Friday, September 22, 2017 -
12:00pm to 1:00pm
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Pierce 100F, 29 Oxford St., Cambridge

Atmospheric & Environmental Chemistry Seminar

Discussion by Ritesh Gautam on "Radiative Characteristics and Impacts of Clouds and Snow in the Presence of Absorbing Aerosols Derived Using Remote Sensing Measurements."

Clouds and snow/ice cover are the two most reflective components of the Earth system. Changes in the reflective properties of clouds and snow can affect the global mean albedo and hence the Earth’s radiation budget. For instance, when viewing from space, clouds and snow generally appear to be bright; however in the presence of light-absorbing aerosols, they turn darker which implies a warming impact, i.e. a shift in the sign of radiative forcing from cooling to warming. Absorbing aerosol layers in the form of smoke or dust plumes, when advected over clouds or deposited over snow cover, cause an apparent darkening at the top of atmosphere. In this presentation, using satellite and suborbital remote sensing measurements, we will examine spectral signatures of clouds and snow in the presence of absorbing aerosols and their radiative impacts – which is something lacking in operational satellite data products and generally not well characterized in climate model simulations. The absorbing aerosol-induced darkening is observed globally from the persistent stratiform cloud decks over southeast Asia to the marine stratocumulus clouds in the southeast Atlantic and even at higher latitudes. We will also examine case studies of snow darkening as a result of mineral dust deposition across snow and ice cover in the Himalaya and the Alps. Finally, some regional climate warming implications in response to cloud and snow darkening will be discussed.

Speaker Bio:

Contact Name: 

Yuzhong Zhang

Research Areas: 

Harvard University
Center for the Environment

Address: 26 Oxford Street, 4th Floor, Cambridge
Phone: (617) 495-0368

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