Re: OT: interesting global warming quote found elsewhwere

In <ro0t8452tp47cpm6veas7t201rrg1lkk64@xxxxxxx>, Jonathan Kirwan wrote:
On Mon, 28 Jul 2008 19:25:13 -0700 (PDT), bill.sloman@xxxxxxxx wrote:

On Jul 28, 3:11 pm, d...@xxxxxxxxxxxxxx (Don Klipstein) wrote:
In <78d062ec-67ec-4845-a52c-6dcc612b2...@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,

bill.slo...@xxxxxxxx wrote:
On Jul 28, 4:40 am, John Larkin
<jjlar...@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
On Sun, 27 Jul 2008 18:06:36 GMT, Jonathan Kirwan

<jkir...@xxxxxxxxxxxxxx> wrote:
On Sun, 27 Jul 2008 04:14:24 +0000 (UTC), d...@xxxxxxxxxxxxxx (Don
Klipstein) wrote:

<snip>
 If Cat-6 is invented, such storms would only exist where there is
extremely warm water to sustain them.

And consistently or increasingly cool stratospheric temperatures to
help power the engine; I gather hurricanes are essentially an engine
driven by moving heat upwards across a temperature differential.

Which is why the bad ones hit in late summer (Galveston was wiped out
on September 8; Betsy hit New Orleans on Sep 9, Katrina August 29) as
the water stays warm but the atmosphere is cooling. It's not the warm
water that powers the storm, it's the differential. So the simplistic
observation that global warming makes the water warm, and warm water
makes for worse hurricanes, doesn't necessarily follow.

The critical feature for hurricanes is a sea surface that is hot
enough (over 26.5C) to get enough water vapour into the rising air to
release enough heat when it condenses higher in the atmosphere to
drive run-away circulation. Over a hurricane, there are rising air
columns driven by heat from the sea surface, matched by falling air
columns going down to get more water and more heat, so the hurricane
carries its own upper air temperature along with it.

  Hurricanes are almost small enough to be mesoscale weather phenomena.
They will weaken or die if the air temperature at pressure level of their
tops a few hundred miles outside their centers is warmer.

http://en.wikipedia.org/wiki/Hurricane

Tropical cyclones reach up to the tropopause, which is to say the
thermodynamic sink for the circulating energy is presumably radiation
to space (from above the "greenhouse" blanket) rather atmospheric
circulation -

  The thermodynamic sink in a hurricane is cooling to prevailing
temperatures at the tropopause level of the tropical atmosphere.  
Hurricane-prone and hurricane-forming tropical areas tend to have a lot of
convection from surface to tropopause during hurricane season.  The global
circulation and prevailing weather lift air in the ITCZ to about 60,000
feet (about 19 km or so) and that air cools during lifting to the
prevailing temperatures in that level of the atmosphere in the tropics.

as it is for mid-latitude hurricanes (at today's
temperatures - a dose of global warming would enlarge the range of
"tropical" hurricanes).

  Hurricanes weaken when reaching mid-latitudes due to running into warmer
air around the 150-100 millibar levels and and also from going over cooler
water.  Hurricanes far north in the Atlantic late in 2005 were less tall
than most and relied mostly on temperature difference between sea surface
and the 200-300 millibar level or so.  I remember the warmer eyewall tops
of those less-tall hurricanes so far north so late in the season such as
Vince and Epsilon and tropical strorm Zeta - I looked a lot at the
satellite maps with the temperature-color-coded cloud top patterns.  
Cooler air at 300 and 500 milibar level compared to typical for tropics
was essential for those storms.  It surely appears that air in hurricane
tops moves outside quickly rather than experiences significant radiation
cooling.

There is a huge mass of relatively dense air at sea level in a
hurricane. At any givien moment, half of it is moving up to the
tropopause to dump the heat it has collected from the sea surface. You
talk as if the heat being dumped by this large mass of air is being
dissipated by the much less dense air at and above the tropopause - my
feeling is that most of it has to be going out into space, because
there isn't enough heat capacity in the upper atmosphere to soak it
up.

Radiation is proportional to the fourth power of temperature, so you
don't have to warm up the top of the optically thick atmosphere all
that much to boost the local radiation level.

All this discussion made me curious enough to do some searches. I
found this, which discusses hurricanes and energy:

http://weather.cod.edu/sirvatka/1115/tropical.meteorology.pdf

It it, I found, "When air radiates to space near the top of the
troposphere, it becomes cooler, losing internal energy and subsides,
thus causing a loss in potential energy." Not a quantitative
statement, but a qualitative one that is suggestive you may be right
about this.

There is a satellite, GERB (Geostationary Earth Radiation Budget
Experiment), that takes measurements and provides false color images
of the outgoing longwave radiation of the Earth. From inspection of
past images, it seems the most intense places for radiation to leave
the Earth are in hurricanes and typhoons. GERB is at:

http://www.ssd.rl.ac.uk/gerb/SCIENCE.HTM

I'm just learning right now, but it seems that from the structures
I've looked at (again, see the PDF mentioned above) for hurricanes and
the flows indicated seem consistent with radiation to space being the
dominant method.

I have looked at enough color-coded-by-temperature tropical Atlantic
infrared images. In whatever wavelength range is used for those, the most
intense radiation is coming from warm water without clouds over it.
Hurricane tops and the tops of similarly tall tropical thunderstorms are
at the cold extreme - though clear air at the same altitude somewhat
outside these storms should be slightly colder still in order for air from
these storms to rise to that level.

- Don Klipstein (don@xxxxxxxxx)
.

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