Wednesday, 12 February 2003: 8:30 AM
Changes in characteristics of United States snowfall over the last half of the twentieth century
Several recent studies have reported that large portions of the mid- and high-latitude land areas of the northern hemisphere (including much of the United States) have experienced increasing precipitation over the last half of the 20th century. From a relatively small number of studies of snowfall trends, the characteristics of northern hemisphere wintertime precipitation over this period have been found to vary over space and time. Over the United States, some specific findings from these studies
include: increasing snowfall in parts of the Great Plains and Northeastern states; increasing interannual variability in nationally averaged snowfall; and, as recently reported by the IPCC, a reduction in a directly related variable - spring snow cover area - in the latter half of the 20th century.
In our current study, daily snowfall amounts from 1948 through 2001 from several hundred stations in the United States Historical Climatology Network (lying north of 35 degrees north latitude) are examined in several ways. We analyze records over the whole year and also over an October through May "snow season" to study trends and variations in variables such as total snowfall, number of snow days, average magnitude of snowfall events, number of events exceeding specific thresholds, near-surface air temperature
on snow days, and the contribution of snowfall liquid water
equivalent to total annual precipitation. Preliminary results indicate interesting regional changes in many of these variables.