Impact of ASOS on 1969–1998 Normals in Lincoln, Nebraska

Automated Surface Observing Systems (ASOS) are thought to measure temperature and other weather variables differently than manual observing stations. This assertion must be of some concern when calculating the "Normals" from a given locale. In the next public release of 30-year Normals, the data from which the calculations are made will have used two different instrument packages to collect the data. Many stations will have a range from two to nine years of ASOS data. There is concern as to how this will affect the next set of Normals.

In this study, Normals temperatures from 1961-1990 are analyzed against derived Normal temperatures from 1969-1998 to preliminarily assess the impact ASOS will have on the ‘71-00 data set. One set of derived Normals utilize ASOS measurements, while the other does not. Using nearby weather stations of similar time period, a spatial analysis scheme is employed in the latter data set to eliminate any ASOS bias that may be present in the ‘69-98 record. Regional differences in the ‘69-98 Normals are also assessed to describe spatial patterns in the conterminous United States.