HYSPLIT Forum: hysplitbbs.arl.noaa.gov

I have conducted a study by using the HYSPLIT web version to simulate the dispersion of noble gas, particulate matter (e.g Cs-137) and gaseous I-131. I found that the outputs of deposition field show very clear-cut edge near sea east of Vietnam (no such problem for air conc. fields). Any clue for this? Attached please find the images.

Also, I want to confirm the way of calculating below-cloud wet removal of particulate on the web version. Is it similar to in-cloud wet removal, also using the time constant βbelow-cloud = K*P^0.79 (where K is a constant with value less than 1 and P is the precipitation rate (mm/h)) ? Since some of the HYSPLIT documents mentioned that the βbelow-cloud is defined as a rate constant and independent of the precipitation rate. Thanks.

Although you did not include a map of deposition, the problem you are seeing is most likely due to the concentration/deposition grid (defined in the CONTROL file) being smaller than the size of you deposition field during the calculation and therefore the deposition plume was cutoff at the edge of the defined grid.

The wet deposition in the current version of the web version uses the removal time constant (/s) for both in-cloud and below-cloud calculations (see the input section in the attached image). If you did not include a value, then only the dry deposition was calculated with the default value of 0.001 m/s.

Maybe the image is lost. Here is the image. And, what do you mean " the size of the deposition field during the calculation" ? Since I cannot control the grid size (0.05 near the source and 0.2 for the others) on the web version, how can I remove the sharp edge and show deposition field in region far away from the source?

For the second question, if I input 8E-5 for both in-cloud and below-cloud, then the system will use 8E-5 *P^0.79 to calcluate the time constant βin-cloud and βbelow-cloud. Is it right?

If you need to do longer range or more specialized calculations, then you should download either the PC or LINUX versions of the model and run them locally. The web version is not meant to solve all complicated applications.

Yes, if you enter a value (X) for either below or in-cloud less than 1.0, then the system will use X *P^0.79 to calcluate the time constant βin-cloud and βbelow-cloud.