caa a22 4500 445799625 CHVBK 20180317145136.0 cr unu---uuuuu 170323e20110101xx s 000 0 eng 10.1007/s00704-010-0278-7 doi (NATIONALLICENCE)springer-10.1007/s00704-010-0278-7 Climatology of winter transition days for the contiguous USA, 1951-2007 [Elektronische Daten] [David Hondula, Robert Davis] In middle and high latitudes, climate change could impact the frequency and characteristics of frontal passages. Although transitions between air masses are significant features of the general circulation that influence human activities and other surface processes, they are much more difficult to objectively identify than single variables like temperature or even extreme events like fires, droughts, and floods. The recently developed Spatial Synoptic Classification (SSC) provides a fairly objective means of identifying frontal passages. In this research, we determine the specific meteorological patterns represented by the SSC's Transition category, a "catch-all” group that attempts to identify those days that cannot be characterized as a single, homogeneous air mass type. The result is a detailed transition climatology for the continental USA. We identify four subtypes of the Transition category based on intra-day sea level pressure change and dew point temperature change. Across the contiguous USA, most transition days are identified as cold fronts and warm fronts during the winter season. Among the two less common subtypes, transition days in which the dew point temperature and pressure both rise are more frequently observed across the western states, and days in which both variables fall are more frequently observed in coastal regions. The relative frequencies of wintertime warm and cold fronts have changed over the period 1951-2007. Relative cold front frequency has significantly increased in the Northeast and Midwest regions, and warm front frequencies have declined in the Midwest, Rocky Mountain, and Pacific Northwest regions. The overall shift toward cold fronts and away from warm fronts across the northern USA arises from a combination of an enhanced ridge over western North America and a northward shift of storm tracks throughout the mid-latitudes. These results are consistent with projections of climate change associated with elevated greenhouse gas concentrations. Springer-Verlag, 2010 Hondula David Department of Environmental Sciences, University of Virginia, P.O. Box400123, 22903, Charlottesville, VA, USA aut Davis Robert Department of Environmental Sciences, University of Virginia, P.O. Box400123, 22903, Charlottesville, VA, USA aut Theoretical and Applied Climatology Springer Vienna 103/1-2(2011-01-01), 27-37 0177-798X 103:1-2<27 2011 103 704 https://doi.org/10.1007/s00704-010-0278-7 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s00704-010-0278-7 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Hondula David Department of Environmental Sciences, University of Virginia, P.O. Box400123, 22903, Charlottesville, VA, USA aut NATIONALLICENCE 700 1- Davis Robert Department of Environmental Sciences, University of Virginia, P.O. Box400123, 22903, Charlottesville, VA, USA aut NATIONALLICENCE 773 0- Theoretical and Applied Climatology Springer Vienna 103/1-2(2011-01-01), 27-37 0177-798X 103:1-2<27 2011 103 704 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer