Threshold sea surface temperature for hurricanes and tropical thunderstorms is rising

Nov 08, 2010
Tropical ocean thunderstorms tend to occur above a threshold sea surface temperature. Credit: Image courtesy NASA Image Science & Analysis Laboratory

Scientists have long known that atmospheric convection in the form of hurricanes and tropical ocean thunderstorms tends to occur when sea surface temperature rises above a threshold. The critical question is, how do rising ocean temperatures with global warming affect this threshold? If the threshold does not rise, it could mean more frequent hurricanes.

According to a new study by researchers at the International Pacific Research Center (IPRC) of the University of Hawaii at Manoa (UHM), this threshold sea surface temperature for convection is rising under at the same rate as that of the tropical oceans. Their paper appears in the Advance Online Publications of Nature Geoscience.

In order to detect the annual changes in the threshold sea surface temperature, Nat Johnson, a postdoctoral fellow at IPRC, and Shang-Ping Xie, a professor of at IPRC and UHM, analyzed satellite estimates of tropical ocean rainfall spanning 30 years. They find that changes in the threshold temperature for convection closely follow the changes in average tropical sea surface temperature, which have both been rising approximately 0.1°C per decade.

"The correspondence between the two time series is rather remarkable," says lead author Johnson. "The convective threshold and average are so closely linked because of their relation with temperatures in the atmosphere extending several miles above the surface."

Threshold sea surface temperature for hurricanes and tropical thunderstorms is rising
The average tropical sea surface temperature (black) and an estimate of the sea surface temperature threshold for convection (blue) have risen in tandem over the past 30 years. Credit: IPRC/SOEST/UHM

The change in tropical upper atmospheric temperatures has been a controversial topic in recent years because of discrepancies between reported temperature trends from instruments and the expected trends under according to global climate models. The measurements from instruments have shown less warming than expected in the upper atmosphere. The findings of Johnson and Xie, however, provide strong support that the tropical atmosphere is warming at a rate that is consistent with climate model simulations.

"This study is an exciting example of how applying our knowledge of physical processes in the tropical atmosphere can give us important information when direct measurements may have failed us," Johnson notes.

The study notes further that global climate models project that the sea surface temperature threshold for convection will continue to rise in tandem with the tropical average sea surface temperature. If true, hurricanes and other forms of tropical convection will require warmer ocean surfaces for initiation over the next century.

Explore further: New discovery helps solve mystery source of African lava

More information: N.C. Johnson and S.-P. Xie, 2010: Changes in the sea surface temperature threshold for tropical convection. Nature Geoscience, doi:10.1038/ngeo1004

Provided by University of Hawaii at Manoa

4.6 /5 (7 votes)

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User comments : 32

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tadchem
4.2 / 5 (6) Nov 08, 2010
Convection is driven by a temperature *differential*.
GSwift7
2 / 5 (8) Nov 08, 2010
"This study is an exciting example of how applying our knowledge of physical processes in the tropical atmosphere can give us important information when direct measurements may have failed us"

I am speechless. The measurements are wrong, but the models are correct? Uh, what are the models based on if the measurements are wrong? If the measurements are wrong, then what is the input for the models? I think somebody needs to tell this guy "ixnay on the odelmay incorrectus stuff". The first rule of climate club is: "You do not talk about problems with the temperature data". The second rule of climate club is: "YOU DO NOT TALK about problems with the temperature data".
sstritt
2.6 / 5 (5) Nov 08, 2010
@GSwift7-
I thought the same thing!
StarDust21
1 / 5 (3) Nov 08, 2010
soo thats a good thing...But if this threshold is rising then why are we getting more hurricanes?
GSwift7
2.3 / 5 (3) Nov 08, 2010
"soo thats a good thing...But if this threshold is rising then why are we getting more hurricanes?"

We aren't. That historical data is easily available on the NOAA web site. They have a detailed record on the site, with a year by year account including all the major storms since records first became available. The trend has been steadily decreasing since the 19th century, and there's been an especially sharp decline since the sixties, when satellite data became available. But to be fair, that's really not enough time to say whether there's a real pattern or just a coincidence of noise in the data. There aren't really any good proxy records of storms, so it's hard to say. Records prior to the past few decades were kept by the Commerce Department. lol.
MikPetter
not rated yet Nov 08, 2010
The Layers of Our Atmosphere
These layers are divided based on the characteristics of the gases found at that height. Imagine a layered cake. A layered cake is made out of layers of different ingredients. The first layer might be cake mix. On top of that a cook could put a layer of pudding. On top of that layer they perhaps could put another layer of cake mix, followed by a layer of whip cream, and so forth. Each layer in our atmosphere is referred to as a sphere.
The first layer of the atmosphere is fortunately not made out of cake, but rather it is made out of the gases that we breath everyday. This layer is called the troposphere. The troposphere is the layer that we live in. The next layer of our atmosphere is called the stratosphere. Above the stratosphere lies the mesosphere, followed by the thermosphere, and finally the exosphere. Source "http://www.kidsge...p"
PinkElephant
3.2 / 5 (5) Nov 08, 2010
@GSwift7,
The measurements are wrong, but the models are correct?
With respect to the tropical upper troposphere measurements, it increasingly looks like that's the case.

For more info:
http://en.wikiped...e_models
Uh, what are the models based on if the measurements are wrong?
They're based on fundamental physics.
If the measurements are wrong, then what is the input for the models?
The INPUTS for the models do not include the FINAL temperature or humidity profile of the atmospheric column. Rather, this would comprise the OUTPUT from the models.
M_N
2 / 5 (4) Nov 09, 2010
With respect to the tropical upper troposphere measurements, it increasingly looks like that's the case.

PinkElephant, this is one of the most fraudulent "adjustments" in the history of climate "science". Weather balloons take VERY accurate temperature measurements; it's just that the results weren't what the alarmists' models were predicting. Instead of questioning their models, they discarded VERY accurate temperature in favor of "proxy" data that happened to fit their agenda.
PinkElephant
3.4 / 5 (5) Nov 09, 2010
Weather balloons take VERY accurate temperature measurements
Or so you like to imagine. I'd encourage you to read that wikipedia article I linked above. But somehow I suspect you wouldn't want to actually learn anything...
M_N
2 / 5 (4) Nov 09, 2010
Weather balloons take VERY accurate temperature measurements
Or so you like to imagine. I'd encourage you to read that wikipedia article I linked above. But somehow I suspect you wouldn't want to actually learn anything...

Actually, I did read the article, and I'm very familiar with this issue. As an engineer who has designed weather monitoring systems, I can assure you that weather balloons are indeed a very accurate way to measure temperature.

The "scientists" who came up with the idea that the measurements couldn't be accurate (because they didn't match their expectations) seemed not to understand even basic concepts of taking measurements in the real world.
GSwift7
1 / 5 (2) Nov 09, 2010
Pink, once again you are defending the models as if I'm trying to say they aren't any good. I'm just saying that the statements by this one guy, in this one article are a bunch of crap. He may even have been misquoted, or his comments could have been taken out of context. What this article says doesn't make any logical sense. Are you defending this article, or are you defending something else, which I wasn't really talking about?

FYI Pink, the actual measurements of temperature and pressure in the real world are inputs for the models. Do you agree with that? If not I'll provide links from NASA, NOAA, IPCC and CRU to prove it.

In this case, the real world doesn't match the model. That means either the measurements are wrong and have been wrong all along, or the model is off in some way. It really may not be a big deal. This article doesn't talk about the magnitude of the discrepancy.
PinkElephant
3.7 / 5 (3) Nov 09, 2010
@GSwift7,
the actual measurements of temperature and pressure in the real world are inputs for the models. Do you agree with that?
No I don't.
If not I'll provide links from NASA, NOAA, IPCC and CRU to prove it.
Go right ahead.
What this article says doesn't make any logical sense.
What this article says is that the temperature gradient between surface and upper troposphere has remained constant, while the surface has warmed. Ergo, upper troposphere must have warmed too. I've seen it argued from other evidence as well, so there are multiple indications that either measurements of the upper tropospheric temperatures are off, or there's some REALLY fundamental physics about gases that everybody in the world's been missing.

@M_N,

You can measure something very accurately, but if your calibration is poor or you're being biased by unforeseen factors, then your measurements will be systematically incorrect -- even while remaining very precise and highly reproducible.
PinkElephant
3.6 / 5 (5) Nov 09, 2010
ctd.

What the article above says is this: if you assume the measurements from radiosondes and satellites are accurate (i.e. upper troposphere isn't warming as much as the surface), then threshold temperature for storms should not be rising, and we should be seeing more storms.

On the other hand, the climate models predict that upper tropospheric temperature should be rising alongside surface temperature, and that therefore the threshold temperature for storms should be rising, and therefore we shouldn't have more storms.

Measuring actual frequency of storms and threshold temperature, confirms model predictions and goes against the data from radiosondes and satellites.

This, plus the moist->dry adiabatic transition all but DEMANDS via hard math and laws of thermodynamics that upper troposphere warms along with the surface.

All of which strongly hints that the instrumental measurements to date have been having problems. Or else there's some fundamental new physics to be found...
PinkElephant
3.8 / 5 (6) Nov 09, 2010
ctd.

Or else, surface temperatures are just plain wrong and there's been no warming at all.

However, this would go against the massive and multi-factorial evidence including ice extent, glacier retreat, upper ocean temperatures, surface temperature data, ecosystem migration, onset of spring and growing season, etc, etc, etc. Basically, there is SO MUCH evidence from SO MANY sources that the surface is warming, that this is quite beyond dispute. And that's just empirical evidence alone, before you even consider theoretical arguments such as convective/radiative transfer energy balance calculations. Even those same radiosondes and satellites say it is so.
Skeptic_Heretic
5 / 5 (3) Nov 09, 2010
This is what I call a junk abstract.

The measurements from instruments have shown less warming than expected in the upper atmosphere.
The measurement from a small subset of instruments has shown a lack of an upper tropospheric hotspot. The model stating there would be one was demonstrably wrong. It was a bad model. The physical measurements showed the problem with the model.

Then the abstract completely changes topics, without showing a topic change.
"This study is an exciting example of how applying our knowledge of physical processes in the tropical atmosphere can give us important information when direct measurements may have failed us,"

This looks like he's saying when reality deviates from model world, trust model world....

Never, never, ever do that, ever. If your measurements show your model to be wrong, then your model is based on prior measurements of a same or similar type. To impeach the measurement, impeaches the model based on the measurements
Skeptic_Heretic
5 / 5 (3) Nov 09, 2010
Now, where that quote can be taken in proper context, and accurately referenced is in one instance alone.

When your model shows something you can't account for by measurement, and then OBSERVATION shows the model to be correct, then you know your measurements are faulty.

You require a manner in which to observe the error before you can say "screw reality, we're going a modelin'!"

GSwift7
2.3 / 5 (3) Nov 09, 2010
Wow, SH actually agrees with me that the above article is a pile of puke.

Pink, here's a link to the Wiki page for NCEP dataset. There are reference links at the bottom to NOAA.

http://en.wikiped...analysis

Which of course makes this guy's statement about convection in the model not matching real world observations rather puzzelling. Maybe he's talking about a small box model in stead of a GCM? I don't know, the article is sparse on details. You have to use a model with an extremely small grid size to model cloud formation and convection anywhere near the real world. It's a huge deal just to model one cloud. I don't think hurricaine formation is really what GCM's are made to predict.
GSwift7
2.3 / 5 (3) Nov 09, 2010
Oh, okay this silly web site deleted the middle of my post.

After my link it was supposed to say:

Convection isn't actually simulated in AGCM's. It's what is called a parameterization because it would be too complex to try to model it. That means the circulation is just an estimate and it's kinda like a fixed or arbitrary set of values. Here's a link that to explain, which got cut out of my previous post somehow.

http://en.wikiped...climate)
Skeptic_Heretic
5 / 5 (3) Nov 09, 2010
Wow, SH actually agrees with me that the above article is a pile of puke.
Why wouldn't I? A shitty abstract is a shitty abstract regardless of whose ideology it touts. It's not logical, and it looks like the vast majority of it was taken entirely out of context.

If this researcher is actually insisting that untested models are a better measure than measurement, well, GTFO.
PinkElephant
4 / 5 (4) Nov 09, 2010
@GSwift7,
Pink, here's a link to the Wiki page for NCEP dataset.
Nice. Here's a quote:

"Uses
* Initializing a smaller scale atmospheric model
* Climate assessment"

Used in GCM's? Nope. Here's another quote:

"The NCEP/NCAR Reanalysis reanalysis data set is a continually updating gridded data set representing the state of the Earth's atmosphere, incorporating observations and numerical weather prediction (NWP) ***model output*** dating back to 1948"

Do you even read your own "references"?
Convection isn't actually simulated in AGCM's. It's what is called a parameterization
Apparently you don't. Quote:

"This can be contrasted with other processes—e.g., large-scale flow of the atmosphere—that are explicitly resolved within the models."

We aren't talking about small-scale turbulence here. The tropospheric hot spot is supposed to be a huge belt girdling the globe. And this is why:

http://en.wikiped...pse_rate
GSwift7
1 / 5 (2) Nov 10, 2010
Pink, where do the starting conditions for the models come from? Are the real world measurements of temperature used in any way in the models? If you are claiming that real world temp measurements are not used to set up the model before they run it, then you are out of your mind.
PinkElephant
2.7 / 5 (3) Nov 10, 2010
where do the starting conditions for the models come from?
The starting conditions are set from observation. However, CLIMATE models are far less sensitive to initial conditions, than are WEATHER forecasting models.

Because climate models are run over very long spans (years, decades) of simulated time, the physical dynamics take over and quickly eliminate any thermodynamical imbalances in initial conditions (assuming those errors aren't utterly egregious, such as initializing an Earth simulation with the parameters of Venus...)

The important parameters include extent and composition of the atmosphere, surface topography and albedo of the planet and its oceans, and radiative flux from the Sun. The detailed temperature/pressure profile of the atmosphere at the beginning of the simulation is unimportant (can indeed be seeded with random values multiplied by an envelope function.)

E.g. see here for more details:

http://www-das.uw...gcm.html
Jimee
1 / 5 (3) Nov 10, 2010
When people want to deny, they find reasons to deny, hence Obama's birth certificate isn't really a birth certificate ("a rose by any other name..."), even when it is contrary to their own self interests. It seems to be human nature.
ArtflDgr
2.3 / 5 (3) Nov 13, 2010
At some point ya kind of wish the world would end so you wouldn't have to listen to all the people telling you it will end...
ArtflDgr
2.3 / 5 (3) Nov 13, 2010
Hence Obama's birth certificate isn't really a birth certificate

If your going to say it at least get the details right...

Hence Obama's "certificate of live birth" (COLB) isn't really a birth certificate (BC)

sounds the same to me, how bout you?
after all, they are two different types of documents which do not have the same information on them, with one having more. Also one can be obtained by non citizens, and the other no.

So yes i see how you can see they are the same...
If they weren't then you would have no point, since you dont want to have no point, you ignore that problem to continue making a point as if its real without that detail. which i guess is true if your talking to people who also dont know.

Quantum_Conundrum
2.3 / 5 (3) Nov 13, 2010
Convection is driven by a temperature *differential*.

Correct, as are all heat engines.

Raising the temperature of the atmosphere increases the temperature of the "cold" reservoir in the hurricane, therefore decreasing it's potential intensity.
Vendicar_Decarian
1 / 5 (1) Nov 14, 2010
"I am speechless" - Kloog

And scientifically illiterate as well. The comment you are speechless about refers to a statistical anomaly.

"The measurements are wrong, but the models are correct?" - Kloog

I suppose the average fool from Planet Conservadopia might think so.

The scientifically literate know better.

Vendicar_Decarian
1 / 5 (1) Nov 14, 2010
"Uh, what are the models based on if the measurements are wrong?" - Kloog

Then all of the science developed over the last 150 years is wrong.

And that isn't very likely is it, John Boy?
Vendicar_Decarian
1 / 5 (1) Nov 14, 2010
"Weather balloons take VERY accurate temperature measurements; it's just that the results weren't what the alarmists' models were predicting" - Kloog Fart

Oh look... Yet another lie from the Conservative Denialist camp.

Surprise. surprise...
Vendicar_Decarian
1 / 5 (1) Nov 14, 2010
"If you are claiming that real world temp measurements are not used to set up the model before they run it, then you are out of your mind."-FlogFart

They aren't of course, and no one would want them to be since the desired result is the average result from an ensemble of runs with different initial conditions

It is laughable that these Conservative Denailist Tards are ignorant of virtually every aspect of climate science and science in general.

GSwift7
1 / 5 (2) Nov 14, 2010
"They aren't of course, and no one would want them to be since the desired result is the average result from an ensemble of runs with different initial conditions

It is laughable that these Conservative Denailist Tards are ignorant of virtually every aspect of climate science and science in general"

The usual leftist response, straight from the pages of sites which describe how to respond when you don't know anything. Name calling, repetition, politicization, change of focus to other issues, denial of simple facts, flat out lies, etc, but I really love the name calling because it is most easily recognized by other people as a mark that you are here for some purpose other than discussion of the article above.
GSwift7
1 / 5 (2) Nov 15, 2010
"This study is an exciting example of how applying our knowledge of physical processes in the tropical atmosphere can give us important information when direct measurements may have failed us"

There are two possibilities when observation doesn't match theory. One is that the observations are somehow incomplete or inaccurate, as they suggest here. More than 50 years of observation by NASA, NOAA, US Air Force, climate and weather scientists around the world, satelites, etc. ...all wrong. The other possibility is that the theory needs some modification to account for the difference between theory and observation. I would say that it's time to go back to the field and make some more observations to either confirm or deny those two possibilities. That's what scientists in any other branch of science would do. In similar stories regarding dark matter, for example, the result of conflicts between theory and observation leads to questions, rather than conclusions. This is political science.

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