New Way of Looking at Clouds Proves Successful for Arctic Conditions


Using radiative transfer simulations ARM scientists developed a new method to estimate cloud phase (the amount of liquid water and/or ice in clouds) from ground-based measurements. The cloud phase is an important component for correctly modeling cloud microphysical and optical properties, and thus the impact of the cloud on the solar and terrestrial radiation budget. Assuming an incorrect phase for the model can lead to errors up to 100% in particle size and optical thickness, resulting in errors of 5-20% in the amount of modeled radiation reaching the surface. The determination of cloud phase for the Arctic has been a scientific challenge, since the underlying snow-covered surface, persistent temperature inversions, and long periods of polar night make satellite retrievals very difficult. Currently there are no instruments at the Barrow site or elsewhere in the Arctic for measuring the cloud phase; thus, scientists have had little information about cloud phase there. Using the new algorithm, the investigators have created the first data set of cloud phase at the ARM site in Barrow, Alaska. These data are being used to refine climate models and parameterizations as they relate to the Arctic environment, which is the most sensitive region to climate change.