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Apr 26, 2004 Title: Speaker: |
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Abstract:
Low-latitude cumulonimbus systems have been hypothesized to play a powerful role in global climate sensitivity and their impact on moisture levels at the tropopause may also modulate stratospheric water vapor concentrations. But the properties of cumulonimbus clouds and the factors controlling their long-lived anvil cirrus remain poorly understood and poorly constrained in climate models. Thus motivated, NASA's CRYSTAL-FACE field experiment -- one of the largest cloud field experiments to date -- focused on the development and evolution of cumulonimbus anvils in southern Florida throughout July 2002. Ground stations, satellite platforms, and six aircraft were coordinated to obtain extensive simultaneous remote and in-situ measurements of aerosols and cloud particles throughout the atmospheric column during multiple storm events. Using July 18 as a case study and coupling these field measurements with large-eddy simulations that also resolve the size distributions of both aerosols and cloud particles, we have found several lines of evidence pointing to the predominance of free tropospheric aerosols as the seminal cloud nuclei for anvil crystals, in contrast to the general assumption that boundary layer aerosols are the significant source. Using seven additional case studies (July 3, 11, 16, 19, 21, 28, and 29), we further attempt to quantify the response of anvil properties to the observed variability of overall aerosol profiles, thermodynamic profiles, and wind shear profiles. These results, which rely heavily on the unique in situ data gathered during CRYSTAL-FACE, point the way to future work that can exploit the strengths of remote-sensing data on aerosol and cloud properties.