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GEOPHYSICAL RESEARCH LETTERS, VOL. 30, NO. 15, 1822, doi:10.1029/2003GL017545, 2003

Impact on regional winter climate by CO2 increases vs. by maritime-air advection

J. Otterman

Land-Atmosphere-Ocean-Research (LAOR), at Data Assimilation Office, CODE 910.3, NASA/GSFC, Greenbelt, Maryland, USA


R. Atlas

NASA/GSFC, Greenbelt, Maryland, USA


G. L. Russell

NASA/GISS, New York, New York, USA


H. Saaroni

Dept. of Geography and the Human Environment, Tel Aviv Univ., Tel Aviv, Israel


Abstract

Fractional Outgoing Radiation, FOR (dimensionless), defined as the ratio of Outgoing Longwave Radiation, OLR (W/m2), to upward Surface Longwave Emission, SLE (W/m2), is a basic parameter for analyzing regional greenhouse effect. Here, FOR values are derived from a General Circulation Model by extracting OLR and SLE over areas in east-central Europe (at about 60°N) one hour after injecting appropriate CO2 concentration (adjustments to the atmospheric profile are thus excluded) to the Feb. 1 midnight simulation. The reduction in FOR is 0.00051 when atmospheric CO2 increases by 14 ppm, which is the currently expected per-decade increase. Fluctuations in the North-Atlantic surface winds produce fluctuations in FOR over central Europe: monthly-mean FOR in strong-wind February 1990 was 0.679, but 0.758 in weak-wind, lower cloud-fraction February 1996. Strong maritime-air advection in 1990 resulted thus in FOR reduced by 0.079, effect by two orders-of-magnitude stronger than the decrease effected by the per-decade increase in CO2.

Received 16 April 2003; accepted 15 July 2003; published 14 August 2003.

Index Terms: 3309 Meteorology and Atmospheric Dynamics: Climatology (1620); 3314 Meteorology and Atmospheric Dynamics: Convective processes; 3359 Meteorology and Atmospheric Dynamics: Radiative processes.

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Citation: Otterman, J., R. Atlas, G. L. Russell, and H. Saaroni (2003), Impact on regional winter climate by CO2 increases vs. by maritime-air advection, Geophys. Res. Lett., 30(15), 1822, doi:10.1029/2003GL017545.