Naked Science Forum
Life Sciences => The Environment => Topic started by: Don_1 on 26/08/2008 14:36:28
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We are being told by marine biologists, meteorologists and a host of others, that the oceans temperatures are rising. Cited as evidence for this is the retreat of the polar ice caps and migration of fish toward the cooler waters, amongst other natural phenomena.
Would I be right, therefore, in coming to this conclusion?
The higher ocean temperatures result in more evaporation. This increase in evaporation leads to more condensation when the water vapour laden air reaches land causing the increase in cloud cover and precipitation that the British mainland is currently experiencing. As this cloud cover prevents the Sun’s rays from warming the land, the condensation increases, the cloud cover increases and so it goes on in a vicious circle.
If this is correct, can we in Britain expect to see a repetition of this type of summer weather in future years?
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That makes good sense to me although I am no Scientist! It follows a path of basic common sense!
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I'd guess the answer is no. The main characteristic of British weather is that it is unpredictable! So you can't really 'expect' anything.
On your conclusion about climatic effects:
I see that higher sea temp leads to more evaporation, but I don't see why cooler land increases precipitation.
Warm moist air passing over cool land (or cool sea) forms low level mist/fog, but I don't think it causes rain.
I think rain clouds form simply by warm moist air rising (over land or sea). The air cools as it rises and forms clouds when it reaches the dew point. Maybe these clouds will eventually become rain, but the air continues to rise and cool (albeit at a slower rate) and eventually starts to form ice crystals, which will initiate rain. As far as I can see, this does not require any further energy input (nor energy loss) from land or any other source.
Some clouds form when the air is forced to rise higher by flowing over land (especially hills/mountains), but this can occur whether or not the land is warmed by the sun.
My own guess would be that greater evaporation would lead to more cloud (everywhere) and reduce the warming of the seas by the sun, so that would tend to stabilise sea temperature.
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But don"t more heavy clouds produce more rain... ????
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My assumption is based on more evaporation producing not just more cloud, but denser cloud when it arrives over cooler land masses. This would indeed cause land temperatures to drop. The combined effect of denser cloud and lower land temperatures would result in lower temperatures within the clouds resulting in more condensation, thus larger and heavier water droplets, thus more precipitation over land.
The higher sea temperatures would not only produce more evaporation, but also keep the underside of clouds relatively warm. This together with the sun's effect from above would prevent cooling of the water droplets in the cloud while over the oceans. The cloud remains fairly dispersed and translucent allowing the sun's rays to continue to warm the oceans.
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Weather systems are stochastic - that is, they don't follow any physical laws and are only analysable statistically.
The last two summers' bad weather is mainly due to the Jet Stream being a bit further south than it 'normally' is so that the customary anticyclones that we associate with 'good' weather are fewer.