Wednesday, 9 July 2014
We use mid-latitude cyclone centers from the ERA-Interim reanalysis to develop composite NASA Aqua satellite Atmospheric Infrared Sounder (AIRS)/Advanced Microwave Sounding Unit (AMSU) temperature, water vapor and cloud fields (thermodynamic phase, cloud top temperature, and ice cloud optical thickness and effective diameter). We investigate hemispheric and land/ocean differences in the warm frontal region, as a function of the cyclone's genesis, peak intensity, and dissipation phases. We also use composites of dynamical variables from the Modern Era Retrospective-Analysis for Research and Applications (MERRA), and relate them to the cloud property behavior.
We find that the relative size of the cloud field is more confined near the cyclone center over land than ocean. A significant seasonal cycle in cloud properties is also found in both hemispheres. When comparing the same seasons, systematic differences remain between the hemispheres with regard to the relative positioning and frequency of clouds in the warm frontal region. Furthermore, the SH cyclones occur in an environment of slightly lower lapse rates compared to the NH, with some differences in the free tropospheric humidity in the surrounding warm and cold sectors. We will discuss how the dynamics and thermodynamics of the cyclone impact the ice cloud processes in warm frontal zones.
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