Bulletin of the American Meteorological Society, 2019
A configuration of the High-Altitude Long-Range Research Aircraft (HALO) as a remote sensing clou... more A configuration of the High-Altitude Long-Range Research Aircraft (HALO) as a remote sensing cloud observatory is described, and its use is illustrated with results from the first and second Next-Generation Aircraft Remote Sensing for Validation (NARVAL) field studies. Measurements from the second NARVAL (NARVAL2) are used to highlight the ability of HALO, when configured in this fashion, to characterize not only the distribution of water condensate in the atmosphere, but also its impact on radiant energy transfer and the covarying large-scale meteorological conditions—including the large-scale velocity field and its vertical component. The NARVAL campaigns with HALO demonstrate the potential of airborne cloud observatories to address long-standing riddles in studies of the coupling between clouds and circulation and are helping to motivate a new generation of field studies.
Trade-wind cumuli constitute the cloud type with the highest frequency of occurrence on Earth, an... more Trade-wind cumuli constitute the cloud type with the highest frequency of occurrence on Earth, and it has been shown that their sensitivity to changing environmental conditions will critically influence the magnitude and pace of future global warming. Research over the last decade has pointed out the importance of the interplay between clouds, convection and circulation in controling this sensitivity. Numerical models represent this interplay in diverse ways, which translates into different responses of trade-cumuli to climate perturbations. Climate models predict that the area covered by shallow cumuli at cloud base is very sensitive to changes in environmental conditions, while process models suggest the opposite. To understand and resolve this contradiction, we propose to organize a field campaign aimed at quantifying the physical properties of trade-cumuli (e.g., cloud fraction and water content) as a function of the large-scale environment. Beyond a better understanding of clou...
Ground-penetrating radar (GPR) signals are attenuated by both absorption and scattering. We perfo... more Ground-penetrating radar (GPR) signals are attenuated by both absorption and scattering. We performed low-frequency (< 100 MHz) GPR surveys at the Volcanic Tableland of the Bishop (California) Tuff to evaluate the factors that control GPR depth of investigation and to develop insight into the capabilities of such radars for Mars. The subsurface reflection character was very different for two different commercial systems used; together, they revealed both internal welding contacts in the tuff and an abundance of discrete scatterers ...
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Papers by David Farrell