What is the net advection of sensible and latent heat?

[AppeltjeBosheuvel]

I am looking at an Energy Balance equation (see images) for latent and sensible heat. However, I don't understand the terms 'advection of latent heat' Alat and 'advection of sensible heat' Ah. They positively enter the system, but how do they differ from latent and sensible heat itself?

 

[CWatters]

Advection means transported or carried by a fluid. So for example if you had some steam flowing in a pipe that condensed at it's destination you could say you had both the advection of latent heat and the advection of sensible/specific heat. Advection can also be used in other contexts such as the transport or advection of salt or freshwater or pollution etc

 

[AppeltjeBosheuvel]

Thanks for your reply!

Advection of Latent Heat
So when it happens in air, does advection of latent heat mean that water vapor gets carried into the control volume? Cause it carries the latent heat needed to potentially evaporate? And when it does evaporate does it then leave the control system as 'regular' latent heat LvE?

Advection of Sensible Heat
One more question, how does sensible heat then get transported through air? I find it hard to imagine.

 

[CWatters]

So when it happens in air, does advection of latent heat mean that water vapor gets carried into the control volume?

Yes.

Cause it carries the latent heat needed to potentially evaporate? And when it does evaporate does it then leave the control system as 'regular' latent heat LvE?

No. Water vapour is water that has already been evaporated. So water vapour brings sensible and (if it condenses) latent heat into the control volume.

One more question, how does sensible heat then get transported through air? I find it hard to imagine.

It's not "through air", its movement of the air. If hot air flows into a control volume it carries sensible heat with it. At the same time cooler air may flow out of the control volume taking less heat with it. The net heat flow into the control volume will be the difference between the two heat flows (and any others).

The reverse happens in your house in winter. Cold air comes in (ventilation) and warm air escapes. The heat loss by this advection is hopefully replaced by your heating system. Some houses like mine have a vent system with a heat exchanger to mitigate the problem by extracting heat from the outgoing air and using it to warm the incoming air.

 

[AppeltjeBosheuvel]

Ok. I get that part now :D

Advection latent: is energy that moves with watervapor in air through advection. Watervapor has 'potential' latent heat that doesn't release until it condenses.
Advection sensible: is heat that moves with air through advection
LvC: when water condensate or evaporates within control volume.
LvE out: when latent heat associated with evaporation leaves the control (when watervapor leaves control volume)

And then how does advective sensible heat (Ah) differ from sensible heat (H)? Is H just sensible heat leaving the system in any other way than advective (with for example convection?).

Thank you!

:)

 

[CWatters]

Convection would also be advection as the air is moving.

Where did you get the picture/diagram from? I think H might be radiated heat.

 

[AppeltjeBosheuvel]

Got it from my the pdf atmospherebook. It states sensible heat is on left, latent heat on right. Also that H is sensible heat flux, Q net radiation, LvE latent heat flux (with Lv latent heat of evaporation). With storage of sensible heat in air, vegetation and soil on left, and only one type of latent storage on right.

 

[CWatters]

So my interpretation would be:

On the left..
Heat flows..
Ah = Sensible heat carried into the control area (eg warm/cold winds)
Q = Net heat flow by radiation
H = Sensible heat flow by conduction
G = Sensible heat flow by conduction
Heat stores..
ΔSha = change in Sensible heat in the air (air temperature change)
ΔShv = change in Sensible heat in vegetation (veg temperature change)
ΔShs = change in Sensible heat in soil (soil temperature change)

On the right..
Heat flows..
Alat = Latent heat carried into the control area (water vapour)
LvE = Latent heat carried out of the control area (water vapour)
Heat stores..
ΔSlat = change in Latent heat in the air (change in humidity)

The arrows between the two sides..
LvCl-g = Heat converted between Sensible and Latent that stays in the control area (ice-water, water-vapour)

I'm not 100% certain about Alat and LvE. Why don't they just have one arrow indicating the net flow of latent heat.