radmflux −− computes vertical and detrained mass fluxes and integrated momentum fluxes
radmflux divergence vertical_velocity x_velocity y_velocity
Radmflux accepts Doppler radar data processed by radvert on the standard input. Vertical and detrained mass fluxes and integrated vertical fluxes of horizontal momentum are computed and sent to the standard output. Command line arguments aid the interpretation of the input. The first argument is the name of the divergence field, while the second argument names the vertical air motion field to be used in the calculations. The third and fourth arguments respectively name the x and y velocity field components to be used in the momentum flux calculations.
The output is in the form of a common data format file with incoming comments, parameters, static field definitions, and scalar variable field "time" passed to the output. Radmflux adds a single comment line. Any number of variable slices are processed.
The output variable fields are as follows: Mflux is the horizontally integrated vertical velocity as a function of height, multiplied by the ambient air density. The density is obtained from radvert via the static field rho. Mfluxu is like mflux restricted solely to updrafts, while mfluxd is restricted to downdrafts. Dflux is the vertical profile of horizontally integrated divergence, while dflux2 is minus the z−derivative of mflux divided by the density times the acceleration of gravity. If radar were able to see all air in vertical motion, dflux and dflux2 would be equal. Uflux is the horizontally integrated product of x velocity perturbation and vertical velocity multiplied by the density. Vflux is the same for y velocity. The velocity perturbation is the actual velocity minus the mean velocity at the level of interest over the observation volume.
Expected units on input fields are m/sec for velocities, 1/ksec for divergence, and km for lengths. Output units are mb*km^2/sec on vertical mass fluxes, km^2/sec on detrained mass fluxes, and (km*m/s)^2 for momentum fluxes.
kestrel%radmflux d wi u v < infile > outfile
In this example radmflux looks for a divergence field named d and a vertical air motion field named wi in the file infile. Also sought are horizontal velocity fields u and v. The various flux fields are output to outfile.
The correctness of the momentum flux calculation is in doubt because of the implicit assumption that the mean horizontal wind within a cloud at each level equals the mean horizontal wind in the compensating subsidence region at that level. If all compensating motion occurs within the observed region, this problem doesn’t arise.