Spacing Lat, Lon
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SoledadOsores
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- Joined: June 15th, 2022, 1:06 pm
- Registered HYSPLIT User: Yes
Spacing Lat, Lon
What is the numerical meaning of the Spacing Lat, Lon in the Definition of Concentrarion grid? Is the horizontal size of each particle?
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Miguel Cahuich
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Re: Spacing Lat, Lon
The "Grid spacing (degrees) Latitude, Longitude" parameter determines the horizontal resolution of the grid over which the particle mass is summed (https://www.ready.noaa.gov/hysplitusersguide/S313.htm).
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SoledadOsores
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- Joined: June 15th, 2022, 1:06 pm
- Registered HYSPLIT User: Yes
Re: Spacing Lat, Lon
Thank you Miguel for the answer and the link. So base on that it is:
17(2)- Grid spacing (degrees) Latitude, Longitude
Default: 1.0 1.0
Sets the interval in degrees between nodes of the sampling grid. Puffs must pass over a node to contribute concentration to that point and therefore if the spacing is too wide, they may pass between intersection points. Particle model calculations represent grid-cell averages, where each cell is centered on a node position, with its dimensions equal to the grid spacing. Finer resolution concentration grids require correspondingly finer integration time-steps. This may be mitigated to some extent by limiting fine resolution grids to only the first few hours of the simulation.
In the special case of a polar (arc,distance) concentration grid, defined when the namelist variable cpack=3, the definition changes such that the latitude grid spacing equals the sector angle in degrees and the longitude grid spacing equals the sector distance spacing in kilometers.
How finer could be the HYSPLIT resolution regarding the meteorological resolution? Is there a critical threshold between the Meteorological data resolution and the HYSPLIT resolution to be considered?
17(2)- Grid spacing (degrees) Latitude, Longitude
Default: 1.0 1.0
Sets the interval in degrees between nodes of the sampling grid. Puffs must pass over a node to contribute concentration to that point and therefore if the spacing is too wide, they may pass between intersection points. Particle model calculations represent grid-cell averages, where each cell is centered on a node position, with its dimensions equal to the grid spacing. Finer resolution concentration grids require correspondingly finer integration time-steps. This may be mitigated to some extent by limiting fine resolution grids to only the first few hours of the simulation.
In the special case of a polar (arc,distance) concentration grid, defined when the namelist variable cpack=3, the definition changes such that the latitude grid spacing equals the sector angle in degrees and the longitude grid spacing equals the sector distance spacing in kilometers.
How finer could be the HYSPLIT resolution regarding the meteorological resolution? Is there a critical threshold between the Meteorological data resolution and the HYSPLIT resolution to be considered?
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christopher.loughner
- Posts: 81
- Joined: August 15th, 2017, 3:59 pm
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Re: Spacing Lat, Lon
This will be covered shortly during the Chapter 12 presentation.
The concentration grid resolution can be finer than the meteorology. The main consideration for choosing the concentration grid resolution is to make sure it is not too high of a resolution that undersampling will occur based on the number of particles you use. If you are considering a very high resolution concenctration grid, you also have to make sure that the resolution is not so fine that a particle will skip over a grid cell within the minimum advection timestep, which is 1 minute.
The concentration grid resolution can be finer than the meteorology. The main consideration for choosing the concentration grid resolution is to make sure it is not too high of a resolution that undersampling will occur based on the number of particles you use. If you are considering a very high resolution concenctration grid, you also have to make sure that the resolution is not so fine that a particle will skip over a grid cell within the minimum advection timestep, which is 1 minute.