Development of climate monitoring indices for California

The prospect of climate change in California and the potential impacts on human and natural systems has led to the establishment of a variety of climate activities in the state. Among these are the university-based California Climate Change Center, and one of its components, the California Climate Data Archive (CCDA) project (www.calclim.dri.edu) at the NOAA Western Regional Climate Center. Of particular interest to both the research community, policy makers, and the public at large is whether, or which, facets of California climate are exhibiting trends or other long term variability. The CCDA web pages and California Climate Watch offer daily and monthly updates, but there has been a need for several simple index quantities to track the state's climate. We here focus on aggregates of carefully selected stations for temperature and precipitation. A number of criteria are considered for inclusion of stations. Minimum record lengths of 50-100 years are desired, with access to original observations and no more than 10-15 percent missing. Each of the state's physiographic and climatic provinces should be adequately represented. Stations that exhibit pronounced inhomogeneities will not be favored. The same station set need not apply for temperature and precipitation. Stations should have an adequate potential for continuation into the future. All stations are in the NOAA Summary of the Day dataset (TD3200), as updated by the pre-1948 TD3206 data. The eventual goal is about a hundred stations. Subsets for particular areas (high elevations, coastal locations) and timescales are of special importance and will have supplemental time series. Preliminary findings about trends will be discussed and presented.