Department of Environmental Sciences

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Seminar Abstracts
Environmental Sciences Seminar Abstract            

  Radiative Forcing of Cirrus Clouds and Troposperic and Stratospheric Aerosols
Juan Carlos Antuña Marrero
Camagüey Lidar Station, Camagüey, Cuba

I discuss the radiative forcing produced by cirrus clouds, tropospheric and stratospheric aerosols over Camagüey, Cuba. For such a goal, a-state-of-the-art radiative code was adjusted to local conditions. Optical and geometrical properties of cirrus clouds and stratospheric aerosols, derived from lidar measurements, were used to initialize simulations of their effects on solar radiation. For the initialization of the tropospheric aerosols, optical properties were derived from broadband solar radiation measurements using Gueymard's approach. The magnitudes of the forcing agree in general with reports in the literature. The diurnal cycle of the radiative forcing from cirrus clouds with high optical depth values shows two maxima in hours around local noon. Those maxima are in the range of -20 to -200Wm-2 for cirrus optical depths ranging between 0.2 and 3. Extrapolating stratospheric aerosol optical depth temporal series measured with lidar at Camagüey from the 1991 Mount Pinatubo volcanic eruptions, estimates of the temporal evolution of the radiative effects of intense and catastrophic eruptions 10-200 times the size of Pinatubo were calculated. The time necessary for the recovery to normal radiation values at the surface ranged between 2 and 3 times with respect to that for Pinatubo, depending on the magnitude of the eruption. The radiative effects over Camagüey of Saharan dust were studied for several individual cases. Radiative forcing values are similar to those from the few studies previously conducted in the Caribbean.

Last updated: 05/19/2009