Posted by You on July 14, 2008, 9:21 pm
> >
> >> I frequently hear weather reports
> >> that speak of temperatures being higher in cities.
> >
> > Temps are ALWAYS higher in a city, because that is where ALL that power
> > is dissipated. Duh......
>
> Hmmm...
>
> On a clear sunny day about 1 KW/M^2 (kilowatt per square meter) reaches the
> surface of the earth. That's about 2.6 megawatts per square mile.
>
> I know that if that energy falls on concreate or asphalt (a good thermal
> mass) the heat is stored and re-released at night. If it falls on foliage
> it tends to get converted into chlorphyll.
>
> It is certainly not obvious to me that this is a small effect. Especially
> when you consider how much of the earths surface we have covered with
> concrete and asphalt. Just bring up google earth and zoom in just about
> anywhere in the US and you will find a lot of thermal mass.
>
> Regards,
> Steve
but you seem to be ignoring the FACT that the suns energy is only PART
of the Total Energy being dissipated in any one area. Think of ALL the
electrical energy we pump into cities. Thousands of Megawatts. Where
does all that energy go? It goes up in HEAT, in the cities where it is
USED. That heats the AIR in those cities, and that causes a Temp Rise
in cities that isn't there in rural areas. How much energy does a tree
dissipate, or grass, or small animals, compared to the amount of
electrical energy dissipated, per square mile, in a city? Duh......
Posted by J. Clarke on July 15, 2008, 2:26 am
You wrote:
>>>
>>>> I frequently hear weather reports
>>>> that speak of temperatures being higher in cities.
>>>
>>> Temps are ALWAYS higher in a city, because that is where ALL that
>>> power is dissipated. Duh......
>>
>> Hmmm...
>>
>> On a clear sunny day about 1 KW/M^2 (kilowatt per square meter)
>> reaches the surface of the earth. That's about 2.6 megawatts per
>> square mile.
>>
>> I know that if that energy falls on concreate or asphalt (a good
>> thermal mass) the heat is stored and re-released at night. If it
>> falls on foliage it tends to get converted into chlorphyll.
>>
>> It is certainly not obvious to me that this is a small effect.
>> Especially when you consider how much of the earths surface we have
>> covered with concrete and asphalt. Just bring up google earth and
>> zoom in just about anywhere in the US and you will find a lot of
>> thermal mass.
>>
>> Regards,
>> Steve
> but you seem to be ignoring the FACT that the suns energy is only
> PART
> of the Total Energy being dissipated in any one area. Think of ALL
> the electrical energy we pump into cities. Thousands of Megawatts.
> Where does all that energy go? It goes up in HEAT, in the cities
> where it is USED. That heats the AIR in those cities, and that
> causes a Temp Rise in cities that isn't there in rural areas. How
> much energy does a tree dissipate, or grass, or small animals,
> compared to the amount of electrical energy dissipated, per square
> mile, in a city? Duh......
Google "heat island".
--
--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)
Posted by RF on July 23, 2008, 4:25 am
You wrote:
>
>>>
>>>> I frequently hear weather reports
>>>> that speak of temperatures being higher in cities.
>>> Temps are ALWAYS higher in a city, because that is where ALL that power
>>> is dissipated. Duh......
>> Hmmm...
>>
>> On a clear sunny day about 1 KW/M^2 (kilowatt per square meter) reaches the
>> surface of the earth. That's about 2.6 megawatts per square mile.
>>
>> I know that if that energy falls on concreate or asphalt (a good thermal
>> mass) the heat is stored and re-released at night. If it falls on foliage
>> it tends to get converted into chlorphyll.
>>
>> It is certainly not obvious to me that this is a small effect. Especially
>> when you consider how much of the earths surface we have covered with
>> concrete and asphalt. Just bring up google earth and zoom in just about
>> anywhere in the US and you will find a lot of thermal mass.
>>
>> Regards,
>> Steve
>
> but you seem to be ignoring the FACT that the suns energy is only PART
> of the Total Energy being dissipated in any one area. Think of ALL the
> electrical energy we pump into cities. Thousands of Megawatts. Where
> does all that energy go? It goes up in HEAT, in the cities where it is
> USED. That heats the AIR in those cities, and that causes a Temp Rise
> in cities that isn't there in rural areas. How much energy does a tree
> dissipate, or grass, or small animals, compared to the amount of
> electrical energy dissipated, per square mile, in a city? Duh......
With concreted or asphalted areas there should be
a certain minimum coverage with trees to provide
shade, reduce the overall heating effect, and make
it a more comfortable place to be.
Posted by T. Keating on July 18, 2008, 7:56 pm
On Sun, 13 Jul 2008 16:52:51 -0700, "Steve"
>>
>>> I frequently hear weather reports
>>> that speak of temperatures being higher in cities.
>>
>> Temps are ALWAYS higher in a city, because that is where ALL that power
>> is dissipated. Duh......
>Hmmm...
>On a clear sunny day about 1 KW/M^2 (kilowatt per square meter) reaches the
>surface of the earth. That's about 2.6 megawatts per square mile.
Exponent error... that would be 2.6 gigawatts per square mile.
>I know that if that energy falls on concreate or asphalt (a good thermal
>mass) the heat is stored and re-released at night. If it falls on foliage
>it tends to get converted into chlorphyll.
>It is certainly not obvious to me that this is a small effect. Especially
>when you consider how much of the earths surface we have covered with
>concrete and asphalt. Just bring up google earth and zoom in just about
>anywhere in the US and you will find a lot of thermal mass.
>Regards,
>Steve
Posted by Steve on July 16, 2008, 2:11 am
> On 07/13/2008 6:52 PM, nospam_steved94@comcast.net wrote to All:
> -> On a clear sunny day about 1 KW/M^2 (kilowatt per square meter)
> reaches the
> -> surface of the earth. That's about 2.6 megawatts per square mile.
> ->
> -> Regards,
> -> Steve
> Ummm... There are about 1600 metres in a mile, so 1600 x 1600 or 2,560,000
> square metres in a square mile. So there are about 2.6 GIGAwatts of solar
> energy falling on each square mile of ther earth´s surface.
> dow
I stand corrected. Those nasty decimal places anyhow.
A few interesting statistics from:
http://www.solcomhouse.com/solarpower.htm
---
All the energy stored in Earth's reserves of coal, oil, and natural gas is
matched by the energy from just 20 days of sunshine.
In 40 minutes of daylight The SUN releases upon The Earth the amount of
energy that is consumed by the entire population of the planet in ONE YEAR.
Each day more solar energy falls to the Earth than the total amount of
energy the planet's 6 billion inhabitants would consume in 27 years.
---
If these statistics are true, I would not be a bit surprised if the "Heat
Island" effect is more significant than the greenhouse effect. Of course
they are not independent, and the global effect of either are extremely hard
to measure with any certainty.
Regards,
Steve
XML site map
> >> I frequently hear weather reports
> >> that speak of temperatures being higher in cities.
> >
> > Temps are ALWAYS higher in a city, because that is where ALL that power
> > is dissipated. Duh......
>
> Hmmm...
>
> On a clear sunny day about 1 KW/M^2 (kilowatt per square meter) reaches the
> surface of the earth. That's about 2.6 megawatts per square mile.
>
> I know that if that energy falls on concreate or asphalt (a good thermal
> mass) the heat is stored and re-released at night. If it falls on foliage
> it tends to get converted into chlorphyll.
>
> It is certainly not obvious to me that this is a small effect. Especially
> when you consider how much of the earths surface we have covered with
> concrete and asphalt. Just bring up google earth and zoom in just about
> anywhere in the US and you will find a lot of thermal mass.
>
> Regards,
> Steve