California Drought- Annual scPDSI 1896 to 2013

We used remotely sensed self calibrating Palmer Drought Severity Index (scPDSI), made available through the Western Regional Climate Center (www.wrcc.dri.edu/wwdt/data/PRISM/scpdsi/). The scPDSI ranges from -5.0 to 5.0. The number shows the magnitude and the sign denotes (+) wetter than average or (-) drier than average conditions for a location based on historical climate and sensitivity to changes in water availability. Absolute values greater than 4 represent extreme conditions and unlike earlier versions of the PDSI, extreme conditions occur based on the history of the location and are not determined relative to a default location. The scPDSI allows more exact comparisons between location and times and is a more accurate index compared to PDSI for extreme events. A detailed description of scPDSI can be found in Wells, N., Goddard, S., & Hayes, M. J. (2004). A self-calibrating Palmer Drought Severity Index. Journal of Climate, 17, 2335â 2351.