Grex Science Conference

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Grex Science Item 54: Weather
Entered by rcurl on Mon Sep 20 06:08:21 UTC 1999:

    Weather to be, or
    Weather not to be;
    That is the question.

4 responses total.

#1 of 4 by rcurl on Mon Sep 20 06:13:37 1999:

My first question is, what is the distribution of sources of rain that
falls on some area, say Michigan, in some period, say September? Sources
could be taken as relatively large sources of evaporation; the Pacific,
Caribbean, Arctic Ocean, Canada, China, etc. What percentage comes
from each?

If the source areas and target areas are all finite, this could be
represented by a matrix, or it could be defined point by point with
a kernel. Regardless of the representation....are any values available
at all for this?

#2 of 4 by rickyb on Thu Sep 23 21:05:50 1999:

I'm not certain how to go about determining this info, but, the UofM weather
underground has some really deep info available (waaayyyyy beyond what you
find at their 'check the weather' sites).  In fact, their project "Blue Sky"
is a browser that has graphical links (similar to hypertext links) which lets
you click into various things to get deeper explanations/details.  they get
tons of _raw data_ direct from NASA satellites (before NASA screens out
anything they might not want 'leaked') and incorporate real-time as well as
historical and projected trends (such as photos of the ozone 'hole' at the
south pole).  you have to contact them, download their (free) blue skys
browser and then connect.  Maybe they can just lead you to some sources for
your quiery without the Blue sky browsing anyway.

#3 of 4 by russ on Sat Sep 25 06:00:18 1999:

Since water is pretty much water, and any water "coming from" a land
mass (or a freshwater body thereon) had to have fallen there as rain
and thus come from somewhere else, how can you even conclusively
define the source of rain other than "the ocean"?

I know, it depends on the definition.

#4 of 4 by rcurl on Mon Sep 27 03:56:17 1999:

Each molecule of water that evaporates somewhere eventually falls to earth
somewhere else. There is an origin and a distination. Of course, it will
do it again, eventually, but I am just asking for the single-trip matrix
or kernel - and that is well defined. One could measure it, for example,
by allowing water containing tritium or, better, a rare isotope of oxygen,
evaporate at one location, and then measure where the molecules of that
sample fell throughout the world. I agree that there are nearly
insurmountable problems in doing this (analytical, and not knowing that a
molecule has not fallen and reevaporated on its ways), but in principle it
could be done. 

The question arises as I am trying to obtain paleometeorological data for
upper Michigan, and theisled to information suggesting that there have
been periodic megafloods in the midwest (larger orders of magnitude than
anything that has been observed) over the past 5000 years, due to a shift
of a flow of warm Caribbean water into the Gulf of Mexico. Those
megafloods thus consisted of water evaporated from the Gulf. This raised
in my mind the general question of where does water that falls here come
from now, and throughout the year? 

Only a fraction comes from the oceans, incidentally, as a very large
fraction of water that falls on land evaporates, or is transpired, again.

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