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Air Temperature in Leonardo

Posted: Fri Oct 25, 2019 12:56 pm
by ajsuleiman007
Hi,

I am fairly new to Envi-Met, so please bare with me, I have gone through the forum to look for already answered questions, but I still have a few questions.

1) I ran simulation with Trees (Palm Trees) and without Trees as seen in the images below. In the image with trees, there's an area (circled red) showing higher Air temperature next to the building, could there be an explanation for this please?

2) Additionally, shouldn't the air temperature remain constant at all times? or how does Envi-met calculate the air temperature after extracting from the epw files?

Note: I used fullforcing for the simulation, using .epw files for Abu Dhabi in peak summertime of June 21 @12pm

WithTrees.png
With Trees (Palm Trees)


WithoutTrees.png
Without Trees

Re: Air Temperature in Leonardo

Posted: Fri Oct 25, 2019 1:41 pm
by Tim
Hi,

1) That can have multiple reasons depending on the local model area and the meteorological boundary conditions. If it gets too hot, plants close their stomata and leafs stop evaporating which heats up the leafs, so they can also heat up the environment under specific circumstances. They can also block the wind flow and thus stopping ventilation of the area causing the hot air to accumulate there in front of the building.
2) No, air temperature values of course differ for the different times of the day as they do in reality. I think I did not understand that question correctly.
I hope that you did not simulate only that one hour at 12 pm but a full day giving the model time to spin up.

Best regards,
Tim

Re: Air Temperature in Leonardo

Posted: Fri Oct 25, 2019 2:25 pm
by ajsuleiman007
Tim wrote:Hi,

1) That can have multiple reasons depending on the local model area and the meteorological boundary conditions. If it gets too hot, plants close their stomata and leafs stop evaporating which heats up the leafs, so they can also heat up the environment under specific circumstances. They can also block the wind flow and thus stopping ventilation of the area causing the hot air to accumulate there in front of the building.
2) No, air temperature values of course differ for the different times of the day as they do in reality. I think I did not understand that question correctly.
I hope that you did not simulate only that one hour at 12 pm but a full day giving the model time to spin up.

Best regards,
Tim


Hi Tim,

Thanks for your quick response.

1) For the first question, that would make sense as to why the result appears the way it does. it's really cool that envi-met can simulate the effect of trees to that extent.

2) Sorry if my question wasn't clear, I was assuming that the air temperature is similar to the dry bulb temperature from the weather file. So that's why I was asking if Envi-met takes into consideration the different changes within the environment and simulates the air temperature even though it's at the same time of the day.

Re: Air Temperature in Leonardo

Posted: Fri Oct 25, 2019 2:49 pm
by Tim
Hi,

The values of the EPW file are transformed in the shape of the FOX-file and used as input for the ENVI-met simulation. These meteorological boundary conditions are set for the inflow border. Within the model area you find changes of all meteorological parameters due to the model area characteristics such as buildings, plants, soils etc. If the model would not do that, it would not make sense to run it at all.

Best regards,
Tim

Re: Air Temperature in Leonardo

Posted: Fri Oct 25, 2019 3:33 pm
by ajsuleiman007
Tim wrote:Hi,

The values of the EPW file are transformed in the shape of the FOX-file and used as input for the ENVI-met simulation. These meteorological boundary conditions are set for the inflow border. Within the model area you find changes of all meteorological parameters due to the model area characteristics such as buildings, plants, soils etc. If the model would not do that, it would not make sense to run it at all.

Best regards,
Tim


Thanks Tim, much appreciated,

One thing I forgot to add is that I only ran the simulation for 1 hour, because the it was taking a long time for the simulation to complete. And I know from ENVIGuide and other posts here, it's recommended not to increase the timestep.

Re: Air Temperature in Leonardo

Posted: Fri Oct 25, 2019 3:40 pm
by Tim
Hi,

Yes, that is very true. Nevertheless, I would then try to decrease the model area size and still run the model with the start at sunrise. All materials, objects etc. heat up during the day and definitely affect your simulation results. We often run the model for more than 48 hours since the model might take 24 hours to initialize all material temperatures with senseful values.
Only picking the hour of interest and simulating that one does not give valuable results.

Best regards,
Tim

Re: Air Temperature in Leonardo

Posted: Fri Oct 25, 2019 3:46 pm
by ajsuleiman007
Tim wrote:Hi,

Yes, that is very true. Nevertheless, I would then try to decrease the model area size and still run the model with the start at sunrise. All materials, objects etc. heat up during the day and definitely affect your simulation results. We often run the model for more than 48 hours since the model might take 24 hours to initialize all material temperatures with senseful values.
Only picking the hour of interest and simulating that one does not give valuable results.

Best regards,
Tim


Thanks a lot for your quick response Tim.

And sorry one last question, to reduce the model size what's the best way to that? also is it possible to run the simulation for a specific area only, e.g only where the Trees are?

Thanks again.

Re: Air Temperature in Leonardo

Posted: Fri Oct 25, 2019 3:57 pm
by Tim
Hi,

Yes, of course you can run it only for that specific location. You will of course lose the information about shading from surrounding buildings etc.
The best method would be to choose a coarser resolution.... you can then simulate the same area but with less grid cells.

Best regards,
Tim

Re: Air Temperature in Leonardo

Posted: Fri Oct 25, 2019 4:04 pm
by ajsuleiman007
Thank you for the responses Tim.

Re: Air Temperature in Leonardo

Posted: Mon Nov 25, 2019 2:46 am
by sara5759
I am going to compare Ts and air temperature for 5 different neighborhoods in a city. How can I use the same palette in which, each color represents a certain temperature? Because Leonardo constantly change legend base on Min and max temperature in each map?

Re: Air Temperature in Leonardo

Posted: Mon Nov 25, 2019 9:54 am
by Tim
Hi,

In future, if your topic is not related to an existing one, please create a new one!
Check our tutorial videos about Leonardo to see how that works:
https://www.youtube.com/watch?v=nRS-w4RRi7U&list=PL38puK0ekg-RfrD9ShjUwN6_EvBuFR_Pf&index=5
https://www.youtube.com/watch?v=HnTn0sqmPdQ&list=PL38puK0ekg-RfrD9ShjUwN6_EvBuFR_Pf&index=3

Best regards,
Tim

Re: Air Temperature in Leonardo

Posted: Tue Dec 10, 2019 4:45 am
by sara5759
Many thanks Tim
Sara