Investigation of the Summer Climate of the Contiguous United States and Mexico Using the Regional Atmospheric Modeling System (RAMS). Part I Model Climatology (1950–2002)

• Published in: Journal of climate Vol. 20; no. 15; pp. 3844 - 3865
• Main Authors: Castro, Christopher L., Pielke, Roger A., Adegoke, Jimmy O.
• Format: Journal Article
• Language: English
• Published: Boston, MA American Meteorological Society 01.08.2007
• Subjects: Atmospheric models; Atmospherics; Climate; Climate models; Climatology; Climatology. Bioclimatology. Climate change; Data assimilation; Earth, ocean, space; Exact sciences and technology; External geophysics; General circulation models; Meteorology; Monsoons; Precipitation; Rain; Rainfall; Rainy seasons; Research methodology; Soil water; States; Studies; Summer; Surface temperature; United States; Mexico; USA, Great Plains; USA; Atmosphere model; Scale reduction; Regional scope; Time series; 1950-2000; Summer; Climate models; digital simulation; North America; Dynamical climatology; algorithm performance; Climate variability; Observation data; Reanalysis
• ISSN: 0894-8755; 1520-0442
• DOI: 10.1175/JCLI4211.1

Fifty-three years of the NCEP–NCAR Reanalysis I are dynamically downscaled using the Regional Atmospheric Modeling System (RAMS) to generate a regional climate model (RCM) climatology of the contiguous United States and Mexico. Data from the RAMS simulations are compared to the recently released North American Regional Reanalysis (NARR), as well as observed precipitation and temperature data. The RAMS simulations show the value added by using a RCM in a process study framework to represent North American summer climate beyond the driving global atmospheric reanalysis. Because of its enhanced representation of the land surface topography, the diurnal cycle of convective rainfall is present. This diurnal cycle largely governs the transitions associated with the evolution of the North American monsoon with regards to rainfall, the surface energy budget, and surface temperature. The lower frequency modes of convective rainfall, though weaker, account for rainfall variability at a remote distance from elevated terrain. As in previous studies with other RCMs, RAMS precipitation is overestimated compared to observations. The Great Plains low-level jet (LLJ) is also well represented in both RAMS and NARR, but the Baja LLJ and associated gulf surges are not.