I don't have a reference; however, I can provide an approache I have employed on a number of occasions for CSO studies in the past where we we interested in finding a year that best reflects average conditions in the historical record. This does not identify a theoretical average year, if that is what you are after.

Use the Rain and Stats block to analyze your availabe years of say hourly data. From this analsis you can begin to select years with the representative characteristics in the following order: annual precip., annual number of events, monthly volumes, monthly # of events, and any other characteristics that you may be interested in. I have included monthly maximum intensities as well. We've done this kind of analysis on 30-years of data in just a few hours and ended up choosing an historical year as a an "average year". It's not perfect, but I have found it a useful strategy depending on the objectives.

Daniel P. Davis, P.E.
dpdavis@brwncald.com