On the effect of relative timing of diurnal and large-scale forcing on summer extreme rainfall characteristics over the Central United States

• Published in: Monthly weather review Vol. 130; no. 5; pp. 1442 - 1541
• Main Authors: SEGAL, Moti, ZAITAO PAN, ARRITT, Raymond W
• Format: Journal Article
• Language: English
• Published: Boston, MA American Meteorological Society 01.05.2002
• Subjects: Earth, ocean, space; Exact sciences and technology; External geophysics; Extreme weather; Meteorology; USA, Central; Water in the atmosphere (humidity, clouds, evaporation, precipitation); United States; North America; America; Rain; Flood; Extreme value; Wind velocity; Summer; Numerical simulation; Climate models; Forcing; Timing; Drought; Rainfall rate
• ISSN: 0027-0644; 1520-0493
• DOI: 10.1175/1520-0493(2002)130<1442:oteort>2.0.co;2

Impacts of diurnal radiative forcing on flow and rainfall patterns during summer flood and drought conditions (1993 and 1988, respectively) in the central United States were investigated using a regional climate model. The modeling approach, which included evaluation of sensitivity to modification in the solar hour. enabled evaluation of the impact on an event-by-event basis. The effect of the solar hour forward shift of 12 h on boundary layer wind speed over north-central Texas, which is often related to rainfall in the central United States through northward moisture advection, followed almost exactly the shift in solar hour. Domain-averaged daily rainfall in the central United States simulated with 12-h solar shift frequently showed in the flood year a backward or forward time shift of similar to 12 h in the timing of its peak, an increase or decrease of rainfall rate, and on a few occasions noticeable formation of short-lived rainfall events. This pattern suggests relatively high sensitivity to the timing of the diurnal radiative forcing with respect to the large-scale perturbations. In contrast, in the drought year 12-h solar shifted simulations these modifications were weaker. The climatological domain-average diurnal cycle of rainfall showed for the flood year a well-defined 12-h shift when comparing the control and perturbed simulations. In contrast, in the drought year such a shift was not well defined.