Rainfall trends DC and C-Ville

[EricPeterson]

I added up days of rainfall for DCA and Charlottesville.  There is an increase in days of measureable rain (a hundredth or more) but a slight decrease in "real" rain (a tenth or more).  That decrease is probably negligible.  That plot is here:
Because of that slight divergence, I got interested in the trend in each bin of rainfall from very light to very heavy.  Unfortunately the daily rainfall totals don't indicate the timing so there's no way to know if 0.2 one day and 0.8 the next day is really one rainfall of 1.0 falling before and after midnight.  So I double counted the days and trended that.  Double counting creates a few trend artifacts.   Finally I did the seven day totals (not double counted).  The seven day plots show an increase in seven day rain amounts of about 2 inches.  For our area that's a relatively wet week.  More plots and links to the code here: https://virtualcoinclub.com/wx/rftrends/  The README has instructions to download the data for any location although you have to search a bit to find longer complete records.

[ChrisSmolinski]

My suspicion is that given the large number of reporting stations and relative short history, it would be possible to show any desired results. And even given the same station selection and analysis method, the results will change every few years as new data is added.

[EricPeterson]

Well there's not much change regardless of how you look at it.  One thing I think is noteworthy though, the decrease in weeks with zero or almost no precip on the seven day plots.  I suspect that would hold for much of the midwest through the east but I'd have to look at a lot more stations to show that effect is real.

[ChrisSmolinski]

Sorry, what I was trying to convey was that it would be possible to torture the data to try and show rainfall was increasing/decreasing/etc due to climate change. Maybe both, even at the same location