Help with heat fluxes

[Arlex Marin Ramirez]

Hello Mike,

I’m implementing a simulation of a tropical pitlake. So far, with a grid of the lake configurated with 52 0.5m-height layers and 20 100m-length segments, I’ve run some simulations using the local meteorology forcing, precipitation, and one tributary. However, the temperature results I’ve been getting from these simulations are quite inconsistent, compared with measured data and basic limnological knowledge. This has led me to the idea that there might be an error with the configuration files of the simulation.

In the attached image file (contour.png), it can be observed that, except for the surface, the lake has a constant steady cooling from 29°C (initial condition) to approximately 4°C. This cooling seems to stem from the bottom, not from the surface, because the surface temperature never goes down to values such as 4°C, like we would expect from a tropical lake. Moreover, for this particular simulation, there’s no tributary inflow (the flow rate it’s set to zero) and the bottom_heat_exchange_coefficient on the w2.yaml file it’s also set to zero. So, there’s no heat exchange with the sediment. I’m not clear on what process it’s being simulated on the W2 model to get this cooling effect. 

Additionally, I have a couple of questions, regarding the superficial heat flow:

Is it possible to input measured solar radiation data?

Is there any way to modify the parameters of the wind function used to calculate the latent and sensible heat flows? Or, at least, is there another parameter related to the superficial heat flow (besides the light extinction coefficient), that allows me to calibrate the superficial temperature?

I really appreciate any help...

Thank you

Arlex.

[Dr. Mike Mueller]

Dear Arlex ,

Am 08.08.18 um 22:11 schrieb Arlex Marin Ramirez:

> Hello Mike,
>
> I’m implementing a simulation of a tropical pitlake. So far, with a grid of the
> lake configurated with 52 0.5m-height layers and 20 100m-length segments, I’ve
> run some simulations using the local meteorology forcing, precipitation, and
> one tributary. However, the temperature results I’ve been getting from these
> simulations are quite inconsistent, compared with measured data and basic
> limnological knowledge. This has led me to the idea that there might be an
> error with the configuration files of the simulation.
>
> In the attached image file (contour.png), it can be observed that, except for
> the surface, the lake has a constant steady cooling from 29°C (initial
> condition) to approximately 4°C. This cooling seems to stem from the bottom,
> not from the surface, because the surface temperature never goes down to values
> such as 4°C, like we would expect from a tropical lake. Moreover, for this
> particular simulation, there’s no tributary inflow (the flow rate it’s set to
> zero) and the bottom_heat_exchange_coefficient on the w2.yaml file it’s also
> set to zero. So, there’s no heat exchange with the sediment. I’m not clear on
> what process it’s being simulated on the W2 model to get this cooling effect.

Indeed a strange behavior. I haven't seen anything like this before.
What is the temperature of your tributary? To me it looks like you set it 0°C
instead of the flow rate.

> Additionally, I have a couple of questions, regarding the superficial heat flow:
>
> Is it possible to input measured solar radiation data?
>
> Is there any way to modify the parameters of the wind function used to
> calculate the latent and sensible heat flows? Or, at least, is there another
> parameter related to the superficial heat flow (besides the light extinction
> coefficient), that allows me to calibrate the superficial temperature?

All heat processes are from CE-QUAL-W2. Please read the relevant sections from
the manual: https://pitlakq.com/downloads/w2v2-manual.pdf

It describes all the theory and the input parameter for the model heat
processes.

HTH.

Best,
Mike

> I really appreciate any help...
>
> Thank you
> Arlex.
>

> 01_Contour.png <about:invalid#zClosurez>
>
>
>
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[Arlex Marin Ramirez]

Hello Mike, 

I appreciate your answer. 

For the simulation I exclude the evaporation and precipitation from the mass balance and as you can see, there isn't change in water level so the flow rate must be zero. Anyway, I ran another simulation including a constant tributary inflow (0.05 m3/s) with 30°C temperature. However the cooling effect is still observed (see attached image contour2.png). 

Regarding the heat fluxes, I've looked at the manual extensively, but i couldn't find any way to calibrate surface heat fluxes. In version 3 of Ce-Qual-W2 which I've used before it's possible to calibrate heat fluxes by adjusting the wind function coefficients, but in version 2 (the one that uses pitlakq) there seems to be no way to modify these or another parameters. Moreover in W2 V3 it's possible to provide solar radiation data, but I can't find how to do that in W2 V2. ¿It is possible?

I have attached the simulation input folder with all files I've been used. Any guidance would be greatly appreciated.

Thank you

Arlex.

> <mailto:pitlakq-users+unsub...@googlegroups.com>.

[Dr. Mike Mueller]

Hi Arlex,

I did extensive checks. Looks like the algorithms does not work for this
combination of high humidity and latitude.

This is the relevant part of the manual:

Also required in either approach to computing surface heat exchange is the
solar radiation rate. In this subroutine, it is computed from time, solar
altitude and cloud cover (Ryan and Stolzenbach, 1972; Wunderlich, 1972).
Equilibrium temperature is computed iteratively using the methods in Edinger,
et al. (1974). The calculations are done in British units and converted to
SI units prior to the return.

The corresponding references:

Edinger, J.E., Brady, D.K., and Geyer, J.C. 1974. "Heat Exchange and Transport
in the Environment", Rpt. No. 14, EPRI Publication No. 74-049-00-34, prepared
for Electric Power Research Institute, Cooling Water Discharge Research Project
(RP-49), Palo Alto, CA.

Wunderlich, W. 1972. "Heat and Mass Transfer between a Water Surface and the
Atmosphere", Rpt. No. 14, Rpt. Publication No. 0-6803, Water Resources Research
Laboratory, Tennessee Valley Authority, Division of Water Control Planning,
Engineering Laboratory, Norris, TN.

If you feel inclined, you can dig up these references. I would be interested in
reading them, ;)

I looked into the implementation of the heat exchange in the current version
of CE-QUAl-W2, 4.1, and added the relevant parts to PITLAKQ. It works a bit
differently but gives very similar results. Unfortunately, it still calculates
unreasonable values for high humidity in equatorial regions.

I checked how reading the radiation as input in version 4.1 works. I think I
can modify PITLAKQ to also read radiation directly. This will be a few days
of work. I am currently involved in some other projects and cannot work on this
immediately. I think I will put it in eventually.

Best,
Mike

PS: You can also speed up development or get some new features into PITLAKQ
by taking advantage of our commercial support.


Am 10.08.18 um 14:57 schrieb Arlex Marin Ramirez:

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