To better understand the effects of clouds on climate, Andy Heymsfield studies the microphysical and radiative properties of ice clouds. He uses instruments aboard research aircraft to measure cloud particle shapes and particle size distributions. Heymsfield has played a key role in developing software packages and analytic models to interpret those observations. His products are used in both cloud and general circulation models. Heymsfield is a researcher in NCAR's Mesoscale and Microscale Meteorology Division.