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Climate Studies with a Multilayer Energy Balance Model. Part III: Climatic Impact of Stratospheric Volcanic Aerosols

Ming-Dah ChouGoddard Laboratory for Atmospheric Sciences, NASA Goddard Space Flight Center, Greenbelt, MD 20771

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Li PengGoddard Laboratory for Atmospheric Sciences, NASA Goddard Space Flight Center, Greenbelt, MD 20771

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Albert ArkingGoddard Laboratory for Atmospheric Sciences, NASA Goddard Space Flight Center, Greenbelt, MD 20771

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Abstract

The radiative and climatic effects of stratospheric volcanic aerosols are studied with a multilayer energy balance model. The results show that the latitudinal distribution of aerosols has a significant effect on climate sensitivity. When aerosols are assumed to be distributed uniformly in the 30–90°N region and decay exponentially with an e-folding time constant of 1 year, the maximum response is in the 60–70°N zone where the ice-albedo feedback is most active. The maximum occurs shortly (<0.5 years) after the eruption due to the large extent of land and, therefore, the small thermal inertia in that latitude zone. When the same amount of aerosols is assumed to be in the 0–30°N region, the response is much weakened due to smaller radiative forcing and lack of ice-albedo feedback in the tropics, but is prolonged due to the larger extent of the oceans. The maximum response is reduced to ⅕ of that of the former case and occurs at a much later time (∼1.5 years). A secondary maximum appears in the polar region as a result of ice-albedo feedback.

The climate sensitivity to some of the aerosol properties has also been studied. Model simulations indicate that the absorption of solar energy in the ultraviolet and visible spectral regions by the aerosols enhances the sensitivity of surface temperature due to the reduced solar radiation incident at the surface. With the same amount of forcing at the top of the atmosphere, the solar radiation is more important than the thermal IR radiation in affecting the surface temperature.

Abstract

The radiative and climatic effects of stratospheric volcanic aerosols are studied with a multilayer energy balance model. The results show that the latitudinal distribution of aerosols has a significant effect on climate sensitivity. When aerosols are assumed to be distributed uniformly in the 30–90°N region and decay exponentially with an e-folding time constant of 1 year, the maximum response is in the 60–70°N zone where the ice-albedo feedback is most active. The maximum occurs shortly (<0.5 years) after the eruption due to the large extent of land and, therefore, the small thermal inertia in that latitude zone. When the same amount of aerosols is assumed to be in the 0–30°N region, the response is much weakened due to smaller radiative forcing and lack of ice-albedo feedback in the tropics, but is prolonged due to the larger extent of the oceans. The maximum response is reduced to ⅕ of that of the former case and occurs at a much later time (∼1.5 years). A secondary maximum appears in the polar region as a result of ice-albedo feedback.

The climate sensitivity to some of the aerosol properties has also been studied. Model simulations indicate that the absorption of solar energy in the ultraviolet and visible spectral regions by the aerosols enhances the sensitivity of surface temperature due to the reduced solar radiation incident at the surface. With the same amount of forcing at the top of the atmosphere, the solar radiation is more important than the thermal IR radiation in affecting the surface temperature.

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