Characteristics of Dryline Passage during COPS-91

Abstract

The characteristics of dryline passage are documented through an analysis of data from an instrumented surface mesonetwork in the Texas panhandle, and western and central Oklahoma during the Cooperative Oklahoma Profiler Studies field program. Some eastward-moving drylines at the surface during the day were characterized by monotonic drops in dewpoint after dryline passage; others were marked by a series of rapid drops punctuated by periods of no change after dryline passage, which suggests that the dryline often progresses in discrete steps, rather than continuously. The dryline during the daytime was not always collocated with a pressure trough, although the strongest dryline observed was. Analyses of surface pressure traces indicated that westward-moving drylines during the evening did not display behavior characteristic of strong, intense density currents, as had been found in other studies. Evidence is presented, in one case, of 90-min oscillations in water vapor and wind behind the dryline, which may have been associated with the downward transport of momentum associated with gravity waves aloft.