PAOC Retreat

2011 Retreat - Talk
Date Time Location
September 25th, 2011 9:45am-10:45am Hancock Room
Dan Cziczo (MIT) How do aerosol particles affect ice clouds and climate? Cirrus ice clouds are an important factor in the climate system. These clouds exert a large radiative forcing due to their
extensive global coverage and high altitude despite minimal physical
and optical thickness. We have measured chemical and physical
properties of the aerosols on which cirrus ice crystals formed in situ
and in real time using single particle mass spectrometry. Ice residual
particles were also collected for laboratory investigation including
electron microscopy. The high altitude clouds were accessed using the
NASA WB-57F aircraft equipped with a novel counter flow virtual
impactor which measured evaporated cirrus ice crystal residuals.
Sampling was performed during a number of aircraft studies; data have
now been acquired from the mid-latitudes to the tropics and during
multiple seasons. Size measurements show that large particles
preferentially froze over smaller ones. Chemical composition is an
important determinate of ice formation and shows heterogeneous and
homogeneous freezing can occur in cirrus clouds.