The method is documented in:
Dai, A., R. M. Rasmussen, C. Liu, K. Ikeda, and A. F. Prein, 2017: A new mechanism for warm-season precipitation response to global warming based on convection-permitting simulations. Clim. Dyn., 0, 1–26, https://doi.org/10.1007/s00382-017-3787-6