The second (and far more extensive) improvement is to the computational methodology, which now addresses topographic and network variability via climatologically aided interpolation (Willmott and Robeson, 1995).The outcome of these improvements is a new divisional dataset that maintains the strengths of its predecessor while providing more robust estimates of areal averages and long-term trends.

These new methodologies include the transition to a grid-based calculation, the inclusion of many more stations from the pre-1930s, and the use of NCEI's modern array of quality control algorithms.

These have improved the data coverage and the quality of the dataset, while maintaining the current product stream.

The n Clim Div dataset is designed to address the following general issues inherent in the Drd964x dataset: The first (and most straightforward) improvement to the n Clim Div dataset involves updating the underlying network of stations, which now includes additional station records and contemporary bias adjustments (i.e., those used in the U. Historical Climatology Network version 2; Menne et al., 2009).

The Alaska n Clim Div data were created and updated using similar methodology as that for the CONUS, but with a different approach to establishing the underlying climatology.

The Alaska data are built upon the 1971-2000 PRISM averages whereas the CONUS values utilize a base climatology derived from the n Clim Div dataset.

More information on this new dataset can be access here: Alaska FAQ's Traditionally, climate division values have been computed using the monthly values for all of the Cooperative Observer Network (COOP) stations in each division are averaged to compute divisional monthly temperature and precipitation averages/totals. For the 1895-1930 period, statewide values were computed directly from stations within each state.Divisional values for this early period were computed using a regression technique against the statewide values (Guttman and Quayle, 1996). The n Clim Div dataset is based on the GHCND dataset using a 5km gridded appoach.For many years the Climate Divisional Dataset was the only long-term temporally and spatially complete dataset from which to generate historical climate analyses (1895-2013) for the contiguous United States (CONUS).It was originally developed for climate-division, statewide, regional, national, and population-weighted monitoring of drought, temperature, precipitation, and heating/cooling degree day values.Since the dataset was at the divisional spatial scale, it naturally lent itself to agricultural and hydrological applications. For each climate division, monthly station temperature and precipitation values are computed from the daily observations.The divisional values are weighted by area to compute statewide values and the statewide values are weighted by area to compute regional values. In March 2015, historical data for thirteen Alaskan climate divisions were added to the n Clim Div database and will be updated each month with the CONUS n Clim Div data.