Tropical Cyclones & Global Warming

[tropical madness]

heya guys,

Obviously this topic is a highly debated one and theres countless theories/global climate models and their projections simulating how global warming might affect the intensity, duration, frequency or even location of these TCs. A huge uncertainty in the area is also apparent due to the lack of longterm reliable data, biased observation techniques prior to the satellite era and the resolution of these models. However, I was just wondering and curious to hear what your thoughts are since this is part of my dissertation topic . hehe. some specific ideas might be...

- how the vertical wind shear, area susceptible to TCs, atmospheric temperature profile, etc may be altered due to an increase in atmospheric greenhouse gasses.

- how not only does global warming but large scale natural variability such as ENSO, Madden-Jullian Oscillation, North Atlantic Oscillation, Quasi-Biennial Oscillation, etc affect tropical cyclogenesis.

- agreed/disagree with Kerry Emanuel or other proposed theories/simulations.

- or any other relevant comments really!

cheers :lol:

[kold weather]

Oh a very interestin topic indeed

Its really tough to know how global warming will affect TC. I think its logial that there would be higher precip totals due to greater energy due to higher temps but whether stronger convective properties would lead atomatically to deeper tropcal systems I'm not sure it would be interesting to study. I suspect however as well as sea surface temps it would be ineresting to study upper temps as well because at least at polar latitdues they are cooling and if its the same in the tropics then vertical lapse rates would be higher causing greater instablity and therefore greater chance of warm cored lows forming...I've not looked into it though so it would be interesting.

As for the other factors I can't disagree with the ones you mention. Whilt sea surface temps rising is major plus it has been argued that it would also enduce El Nino condtions more often...also GW is likely to only advance the development of deserts in African which of course would reduce moisture in the ITCZ.

[tropical madness]

ohhh interesting insight mate. Ive been using the HadCM3 model (that the IPCC greatly relied on during the 3rd assessment report) as part of my dissertation and it does show for doubled CO2 levels that a generally wetter, and warmer tropics will be established. I have still yet to work out what the change in wind shear would be. However, this model doesn't have the upper tropospheric temperatures which is a shame. Because what you proposed about if temperatures do cool, which might be a possibility due to the aerosols (not too sure), then indeed a greater lapse rate could enhance the genesis of stronger or more frequent TCs. hmmmm

Switching to another aspect, a huge increase in temperature in the Amazon was observed on the temperature charts ive constructed. Which sort of hints to me that the dying vegetation would aid the dispersion of carbon hence increasing the greenhouse gas concentration. And with all the temperature increasing in the polar regions, the melting of the permafrost would inevitably release vast amounts of trapped Methane. With Methane a more effective greenhouse gas, I reckon the increase in global temperatures could be higher than the 1-4C I obtained. Maybe 1-6C could be a reasonable guess. Anyway Ive veered off the topic a bit hehe

thanks for your opinion tho. very interesting, if u come of with more good stuff, keep the comments goin

[kold weather]

I seem to recall an interesting graph about theortical min pressures based on sea surface temps and how it would change depending on various factors but I have to admit I don't know wher eit is now sorry.

Still it was interesting and as you can imagine as SST's increased so the pressure dropped.

Just a thought but if the surface is warming then and the Arctic is shrinking then surely that will mean the poler jet will contract which will mean a greater area of sea in the tropical zones which should in theory at least mean also more chance of tropical cyclones developing. i think thats part of the reason why we've been seeing more December systems then in the past though detection rates may have improved as well its hard to know!

It's a very complex matter and I may well have a little better look myself someday soon, there are many variables that go into these systems as you know.

Anyway I'll be very interested to hear the results of the shear trends...also would be cool if you would stay on for the hurricane seasons later this year.

[tropical madness]

Ive just found some interesting theory by Kerry Emauel which relates to our discussion about the global warming induced area theoretically increasing the likelyhood of TCs.

"An oft-stated misconception about tropical cyclones is that were the area enclosed by the 26 C SST isotherm to increase, so too would the area experiencing tropical cyclogenesis. Regions prone to tropical cyclogenesis are better characterized as places where the atmosphere is slowly ascending on the largest scales. Since about as much atmosphere is descending as ascending, it is hard to change the total area experiencing ascent. Thus there is little basis for believing that there would be any substantial expansion or contraction of the area of the world prone to tropical cyclogenesis. This is borne out by the GCM simulations performed by Haarsma et al. (1992), who show that while there is a substantial increase in the area enclosed by the 26 C SST isotherm is a double CO2 environment, there is no perceptible increase in the area experiencing tropical cyclones. It is conceivable, though, that changes in the large-scale circulation of the atmosphere would increase or decrease the rate of movement of tropical cyclones out of their genesis regions and into higher latitudes. It is also likely that changes in atmospheric circulation and SST distribution within the tropics would be associated with variations in the distribution of storms and of the tracks they follow, thus affecting the locations and frequency of landfall.

INTERESTING! lol