Investigating the Shortwave Radiative Effects of Cloud Field Geometry in the Tropical Western Pacific
Abstract
In the last decade numerous advances have been made in parameterizing cloud-radiation interactions. Recent improvements have involved statistical representations of the influence of three-dimensional cloud fields on the domain averaged radiation. A stand-alone comparison of traditional plane-parallel shortwave radiative transfer code against a statistical algorithm and observations is performed using four years of data from the Atmospheric Radiation Measurement Program's Tropical Western Pacific Clouds and Radiation Testbed Site. Statistical cloud properties are derived from observed cloud chord lengths and input into the stochastic model, removing the necessity of explicitly simulating individual cloud fields and allowing for extended model runs. The purpose of the comparison is to identify objectively meteorological situations where 3-dimensional cloud field geometries are radiatively significant such that a statistical approach to radiative transfer, such as the stochastic technique, is more appropriate than the traditional plane-parallel approach. Results suggest that the relationship between vertical extent of liquid cloud and liquid water path is one indicator of radiatively important cloud regimes, as is the relationship between solar zenith angle and cloud fraction. A simple-parameterization based on criteria developed from these results is applied to the plane-parallel model to represent the effect of complex cloud field geometry. The preliminary runs show improvement in the performance of the plane-parallel model when compared to observations.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2007
- Bibcode:
- 2007AGUFM.A41B0433F
- Keywords:
-
- 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0321 Cloud/radiation interaction