Trajectory does not resemble conc/disp plot

[fmet.metoc]

Hello,
(I think my first post didn't go through. I tried attaching a kmz file)

I ran a trajectory using the NAMCNEST (4km) model from Aug 6, 2014 12Z for 19Z for 3 hours. The start point was station CWPF (Esquimalt, BC, Canada).
The trajectory starts off heading to the NE, then curls back to the NW.

When the conc/deposition plot is run using the same source model, the plume heads East for the entire 3 hour period.

The release point was set at 50m.

I also looked at the ensemble plots of trajectory, and it was interesting to see there were 2 clusters....one of which was similar to the trajectory plot, and the other was similar to the conc/deposition plot.

I do not understand why the one trajectory differed so much from the concentration/dispersion plot.

Jim

[ariel.stein]

Differences between trajectories and concentration runs are expected because the trajectories do not include the atmospheric dispersion of the pollutant.
In the concentration calculation many lagrangian particles are released, transported and dispersed through the domain while for the trajectories only the transport by the mean wind is taken into account.
I am not sure how you created the trajectory ensemble but varying the initial height or stating them after a certain time period can also generate part of the variability that you see in the concentration run.

[fmet.metoc]

Thanks for the reply.
I can understand minor differences as the dispersion would spill around the edges of the mean trajectory. However, I would expect that generally the trajectory should lie within the dispersion "plume". In this case, the trajectory was barely touching the colored edge of the plume within the first hour, then turned sharply away.

[ariel.stein]

Can you please send me the control files you are using to run the trajectories and the concentrations?

[fmet.metoc]

Here is a different example than I described earlier, but it too shows a similar result. Over 3 hours, the trajectory starts off heading WNW then turns N. The concentration mostly goes west. If the two plots are overlaid, the trajectory goes well outside the plume. I chose a 10 minute emission for the concentration plot, which should be close to "instantaneous" which is what I believe the trajectory uses.


TRAJECTORY CONTROL FILE:
14 08 11 19 #STARTING TIME: YEAR MONTH DAY HOUR
1 #NUMBER OF STARTING LOCATIONS
48.43 -123.43 50 #STARTING 1: LATITUDE LONGITUDE HEIGHT (m-agl)
3 #TOTAL RUN TIME (hours)
0 #VERTICAL MOTION CALCULATION METHOD
10050 #TOP OF MODEL DOMAIN (m-AGL)
4 #NUMBER OF INPUT DATA GRIDS
/pub/forecast/20140811/
hysplit.t12z.namsf00.CONUS
/pub/forecast/20140811/
hysplit.t12z.namsf06.CONUS
/pub/forecast/20140811/
hysplit.t12z.namsf12.CONUS
/pub/forecast/20140811/
hysplit.t12z.namsf18.CONUS
/pub/ready/hypub/
tdump.15081

############################################################

DISPERSION CONTROL FILE:
14 08 11 19 #STARTING YEAR MONTH DAY HOUR
2 #NUMBER OF SOURCE LOCATIONS
48.43 -123.43 50 #SOURCE 1 LATITUDE LONGITUDE HEIGHT(m-agl)
48.43 -123.43 0 #SOURCE 2 LATITUDE LONGITUDE HEIGHT
3 #TOTAL RUN TIME (hours)
0 #USE MODEL VERTICAL VELOCITY
10000 #TOP OF MODEL DOMAIN (m-AGL)
4 #NUMBER OF INPUT DATA GRIDS
/pub/forecast/20140811/
hysplit.t12z.namsf00.CONUS
/pub/forecast/20140811/
hysplit.t12z.namsf06.CONUS
/pub/forecast/20140811/
hysplit.t12z.namsf12.CONUS
/pub/forecast/20140811/
hysplit.t12z.namsf18.CONUS
1 #NUMBER OF DIFFERENT POLLUTANTS
Unit #POLLUTANT IDENTIFICATION
6 #EMISSION RATE (per hour)
0.166666666666667 #HOURS OF EMISSION
14 08 11 19 0 #RELEASE START TIME:YEAR MONTH DAY HOUR MINUTE
1 #NUMBER OF CONCENTRATION GRIDS
0 0 #CONC GRID CENTER LATITUDE LONGITUDE
0.004 0.004 #CONC GRID SPACING (degrees) LATITUDE LONGITUDE
7.0 7.0 #CONC GRID SPAN (degrees) LATITUDE LONGITUDE
/pub/ready/hyreg/
cdump.2135
2 #NUMBER OF VERTICAL CONCENTRATION LEVELS
0 100 #HEIGHT OF EACH CONCENTRATION LEVEL (m-agl)
14 08 11 19 0 #SAMPLING START TIME:YEAR MONTH DAY HOUR MINUTE
00 00 00 3 00 #SAMPLING STOP TIME:YEAR MONTH DAY HOUR MINUTE
0 1 0 #SAMPLING INTERVAL: TYPE HOUR MINUTE
1 #NUMBER OF DEPOSITING POLLUTANTS
0.0 0.0 0.0 #PARTICLE:DIAMETER (um), DENSITY (g/cc), SHAPE
0.001 0.0 0.0 0.0 0.0 #DEP VEL (m/s), MW (g/Mole), SFC REACT. RATIO, DIFFUSIVITY RATIO, HENRY'S CONSTANT
0.0 0.0 0.0 #WET REMOVAL: HENRY'S (Molar/atm), IN-CLOUD (L/L), BELOW-CLOUD (1/s)
8 #RADIOACTIVE DECAY HALF-LIFE (days)
0.0 #POLLUTANT RESUSPENSION (1/m)

[ariel.stein]

Based on the plots from our webpage, I can see that the particles that are used in the concentration calculation mix up to 750 m very quickly. So, to make the trajectories to resemble the concentrations you will have to start the trajectories at different heights up to 750 m.