One idea is for cloud seeding, I do not know if this has already be attempted but I think a way that could be used to find out if seeding is productive is to look at rain plots. 3-D graphs of rain per minute laided on top of each other with tracks of seeding planes and winds. Also don't just look at rain but also humidity, wind changes and pressures.
I don't think anyone has done cloud seeding over the ocean. I know it doesn't help with giving water to plants but we know that there is more nuclei over oceans maybe it could effect the outcome I have refined this idea because over the ocean is not productive since we are only interested in what happens over land, so I have looked at what some groups are doing and I have noticed that SOAR is going to be putting salt particles in clouds around Texas this is a much better way to do this then my idea about doing things over the ocean.
My final idea has to do with the precipitation and evaporation graphs for the world. There is a average rate that precipitation and evaperation affect the planet, they have to balance each other out maybe there could be a lot of work done at a certain latitude and if we could measure the evaporation and precipitation right away we might be able to find out if there is a major change to prove that we are affecting the rainfall.