Setting source rate for a tracer for the source pixel

[HP1801]

I am trying to do a WRF-LES simulation to get a simulation for a tracer plume at a 10 m resolution. I am trying to figure out how to set/determine the source rate of the source pixel for the tracer in units/second. I tried setting it in the WRFV3/dyn_em/solve_em.F file using the following code (see the bold line):

   IF (config_flags%tracer_opt .eq. 2) THEN
     DO j = (jde + jds)/2, (jde + jds)/2,  1
       DO i = 3*(ide + ids)/4, 3*(ide + ids)/4, 1
          IF ( ips .LE. i .and. ipe .GE. i .and. jps .LE. j .and. jpe .GE. j ) THEN
           tracer(i, 1, j, P_tr17_1) = 50.
          END IF
       END DO
     END DO
   END IF

However, this sets the source pixel value to 50 for the whole history interval of 30 s. I am not sure how to determine the rate per second from this integrated value since the tracer would be transported during those 30 seconds.

 

[kwerner]

Hi,
I apologize for the delay in response. I'm trying to find someone in our group who may be able to help with this. Hopefully we will have a response for you soon. Thank you for your patience.

 

[HP1801]

Hi,
I apologize for the delay in response. I'm trying to find someone in our group who may be able to help with this. Hopefully we will have a response for you soon. Thank you for your patience.

Thank you so much, I look forward to discussing this question.

 

[davegill]

I am not quite sure that I understand the question.

In WRF, the tracer array contains only passive scalars. The values in the tracer array do not impact the rest of the WRF simulation. The tracers have no mass, and do not physically interact with the physics or dynamics. Other than being advected, taking additional memory and computational time for transport, the tracer arrays do not change the WRF solution at all.

For a single WRF timestep in the solve_em.F file that is outside of the Runge-Kutta loop, setting the value of a tracer is fairly arbitrary. Instead of setting the value to 50, let us assume that you chose to set the grid point to 1. Then, the value that you are setting is basically "one unit of tracer". Since you do this every timestep, you are introducing "one unit of tracer per model timestep".

Assuming that no tracer leaves your domain through the lateral boundaries, then the total amount of tracer in the domain = the amount of tracer introduced per time step x the number of time steps. With a conversion to time (instead of time steps), you get the source rate is just the total tracer source added / the simulation length.

Again, I am not sure I quite understand the question. We can iterate on this.