While it is quite probable that hurricanes result in radiation escaping to space more easily, the short term local effect, I believe, is to suppress outgoing longwave radiation (OLR):
"Positive values of OLR are indicative of suppressed convection, while negative values suggest enhanced convective activity. More convective activity in the central and eastern equatorial Pacific implies higher, colder cloud tops, which emit much less infrared radiation into space. " http://www.ncdc.noaa.gov/oa/climate/research/teleconnect/discussion.html http://svs.gsfc.nasa.gov/vis/a000000/a001200/a001296/a001296.mpg or " The blue swaths represent thick clouds, the tops of which are so high they are among the coldest places on Earth. " http://mix.msfc.nasa.gov/IMAGES/MEDIUM/0300805.jpg http://mix.msfc.nasa.gov/abstracts.php?p=2622 ___________________________________________________ Ken Caldeira Carnegie Institution Dept of Global Ecology 260 Panama Street, Stanford, CA 94305 USA [email protected]; [email protected] http://dge.stanford.edu/DGE/CIWDGE/labs/caldeiralab +1 650 704 7212; fax: +1 650 462 5968 On Sun, Jun 7, 2009 at 7:15 AM, Andrew Lockley <[email protected]>wrote: > A few random thoughts on this very long thread. > 1) Steering > Could you steer a hurricane by cooling one side and heating another - kinda > like how a tank steers by slowing down one track. Done early enough, even a > small change in angle would adjust the landfall by miles. > > 2) Suppression > The idea of using soot to change albedo and thus forcing of the area around > a hurricane has been previously discussed. Is it promising? > > 3) Geoengineering > Could blowing soot, or changing the CCN size, be used in night/day > respectively to make the hurricane radiate/absorb more heat into space and > thus alter the planet's radiative balance. > > 4) Sea cooling > Can anyone estimate the duration of the sea cooling effect? Does the warm > water stay down for thousands of years, or is the energy balance returned to > baseline level in a matter of weeks? > > 5) Upwelling > Using icebergs etc. to achieve cooling of surface waters has been > discussed, but upwelling has not been considered in this thread in detail. > Can forced upwelling be used effectively to drive hot water down, locking > up heat, and cold water up, suppressing hurricanes? > > A > > 2009/6/7 dsw_s <[email protected]> > > >> MMC: >> > Air goes up at moist adiabatic rate, but has to be forced down at the >> > dry adiabatic rate >> >> Of course. Thanks. >> >> Does it follow that although the net effect of moist convection is to >> transport heat upward, the actual circulation of air transports heat >> downward whenever air is being forced to rise despite a lapse rate >> lower (more stable) than the dry adiabatic rate? >> >> I had actually thought that typical lapse rates were near dry >> adiabatic, and that dry convection was fairly common wherever there's >> not enough moisture to condense into clouds, and enough sunshine to >> exceed losses by long-wave radiation from the surface. >> >> f.m.maugis: >> > Concerning hurricane and energy, nobody is speaking about Coriolis >> forces. >> >> That's partly because these are tropical storms, and the Coriolis >> force is small in the tropics. Also, in a low-pressure system the >> Coriolis force acts outward same as centrifugal force does, so it >> doesn't introduce a qualitative difference. >> >> > Anyway, there is a continuum between the very hot center of our planet >> and >> > the very cold space. >> >> It's not generally monotonic: it's often cooler underground than than >> at the surface, because groundwater is derived from precipitation that >> falls from cooler altitudes. >> >> Alvia Gaskill >> > http://www.aoml.noaa.gov/hrd/tcfaq/C5e.html >> > Subject: C5e) Why don't we try to destroy tropical cyclones by >> cooling >> > the surface waters with icebergs or deep ocean water ? >> >> That seems to presume that the strategy would be to simply starve the >> hurricane of energy by brute-force cooling of the entire area beneath >> it. That approach is obviously implausible. But can a hurricane >> remain at full strength, or close to it, if a little of the area >> beneath it is much cooler than the rest? Or will that mean that part >> of it is being driven at one rate and part at another, so that both >> dissipate much of their kinetic energy in turbulence? >> >> > >> http://groups.google.com/group/geoengineering/attach/2ea05e9f69344c48/250px-Hurricane_profile.svg.png?part=4&view=1 >> >> That looks as though the hurricane is being driven in part by heat >> from the stratosphere. Of course, it takes energy to move hot air >> downward and have it replaced with cooler air from below. It's >> stratified; that's why it's the stratosphere. But even if the >> hurricane as a whole is losing energy by bringing air with high >> potential temperature down from the stratosphere, part of it could be >> strengthened where that heat is going back up to the cool upper >> troposphere. >> >> In principle, I think the net effect could be to make an inefficient >> heat engine less inefficient. Sort of like how a turbojet engine has >> to extract more energy from its exhaust than the amount of work it >> does compressing its intake air, since the turbine and compressor >> aren't a perpetual motion machine, but the effect is to make the >> combustion faster and more complete so the whole thing works better. >> >> On Jun 6, 8:38 pm, "Alvia Gaskill" <[email protected]> wrote: >> > Some more info about the effect of hurricanes or more generally, >> tropical >> > cyclones on SST (sea surface temperature) from NOAA and the Wikipedia. >> Most >> > of the temperature decrease is due to the mixing of water in the upper >> layer >> > of the ocean by winds and most of the decrease occurs after the storm >> has >> > passed. Limited data show that the decrease from evaporation of water >> is >> > much less. NOAA also throws some cold water on artificial dissipation >> > strategies including the one that got this discussion started, ocean >> pipes. >> > They didn't address indirect approaches like the cloud ships and the >> desert >> > cover. >> > >> > http://www.aoml.noaa.gov/hrd/tcfaq/H7.html >> > >> > Subject: H7) How does the ocean respond to a hurricane and how >> does >> > this feedback to the storm itself? >> > Contributed by Joe Cione >> > >> > The ocean's primary direct response to a hurricane is cooling of >> the >> > sea surface temperature (SST). How does this occur? When the strong >> winds of >> > a hurricane move over the ocean they churn-up much cooler water from >> below. >> > The net result is that the SST of the ocean after storm passage can be >> > lowered by several degrees Celsius (up to 10° Fahrenheit). >> > >> > Figure 1 shows SSTs ranging between 25-27°C (77-81°F) several >> days >> > after the passage of Hurricane Georges in 1998. As Figure 1 illustrates, >> > Georges' post storm 'cold wake' along and to the right of the >> superimposed >> > track is 3-5°C (6-9°F) cooler than the undisturbed SST to the west and >> south >> > (i.e. red/orange regions are ~30°'C [86°'F]). The magnitude and >> distribution >> > of the cooling pattern shown in this illustration is fairly typical for >> a >> > post-storm SST analysis. >> > >> > One important caveat to realize however is that most of the 3-5°C >> > (6-9°F) ocean cooling shown in Figure 1 occurs well after the storm has >> > moved away from the region (in this case several days after Georges made >> > landfall). The amount of ocean cooling that occurs directly beneath the >> > hurricane within the high wind region of the storm is a much more >> important >> > question scientists would like to have answered. Why? Hurricanes get >> their >> > energy from the warm ocean water beneath them. However, in order to get >> a >> > more accurate estimate of just how much energy is being transferred from >> the >> > sea to the storm, scientists need to know ocean temperature conditions >> > directly beneath the hurricane. Unfortunately, with 150kph+ (100mph+) >> winds, >> > 20m+ (60ft+) seas and heavy cloud cover being the norm in this region of >> the >> > storm, direct (or even indirect) measurement of SST conditions within >> the >> > storm's "inner core" environment are very rare. >> > Thankfully in this case "very rare" does not mean "once in a >> > lifetime". Recently, scientists at the Hurricane Research Division were >> able >> > to get a better idea of how much SST cooling occurs directly under a >> > hurricane by looking at many storms over a 28 year period. By combining >> > these rare events, HRD scientists put together a "composite average" of >> > ocean cooling directly under the storm. >> > >> > Figure 2 illustrates that, on average, cooling patterns are a lot >> > less than the post storm 3-5°C (6-9°F) cold wake estimates shown in >> Figure >> > 1. In most cases, the ocean temperature under a hurricane will range >> > somewhere between 0.2 and 1.2°C (0.4 and 2.2°F) cooler that the >> surrounding >> > ocean environment. Exactly how much depends on many factors including >> ocean >> > structure beneath the storm (i.e. location), storm speed, time of year >> and >> > to a lesser extent, storm intensity (Cione and Uhlhorn 2003). >> > While the estimates in Figure 2 represent a dramatic improvement >> when >> > it comes to more accurately representing actual SST cooling patterns >> > experienced under a hurricane, even small errors in inner core SST can >> > result in significant miscalculations when it comes to accurately >> assessing >> > how much energy is transferred from the warm ocean environment directly >> to >> > the hurricane. With all other factors being equal, being "off" by a mere >> > 0.5°C (1°F) can be the difference between a storm that rapidly >> intensifies >> > to one that falls apart! With that much at stake, scientists at HRD and >> > other government and academic institutions are working to improve our >> > ability to accurately estimate, observe and predict "under-the-storm" >> upper >> > ocean conditions. These efforts include statistical studies, modeling >> > efforts and enhanced observational capabilities designed to help >> scientists >> > better assess upper ocean thermal conditions under the storm. With such >> > improvements, it is believed that future forecasts of tropical cyclone >> > intensity change will be significantly improved. >> > >> > Reference >> > Cione, J. J., and E. W. Uhlhorn, 2003: Sea Surface Temperature >> > Variability in Hurricanes: Implications with Respect to Intensity >> Change. >> > Monthly Weather Review, 131, 1783-1796. >> > >> > Last updated August 13, 2004 >> > >> > http://en.wikipedia.org/wiki/Typhoons >> > >> > Tropical cyclones are characterized and driven by the release of >> large >> > amounts of latent heat of condensation, which occurs when moist air is >> > carried upwards and its water vapour condenses. This heat is distributed >> > vertically around the center of the storm. Thus, at any given altitude >> > (except close to the surface, where water temperature dictates air >> > temperature) the environment inside the cyclone is warmer than its outer >> > surroundings.[2] >> > >> > Mechanics >> > >> > Tropical cyclones form when the energy released by the >> condensation of >> > moisture in rising air causes a positive feedback loop over warm ocean >> > waters.[14] >> > A tropical cyclone's primary energy source is the release of the >> heat >> > of condensation from water vapor condensing at high altitudes, with >> solar >> > heating being the initial source for evaporation. Therefore, a tropical >> > cyclone can be visualized as a giant vertical heat engine supported by >> > mechanics driven by physical forces such as the rotation and gravity of >> the >> > Earth.[15] In another way, tropical cyclones could be viewed as a >> special >> > type of mesoscale convective complex, which continues to develop over a >> vast >> > source of relative warmth and moisture. Condensation leads to higher >> wind >> > speeds, as a tiny fraction of the released energy is converted into >> > mechanical energy;[16] the faster winds and lower pressure associated >> with >> > them in turn cause increased surface evaporation and thus even more >> > condensation. Much of the released energy drives updrafts that increase >> the >> > height of the storm clouds, speeding up condensation.[17] This positive >> > feedback loop continues for as long as conditions are favorable for >> tropical >> > cyclone development. Factors such as a continued lack of equilibrium in >> air >> > mass distribution would also give supporting energy to the cyclone. The >> > rotation of the Earth causes the system to spin, an effect known as the >> > Coriolis effect, giving it a cyclonic characteristic and affecting the >> > trajectory of the storm.[18][19] >> > >> > What primarily distinguishes tropical cyclones from other >> > meteorological phenomena is deep convection as a driving force.[20] >> Because >> > convection is strongest in a tropical climate, it defines the initial >> domain >> > of the tropical cyclone. By contrast, mid-latitude cyclones draw their >> > energy mostly from pre-existing horizontal temperature gradients in the >> > atmosphere.[20] To continue to drive its heat engine, a tropical cyclone >> > must remain over warm water, which provides the needed atmospheric >> moisture >> > to keep the positive feedback loop running. When a tropical cyclone >> passes >> > over land, it is cut off from its heat source and its strength >> diminishes >> > rapidly.[21] >> > >> > Chart displaying the drop in surface temperature in the Gulf of >> Mexico >> > as Hurricanes Katrina and Rita passed over >> > The passage of a tropical cyclone over the ocean can cause the >> upper >> > layers of the ocean to cool substantially, which can influence >> subsequent >> > cyclone development. Cooling is primarily caused by upwelling of cold >> water >> > from deeper in the ocean because of the wind. The cooler water causes >> the >> > storm to weaken. This is a negative feedback process that causes the >> storms >> > to weaken over sea because of their own effects. Additional cooling may >> come >> > in the form of cold water from falling raindrops (this is because the >> > atmosphere is cooler at higher altitudes). Cloud cover may also play a >> role >> > in cooling the ocean, by shielding the ocean surface from direct >> sunlight >> > before and slightly after the storm passage. All these effects can >> combine >> > to produce a dramatic drop in sea surface temperature over a large area >> in >> > just a few days.[22] >> > >> > Scientists at the US National Center for Atmospheric Research >> estimate >> > that a tropical cyclone releases heat energy at the rate of 50 to 200 >> > exajoules (1018 J) per day,[17] equivalent to about 1 PW (1015 watt). >> This >> > rate of energy release is equivalent to 70 times the world energy >> > consumption of humans and 200 times the worldwide electrical generating >> > capacity, or to exploding a 10-megaton nuclear bomb every 20 >> > minutes.[17][23] >> > >> > While the most obvious motion of clouds is toward the center, >> tropical >> > cyclones also develop an upper-level (high-altitude) outward flow of >> clouds. >> > These originate from air that has released its moisture and is expelled >> at >> > high altitude through the "chimney" of the storm engine.[15] This >> outflow >> > produces high, thin cirrus clouds that spiral away from the center. The >> > clouds are thin enough for the sun to be visible through them. These >> high >> > cirrus clouds may be the first signs of an approaching tropical >> cyclone.[24] >> > >> > http://www.aoml.noaa.gov/hrd/tcfaq/C5e.html >> > >> > Subject: C5e) Why don't we try to destroy tropical cyclones by >> cooling >> > the surface waters with icebergs or deep ocean water ? >> > >> > Contributed by Neal Dorst >> > >> > Since hurricanes draw their energy from warm ocean water, some >> > proposals have been put forward to tow icebergs from the arctic zones to >> the >> > tropics to cool the sea surface temperatures. Others have suggested >> pumping >> > cold bottom... >> > >> > read more » >> > >> > GeorgesSST.jpg >> > 198KViewDownload >> > >> > SSTprofile.jpg >> > 57KViewDownload >> > >> > 250px-Hurricane_profile.svg.png >> > 18KViewDownload >> > >> > magnify-clip.png >> > < 1KViewDownload >> > >> > GulfMexTemps_2005Hurricanes.gif >> > 104KViewDownload >> >> > > > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "geoengineering" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en -~----------~----~----~----~------~----~------~--~---
