I am writing an UDF that will calculate the Mercury Wet Deposition in Indianapolis and display it on a model (most prefferably a fluent/GAMBIT model).

The wet deposition is usually estimated from knowledge of the washout ratio which is: W= Crainwater/Cair. Crainwater is the chemical concentration in rainwater and Cair is the chemical concentration in the gaseous phase. The data used for the formula above was taken from the National Atmospheric Deposition Program, Mercury Deposition Network.

I kind of know how to do it but I need guidance.

I don't know if I should be using a if-else-if statement or go some other way.

I will really appreciate your assistance.

Thank you