Top of the model

Topics about the HYSPLIT dispersion model.
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sidjai
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Top of the model

Post by sidjai »

What exactly happens when a particle hits the top height of the model as defined by the CONTROL file? In the user guide it says "Trajectories will terminate when they reach this level." but what happens to the concentrations? I would think it would just limit the vertical movement and carry on its path but this makes it seem like it causes the particle to stop if it hits the top. I am aware that this is a trade-off between performance and speed but I want to know what type of performance I am getting.
ariel.stein
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Re: Top of the model

Post by ariel.stein »

In the concentration calculation the model top is determined by the top layer of the meteorological data that you are using. The definition of the concentration levels is independent of the vertical levels that are used by the model to calculate the dispersion. For instance if you only define 1 vertical concentration layer at 100 m, the model will output the concentrations in a layer between the surface and 100 m. However, the model will still calculate the transport and dispersion of the particles that are above that height up to the top of the meteorological model.
sidjai
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Re: Top of the model

Post by sidjai »

What if you change 6 -Top of model domain in the control file? This would change the meteorological model height wouldn't it? It seems that it would change the concentration output in some way. Does it just have the particles in a less tall box and have them "bounce off" the top of the model, or would there be a higher concentration at the new top of the model with all the particles that would have been placed higher in the atmosphere, or does the particles drop out as suggested by "Trajectories will terminate when they reach this level"?
glenn.rolph
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Re: Top of the model

Post by glenn.rolph »

Particles in the dispersion calculation are not eliminated once they reach the top of the model, they are reflected off the top of the model.
sidjai
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Re: Top of the model

Post by sidjai »

Thanks, just making sure since that line was kinda weird.
kerryne
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Re: Top of the model

Post by kerryne »

Is there any other way to terminate a particle at the "Top of Model", maybe an advanced configuration parameter that could be used? We are trying to model insect survival and we know an approximate maximum survival height, so it would be good to "kill" or terminate these particles at a particular height.
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