Asymptotic light field in the presence of a bubble-layer

We report that the submerged microbubbles are an efficient source of diffuse radiance and may contribute to a rapid transition to the diffuse asymptotic regime. In this asymptotic regime an average cosine is easily predictable and measurable.Comment: 4 pages, 3 Postscript figures, opex2.sty (enclosed), also available from the Optical Society of America htpp://epubs.osa.org/oearchive/pdf/11948.pd

Scattering by irregular particles in anomalous diffraction and discrete dipole approximations

November 30, 1992.Includes bibliographical references.Sponsored by National Science Foundation ATM-8812353.Sponsored by U.S. Air Force Office of Scientific Research AFOSR-91-0269

Study of second-order turbulence closure technique and its application to atmospheric flows

Fall 1985.Includes bibliographical references (pages 66-69).The applicability of the second-order turbulence closure technique to atmospheric mesoscale flows is investigated. Analytical and numerical studies of various closure schemes are performed. Theoretical investigations of the well-known Mellor and Yamada approach result in new realizability conditions for the Level 2.5 and Level 3.0 schemes. The bulk parameters (eddy exchange coefficients) are calculated from the full second order closure model. The comparison of these parameters with the experimental data reveals that the simple Richardson number-based scaling is not adequate. The Level 2.5 and Level 4.0 models are developed and applied to a California stratocumulus case. The new realizability conditions are applied in the Level 2.5 model. The results are presented and show good agreement with experimental data collected off the California shoreline. On the basis of these studies, conclusions about applicability of simplified second-order turbulence closure technique are formulated.Supported by the Air Force Geophysics Laboratory under contract #F19628-84-C0005.Supported by the Electric Power Research Institute under contract #RFP 1630-25

Radiative properties of visible and subvisible Cirrus: Scattering on hexagonal ice crystals

One of the main objectives of the First International Satellite Cloud Climatology Project (ISCCP) Regional Experiment (FIRE) is to provide a better understanding of the physics of upper level clouds. The focus is on just one specific aspect of cirrus physics, namely on characterizing the radiative properties of single, nonspherical ice particles. The basis for further more extensive studies of the radiative transfer through upper level clouds is provided. Radiation provides a potential mechanism for strong feedback between the divergence of in-cloud radiative flux and the cloud microphysics and ultimately on the dynamics of the cloud. Some aspects of ice cloud microphysics that are relevant to the radiation calculations are described. Next, the Discrete Dipole Approximation (DDA) is introduced and some new results of scattering by irregular crystals are presented. The Anomalous Diffraction Theory (ADT) was adopted to investigate the scattering properties of even larger crystals. In this way the scattering properties of nonspherical particles were determined over a range of particle sizes