HR: 09:00h
AN: A51F-05    [Abstracts]
TI: Climate Trends and Variability over North America Predicted by a Regional Climate Model for Increased CO2
AU: * Chen, M
EM: mchen@gust.sr.unh.edu
AF: University of New Hampshire, Morse Hall, 39 College Road, Durham, NH 03824 United States
AU: Mao, H
EM: hmao@typhoon.sr.unh.edu
AF: University of New Hampshire, Morse Hall, 39 College Road, Durham, NH 03824 United States
AU: Talbot, R W
AF: University of New Hampshire, Morse Hall, 39 College Road, Durham, NH 03824 United States
AU: Pollard, D
EM: pollard@essc.psu.edu
AF: Pennsylvania State University, 2217 Earth&Engineering Sciences Building, University Park, PA 16802 United States
AB: The MM5 regional climate model is adapted for long-term runs and used to perform two 10-year simulations over North America for the present (1991-1999 AD) and for approximately doubled CO2 (2090-2099 AD), driven by an archived transient simulation of the NCAR CSM. Characteristic changes in surface temperature and precipitation are analyzed, emphasizing diurnal ranges, interdiurnal variability of temperature, and frequency and intensity of precipitation events. Relative to the present, strongest wintertime warming in 2091-2099 occurs poleward of 40oN, with increases of ~6oC in some regions. However, the southern and southeastern U.S. experience colder winters, with temperature decreases of 0.5 to 2oC. During the summer, most areas of North America become warmer and increases in daily maximum temperature are much higher than those of daily minimum. Southward of 40oN, winters become more variable with greater storm activity, interdiurnal variability, and increased cold events in winter and hot events in summer. In summer, zones of significant precipitation generally shift northward with increased CO2, leaving some central U.S. regions much drier. In winter, precipitation increases along most coastal regions of U.S. The frequency and intensity of precipitation change significantly over most of the domain with increased CO2 . Averaged over all land, the frequency of weak precipitation events is relatively constant, but the frequency of heavy precipitation events (>=64 mm/day) increases dramatically by 35%-40% in spring and summer. Precipitation intensity increases from March to August due to the greater number of heavy precipitation events, and the ratio of convective to total precipitation increases. These predicted shifts from weak to heavy precipitation events suggest that flooding may become more prevalent over much of North America due to increased CO2 towards the end of the next century.
DE: 3309 Climatology (1620)
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting