Development of 1971–2000 climate normals and supplemental climate summaries

The National Climatic Data Center (NCDC) is developing plans for the production of 1971 - 2000 climatic normals, i.e. 30-year mean values of monthly maximum and minimum temperature, total precipitation and heating and cooling degree days for several thousand locations in the United States. Daily normals of these elements will be computed for several hundred U.S. airports and climate stations from the monthly normals using a spline function that provides a highly smoothed variation of the representative data throughout the year. NCDC is also developing an on-line capability for users to retrieve climate data and standard normals or calculate time series of climate data based on selectable averaging periods. The user will be able to compute on demand a spline-function smoothed set of daily values for any normals station or a more variable and detailed set of daily mean values based on the daily data. The web page, currently titled “Climate Data and Summaries Calculator”, will also enable users to compute supplemental climate summaries such as freeze data tables, first and last occurrence and duration of any selected temperature, degree days to any base temperature, extremes, probabilities and the total or consecutive number of days of occurrence for user selected elements, values and time periods. Plans for producing the 1971 - 2000 standard normals, including plans to determine the influence of Automated Surface Observation System (ASOS) instrumentation on the normals, and the development of the supplemental climate summaries web page will be discussed.