Observed and model‐simulated diurnal cycles of precipitation over the contiguous United States

作者：Aiguo Dai, Filippo Giorgi, Kevin E. Trenberth · 发表于：Journal of Geophysical Research Atmospheres · 年份：1999 · DOI：10.1029/98jd02720 · 被引用次数：491 · 研究领域：Climate variability and models、Meteorological Phenomena and Simulations、Plant Water Relations and Carbon Dynamics

We analyzed diurnal variations in precipitation, surface pressure, and atmospheric static energy over the United States from observations and NCAR regional climate model (RegCM) simulations. Consistent with previous studies, the mean (1963–1993) pattern of the diurnal cycle of summer U.S. precipitation is characterized by late afternoon maxima over the Southeast and the Rocky Mountains and midnight maxima over the region east of the Rockies and the adjacent plains. Diurnal variations of precipitation is weaker in other seasons, with early to late morning maxima over most of the United States in winter. The diurnal cycle in precipitation frequency accounts for most of the diurnal variations, while the diurnal variations in precipitation intensity are small. The broad pattern of the diurnal cycle of summer precipitation is fairly stable, but the interannual variability in the diurnal cycle of winter precipitation is large. The diurnal cycle of July connective available potential energy (CAPE) is dominated by a solar driven march of a high‐CAPE (2–4 kJ kg−1 ) tongue moving from the Southeast into the Northwest, with maximum values in the late afternoon to early evening over most of the United States. The solar driven diurnal and semidiurnal cycles of surface pressure result in significant large‐scale convergence over most of the western United States during the day and over the region east of the Rockies at night. The diurnal cycle of low‐level large‐scale convergence suppresses...