# What are the dimensions/units of Evaporation?

1. Sep 14, 2017

### 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!

2. Sep 14, 2017

### Staff: Mentor

I would imagine L/T is length/time. For example, the evaporation rate from a lake surface could be measured in mm/day.

3. Sep 14, 2017

### Lord Jestocost

4. Sep 14, 2017

### IanPTheAncient

Liters/sec

5. Sep 14, 2017

### lewando

If that is a metric for evaporation, then the dimensional notation would be L3/T.

6. Sep 14, 2017

### hilbert2

Sometimes one encounters "evaporative flux", which has dimensions of mass per unit time per unit area.

7. Sep 14, 2017

### bigfooted

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.

8. Sep 14, 2017

### Orodruin

Staff Emeritus
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.

9. Sep 15, 2017

### Lord Jestocost

There is indeed no need for debating because @Doc Al is right.

10. Sep 15, 2017

### Orodruin

Staff Emeritus
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. Sep 15, 2017

### Lord Jestocost

The OP mentions hydrology and evaporation. From this you can conclude (with dimensions [L] for lenght and [T] for time): The volume of water (dimension [L3] ) per unit area (dimension [L2] ) per unit time (dimension [T] ): [L/T]

12. Sep 15, 2017

### Orodruin

Staff Emeritus
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. Sep 20, 2017

Thank you!