What are the dimensions/units of Evaporation?

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    Evaporation
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Discussion Overview

The discussion revolves around the dimensions or units of evaporation, particularly in the context of hydrology. Participants explore various interpretations of what "evaporation" entails and how it can be quantified, considering both theoretical and practical aspects.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants propose that the dimensions of evaporation can be represented as L/T, interpreted as length per time, with examples such as mm/day for evaporation rates.
  • Others suggest that liters per second could also be a metric for evaporation, leading to a dimensional notation of L3/T.
  • It is noted that "evaporative flux" has dimensions of mass per unit time per unit area, indicating a different perspective on measuring evaporation.
  • One participant mentions that L could refer to latent heat of evaporation, but emphasizes that the context of heat input complicates the interpretation.
  • Several participants express skepticism about the clarity of the original question, arguing that without specific context, multiple interpretations of "evaporation" and its dimensions are possible.
  • There is a contention that the OP's lack of specificity makes it difficult to arrive at a definitive answer, with comparisons made to other physical processes that also have ambiguous dimensions.

Areas of Agreement / Disagreement

Participants generally do not agree on a single interpretation of the dimensions of evaporation. Multiple competing views remain, with some arguing for specific metrics and others highlighting the ambiguity of the term "evaporation" itself.

Contextual Notes

The discussion reveals limitations in the original question due to the lack of clarity regarding what specific aspect of evaporation is being referenced, leading to various interpretations and assumptions about the dimensions involved.

AppeltjeBosheuvel
I am just starting with hydrology, does anybody know what the dimension is of evaporation? I see L/T in some of the slides, but I can't figure out what it stands for. L/Time, I assume.

But what is the L? And in what dimension?
Thanks heaps!
 
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I would imagine L/T is length/time. For example, the evaporation rate from a lake surface could be measured in mm/day.
 
Liters/sec
 
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IanPTheAncient said:
Liters/sec
If that is a metric for evaporation, then the dimensional notation would be L3/T.
 
Sometimes one encounters "evaporative flux", which has dimensions of mass per unit time per unit area.
 
In evaporation, L can also refer to the latent heat of evaporation, and if you divide by the heat input you get the evaporation rate. But heat input is usually Q, and not L.
Just ask the professor, that's what they're for. In the Netherlands they are quite approachable.
 
I do not see why we are debating this when it is clearly guesswork. There can be no reasonable answer unless the OP provides us with an appropriate link to the reference he is looking at. There are just too many possible interpretations of the OP.
 
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Orodruin said:
I do not see why we are debating this when it is clearly guesswork. There can be no reasonable answer unless the OP provides us with an appropriate link to the reference he is looking at. There are just too many possible interpretations of the OP.

There is indeed no need for debating because @Doc Al is right.
 
  • #10
Lord Jestocost said:
There is indeed no need for debating because @Doc Al is right.
There can be no right answer to the OP. Yes, L/T would be length/time, bit the OP has not specified what "evaporation" means - it is a physical process, not a physical quantity. There are many physical quantities related to evaporation (as demonstrated by your own post) that have different physical dimensions and it is impossible to know which is intended unless the OP specifies. It is like asking "what is the physical dimension of gravity?" It is impossible to know whether the answer should be in terms of the dimension of the gravitational constant (L^3/T^2 M), the gravitational force (ML/T^2), the gravitational acceleration (L/T^2), the gravitational source term (M), or something else.

Of course DocAl is right in that it could be measured in L/T, but again it depends on the intended question, which is not clear.
 
  • #11
Orodruin said:
There can be no right answer to the OP.

The OP mentions hydrology and evaporation. From this you can conclude (with dimensions [L] for length and [T] for time): The volume of water (dimension [L3] ) per unit area (dimension [L2] ) per unit time (dimension [T] ): [L/T]
 
  • #12
Lord Jestocost said:
The OP mentions hydrology and evaporation. From this you can conclude (with dimensions [L] for length and [T] for time): The volume of water (dimension [L3] ) per unit area (dimension [L2] ) per unit time (dimension [T] ): [L/T]
No, you really cannot. I agree that this is one possible interpretation, but there are many other possible interpretations - as this thread has clearly demonstrated. What you are quoting is the flux. The OP could be interested in other physical quantities such as flow rate or mass flux. You simply do not know this without further specification on the part of the OP.
 
  • #13
Thank you!
 

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