-----Message d'origine-----
De : [email protected]
[mailto:[email protected]] De la part de Alvia Gaskill
Envoyé : vendredi 5 juin 2009 15:08
À : [email protected]; [email protected];
geoengineering
Objet : [geo] Re: Just in Time for Hurricane Season
Some answers, perhaps to the question of what happens to all that energy in
a hurricane, provided by the aptly named Chris Landsea. Chris was also on
TV last night on the National Geographic program, Hurricanes (2009). In
addition to not knowing much about what happens above 35,000 ft in a
tropical cyclone, including the region of the boundary with the (Overworld)
stratosphere and the upper troposphere, not much is known about what happens
near the marine boundary layer at around 200 ft, where the hurricane draws
the water vapor from the sea surface into its structure. To learn more
about it, pilots flew at around 200 ft above the sea surface of an active
hurricane, Isabel. Brave or crazy. You decide. The danger at high
altitudes is icing. In their case, it was salt spray condensing on the
engines that caused them to end the mission.
As to where does the energy go, it appears that most of it stays in the
troposphere. Hurricanes are heat machines that draw their energy from water
vapor....
AND CORIOLIS FORCES !!!
???
===========================
The water vapor condenses in the thunderstorms of the eyewall and feeder
bands. The air flow is from the surface to the top of the eyewall and then
it spills over and down back into the storm or over the edge of the clouds
at the top. In some ways, hurricanes resemble the tropics, with rising
moisture laden air that reaches a cold point where it is dried out and
spreads out horizontally via the Brewer Dobson circulation.
The air that leaves the top of a hurricane is cold already, so it is not
sending much energy back into space. The kinetic energy used to cause the
winds to circulate is generated at the expense of heat energy from condensed
water vapor, but is small by comparison with that released from producing
clouds and rain.
Eventually all of the heat energy, in the form of infrared radiation, leaves
the Earth's atmosphere and goes into space. Because this process is
continuous, individual photons only spend a fraction of a second in the
atmosphere, replaced by others instantaneously emitted. When a hurricane is
done for, the remnants are typically absorbed by another weather system and
carried, in the case of Atlantic hurricanes, into the N. Atlantic, sometimes
as far east as Ireland. Given the altitudes at which these weather systems
operate, I don't think they send much IR back to space either. Thus, I
don't believe hurricanes are an effective means of reducing the amount of
energy in the troposphere, what we typically mean when we say "the
atmosphere."
Stopping some tropical cyclones or all of them (we can't stop any of them
now, so this is just speculation, no matter what technology is considered)
might impact the regional heating of the planet, but I still doubt it would
have much of any effect on GHG driven warming and overall global warming.
Weakening the wind speeed of these storms would certainly be beneficial in
terms of reduced property damage and loss of life, although storm related
flooding is still the largest cause of death. Shifting their path away from
populated areas would also be beneficial and wouldn't affect the heat
transport fluxes as much as preventing their formation. They do provide
needed rainfall in some cases, but since their paths are unpredictable, they
are not a reliable source of precipitation and thus that shouldn't be used
as a reason to prevent landfall if it ever became possible to do so.
http://www.aoml.noaa.gov/hrd/tcfaq/D7.html
Subject: D7) How much energy does a hurricane release?
Contributed by Chris Landsea
Hurricanes can be thought of, to a first approximation, as a heat engine;
obtaining its heat input from the warm, humid air over the tropical ocean,
and releasing this heat through the condensation of water vapor into water
droplets in deep thunderstorms of the eyewall and rainbands, then giving off
a cold exhaust in the upper levels of the troposphere (~12 km/8 mi up).
One can look at the energetics of a hurricane in two ways:
1.. the total amount of energy released by the condensation of water
droplets or ...
2.. the amount of kinetic energy generated to maintain the strong swirling
winds of the hurricane (Emanuel 1999).
It turns out that the vast majority of the heat released in the condensation
process is used to cause rising motions in the thunderstorms and only a
small portion drives the storm's horizontal winds.
a.. Method 1) - Total energy released through cloud/rain formation:
An average hurricane produces 1.5 cm/day (0.6 inches/day) of rain inside a
circle of radius 665 km (360 n.mi) (Gray 1981). (More rain falls in the
inner portion of hurricane around the eyewall, less in the outer rainbands.)
Converting this to a volume of rain gives 2.1 x 1016 cm3/day. A cubic cm of
rain weighs 1 gm. Using the latent heat of condensation, this amount of rain
produced gives
5.2 x 1019 Joules/day or
6.0 x 1014 Watts.
This is equivalent to 200 times the world-wide electrical generating
capacity - an incredible amount of energy produced!
b.. Method 2) - Total kinetic energy (wind energy) generated:
For a mature hurricane, the amount of kinetic energy generated is equal to
that being dissipated due to friction. The dissipation rate per unit area is
air density times the drag coefficient times the windspeed cubed (See
Emanuel 1999 for details). One could either integrate a typical wind profile
over a range of radii from the hurricane's center to the outer radius
encompassing the storm, or assume an average windspeed for the inner core of
the hurricane. Doing the latter and using 40 m/s (90 mph) winds on a scale
of radius 60 km (40 n.mi.), one gets a wind dissipation rate (wind
generation rate) of
1.3 x 1017 Joules/day or
1.5 x 1012Watts.
This is equivalent to about half the world-wide electrical generating
capacity - also an amazing amount of energy being produced!
Either method is an enormous amount energy being generated by hurricanes.
However, one can see that the amount of energy released in a hurricane (by
creating clouds/rain) that actually goes to maintaining the hurricane's
spiraling winds is a huge ratio of 400 to 1.
Back to Tropical Cyclones Winds Page | Back to Main FAQ Page
----- Original Message -----
From: "Margaret Leinen" <[email protected]>
To: <[email protected]>; "geoengineering"
<[email protected]>
Sent: Friday, June 05, 2009 7:21 AM
Subject: [geo] Re: Just in Time for Hurricane Season
Oliver and all,
Again, this is NOT my area of expertise, but I am aware of a little work
that has been done based on hurricane measurements combined with modeling.
Unfortunately, I haven't found anything that gives flux numbers, but the
NOAA Aeronomy Laboratory group has been looking at this and those that are
interested might contact them. Here's an example that from an AGU meeting
abstract:
Upper Tropospheric-Lower Stratospheric In-Situ Measurements Over Hurricane
Floyd: The Impact of Tropical Cyclones on Stratosphere-Troposphere Exchange
AU: * Richard, E C
EM: [email protected]
AF: NOAA Aeronomy Laboratory, 325 Broadway R/AL6, Boulder, CO 80305 United
States
AU: Rosenlof, K H
EM: [email protected]
AF: NOAA Aeronomy Laboratory, 325 Broadway R/AL6, Boulder, CO 80305 United
States
AU: Ray, E A
EM: [email protected]
AF: NOAA Aeronomy Laboratory, 325 Broadway R/AL6, Boulder, CO 80305 United
States
AU: Kelly, K K
EM: [email protected]
AF: NOAA Aeronomy Laboratory, 325 Broadway R/AL6, Boulder, CO 80305 United
States
AU: Thompson, T L
EM: [email protected]
AF: NOAA Aeronomy Laboratory, 325 Broadway R/AL6, Boulder, CO 80305 United
States
AU: Mahoney, M J
EM: [email protected]
AF: Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109
United States
AB: The structure of hurricanes from the surface up to 200 mb (12 km) has
been extensively studied. However, because of operational limitations of
aircraft, very little in-situ information has been obtained within the
hurricane environment in the upper troposphere-lower stratosphere (UT/LS).
During the ACCENT experiment the WB-57 overflew Hurricane Floyd as it made
landfall near the Georgia-South Carolina coastal boarder. High time
resolution in-situ chemical measurements of ozone, methane and water vapor
as well as meteorological data were obtained over a large area above Floyd,
including regions of the eye-wall and eye. Two days prior, a similar flight
track was followed by the WB-57 allowing for a comparison study of the
influence of Floyd on the UT/LS region. In the UT/LS, ozone and methane
serve as conserved tracers of stratospheric and tropospheric air,
respectively and are used to compare the characteristics of the air masses.
A comparison of the vertical profiles between the tropopause and 80 mb (18
km) for these two days shows lower water vapor, lower ozone and higher
methane mixing ratios during the Floyd overflight. The results are
consistent with local dehydration occurring above the storm, while the lower
ozone and higher methane are indicative of upward transport of ozone poor
and methane rich tropospheric air. In an attempt to quantify the mass flux
into the stratosphere induced by Floyd we have performed an NCAR Mesoscale
Model 5 (MM5) simulation. These results are compared with the in-situ data
to assess the influence of Floyd on the stratosphere above the 400 K
potential temperature level. Additionally, these results allow us to address
the validity of the satellite results from the Total Ozone Mapping
Spectrometer (TOMS) where local changes in the total ozone column have been
used to elucidate hurricane evolution.
On 6/2/09 11:33 PM, "Oliver Wingenter" <[email protected]> wrote:
>
> Dear Margaret,
>
> Can you inform us about the impact of hurricanes on transport of water
> vapor and other gases to the upper troposphere/lower stratosphere (UT/
> LS)?
>
> Sincerely,
>
> Oliver Wingenter
>
> On Jun 2, 11:38 am, Margaret Leinen <[email protected]>
> wrote:
>> Alvia,
>>
>> You are correct that hurricanes and tropical cyclones move heat. It was
>> not
>> clear from your answer whether you were saying that you doubted that they
>> mattered much for heat dissipation on a global scale or whether you were
>> saying that you doubted that they mattered much for heat transport. They
>> are actually an important mechanism for the latter. Estimates based on
>> observations incorporated into models suggested that ocean heating
>> induced
>> by topical cyclones could be as much as 1.4 (± 0.7) × 10^^15 W for a
>> single
>> year (Emanuel, 2001), a significant fraction of the observed peak
>> poleward
>> heat flux and enough to require consideration in the climate system. More
>> recent modeling by Hu and Meehl (Gerry may be on this list and is far
>> more
>> authoritative on this topic than am I) (2009) also suggests that
>> hurricanes
>> can strengthen the meriodional overturning circulation and may play an
>> important role in the climate system.
>>
>> Margaret
>>
>> On 6/2/09 1:12 PM, "Alvia Gaskill" <[email protected]> wrote:
>>
>>
>>
>>> As the article indicates, what hurricanes do is move heat around, not
>>> dissipate it. Whether this actually cools the planet is unknown. Given
>>> the
>>> relatively small number of all tropical cyclones and their short
>>> lifetimes
>>> of
>>> around a week or so, I doubt they matter very much on a global scale.
>>> Another
>>> theory has them increasing atmospheric CO2 by stirring up surface
>>> waters,
>>> although they may also reduce it by upwelling nutrients causing
>>> phytoplankton
>>> blooms. Global warming didn't stop because of all the storms in 2005
>>> (the
>>> year of Katrina) and it didn't get worse in the subsequent years due to
>>> fewer
>>> storms.
>>
>>> http://dsc.discovery.com/news/2009/01/29/hurricane-climate-02.html
>>
>>> Hurricanes' Climate Footprint Felt for Months
>>> Michael Reilly, Discovery News
>>
>>> Jan. 29, 2009 -- Just as a changing climate shapes the strength and
>>> frequency
>>> of hurricanes, the storms may have a huge effect on climate, leaving
>>> "footprints" in the atmosphere and ocean.
>>
>>> Watch a video on hurricane-prone coastlines.
>>
>>> Hurricanes are infamous as harbingers of chaos -- flooding cities,
>>> ripping
>>> houses to shreds, destroying beaches and even whole islands. And
>>> concerns
>>> are
>>> growing that human-induced climate change may lead to stronger storms
>>> whose
>>> intensity will wreak even more havoc on coastal communities around the
>>> world.
>>
>>> But the full interplay between hurricanes and climate remains an enigma.
>>
>>> Robert Hart of Florida State University analyzed two decades of climate
>>> data
>>> from the tropics, and found that each storm leaves a wake of anomalously
>>> cool
>>> water and warm air behind it that can persist anywhere from one to two
>>> months,
>>> depending on the storm's strength.
>>
>>> Scientists have known for years that hurricanes cause cool ocean waters
>>> to
>>> well up, but Hart was surprised at how long the atmosphere retained a
>>> "memory"
>>> of each storm.
>>
>>> That got him thinking: if one storm can have such a lasting impact, what
>>> does
>>> a whole season of storms do to Earth's climate? Would there be a
>>> difference
>>> in
>>> effect between an active hurricane season and a quiet one?
>>
>>> Hart performed a series of calculations and came up with a striking
>>> preliminary answer: hurricane seasons that spawned more storms (like
>>> 2005,
>>> for
>>> example) led to quieter winters in the northern hemisphere, and quiet
>>> hurricane seasons led to winters with lots of storm activity.
>>
>>> The reason, Hart speculates, is that hurricanes bring large amounts of
>>> heat
>>> out of the tropics and toward the poles. When a season has more storms,
>>> more
>>> heat is deposited closer to the poles and the tropics are cooled off
>>> more,
>>> so
>>> that when winter sets in there is less temperature difference between
>>> the
>>> poles and tropics.
>>
>>> "That's what winter weather is -- movement of heat between the tropics
>>> and
>>> the
>>> poles," Hart said. "So it's possible that hurricanes do more than their
>>> fair
>>> share of the work during an active season, and there's less work to be
>>> done
>>> during the winter."
>>
>>> Gabriel Vecchi of the National Oceanic and Atmospheric Association's
>>> Geophyscial Fluid Dynamics Laboratory in Princeton, N.J., said Hart's
>>> work
>>> gets at some of the toughest questions in meteorology today: What are
>>> hurricanes? Do they serve a purpose?
>>
>>> "It may sound like a stupid question, but I wonder what tropical
>>> cyclones'
>>> role in the climate system is," he said.
>>
>>> There are two general theories -- one which states that hurricanes are
>>> simply
>>> the result of more potent forces, like El Nino pushing vast amounts of
>>> heat
>>> and moisture around Earth's atmosphere. The other says hurricanes are
>>> vital
>>> heat engines that transfer energy from the tropics toward the poles.
>>> Through
>>> their fury, they are in fact bringing balance to the planet's climate.
>>
>>> "The list of results about how they affect climate is getting longer,"
>>> Vecchi
>>> said. "This is all hinting that tropical cyclones do something
>>> profound."
>>
>>> ----- Original Message -----
>>> From: f.m.maugis
>>> To: [email protected] ; [email protected]
>>> Sent: Tuesday, June 02, 2009 11:30 AM
>>> Subject: RE: [geo] Just in Time for Hurricane Season
>>
>>> Why killing hurricanes, as far as they cool naturally our climate ?
>>
>>> François MAUGIS
>>> http://assee.free.fr
>>> ===============================================
>>
>>>
----------------------------------------------------------------------------
>>> --
>>> De : [email protected]
>>> [mailto:[email protected]] De la part de Alvia Gaskill
>>> Envoyé : mardi 2 juin 2009 01:09
>>> À : [email protected]
>>> Objet : [geo] Just in Time for Hurricane Season
>>
>>> I was admittedly a little drowsy when I saw the promo for this, but it
>>> appears to be another incarnation of the ocean pipes idea or perhaps the
>>> same
>>> one from Atmocean. One problem for would be hurricane killers is that
>>> they
>>> seem to be appearing in places where they shouldn't, when they shouldn't
>>> and
>>> rapidly intensifying, giving little time to react. Thus, strategies that
>>> prevent the conditions that drive hurricane development should probably
>>> be
>>> considered before filling up the Gulf of Mexico and the Atlantic with
>>> plastic
>>> pipes. The cloud ships, the partial desert cover and the stratospheric
>>> aerosols all could be part of the first line of defense.
>>
>>> http://science.discovery.com/tv-schedules/series.html?paid=48.15725.2...
>>> 4.3
>>
>>> NextWorld
>>> Future Danger
>>> TV-G
>>
>>> Future Danger enters a world where robots safeguard our cities, massive
>>> underwater heating and cooling systems break up hurricanes before they
>>> hit
>>> land, and advanced rocket interceptors protect the planet from asteroids
>>> that
>>> could wipe out humanity.
>>
>>> Air times in the U.S.: June 7, 9pm, June 8, 12am and June 9, 4 am. 60
>>> minutes.
>>
>> --
>> Margaret Leinen, PhD.
>> Climate Response Fund
>> 119 S. Columbus Street
>> Alexandria, VA 22314
>> 202-415-6545
> >
--
Margaret Leinen, PhD.
Climate Response Fund
119 S. Columbus Street
Alexandria, VA 22314
202-415-6545
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