ATYPICAL PRECIPITATION MEASURES: COMPARISONS ALONG AN ENVIRONMENTAL GRADIENT, CENTRAL UNITED STATES

Abstract

Similarities and differences among 11 precipitation measures from 11 central U.S. sites are described. Sites are arrayed along transects that cross a longitudinal environment gradient. Nine derived (precipitation days, hours, events, duration, traces to precipitation hours, four intensity ratios) and two measured (precipitation amounts, trace occurrence) variables are used. Hourly values for 10 growing seasons comprise the data. Measures are compared under normal, wet, and dry conditions. Inclusion of trace occurrences on comparisons is noted.

Normal condition median values decrease westward; significant similarities exist among stations for all variables; trace inclusion raises median precipitation days and event numbers at western stations. Under dry conditions, medians are lower for all variables but overall sample characteristics are similar to normal conditions; trace data inclusion decreases contrasts with normal conditions; trace data inclusion (exclusion) increase (decreases) twofold between wet and dry months.

Wet condition median values are higher than normal; contrasts with normal are few (many) when traces were included (excluded). Trace occurrences are more common early and late in the growing season; diurnal patterns show more traces at eastern sites in early daylight hours, western stations in late afternoon hours; overall trace occurrence is greater at eastern vs. western sites.