Natural sources of antimatter are an interest of mine, and that includes antimatter produced in storms. When I asked a national research lab about investigating storm antimatter, I was told that the production rate is so low that it isn’t practical to send up aircraft to study it. Perhaps that idea needs to be re-examined?
“In the past decade, research by Dwyer and others has shown that storms also produce positrons, as well as highly energetic photons, or γ-rays.” However, the antimatter detected in this particular storm remains unexplained.
“Rogue antimatter found in thunderclouds”
http://www.nature.com/news/rogue-antimatter-found-in-thunderclouds-1.17526