HR: 12:05h
AN: B32A-08 INVITED     [Abstracts]
TI: Aerosol effects on surface and atmospheric energy fluxes and associated climate
AU: * Menon, S
EM: smenon@lbl.gov
AF: LBNL, 1 Cyclotron Road, Berkeley, CA 94720 United States
AU: Nazarenko, L
EM: lnazarenko@giss.nasa.gov
AF: NASA GISS and Columbia University, 2880 Broadway, New York, NY 10025 United States
AB: An observed reduction in land surface radiation over the last several decades (1960-1990)---the so-called "dimming effect"---and more recent evidence of a reversal in "dimming" over some locations beyond 1990 suggest several consequences on climate, notably on the hydrological cycle. Such a reduction in radiation should imply reduced surface temperature (Ts) and precipitation, which have not occurred. We have investigated the possible causes for the above climate features using a climate model coupled to a dynamic ocean model under natural and anthropogenic conditions. To isolate the aerosol influence on surface radiation trends, we analyze transient climate simulations from 1960 to 2002 with and without anthropogenic aerosols. Based on a linear trend with aerosol effects (direct and indirect) included, the global mean change in the surface solar radiation absorbed over land is -0.021ñ0.0033 Wm-2yr-1. Although the overall trend is negative, we do note a reversal in dimming after 1990, consistent with observations. Without aerosol effects, the surface solar radiation absorbed over land increases throughout 1960 to 2002, mainly due to the decrease in cloud cover associated with increased greenhouse warming. In spite of a simulated increase in Ts of 0.012 K yr-1 for 1960 to 2002, the global mean latent heat flux and associated intensity of the hydrological cycle decrease overall, however with increases over some land locations due mainly to moisture advection. Changes to soil moisture and the direct and diffuse component of radiation due to aerosol-cloud effects are also examined to understand the net impact of aerosols on land surface and atmosphere interactions.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0320 Cloud physics and chemistry
DE: 0321 Cloud/radiation interaction
DE: 1626 Global climate models (3337, 4928)
SC: Biogeosciences [B]
MN: Fall Meeting 2005