Atmospheric Sciences seminar is Oct 29 Greg M. McFarquhar, professor with the department of Atmospheric Sciences at the University of Illinois in Urbana, Ill. will present a seminar on “The microphysical and radiative properties of tropical cirrus observed during the Tropical Warm Pool International Cloud Experiment (TWP-ICE): implications for climate studies” at 3 p.m. Thursday, Oct. 29, in 210 Clifford Hall. Abstract: To represent cloud feedbacks in global climate models and to improve predictions of future climate change, the effects of cirrus on longwave and shortwave radiation must be quantified. At a microphysical level, the distributions of crystal sizes and shapes are most important for determining how cirrus impact radiative heating. The Tropical Warm Pool International Cloud Experiment (TWP-ICE), based out of Darwin Australia between Jan. 21 and Feb. 14 2006, was held to study the interaction of convection with its environment, with an emphasis on the microphysical and radiative properties of anvils generated by convection. During TWP-ICE, the Scaled Composites Proteus aircraft made intensive airborne measurements of aged cirrus, fresh anvils, and cirrus of unknown origin. The collected data have been used to quantify the contributions of small ice crystals with maximum dimensions less than 50m to the mass and single-scattering properties of cirrus, a controversial topic in cloud microphysics. The data show that the shattering of large ice crystals on the protruding tips of a probe used to measure small crystals artificially inflated the small crystal concentration during TWP-ICE with significant implications for cirrus radiative effects. The data have also been used to characterize differences in crystal shapes, size distributions and cirrus bulk properties (total number concentrations, mass contents, and median mass diameters) between fresh anvils, aged cirrus and cirrus of unknown origin, the differences being radiatively significant. Implications of these findings for climate studies and remote sensing of cloud properties are discussed. -- Wanda Seyler, Administrative Secretary, Atmospheric Sciences, seyler@aero.und.edu, 777-3884