Parallel climate model (PCM) control and transient simulations

Abstract

The Department of Energy (DOE) supported Parallel Climate Model (PCM) makes use of the NCAR Community Climate Model (CCM3) and Land Surface Model (LSM) for the atmospheric and land surface components, respectively, the DOE Los Alamos National Laboratory Parallel Ocean Program (POP) for the ocean component, and the Naval Postgraduate School sea-ice model. The PCM executes on several distributed and shared memory computer systems. The coupling method is similar to that used in the NCAR Climate System Model (CSM) in that a¯ux coupler ties the components together, with interpolations between the dierent grids of the component models. Flux adjustments are not used in the PCM. The ocean component has 2/3°average horizontal grid spacing with 32 vertical levels and a free surface that allows calculation of sea level changes. Near the equator, the grid spacing is approximately 1/2°in latitude to better capture the ocean equatorial dynamics. The North Pole is rotated over northern North America thus producing resolution smaller than 2/3°in the North Atlantic where the sinking part of the world conveyor circulation largely takes place. Because this ocean model component does not have a computational point at the North Pole, the Arctic Ocean circulation systems are more realistic and similar to the observed. The elastic viscous plastic sea ice model has a grid spacing of 27 km to represent small-scale features such as ice transport through the Canadian Archipelago and the East Greenland current region. Results from a 300 year present-day coupled climate control simulation are presented, as well as for a transient 1% per year compound CO 2 increase experiment which shows a global warming of 1.27°C for a 10 year average at the doubling point of CO 2 and 2.89°C at the quadrupling point. There is a gradual warming beyond the doubling and quadrupling points with CO 2 held constant. Globally averaged sea level rise at the time of CO 2 doubling is approximately 7 cm and at the time of quadrupling it is 23 cm. Some of the regional sea level changes are larger and re¯ect the adjustments in the temperature, salinity, internal ocean dynamics, surface heat¯ux, and wind stress on the ocean. A 0.5% per year CO 2 increase experiment also was performed showing a global warming of 1.5°C around the time of CO 2 doubling and a similar warming pattern to the 1% CO 2 per year increase experiment. El NinÄ o and La NinÄ a events in the tropical Paci®c show approximately the observed frequency distribution and amplitude, which leads to near observed levels of variability on interannual time scales.

Projected change in climate thresholds in the Northeastern U.S.: implications for crops, pests, livestock, and farmers

“…In addition to the HadCM3 results reported here, we also conducted future simulations with the DOE/NCAR PCM model (Washington et al 2000), which has a grid resolution of approximately 2.8 by 2.8 degrees, and climate sensitivity to a doubling of atmospheric CO 2 of 1.3°C, slightly below the IPCC range of 1.5-4.5°C. Those interested in comparing PCM with HadCM3 results are referred to: http://www.northeastclimateimpacts.org.…”

“…(A similar analysis was conducted based on output from the DOE/NCAR PCM model (Washington et al 2000), with results available at: http://www.northeastclimateimpacts.org). Climate thresholds we consider include: the frost-free period; the frequency of high temperature stress thresholds affecting crops and livestock; winter temperature effects on winter chill requirement for maximum yield of fruit and other crops minimum winter temperature effects on potential northward migration of invasive weeds and insect pests, and frequency of summer droughts.…”

Climate Change detection over different land surface vegetation classes

“…Simulations from three climate models: Parallel Climate Model (PCM) (Washington et al, 2000), HadCM2 (Johns et al, 1997), and CGCM2 (Flato and Boer, 2001), are used to estimate the internal variability. These climate models include control integrations of 1009 years with PCM, 1700 years with HadCM2, and 1000 years with CGCM2.…”

Climate Change Projections for the United States Midwest

“…In addition, HadCM3 is the only model which has daily temperature and precipitation data available for all four scenarios, as required for analyses of temperature extremes, frost-free season, heavy rainfall events, etc. We also incorporate monthly temperature and precipitation projections corresponding to the SRES A2 and B2 scenarios from the Parallel Climate Model (PCM), a low-sensitivity model ( T = 1.5 • C for 2×CO 2 ) developed at the U.S. National Center for Atmospheric Research (Washington et al 2000). A1FI and B1 projections for the PCM model are in progress but were not available for inclusion in this study (Meehl, Washington, pers.…”