 pm

Willis your writing is insightful and delightful in equal measure. Never thought I’d meet Tennyson here. Wonderful.
“that which we are, we are;
One equal temper of heroic hearts,
Made weak by time and fate, but strong in will
To strive, to seek, to find, and not to yield.”

February 1, 2013 4:32 pm

30 odd years ago I was a navigator in the British Merchant Marine and I too have never gotten over what Douglas Adams called “the fundamental interconnectedness of stuff”. I go to reunions periodically and friends who are now Senior Masters always bemoan the fact that current junior officers might know the theory of celestial navigation, but would rather accept a SatNav position than produce the inevitable ‘cocked hat’ of a morning or evening stellar observation. My ‘skepticism’ is informed not only by the knowledge that the true position from such a sight is statistically more likely to lie outside said ‘hat’ than in it, but also by the fact that I compiled Met Office Weather Ship observations every six hours and know how inaccurate these were – if I was in traffic I often decided it ‘looked’ about 22 degrees C. In heavy traffic I occasionally produced a random string of numbers and blamed it on the Radio Officer’s transmission…

old construction worker
February 1, 2013 4:56 pm

Thanks Willis. Even this old construction worker understands your findings.

Lil Fella from OZ
February 1, 2013 5:49 pm

I came across this quote which I thought was very apt in the dealing with the so called ‘Climate Change’ debate.
Philosophies of despair and potent occult experiences can convert even those who think they are the least vulnerable: “There is a great deal of research that shows that all people, but especially highly intelligent people, are easily taken in by all kinds of illusions, hallucinations, self-deceptions, and outright bamboozles—all the more so when they have a high investment in the illusion being true.” Maureen O’Hara
I thought this summed up the membership of those promoting man cause climate change.
Off to hear Lord Monckton tonight!!!

Robert Wykoff
February 1, 2013 6:00 pm

As usual, good post Willis. It is kind of funny you bring the moon up in that manner. Many many years ago while working at the Empire Nevada plant (you know where that is), I was cruising around as usual in my jeep, and watching the full moon rise, I turned the other way and saw the sun setting, and walla suddenly 2 and 2 came together. I thought it odd, that I had never considered that before. After that all the other things like figuring out how long till sunrise based on the moon position fell into place. It was about that time that I started using stars to navigate across the playa at night as well.

February 1, 2013 6:21 pm

I always enjoy your posts. I enjoy your writing style. And the analysis.

Louis Hooffstetter
February 1, 2013 6:48 pm

Willis – Another very nice and insightful article. You have a gift most of us wish we had.

February 1, 2013 7:23 pm

Thanks Willis.

February 1, 2013 7:32 pm

Heh. Funny that you never mention the Creator of all these wonderful things….

February 1, 2013 8:30 pm

“Now, here is the oddity that I mentioned in the title of this post. The light red circles show, solely for overcast observations, the average amount of sunlight making it through the clouds, as a percentage of the total sunlight available at that time. The oddity is that it is nearly the same all day. That is to say that no matter what time of day the clouds form, on average they intercept about the 45% of the available sunlight, and that’s how it is.”
MIT developed a different type of solar array that generated more power on cloudy days than on sunlit days, mostly because of your data showing that 45% of the max sunlight is available over a longer period of time.
News Release:
Abstract: (with charts showing cloudy day power)

Keith Minto
February 1, 2013 8:33 pm

The moon can also be used to determine the position of the sun. If you look at a half moon and you imagine it as a drawn bow, you’ll see it shoots its arrow directly at the sun …

I used to think the same too, but if you look at the “drawn bow” and project an imaginary arrow straight out of this bow, it will miss the sun by aiming too high. This error increases with increasing distance between the sun and moon.
You can check this after sunset when you can ‘mark’ the sun’s position on the horizon. Take a look at the drawn bow of the moon’s phase. The imaginary arrow in this bow is sitting on a tangent to the curved path followed by the moon.
As an aside, this path is similar to the path followed by the sun.

February 1, 2013 8:51 pm

Don’t do that!
I’m barely managing to not march in to some organization or other and volunteer for some kind of “helper” gig in some islands somewhere as it is… I sold my boat a few decades back and STILL think about it… I could easily sell the house and buy another one…
But the spouse…
Oh Dear. I’ve got it bad again…
( I’d really like to see French Polynesia before I”m done… wonder if they need folks to run I.T. gear… “will config routers and firewalls for room & board…” )

February 1, 2013 8:56 pm

Did you take into consideration the difference between local sun time and standardised time zone conformance? For example you can have over half a hour difference between sun high noon and your local time zone time.

Half Tide Rock
February 1, 2013 9:13 pm

Willis, The ending of your essay brought tears to my eyes. I circumnavigated before all of this electronic magic. I light up when a GPS sailor calls to get the quick check out on emergency celestial from “the old fart”. How could anyone have a complete experience of this gift of life without being able to stretch their hands and mind to meld with the waltz of the spheres and discern the message of where you fit in, where you are, and perhaps who you are. What a hell of a ride we are on! What a gift to watch this investigation into the interstadial blossom. Your writing, investigations and musings are a pleasure to read.
Long may your big jib draw!

February 1, 2013 9:18 pm

Regarding that oddity. I had a look at the diurnal SST variation for that buoy and it is unusual to go over 1 deg C. I find it difficult to believe that such a small variation over a day would cause any convective cloud.

February 1, 2013 9:23 pm

Seeing Willis Eschenbach means [Continue reading] will be clicked. While consumed, there is that moment, I can stop stringing and restringing my instrument…BAM knowing inspiration inspiration.

Keith Minto
February 1, 2013 9:49 pm

Willis Eschenbach says:
February 1, 2013 at 9:12 pm

This was just an observation of mine, shared with a few friends. I am lucky to have clear inland skies to the west, most of the time.
Give it try, as you say, around the waxing moon sometime around the 18th. To me it is quite a pronounced deviation from the straight line and it helps if the moon is high, waxing and the sun’s position can be ‘marked’ just after sunset on an earthly horizon to avoid eye contact with the sun. Use string or Floss to bisect the bow, if you like.
I could upload a photo if there is interest.
Should work in the NH !
Thoughtful article, Willis, furthering your Thermostat hypothesis.

February 1, 2013 10:40 pm

Willis, I can well appreciate that places like the Solomons and Naru would have convective cloud caused by diurnal temp differences. I seem to remember Heyerdahl of Contiki fame saying that they knew when they were near their first island when they saw a stationary cloud on the horizon.
I’m certainly not criticising your global thermostat hypothesis except I think diurnal convection may be limited to islands and land masses.

February 1, 2013 11:42 pm

Willis Eschenbach says:
February 1, 2013 at 9:12 pm
I’m sorry, but just your unsupported claim doesn’t help in this … if you have pictures or a link or something I might go for it. But it has always pointed towards the sun for me, and I’m a pretty close observer of that kind of thing. And I just modeled it with my 3-D rendering software, and it always points right at the light …
I will support Keith Minto’s claim. You can not tell me from a “linear arrow shot” from the sun to the moon, you did not see the 5-10 degree shift in the lighting of the moon… if you haven’t, check out the next daytime half-moon.
Here is a third to the claim 😉
While I know your “anonymous” call out policy, this one is an interesting phenomenon. Keith is right, and deserves better than an unsupported claim, “claim”.

February 1, 2013 11:52 pm

Good pau hana, bra.

February 2, 2013 1:10 am

Lord how I wish I could think and write as you do. Impressive.

February 2, 2013 1:20 am

intrepid_wanders says:
February 1, 2013 at 11:42 pm (replying to)
Willis Eschenbach says:
February 1, 2013 at 9:12 pm

I’m sorry, but just your unsupported claim doesn’t help in this … if you have pictures or a link or something I might go for it. But it has always pointed towards the sun for me, and I’m a pretty close observer of that kind of thing. And I just modeled it with my 3-D rendering software, and it always points right at the light …
I will support Keith Minto’s claim. You can not tell me from a “linear arrow shot” from the sun to the moon, you did not see the 5-10 degree shift in the lighting of the moon… if you haven’t, check out the next daytime half-moon.

Oh come on. Isn’t it obvious? 8<)
Everybody who has learned their NASA's CAGW physics lesions (er, lessons) the past few years "knows" that the earth is below the sun and moon – after all, simple observation and the consensus of all the experts can easily confirm that the sun and moon are above the earth when both are visible.
Further, from NASA's elementary GISS' physics models it is easy to show that, once shot from Luna's bow, the earth will attract the moon's arrow as it tracks towards the sun; and therefore it's "obvious" from simple averaged physics that the arrow must be aimed up higher than the sun’s apparent position!
/sarchasm -> The gaping hole between a liberal and the truth.

James Bull
February 2, 2013 1:36 am

As ever a very good read with lots of interesting things to think about with some on and off topic wanderings thrown in for good measure. A real pleasure.
And now for my little bit a quote from the late great Spike Milligan
I must go down to the sea again,
to the lonely sea and the sky;
I left my shoes and socks there –
I wonder if they’re dry?
Spike Milligan
All the best
James Bull

February 2, 2013 1:56 am

Willis writes “And I just modeled it with my 3-D rendering software, and it always points right at the light …”
Ugh models. Did you add the appropriate feedbacks?

John Marshall
February 2, 2013 3:07 am

1600 hours is late for Cb to build. My experience working in the tropics is that they start to build mid morning, with heavy showers around 1130 ish. Convection starts as soon as the sun warms the ground.

February 2, 2013 3:29 am

Is there any chance that the water droplets at the top of the cloud heat up, so that some of the energy that doesn’t reach the surface doesn’t get reflected back, either?
Modern junior officers ( and indeed some young masters as well ) don’t look out of the wheelhouse windows enough, either.

Dr. John M. Ware
February 2, 2013 4:11 am

Thanks, Willis, especially for bringing in ‘Ulysses’ by Tennyson, one of my all-time favorite poems; used it in my high-school classes the last several years I taught (prior to that time I taught music, not English). “As though to breathe were life . . .”

February 2, 2013 6:21 am

“I gave the location of the buoy at 165°East. I leave it to you as an exercise to determine the difference between sun high noon and local time zone high noon ”
Sorry Willis, I mistakenly thought you were estimating the time of day with the moon. After reading this post the first time, I had a half four walk home from the coffee shop where I originaly read the post, and I thought of my question. After posting my question, I thought at first I had posted to the wrong article as it was about the tropical buoy. Anyways, I used Wolframalpha to see what I could find on the time zone difference, and so far all I can find is that the sunrise is 11 minutes off from 6 am (7 with the presumed day light saving).
There is some other interesting data Wolframalpha displays with that query that might be interesting to look at.
I once had some code that could calculate various sun position data that I converted from a c language file into the c# language, that I ran on my pocket pc. But I lost it all in a tragic multi-failure hard-drive / backup drive incident.
Anyone interested in the non commercial code use version can find the code here:
NREL’s Solar Position Algorithm (SPA)
I have taken it upon myself a few years ago to learn how to write my own code to do these calculations, as I do not want to use code from the National Renewable Energy Laboratory
Solar Radiation Research Laboratory, and be beholden to them. It’s time I got that project finished.

Doug Huffman
February 2, 2013 6:59 am

Ahh! The “drawn bow”!
I thought that was mine, but for all the reading that I do, and did on sailing, I’m sure I was taught that misty years ago. Thanks for an acute observation. I also use four fingers to estimate an hour of Sun motion.

February 2, 2013 7:28 am

The word “downwelling” might best be reserved for radiation that has already “upwelled”.

buck smith
February 2, 2013 8:58 am

I really enjoy your posts Willis, I live south of you in Marin county. If you are every down this way, i would enjoying buying you a glass or beer or wine or cup of coffee.

Doug Proctor
February 2, 2013 11:06 am

Wow! Citizen scientist at work!
TSI TOA 341.5 W/m2, clear skys all year average 316.0 W/m2 = refracting + clear air absorption = 25.5 W/m2 at near equator, or 7.5%. Less than the 25% I’ve read about before ( 5 + 20).
All sky 244 W/m2, or 98 W/m2 or 29%, more than I thought, though “all sky” confuses me. Partial clouds absorption and reflection, absorption above and below, refraction above, average?
Overcast 177 W/m2: total lost 165 W/m2,, refraction, absorbed by clear air below and above, absorbed and reflected by clouds: 48% TOA TSI.
Refraction, absorption clear air above and below, absorption and reflection clouds 100% and partial. 4 variables, 3 values. If we had the partial cloud number, (4th value) could we solve for all variables?
How do these numbers work with what the IPCC/Trenberth total energy budget of the Earth? And what about +/- estimates, both by themselves and wrt to the IPCC/Trenberth calculations?
This raw data should set the certainty of input for estimates of how much cloud cover could provide the 3.5 W/m2 equivalent of IPCC-doubling of CO2.

Philip Bradley
February 2, 2013 12:35 pm

The TAO bouys are moored. Quite how they manage this over the deep ocean I don’t know. But it seems people have realized that having the Argo floats free-floating wasn’t such a great idea.

February 2, 2013 1:00 pm

Your observations bring tears to my eyes and goose bumps down my back.

February 2, 2013 4:45 pm

Willis Eschenbach says:
February 2, 2013 at 4:07 am
But I’m still waiting for a picture from either of you that shows the phenomenon. I’ve looked and can’t find one. This has nothing to do with anonymity or calling out, it is that neither of you have provided a photograph that shows an actual example of what you are talking about …

Obviously, it is a photography nightmare capturing an illuminated moon and the sun in the same photograph. I have had considerable difficulty in finding even a phrase for this, but this illustration captures the crux of the issue (admittedly, it took several hours to find):
Obviously, it is an illusion, but with 15 degrees of error, it could be an issue with naked-eyeball navigation.
So, anyhow, on February 17 we will have a 1st quarter phase with daylight conditions. Sometime in the afternoon (~12:31pm), check out your moon-bow shot and see if it hits the Sun…

February 2, 2013 5:00 pm

Willis, I’m not pushing any thesis, just trying to get a better understanding of things, that oddity you mention has me curious.
A bit of research has revealed that there is a diurnal fluctuation in tropical convection over the ocean. Clouds < 208K (high clouds) dissipate during daylight hours, while clouds 208 – 235K increase (lower clouds). http://eos.atmos.washington.edu/tropconv.html
I am yet to be convinced on what overall affect this may have on light reaching the ocean.
Regardless of whether I agree or disagree with you, I thank you for providing thought provoking posts.

February 2, 2013 7:46 pm

Bacullen says: February 2, 2013 at 1:00 pm
“….Obviously, it is a photography nightmare capturing an illuminated moon and the sun in the same photograph. I have had considerable difficulty in finding even a phrase for this, but this illustration captures the crux of the issue (admittedly, it took several hours to find):
Obviously, it is an illusion, but with 15 degrees of error, it could be an issue with naked-eyeball navigation….”

A beautiful illustration, and showing something I’d never contemplated before… (but 23 degrees ‘error’ is shown, correct?)
But the trick is, in the illustration shown, that the sun is not really sitting the just to the right of the moon… it is really almost directly in front of it about 150 million kilometers or 93 million miles away.
The way to visualize it perhaps is that if you were standing on the moon looking at the sun at that time, you would be looking in almost the same direction as you are looking on earth, so the part of the moon which would be (and is) illuminated can then be visualized.

Theo Goodwin
February 2, 2013 7:53 pm

Wonderful post. Thanks.

February 2, 2013 8:21 pm

Years on the original graph are from a “0.0” baseline to “20” ..
Is the newest date (newest data) on the right at 20.0, or the left at 0.0 – as if you were to read the graph as “years ago” ?
Seems there’s a yearly trend going on as well over the past 20 years of the buoy data for “radiation received on the surface”. How does that compare to the years since the satellite era of 1979 ?

February 2, 2013 9:04 pm

I confirm the concept by personal experience.
By far the best time to take celestial sights is morning stars. Going from the Galapagos to Tahiti, over a period of 24 days in 1973 I found that the “trade wind clouds” began to accumulate right after the sun came up and by noon it might be hard to get a meridian passage sight. I would still have the sun for a 10:oclock fairly good chance of meridian passage and then less of a chance but still Ok for a 2PM sight. Evening stars were much less satisfactory with a good deal of breeze developed trade wind clouds and poor horizons. If you looked to the East at sunset the trade wind clouds were regularly spaced nimbus and cumulonimbus (occasional rain) looked like the audience at a movie with the light of the setting sun illuminating the clouds….so many faces. We would have a change in the wind direction in the morning just around sunrise the wind would pick up all day clocking and then a puff as the sun set and drop in the evening after sunset and backing. We were on the same tack for the entire trip and just trimmed sails.
The clouds over the islands are very different than the procession of trade wind clouds. They are anvil shaped cumulonimbus with rain and trail off down wind and don’t move. They “swim” against the trade wind clouds. Anvil Shaped clouds are a dead giveaway for a high Island like Tahiti. You know something is there perhaps 80 miles out. The low atolls have large expanses of relatively warm water in the lagoons and thermals form larger than and more emphatically than the generic trade wind clouds over the warm water. They tend to have more rain, move with the trade wind but new ones pop up with more frequency. Sometimes you can almost see the blue reflecting up. Paying attention to the clouds and birds and feeling for reflected or refracted waves is important because a palm tree is visible for only 8 miles and mangroves 3-4 Miles. It is possible to be on a reef before there is any actual sighting of land. The intertropical convergence zones have much more instability and sights are often difficult. The cloud formation during the day more persistent tending to stratus and cumulonimbus and is much more rapid and by noon entirely obscure the sun.
“Long White Cloud ” is a New Zealand description. “Morgan’s Cloud” is Bermuda. There will often be clouds there when the sky is clear everywhere else as well as when the conditions are unstable.

February 2, 2013 10:12 pm

Pastor W now preaches from the redwood pulpit, telling his congregation this egotistically smart-assed sermon:
“jae, I understand where you are coming from, and truly, I was going to mention the Boss, but then a funny thing happened—She told me not to mention Her name under any circumstances.
I was kinda surprised, but She said that talking about Her always leads to fights, so She recommends against discussing Her actions on blogs for any reason. According to Her it never goes anywhere. She said if people had questions they should consider this:
Matthew 6:5
“And when you pray, do not be like the hypocrites, for they love to pray standing in the synagogues and on the street corners to be seen by men. I tell you the truth, they have received their reward in full.
Weird. I don’t think Willis has a clue about where I’m coming from, although he thinks he does. I don’t think he digs Matthew 6:5, either, since there is no obvious connection between that verse and my comment that I can see. Let’s call him “Straw-boy Willis!!!”
I noticed that the big W still DID NOT credit SHE with anything, which again shows his Progressive (Democrat) leanings.
W-boy, do YOU think YOU are talking directly to The SHE in the sky now, eh? What are you smoking down there in the redwoods, eh? YOU must think you are really, really be special, eh? And SHE recommends TO YOU not talking about the most important subjects on the Planet? Because somehow SHE told you to say so??? I just don’t get it, Willis. Maybe you can explain your special connection to the BOSS (SHE??) ???
You got your problems, too, buddy.

February 2, 2013 11:29 pm

jae says:February 2, 2013 at 10:12 pm
[…. a whole lotta odd things… “…problems…” … ]
Jae, the fact that it worries you that others may not share your beliefs, or that they do not pay sufficient homage to your ‘god’, to me says more about your problems than it does anyone else’s.

John Marshall
February 3, 2013 2:47 am

The radiation figures that Trenberth claims are nothing like those calculated or measured. His TOA figure is 240W/m2 when we can measure 1370W/m2 but his figure is that used to justify the GHG theory. Total rubbish.
1370W/m2 gives a temperature of 121C which is what is measured on the moon’s surface in the zenith position. Calculated earth surface radiation is 960W/m2, taking into account albedo and atmospheric adsorption. Your measured data was around 1000W/m2 on cloudless days so correlates well with that calculated and this gives a surface temperature of 88C though atmospheric and surface heating will help to reduce this as will convection. Desert surface temperatures can get close to 60C. So we are not short of heat and in no need of a theory that violates the laws of thermodynamics.

Jens Raunsø Jensen
February 3, 2013 4:53 am

Willis, thanks for your interesting post. In your introduction you define “clear sky” by the statement : “So the observations near and above that wavy black line are clear sky observations,..”. However, although this may be a good operational approximation to the common definition of clear sky global radiation (i.e. downwelling solar), clouds may still be present under this condition. In particular, a few scattered clouds are likely to increase the short-term global solar radiation relative to values under similar cloud free conditions because of scattering and reflection.Therefore, clouds may both decrease and increase global solar radiation. I wonder how that may impact on the analysis.

February 3, 2013 5:51 pm

WOW, at least I know how to light a fire here!
BUT, IMHO, God should not be blocked from ANY discussion, W. AND, if I am, “more than welcome here,” as you state, then I get to put my $0.02 in, eh? And I thank you for that!
Rant and insult away again, if you wish. It speaks volumes to me. Maybe you will get some of the bad things out of your system. Willis, you cannot shame me, as hard as you may try…

February 3, 2013 11:22 pm

Really enjoyed your weather observations from being at sea, makes me a little envious. Might even copy it for future reference. The coral atolls sound like stalactites in reverse, a jumping off point for clouds. I found that interesting about how the trade wind clouds start shortly after dawn. Probably confirms the data I got from Willis Island (yes that’s its name) a speck of coral 400km off the Nth Queensland coast. At this island there is only an increase in 0.14 octas in cloud from 9am to 3pm when you average the daily difference over a year. (last year)
How did you produce the graph in Fig. 8 on albedo along the ITCZ ?
Cloud albedo to me seems a very rough proxy for light reaching the surface. A cirrus cloud could have the same albedo as say something like stratus, but cirrus will let more light through.

February 5, 2013 12:59 am

Willis, thanks for the reply. I hope you used visible images for albedo, otherwise IR would give you an indication on the prevalence of high clouds.

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