Ship-Track Clouds, Aerosol, and Ship Dynamic Effects; A Climate Perspective from Ship-Based Measurements

Ship-track clouds are marine boundary layer clouds that form behind ocean ships and are observed from satellites in the visible and near infrared. Ship-track clouds provide a rare opportunity to connect aerosol cloud condensation nuclei (CCN) emissions and observable changes in marine stratiform clouds. A very small change in the reflectivity of these eastern Pacific and Atlantic clouds (about 4%) provides a climate feedback of similar magnitude to doubling CO{sub 2} (increasing cloud reflectivity corresponds to global cooling). The Department of Energy sponsored research from 1991 to 1995 to study ship-track clouds including two ocean-based experiments in the summers of 1991 and 1994. These experiments showed that ship-track cloud properties were often more complex those related to a reduction of droplet size with an increase in number associated with increasing CCN from the ship's plume. The clouds showed evidence of morphological changes more likely to be associated with cloud dynamic effects either initiated by the increased CCN or directly by the ship's heat output or turbulent air wake. The fact that marine stratiform clouds, that are susceptible to ship track formation, are starved for both CCN and convective turbulence complicates the separation of the two effects

Resuspension of toxic aerosol using MATHEW--ADPIC wind field--transport and diffusion codes

Computer codes have been written which estimate toxic aerosol resuspension based on computed deposition from a primary source, wind, and surface characteristics. The primary deposition pattern and the transport, diffusion, and redeposition of the resuspended toxic aerosol are calculated using a mass-consistent wind field model including topography (MATHEW) and a particle-in-cell diffusion and transport model (ADPIC) which were developed at LLL. The source term for resuspended toxic aerosol is determined by multiplying the total aerosol flux as a function of wind speed by the area of highest concentration and the fraction of suspended material estimated to be toxic. Preliminary calculations based on a test problem at the Nevada Test Site determined an hourly averaged maximum resuspension factor of 10/sup -4/ for a 15 m/sec wind which is within an admittedly large range of resuspension factor measurements using experimental data

Application of digital image analysis techniques to the Geyser's data and topography

This paper describes the results of digital image analysis and techniques applied to acoustic sounder data and topographic relief in the Geyser's region. The two dimensional fast Fourier transform (2DFFT) represents the spacial variability of a photographic image. The spacial variability of topography in complex terrain can be represented in this way and insight into degree of complexity and dominating spacial wavelengths can be gained. This was performed for a 16 km square digitized topographic map of the Geyser's region with 63.5 m resolution. It was also of interest to compare facsimile recordings of acoustic sounder data to optical turbulence measurements

The ASCOT 1988 valley/tributary interaction study

This paper describes a regular oscillation observed in nighttime valley air flows under relatively light upper level wind conditions. The period of these oscillations is about 20 minutes with at least one harmonic at about 10 minutes. These oscillations are important to pollutant dispersion in valley flows at night. The strong coherence of tributary flow and main valley oscillations and the fact that tributary oscillations lead valley oscillation indicate the importance of tributaries as major contributors to the cold air flow in valleys. 13 refs., 12 figs

Statistical analysis of summer winds in Geysers area prior to ASCOT 1979 experiment

Statistical analytical techniques were tested on 73 days and 16 stations of hourly data for the summer of 1977. These stations were located in the region surrounding the Geysers geothermal area. Principal components analysis (PCA) was used to define typical wind patterns in the region and to determine typical days for each station. Power spectral analysis was used to quantify the temporal variation of winds at Anderson Ridge and Anderson Springs (two stations included in the ASCOT 1979 study in the local region of Anderson Creek with very different terrain exposures). These results will help determine year to year difference in the wind fields in the ASCOT study region of complex terrain

Northern Arizona Basin Study (NABS), 1989

An experiment was conducted to better understand a frequent layer of northwest winds found in the Northern Arizona region. This layer has been observed most often in winter near the surface at Page, Arizona, and often opposes larger scale upper level west winds. The results of this experiment improved both the temporal and the down-valley spatial resolution of the flow structure in this region during winter. 11 refs., 9 figs

Review of the atmospheric propagation in the SPC codes. A progress report

This is an initial progress report describing findings in critically analyzing and evaluating the atmospheric propagation submodels in the SPC1 and SPC2 models. These systems performance codes were developed by United Technologies Research Center as general purpose, end-to-end models for determining the overall effects on propagation of a laser beam from its source, either from the earth's surface or from an airborne platform, to a target. The SPC1 model is a trimmed down version of SPC2, while including the same coding for atmospheric propagation effects. As with other system models, the SPC codes attempt to include all essential processes to an accuracy commensurate with the use of the models for overall systems analysis and examination of system deployment scenarios. A basic conclusion of our study is that the SPC codes do appear to provide an appropriate framework for end-to-end model studies determining the overall impact of atmospheric effects on laser beam propagation. Nonetheless, our preliminary analysis has discovered a number of errors and limitations to the existing models. The modular structure of the codes will be an important benefit in making necessary improvements. 30 refs., 15 figs., 4 tabs