Extracting information from snowfall in California 1878-2010

Digital images of Climatological Data for California were accessed from 1891 to 1930 from NCDC. Monthly snowfall totals for stations in these documents were keyed-in to produce machine readable files. Some tables in the documents contained monthly totals for some stations back to 1878. These keyed-in values represent about 25,000 monthly totals not contained in the current NCDC archive. These data were merged with the machine-readable data from NCDC to generate long-time series through June 2010. Stations in California were assigned to one of 18 snowfall-regions and regional average time series were calculated using three techniques. In general, regions with significant snowfall and several stations (mainly central and southern Sierra Nevada) show robust time series replication. Time series for lower elevation and more southern regions revealed less robustness as few stations were available with consistent records, and the fact snowfall events are highly non-gaussian. The difficulties encountered in understanding the data and dealing with these types of records will be discussed. For those regions with robust replication, there were no significant trends since the late 19th century in snowfall.