news@cit-vax.Caltech.Edu (Usenet netnews) (01/08/87)
Organization : California Instititute of Technology Keywords: Hadley cell clouds rain forests From: myers@hobiecat.Caltech.Edu (Bob Myers) Path: hobiecat!myers In article <282@sri-arpa.ARPA> TSOMMER%IRLEARN.BITNET@WISCVM.WISC.EDU writes: >(This is not necessarily a physics question but here goes ) Followup to sci.misc. >Does anyone know if the climatic effect of loss of most of the Earth's >equatorial rain forest has been calculated or even studied ? I ask >this question as I have heard it said that at the present rate, only 15 % >approximately of it will remain in 15 years. Since a large amount of cloud >covers these regions The reason the rain forests are disappearing is because of human created deforestation, not lack of cloud cover. Nor is there any clear direct relationship between the cloud cover and the rain forest. (I don't see how cutting down trees directly affects the clouds in the area.) >and helps cool the planet in these regions (i.e. there >would be a higher net heating if they were not there, ) and thus if they >were destroyed would this affect cloud cover and hence the "Hadley Cells" ? >(The Hadley cells are the currents of air circulating from the equatorial >regions to the tropics of both hemispheres and back again ) The equatorial cloud cover is caused by the Hadley cell circulation. The air is rises at the equator, and the water vapor condenses out into clouds. I don't want to go into the thermo, but it does. Similarly, the downflow of the Hadley cell circulation in the subtropics is very dry (most of the world's major deserts are in this area). > If these air currents were upset even regionally, then I assume they may >affect ocean surface currents. And since the "El Nino" phenomena is related >to oceanic temperature changes etc etc, could this then provide for >instabilities in the weather/climate on a larger scale ? Certainly. El Nino is intimately related to changes in the equatorial winds. It's not clear what causes what, though. ---------------------------------------------------------------- Bob Myers myers@hobiecat.Caltech.Edu
eugene@pioneer.arpa (Eugene Miya N.) (01/08/87)
>> If these air currents were upset even regionally, then I assume they may >>affect ocean surface currents. And since the "El Nino" phenomena is related >>to oceanic temperature changes etc etc, could this then provide for >>instabilities in the weather/climate on a larger scale ? > >Certainly. El Nino is intimately related to changes in the equatorial >winds. It's not clear what causes what, though. > >---------------------------------------------------------------- > >Bob Myers myers@hobiecat.Caltech.Edu I would not go so far as to say it is intimately related. Related, perhaps. What happens at the boundaries of the air-sea interface are poorly understood. El Nino is a fad in some areas of atmospheric science and not others. We don't really understand how heat from the sea gets into the air (vapor sure, but what mechanisms besides incoming solar radiation, etc.) and (harder) how heat gets from the air into the sea. [first sentence] El Nino is a simple handle to describe a SET of phenomena. There are several problems associated with trying to describe it not the least of which are the 3-D ODEs which describe it and the hydrodynamics (state changes are the hard part) which are going on. Be skeptical. Note: you would never have seen the synopic discovery of El Nino with the joint use of orbiting satellites and ocean going ships (sea-state). --eugene miya NASA Ames Research Center eugene@ames-aurora.ARPA "You trust the `reply' command with all those different mailers out there?" {hplabs,hao,nike,ihnp4,decwrl,allegra,tektronix,menlo70}!ames!aurora!eugene
bob@uhmanoa.UUCP (Bob Cunningham) (01/09/87)
> >> If these air currents were upset even regionally, then I assume they may > >>affect ocean surface currents. And since the "El Nino" phenomena is related > >>to oceanic temperature changes etc etc, could this then provide for > >>instabilities in the weather/climate on a larger scale ? > > > >Certainly. El Nino is intimately related to changes in the equatorial > >winds. It's not clear what causes what, though. >... > El Nino is a simple handle to describe a SET of phenomena. There are > several problems associated with trying to describe it not the least of > which are the 3-D ODEs which describe it and the hydrodynamics (state > changes are the hard part) which are going on. Be skeptical. What started out to be a rather straightforward investigation of a simple phenomenon---periodic failure of the anchovy harvest off South America---has turned out to involve rather complex worldwide changes in atmosphere ("Southern Oscillation") and hydrosphere (Equatorial countercurrent and Pacific sea level changes) circulations. Hundreds (at least) well-qualified researchers are studying various aspects of the overall problem (it is the main rationale behind the worldwide Tropical Ocean and Global Atmosphere project, one very extensive study, to name one large project). Perhaps in 3-5 years it will be fairly well understood, but probably not before then. -- Bob Cunningham bob@hig.hawaii.edu
pmk@prometheus.UUCP (Paul M Koloc) (01/11/87)
>In article <282@sri-arpa.ARPA> TSOMMER%IRLEARN.BITNET@WISCVM.WISC.EDU writes: >>(This is not necessarily a physics question but here goes ) >Followup to sci.misc. >>Does anyone know if the climatic effect of loss of most of the Earth's >>equatorial rain forest has been calculated or even studied ? I ask >>this question as I have heard it said that at the present rate, only 15 % >>approximately of it will remain in 15 years. Since a large amount of cloud >>covers these regions In article <1452@cit-vax.Caltech.Edu> myers@hobiecat.UUCP (Bob Myers) writes: >Organization : California Instititute of Technology >Keywords: Hadley cell clouds rain forests >From: myers@hobiecat.Caltech.Edu (Bob Myers) >Path: hobiecat!myers >The reason the rain forests are disappearing is because of human >created deforestation, not lack of cloud cover. Nor is there any >clear direct relationship between the cloud cover and the rain forest. >(I don't see how cutting down trees directly affects the clouds >in the area.) The evaporation rate over vegetated areas can be very high, especially rain forests and crops like corn. Iowa for example is fed by under ground water seeping from the Rockies and also a good amount of natural rainfall. The corn that grows now can send its roots very much deeper than it could even twenty years ago and so it can pull water out of the ground and deliver it to the atmosphere. This vegetations holds the water and slows its flow in the Amazon, and without it things will become quite a different story. Watch the speeded up daily weather shows during the middle and early August in the area of Iowa. You will see as the sun brightens the day, suddenly Iowa turns white like a burst popcorn kernel as afternoon arrives. (Actually, as hundreds of thunderheads form). >> ...... .. and thus if they >>were destroyed would this affect cloud cover and hence the "Hadley Cells" ? >>(The Hadley cells are the currents of air circulating from the equatorial >>regions to the tropics of both hemispheres and back again ) Yep! It would cause more atmospheric heating and this would propel a stronger up surge which would result in a higher proportion of the current going all the way to the to the poles. This could effect the net melting/freezing ratio for the polar caps and the other interesting thing is that the polar surface currents would tend to move further south. That may already be happening, because Florida, for example, has had more damaging frosts over the last 15 years then in previous periods. Yet the poles will be warmer. I heard of a fellow who could tell whether by just looking at a girl +---------------------------------------------------------+--------+ | Paul M. Koloc, President: (301) 445-1075 | FUSION | | Prometheus II, Ltd.; College Park, MD 20740-0222 | this | | {mimsy | seismo}!prometheus!pmk; pmk@prometheus.UUCP | decade | +---------------------------------------------------------+--------+