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Name: Jessica S.
Status: other
Age: 17
Location: N/A
Country: N/A
Date: 5/5/2004

2 questions: In an article about water vapor estimates over different land regions I do not understand the dimensions of evaporotranspiration over a region which is in mm/yr and for which a mean value is shown. That dimension is not a unit of volume. Do you know why? I also do not understand the dimensions of "estimated water vapor" which is expressed in (km3/yr) and for which a mean value is shown. Is that the average partial pressure of water vapor broken up into single km cubes or does the value of say 18.3 represent 18.3 cubic kilometers of water vapor?

It is difficult to say how these units might have come about without going through the derivation. But frequently units are expressed dimensionally. By that I mean the ratio, R, of a volume V (l^3) per unit area A (l^2) is sometimes written: V(l^3) / A(l^2) = R(l^1). I think this is misleading and should be avoided but you find this practice widely in the literature.

Vince Calder

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