AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
The Impact of Decreasing Black Carbon Emissions on California’s Climate
ODELLE HADLEY, Lukas Valin, Surabi Menon, Thomas Kirchstetter, Lawrence Berkeley National Laboratory
Abstract Number: 556 Working Group: Aerosols, Clouds, and Climate
Abstract Ground measurements show that black carbon (BC) aerosol concentrations in California have decreased by approximately a factor of two between 1985 and 2005. In this study, we use the WRF-Chem model to estimate the seasonal scale changes in radiative forcing, surface temperature, and precipitation resulting from the reduced BC concentrations over this period. To do this, two simulations of WRF-Chem were run for the year 2005. In the first simulation, we used a chemical emissions inventory developed by Streets and Bond (2006) for the ARCTAS campaign. For the second simulation, the BC emissions were doubled to mimic the higher concentrations observed in 1985. The results are seasonally averaged to reduce the statistically insignificant noise that dominates on shorter time scales. We find significant BC radiative forcing over CA (+ 5 W m-2 at the surface and + 4 W m-2 at TOA) and differences in precipitation (+ 80 mm) and surface temperatures (+ 0.25 ºC) as a result of the decrease in BC emissions and surface concentrations. The patterns of radiative forcing, as well as temperature and precipitation changes are regionally dependent and, depending on the region, can be either positive or negative. The 2005 simulations are validated against available measurements of BC, total PM2.5, surface solar flux, cloud cover, temperature, and precipitation.