Transitioning from the traditional divisional dataset to global historical climatology network-daily gridded divisional dataset

The National Climatic Data Center's Climate Monitoring Branch uses climate-division data to identify trends and significant climate events in its monthly suite of temperature, precipitation and drought products. These products, some of which are contained within the State of the Climate report, provide a variety of maps and graphics that are generated based on these climate-division scale data. The traditional (station-based) divisional dataset is based upon a feed of near-real-time station data from several NOAA collection points. The Global Historical Climatology Network-Daily (GHCN-D) gridded divisional dataset will be based on a similar station inventory, however new methodologies will be used to compute temperature and precipitation for United States climate divisions. These new methodologies include the transition from a station-based to a grid-based calculation, the inclusion of many more stations from the pre-1930s, and the use of NCDC's modern array of quality control algorithms. These are expected to improve the data coverage and the quality of the dataset, while maintaining the current product stream. The primary focus of this discussion is to provide historical differences in the traditional and grid-based GHCN -D divisional datasets. A discussion of monthly, seasonal, and yearly climate trends in temperature and precipitation will be included.