# Exercise #11

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• Problem #1 - The previous wet deposition simulation for particles showed deposition results 10,000 times larger than for the gaseous simulation. What Henry's constant is required for a gas to match the magnitude of the particle deposition?

• Hint - Reconfigure the gaseous wet deposition simulation using a more appropriate removal constant. For example, Henry's constant for OH is about 1000 and for H2O2 it is about 10,000.

• Solution - concplot.html

• Problem #2 - How sensitive is the wet removal to the location of the precipitation with respect to the pollutant? The particle wet deposition calculation showed only about 1 kg of mass was lost. Earlier it was mentioned that the precipitation started on the 26th at 0600 UTC. Instead of Dayton, start the particle calculation from the location of the initial wet deposition period (0600-0900) through 1500 UTC and compare the differences in the loss of mass.

• Hint - Using the results from one of the simulations in problem #1, output the deposition for each time period to determine the location of the first deposition to be about 42N 79W.

• Solution - About 4 kg lost in 9 h instead of 1 kg over 24 h because the calculation started in the precipitation region resulting in wet removal over the entire spatial extent of the pollutant.

• Problem #3 - How important are the threshold relative humidities used to define the cloud base and top in determining the amount of wet deposition? Rerun problem #2 with different thresholds to estimate the impact of this parameter.

• Hint - The SETUP.CFG file namelist parameters for the cloud top and bottom, RHT and RHB, relative humidities are not available through the GUI but can be found listed in the MESSAGE file. Therefore, open the SETUP.CFG file created in problem #2 in an external editor and add the two lines for RHT and RHB, and then you can rerun the simulation with different values, either on the command line or through the GUI. Check the MESSAGE to confirm that your modified values were used in the simulation.

• Solution - After trying different values for RHT and RHB, you should find that the mass remaining, as shown in the MESSAGE file, is insensitive to RHT; but after RHB reaches 95%, the mass remaining starts to increase. At 96% about 198.8 kg remains and by 98% hardly any mass was deposited.