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The longwave effective cloud fraction in the Cloudiness Intercomparison

Takara, Ezra Florida State University
Ellingson, Robert Florida State University

From February-May 2003 the Cloudiness Intercomparison IOP was conducted at the ARM Southern Great Plains Central Facility to compare cloud amount measurements from various instruments. The longwave effective cloud fraction (Ne) is the weighting factor for plane parallel overcast flux that is necessary to yield the surface downward longwave flux irradiance when averaging the plane parallel clear and overcast fluxes. The Ne in the Cloudiness Intercomparison were derived from measurements. Radiances from the Atmospheric Emitted Radiance Interferometer (AERI) and pyrgeometer fluxes are combined with the cloud base altitude taken from the Active Remote Sensing of Cloud Layers (ARSCL) combined data product. Pairing the AERI narrow field of view and pyrgeometer wide field of view enables this technique to work in broken cloud conditions. Previous results indicate that the derived Ne can be comparable to the total cloud amounts measured by the Total Sky Imager (TSI) for single layers of fair weather cumulus. In this work, the derived Ne will be compared to some of the measurements in the cloudiness intercomparison over a variety of cloud types, fractions, and base heights.

This poster will be displayed at the ARM Science Team Meeting.