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Colloquium|Department of Atmospheric Science

Seminar: Friday, 25 April, 3:10 pm, EN6085 

Southern Ocean Cloud Regimes Using Combined Active
and Passive Satellite Observation

John M. Haynes, Ph.D.
Research Scientist
Colorado State University
Cooperative Institute for Research in the Atmosphere (CIRA)

The Southern Ocean region is an important but often-overlooked part   of the earth's climate system that is associated with significant   uncertainties in models.  It is amongst the cloudiest locations on   the planet, with frequent cyclone activity and a high fraction of   relatively low clouds containing significant amounts of supercooled water.  Clouds in this region are often poorly represented in climate   models; in particular, modeled shortwave albedos are typically lower   than what is observed such that too much radiation reaches the ocean   surface.  As a step toward addressing this issue, we seek to quantify   the organization, vertical structure, and radiative characteristics   of clouds over the Southern Ocean using a combination of active and   passive satellite sensors.

This study uses geostationary and polar orbiter satellite data   (ISCCP) to classify clouds into large-scale, recurring cloud regimes   (sometimes referred to as weather states) using a statistical clustering method.  Radar and lidar observations from CloudSat and CALIPSO are then used   to examine the vertical structure, microphysics, precipitation   characteristics, and radiative heating of these large-scale regimes.    It is found that the regimes associated with ascent in cyclones have   the highest shortwave cloud radiative effect at the   top-of-atmosphere, but the low-cloud regimes, by virtue of their high   frequency of occurrence, dominate both top-of-atmosphere and surface   shortwave effects.  Finally, radiation errors in one particular CMIP5   model (the Australian Community Climate and Earth System Simulator)   are assessed using a hybrid model-observation clustering method.

 

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