Some Informal Weather Notes Related to the Sword Fern Die-off

We sometimes speculate that recent drought and high temperatures, particularly in the summer, may have caused, or may contribute to the sword fern die-off.   The research presented in a blog post from earlier today (from the Pittermann lab at UCSC) shows a strong correlation, and plausible mechanisms for, sword fern die-back and the California drought.  Perhaps our die-off is similar correlated to weather?

Here I show some data which suggests that our precipitation levels are well within normal Seattle ranges; indeed, they are higher than average over all but one of the last seven years.  Month-by-month reports show more variability, and three of the last six summers may be somewhat unusally dry.  It will require more data to illuminate that.

First, here is the 120 years of California PDSI (Palmer Drought Severity Index - which combines precipitation and temperature data).    Following that are precipitation records (only) from Seattle, measured at SeaTac Airport.  California's drought has been historically severe, and quite anomalous.