Climate and Weather Observation Data

Although for many analytical purposes it is preferable to work with gridded climate data rather than point data, it can still be useful to access raw observation data, if only to understand some of the sources behind the models that produce the gridded datasets. The following describes some of the main access points for these observation data.

It is important to recognize a distinction between climate observation data and weather observation data. Although data variables and the instrumentation may be similar, weather data is oriented towards short-term forecasting, whereas climate data is intended for elucidation of long-term patterns, and hence stability and stringent data quality is especially valued in climatological stations. (This point is made well in Paul Edwards' excellent history of informatics in climatology A Vast Machine). This distinction has resulted in different observation networks for the two types of data.

The basis for the climatological observation record in the United States is the National Weather Service Cooperative Observer Program, a program which was established in 1890 and now consists of more than 10,000 stations. A subset of these of about 1200 stations with a particularly long and stable observation record have been chosen to form the United States Historical Climatology Network. Daily and monthly data from the Historical Climatology Network is available for download from a repository hosted by Oak Ridge National Laboratory.

In California, the primary access point for the majority of climatological observation data is the Western Regional Climate Center, based at the Desert Research Institute in Reno. They provide climate summaries for individual stations for download here. Information about individual stations is also available through the National Climatic Data Center.

Current weather observation data comes from a diverse array of sources. For meteorological data in the western United States, an excellent aggregation site for these data is MesoWest, hosted at the University of Utah. Their list of weather stations tracked in California includes sources such as National Weather Service stations at airports (NWS/FAA), remote automated weather stations (RAWS) typically in forests, the California Irrigation Management Information Stations (CIMIS), stations, weather data from the California Air Resources Board (CARB), and Citizen Weather Observation Program (APRSWXNET/CWOP) stations. MesoWest provides many interfaces for these data, including map displays and spreadsheet downloads.