by Dr Vincent Gray
February 19th 2013
THE ENERGY OF HURRICANES
A most
interesting calculation of the energy released
by hurricanes was published as a “Frequently Asked Question at
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:
 the total amount of energy released by the condensation of water
droplets or ...
 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.

 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 10^{16} cm3/day. A cubic cm of rain weighs 1 gm. Using the latent heat of condensation, this amount of rain produced gives5.2 x 10^{19} Joules/day or 6.0 x 10^{14} Watts.This is equivalent to 200 times the worldwide electrical generating capacity  an incredible amount of energy produced! 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) of1.3 x 10^{17} Joules/day or
1.5 x 10^{12}Watts.This is equivalent to about half the worldwide 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 spiralling winds is a huge ratio of 400 to 1.  Method 1)  Total energy released through cloud/rain formation:
A single hurricane could
provide convective cooling of 1.5x 10^{14} Watts per day and latent
heat transfer of 6x10^{14 }Watts^{
}per day. If a hurricane lasts a
week and there are 11 hurricanes a year. If the area of the earth is 5x 10^{14}m^{2 }each day
supplies^{ }0.3Wm^{2}of convection and 2,1Wm^{2} of
latent heat negative forcing.
and it is spread over 365 days to get an
annual average, If^{,}a hurricane lasts a week and there are 11
hurricanes a year 77 days of hurricane
forcing has to be spread over 365 days to get an annual average. So multiply by 77/365 and we get 0.032Wm^{2} from
convection and 0.25Wm^{2} from
latent heat.
And this was only hurricanes.
There are 180 thunderstorms each year plus normal convection and evaporation. The
IPCC gives an annual figure of 17Wm^{2} for convection loss and 80Wm^{2}
for latent heat loss, but these have been recently increased to 20Wm^{2}
and 85Wm^{2}
^{}
This should be compared with
the 1.5Wm^{2} claimed to have been supplied by the greenhouse effect
between 1750 and 2005, 0.006 Wm^{2 }increase per year.
The IPCC projects between 5
and 9 Wm^{2} increase in radiative forcing from increases in
greenhouse gases between 1990 and 2010, an annual averge of between
0.045 and 0.082Wm^{2} over this period.
The enormous amounts of
energy involved in convection and latent heat exchanges are removed in one
place and deposited elsewhere, partly in the oceans, partly reducing cooling at
night and partly, as Landsea says, radiated to space. Their behaviour,
dependent on the chaotic properties of fluid flow, is unpredictable. They
conceal any possible much smaller effects of greenhouse gases which could never
be identified. The models are not only wrong. They are irrelevant.
Cheers
Vincent
Gray
75
Silverstream Road. Crofton Downs
Wellington
6035, New Zealand
"an annual averge of between 0.045 and 0.082Wm2 " What is this term referring to?
ReplyDeleteIt is not the change in power rate assuming you meant that the power increased by 59 wm2 over the 20 year period. 59 wm2 is implied ~average power for 100 years to get the CO2 doubling temp. increase of ~3C.