Publications

A high-resolution climate model for the U.S. Pacific Northwest: Mesoscale feedbacks and local responses to climate change

Citation

Salathé, E.P., Steed, R., Mass, C.F., Zahn, P.  2008. A high-resolution climate model for the U.S. Pacific Northwest: Mesoscale feedbacks and local responses to climate change. Journal of Climate 21(21): 5708-5726, doi:10.1175/2008JCLI2090.1.


Abstract

Simulations of future climate scenarios produced with a high-resolution climate model show

markedly different trends in temperature and precipitation over the Pacific Northwest than in the

global model in which it is nested, apparently due to mesoscale processes not resolved at coarse

resolution. Present-day (1990-1999) and future (2020-2029, 2045-2054, and 2090-2099)

conditions are simulated at high resolution (15-km grid spacing) using the MM5 model system

and forced by ECHAM5 global simulations. Simulations use the IPCC Special Report on

Emissions Scenarios (SRES) A2 emissions scenario, which assumes a rapid increase in

greenhouse gas concentrations. The mesoscale simulations produce regional alterations in snow

cover, cloudiness, and circulation patterns associated with interactions between the large-scale

climate change and the regional topography and land-water contrasts. These changes

substantially alter the temperature and precipitation trends over the region relative to the global

model result or statistical downscaling. Warming is significantly amplified, through snow-albedo

feedback, in regions where snow cover is lost. Increased onshore flow in the spring reduces the

daytime warming along the coast. Precipitation increases in autumn are amplified over

topography due to changes in the large-scale circulation and its interaction with the terrain. The

robustness of the modeling results is established through comparisons with the observed and

simulated seasonal variability and with statistical downscaling results.