The Dependence of Cirrus Cloud-Property Retrievals on Size-Distribution Shape
| d'Entremont, Robert | Atmospheric and Environmental Research, Inc. |
| Mitchell, David | Desert Research Institute |
Category: Cloud Properties
Our project has focused on using satellite- and ground-based passive thermal infrared radiance observations to retrieve cirrus cloud properties, most importantly ice water path (IWP), effective particle size (Deff), and visible extinction optical thickness (tau). During this past year we began comparing our cirrus retrieval results with aircraft observations at the ARM CART site, and we are participating in a summary intercomparison study with other retrieval algorithms as a member of the high-clouds working group. Our passive-infrared retrieval scheme, based on different wavelength bands for terrestrial radiation, includes scattering and absorption effects of ice particles. The treatment of scattering effects requires knowledge of the asymmetry parameter “g” and single-scattering albedo "w0." The Modified Anomalous Diffraction Approximation (MADA) codes developed at DRI by David Mitchell is used in our retrieval techniques. In his codes, cirrus ice-particle size distributions are taken as bi-modal in nature, and the tropical and mid-latitude cirrus models therein have distinct differences in radiative properties that noticably influence both the cirrus retrievals and subsequent cloud-forced radiative fluxes. These differences are due in large part to the presence and shape of a small mode of ice particles in the overall size distribution. We will summarize our project results and demonstrate the sensitivity of cloud-forced radiative fluxes to the type of cirrus size-distribution shapes assumed by our satellite- and AERI-based cirrus retrieval algorithms.
This poster will be displayed at the ARM Science Team Meeting.
