Climate change will drive stronger, smaller storms in US

Climate change will drive stronger, smaller storms in U.S.
Rainstorms constructed by the authors' tracking algorithm in three consecutive example time steps in model output, showing how it can efficiently track multiple events simultaneously and represent various storm merging and splitting situations. This example contains a storm merger in the northwest (orange and dark-green storms combine) and a storm split in the southeast (light-green storm splits into multiple segments). Credit: University of Chicago

The effects of climate change will likely cause smaller but stronger storms in the United States, according to a new framework for modeling storm behavior developed at the University of Chicago and Argonne National Laboratory. Though storm intensity is expected to increase over today's levels, the predicted reduction in storm size may alleviate some fears of widespread severe flooding in the future.

The new approach, published today in Journal of Climate, uses new statistical methods to identify and track storm features in both observational weather data and new high-resolution climate modeling simulations. When applied to one simulation of the future effects of elevated atmospheric carbon dioxide, the framework helped clarify a common discrepancy in model forecasts of precipitation changes.

"Climate models all predict that storms will grow significantly more intense in the future, but that total precipitation will increase more mildly over what we see today," said senior author Elisabeth Moyer, associate professor of geophysical sciences at the University of Chicago and co-PI of the Center for Robust Decision-Making on Climate and Energy Policy (RDCEP). "By developing new statistical methods that study the properties of individual rainstorms, we were able to detect changes in storm frequency, size, and duration that explain this mismatch."

While many concerns about the global impact of climate change focus on increased temperatures, shifts in precipitation patterns could also incur severe social, economic, and human costs. Increased droughts in some regions and increased flooding in others would dramatically affect world food and water supplies, as well as place extreme strain on infrastructure and government services.

Most agree that high levels of atmospheric carbon will increase precipitation intensity, by an average of approximately 6 percent per degree temperature rise. These models also predict an increase in total precipitation; however, this growth is smaller, only 1 to 2 percent per degree temperature rise.

Understanding changes in storm behavior that might explain this gap have remained elusive. In the past, climate simulations were too coarse in resolution (100s of kilometers) to accurately capture individual rainstorms. More recently, high-resolution simulations have begun to approach weather-scale, but analytic approaches had not yet evolved to make use of that information and evaluated only aggregate shifts in instead of individual storms.

Climate change will drive stronger, smaller storms in U.S.
Fractional changes in total precipitation and rainstorm characteristics between model baseline and future runs, for both (left) summer and (right) winter. Credit: University of Chicago

To address this discrepancy, postdoctoral scholar Won Chang (now an assistant professor at the University of Cincinnati) and co-authors Michael Stein, Jiali Wang, V. Rao Kotamarthi, and Moyer developed new methods to analyze rainstorms in observational data or high-resolution model projections. First, the team adapted morphological approaches from computational image analysis to develop new statistical algorithms for detecting and analyzing individual rainstorms over space and time. The researchers then analyzed results of new ultra-high-resolution (12 km) simulations of U.S. climate performed with the Weather Research and Forecasting Model (WRF) at Argonne National Laboratory.

Analyzing simulations of precipitation in the present (2002-2011) and future (years 2085-2094), the researchers detected changes in storm features that explained why the stronger storms predicted didn't increase overall rainfall as much as expected. Individual storms become smaller in terms of the land area covered, especially in the summer. (In winter, storms become smaller as well, but also less frequent and shorter.)

"It's an exciting time when models are starting to look more like weather models," Chang said. "We hope that these new methods become the standard for model evaluation going forward."

The team also found several important differences between model output and present-day weather. The model tended to predict storms that were both weaker and larger than those actually observed, and in winter, model-forecast storms were also fewer and longer than observations. Assessing these model "biases" is critical for making reliable forecasts of future storms.

"While our results apply to only one model simulation," Moyer said, "we do know that the amount-intensity discrepancy is driven by pretty basic physics. Rainstorms in every model, and in the real world, will adjust in some way to let intensity grow by more than total rainfall does. Most people would have guessed that storms would change in frequency, not in size. We now have the tools at hand to evaluate these results across models and to check them against real-world changes, as well as to evaluate the performance of the models themselves."

New precipitation forecasts that include these changes in storm characteristics will add important details that help assess future flood risk under . These results suggest that concerns about higher-intensity storms causing severe floods may be tempered by reductions in storm size, and that the tools developed at UChicago and Argonne can help further clarify future risk.


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More frequent, more intense and longer-lasting storms cause heavier spring rain in central US

More information: Won Chang et al. Changes in Spatiotemporal Precipitation Patterns in Changing Climate Conditions, Journal of Climate (2016). DOI: 10.1175/JCLI-D-15-0844.1
Journal information: Journal of Climate

Citation: Climate change will drive stronger, smaller storms in US (2016, December 5) retrieved 13 October 2019 from https://phys.org/news/2016-12-climate-stronger-smaller-storms.html
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Dec 05, 2016
Anecdotally, I believe a review of the total amount of time with significant precipitation in the mid-Atlantic U.S. would show a big decrease over the last 50 years, especially in the summer. It seems that every rainstorm this past summer here came with a flash flood warning, with not one single gentle summer rain. So even if the summer rainfall total was comparable to 50 years ago, the way it came down was very different.

Dec 05, 2016
Get ready for the conservative climate, one we hope will be beneficial to Humans. But the chances of that are not good.

We have destabilized the interactions of complex systems, which have had a stable state for Human habitation. In the far past, we could not exist. What makes the uneducated assume we will be able to survive climate change?

Dec 05, 2016
Globull warming, now with 100% more bull.
My data analysis predicted more stronger and smaller loads of BS from the AGW Cult.

Dec 05, 2016
here is an odd one , from skeptical science , who knew ? re the upper atmosphere and co2 ,, things get warmer when its cold ,

''How much heat escapes to space from this altitude then depends on how cold the air is at that height. The colder the air, the less heat it radiates.''

so the next time i have to cool something hot i will be sure not to put it somewhere cold.

Dec 08, 2016
what was it Hillary's been going on about, Fake News?

The climate changes, AGW is a hoax and that's all that needs be said about that. Good day.

Dec 09, 2016
here is an odd one , from skeptical science , who knew ? re the upper atmosphere and co2 ,, things get warmer when its cold ,

''How much heat escapes to space from this altitude then depends on how cold the air is at that height. The colder the air, the less heat it radiates.''
This seems counter-intuitive until you think about it carefully, but the statement you quoted makes a lot of sense: it's saying that the colder something is, the less heat it radiates. You can verify this yourself simply by noting that less heat is radiated by ice than by boiling water.

In the case of atmospheric warming, what's happening is that the lower atmosphere retains more heat, meaning the upper atmosphere gets less heat. The ground, then, gets warmer, but from space the Earth is cooler; this is because less of the heat makes it to the upper atmosphere, and from there to space.
[contd]

Dec 09, 2016
[contd]
In the same way, a thermos filled with hot coffee is much cooler to the touch than the same amount of coffee at the same temperature in a glass carafe. The heat is retained inside instead of being radiated to the outside.

Dec 10, 2016
Schneib , but co2 in the stratosphere [ the glass carafe] has no impact on GW , the rest of your arguement still makes no sense , cold things cool other things off.

Dec 10, 2016
i'll put it this way, the GW argument is really that co2 is not saturated in the troposphere,, ok,,, but that still is an odd statement about cold objects and it seems strange to frame the GW argument that way

Dec 10, 2016
Schneib , but co2 in the stratosphere [ the glass carafe] has no impact on GW,
Of course not. There are two reasons for this:
1. The density of the stratosphere is far lower. This means it can contain far less heat.
2. By the time the heat from the ground has gone through the troposphere, most of it has been absorbed.

Understanding this requires a certain amount of knowledge of physics.

the rest of your arguement still makes no sense , cold things cool other things off.
That's not actually correct. Heat tends to move from a hotter area to a cooler one, until the two areas are equalized; but it does not do so instantly. Three processes move heat:
1. Conduction
2. Convection
3. Radiation

Conduction between the troposphere and stratosphere is limited by the density of the stratosphere; it simply can't absorb much heat because it isn't dense enough.

[contd]

Dec 10, 2016
[contd]
Convection between the troposphere and stratosphere is again limited by the density of the stratosphere, and by the tropopause; it's obvious that even if the troposphere and stratosphere were completely exchanged regularly, and even if the tropospheric molecules retained their heat indefinitely (which they cannot, photon-excited molecules decay and re-radiate their heat as a photon, in a random direction, with a half-life of seconds) there simply isn't enough stratosphere to contain much heat. Meanwhile the tropopause interferes with convection between the troposphere and stratosphere.

The only way left is radiation, and most of the heat absorbed by the troposphere is re-radiated in a random direction, so most of it stays in the troposphere or is re-absorbed by the ground. This is simply because of the sightlines.
[contd]

Dec 10, 2016
[contd]
So when you say, "cold things cool other things off," you've vastly oversimplified. It doesn't really work that way, and the ways it does work are statistical and probabilistic, not inevitable on the timescale of the absorption and re-radiation of photons.

After all, if you were correct, then thermoses wouldn't work.

Dec 10, 2016
sorry i mixed up troposphere and stratosphere :{ ,, but to continue

''limited by the density of the stratosphere; it simply can't absorb much heat because it isn't dense enough. ''

so are you saying the vacuum of space is an insulator ? and if i put a thermos in a cold space its still going to cool. one way or another.


Dec 10, 2016
''limited by the density of the stratosphere; it simply can't absorb much heat because it isn't dense enough. ''

so are you saying the vacuum of space is an insulator ?
Your reasoning here is not clear.

Do you understand that a thermos is a vacuum flask? And that the vacuum in a thermos is part of the insulation, but not all?

The vacuum prevents conduction and convection. To prevent radiation, a coating of silver is used to reflect it.

Now, what exactly do you mean by "insulator?"

and if i put a thermos in a cold space its still going to cool. one way or another.
But the point is that it cools much more slowly.

And you forgot there's no heat going in to the thermos; but on Earth, we have that big yellow thing up in the sky you seem to think it's OK to ignore.

Like I said: you need to know some physics.

Dec 10, 2016
To answer your question, it seems pretty obvious to me that neither convection nor conduction can occur in the absence of matter, which is what the vacuum of space is. Therefore, yes, space is an insulator- for convection and conduction. Heat can only enter or leave the Earth's atmosphere by radiation.

Ultimately, the temperature of the Earth and its atmosphere is dependent upon the balance between incoming and outgoing radiation. It's the only game in town. If there is more radiation coming in than goes out, then the Earth will get warmer. It will continue to do so until its radiation, which increases with temperature, equals the incoming radiation from the Sun.

So, if
1. Radiation absorbed from the Sun remains the same, and
2. Radiation emitted to space from the Earth is reduced,
what happens?

Simple, easy, obvious. This is thermodynamics 101.

Like I said: you need to know some physics.

Dec 10, 2016
thanks for explaining heat loss in a vacuum,,

but
'''and if i put a thermos in a cold space its still going to cool. one way or another.''

'''But the point is that it cools much more slowly. '''

so i put something in a cooler space and it cools more slowly ??


Dec 10, 2016
This comment has been removed by a moderator.

Dec 10, 2016
This comment has been removed by a moderator.

Dec 10, 2016
but so this statement should read

''How much heat escapes to space from this altitude then depends on how cold the air is at that height. The colder the air, the less heat it radiates.''

depends on how thin the air is at that height. The thinner the air, the less heat it radiates.''


Dec 10, 2016
but so this statement should read

''How much heat escapes to space from this altitude then depends on how cold the air is at that height. The colder the air, the less heat it radiates.''

depends on how thin the air is at that height. The thinner the air, the less heat it radiates.''

But that's not correct. It's not just the air radiating at that height; there is also radiation coming up from below, which could still be scattered in the stratosphere; but the probability of it scattering is much lower in the much less dense stratosphere. So in fact, how much heat escapes to space from the height of the stratosphere is subject to two different influences:
1. How much it radiates
2. How much it scatters

How much it radiates depends upon its temperature; if it is cooler it radiates less. How much it scatters doesn't depend upon its temperature, only on its density.

Dec 10, 2016
Oh, and of course the scattering also depends upon the composition of the air in the stratosphere; there will be more scattering if there is more CO2, since CO2 absorbs radiated heat (infrared) at frequencies near the peak of the Wien curve for the temperature lower down.

The particular quote you picked is incomplete, but there could be additional information in the article that puts it in context and makes the idea complete.

The big point I'm making here is that conduction, convection, and radiation can all fairly be called "heat" but the ways they work are very different.

Conduction is when one excited molecule bounces off another and there is a momentum transfer between them; in this case, "heat" is defined as the velocity of the molecules.

[contd]

Dec 10, 2016
[contd]
Convection is when a population of hot, i.e. high-velocity molecules, is mixed with a population of cool, i.e. low-velocity molecules. Ignoring conductive momentum transfers, the average temperature of each population will move toward a point between the original temperatures of the two populations. In this case, "heat" is defined as the *average* velocity of the molecules.

Radiation is when a molecule emits a photon of infrared light. In this case, "heat" is defined as the flux of infrared photons.

These three different definitions make it clear that without context, it is very dangerous to quote a single sentence containing the word "heat" without context to indicate what kind of heat the article is talking about.

Dec 11, 2016
Thanks for your patience , but it seems to me they are taking the idea that radiation slows as the object gets cooler out of context ie a hot object in space will cool rapidly at first ( but slower in comparison to an object in air)

Dec 11, 2016
You're welcome. I was able to identify the article you're referring to, I think. Please confirm: https://www.skept...hp?r=190

I have to agree that the explanation leaves a bit to be desired. However, the assertion that the temperature of an object is the only thing that governs how much it radiates is correct. That is not the problem with the explanation. The problems are:

1. The effects of incoming radiation are not dealt with; because of this the explanation only works for the nightside of Earth. On the dayside, there are both outgoing and incoming radiation, and a balance between them. This is never mentioned.
2. In a regime where CO2 is well mixed throughout the atmosphere, convection and conduction operate as well.
[contd]

Dec 11, 2016
[contd]
3. Density is never explicitly dealt with either. Thus, atmospheric temperature is used as a direct proxy for heat content, which ignores the fact that the amount of heat in the upper atmosphere-- despite its temperature-- must be much lower.

The article could be far better written if these factors were taken into account. It is still correct; but it is incomplete.

For example, the quote you made would better describe the situation if it took both the temperature and the density into account. The prior explanation would be better if it did, too, and it should also take into account the effects of density on *scattering*. And in fact, it's not just simple scattering; it's actually deep inelastic scattering, specifically. Deep inelastic scattering in this regime is absorption followed by re-emission of photons.

[contd]

Dec 11, 2016
[contd]
Worst of all, the article does not give a complete answer to the also correct but also incomplete statement that CO2 is near saturation. While this is true, it is immaterial.

Infrared photons from the Earth's surface mostly don't make it to space. What actually happens is a relay, from one layer of the atmosphere to another. When a photon traveling upward toward space is absorbed, it is re-emitted in a random direction. About half of all such emissions are back toward where the photon came from (the ground and lower atmosphere), and about half are onward more-or-less in the direction it was going (toward space and eventual emission from the atmosphere). This is the raw greenhouse effect, which makes the Earth about 33C warmer at the surface than the average temperature of the Moon's surface at the same distance from the Sun.
[contd]

Dec 11, 2016
[contd]
Of this 33C, about 13C is due to CO2. The remainder is due to other greenhouse gases, like water vapor, which accounts for almost all of it.

But here's the thing: while CO2 may be saturated in the lower atmosphere, the lower atmosphere isn't the part that radiates to space. It's the upper atmosphere that does this, and this is because of density. It is the lower density of the upper atmosphere that causes it to be less and less saturated, and to allow more and more heat to radiate to space from higher and higher levels.

So moving upward in the atmosphere, lower and lower densities allow more and more heat to escape.

Now, what is the effect of increased CO2? Simply this: the saturation level moves higher in the atmosphere. The density at the various levels doesn't change; but the concentration of CO2 does. Since both density and CO2 concentration affect the level of saturation, this result is obvious.
[contd]

Dec 11, 2016
[contd]
Note also that this is true no matter how the heat gets to the upper atmosphere, whether by radiation and absorption, by convection, or by conduction. However it gets there, the only operative variable in the state equation that controls the temperature of the Earth is the amount of heat that gets radiated to space, compared with the amount that is absorbed from the Sun.

This implies that the extinction ratio at the surface is immaterial; it is the extinction ratio (directly controlled by the saturation level) in the upper atmosphere, where the heat is radiated, that is important, and the argument that CO2 is at saturation ignores this and so fails.

The argument against also fails; but not because it is incorrect. It also ignores density, though it does at least manage to mention the upper atmosphere. Because it doesn't discuss density it doesn't discuss the decline in saturation with altitude.

Dec 11, 2016
schnieb , thanks for that clear explanation [ way to much typing on my behalf] , i should know better than to argue with pros , but

''It's the upper atmosphere that does this, and this is because of density. It is the lower density of the upper atmosphere that causes it to be less and less saturated, and to allow more and more heat to radiate to space from higher and higher levels. ''

so if we push the boundary higher won't that increase heat loss ? or compensate for the higher co2 not being saturated.?

Dec 11, 2016
It's not you, that's how much has to be said to make the point clear. If the explanation is long it means you asked a good question. ;)

It's the upper atmosphere that does this, and this is because of density. It is the lower density of the upper atmosphere that causes it to be less and less saturated, and to allow more and more heat to radiate to space from higher and higher levels.
so if we push the boundary higher won't that increase heat loss?
Please explain your reasoning here. Remember density.

Dec 11, 2016
i understand that since its less saturated adding more co2 increases the greenhouse effect but as you say '' and to allow more and more heat to radiate to space from higher and higher levels.'',
so the idea is this is slowing the release of heat by a tiny amount but i would wonder how much makes its way back to the troposphere even by chain reaction .

by the way GW is freezing my ass off here in BC right now , so i often wonder how we still lose so much heat so easily

Dec 11, 2016
i understand that since its less saturated adding more co2 increases the greenhouse effect
The important point is that the less dense air at higher altitude means it has less heat content and will therefore radiate less heat. Add this to the fact that the temperature is colder, meaning the atmosphere at these higher altitudes radiates less. It adds up.

but as you say '' and to allow more and more heat to radiate to space from higher and higher levels.'',
so the idea is this is slowing the release of heat by a tiny amount
The whole point is, it doesn't matter if it's a tiny amount, it adds up. Even if it's only a few percent, over time it adds up. And the thing is, it's never catching up, because we're so far only talking about reducing the rate at which we're increasing the CO2. We haven't even started talking about reducing the CO2 yet. So the heat is still increasing and will keep on until well after we stabilize the CO2 content of the atmosphere.
[contd]

Dec 11, 2016
[contd]
but i would wonder how much makes its way back to the troposphere even by chain reaction
Heat doesn't go away. That's the point. It doesn't matter if it's slow, and it doesn't matter if it's only a small fraction. It keeps on adding up.

And the rate isn't staying steady; it's increasing, because we're still increasing atmospheric CO2.

by the way GW is freezing my ass off here in BC right now , so i often wonder how we still lose so much heat so easily
It's only a tiny amount each day because the Sun doesn't get as high in the sky. What are you complaining about?

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