Incidence of rough and irregular atmospheric ice particles from Small Ice Detector 3 measurements

NERC, NE/E011225/1 © Author(s) 2013. This work is distributed under the Creative Commons Attribution 3.0 LicenseThe knowledge of properties of ice crystals such as size, shape, concavity and roughness is critical in the context of radiative properties of ice and mixed phase clouds. Limitations of current cloud probes to measure these properties can be circumvented by acquiring two-dimensional light scattering patterns instead of particle images. Such patterns were obtained in situ for the first time using the Small Ice Detector 3 (SID-3) probe during several flights in a variety of mid-latitude mixed phase and cirrus clouds. The patterns are analyzed using several measures of pattern texture, selected to reveal the magnitude of particle roughness or complexity. The retrieved roughness is compared to values obtained from a range of well-characterized test particles in the laboratory. It is found that typical in situ roughness corresponds to that found in the rougher subset of the test particles, and sometimes even extends beyond the most extreme values found in the laboratory. In this study we do not differentiate between small-scale, fine surface roughness and large-scale crystal complexity. Instead, we argue that both can have similar manifestations in terms of light scattering properties and also similar causes. Overall, the in situ data is consistent with ice particles with highly irregular or rough surfaces being dominant. Similar magnitudes of roughness were found in growth and sublimation zones of cirrus. The roughness was found to be negatively correlated with the halo ratio, but not with other thermodynamic or microphysical properties found in situ. Slightly higher roughness was observed in cirrus forming in clean oceanic airmasses than in a continental, polluted one. Overall, the roughness and complexity is expected to lead to increased shortwave cloud reflectivity, in comparison with cirrus composed of more regular, smooth ice crystal shapes. These findings put into question suggestions that climate could be modified through aerosol seeding to reduce cirrus cover and optical depth, as the seeding may result in decreased shortwave reflectivity.Peer reviewe

Observations of a midlatitude squall line boundary layer wake

Includes bibliographical references (pages 90-93).June 1987.Mesoscale pressure perturbations frequently observed with mesoscale convective systems (MCS) are examined with special emphasis on the characteristics, structure, lifecycle and driving mechanism of the "wake depression" found in the wake region of the convection. A severe squall line which traversed the OK PRE-STORM surface and upper air mesonetwork on 10-11 June 1985 is the focus of this observational study. Extensive surface, upper air and digitized radar data collected during the OK PRE-STORM field experiment were used for analysis. Various mesoanalyses of this squall line at the surface and aloft have allowed for intensive examination of three pressure features observed with this squall line: the mesohigh, wake depression and pre-squall mesolow. Their relationship to and interaction with other meteorological parameters such as precipitation, temperature, potential temperature and moisture are explored. Furthermore, the mesoscale system-relative "jets" observed with midlatitude squall lines are examined for their possible influence on the pressure field. The mesohigh develops quickly during the early growth of the squall line and precedes the wake depression by several hours. The predominant mesohigh is linked to the formation of a large cold pool which developed as a result of widespread hail and intense rainfall from a supercell ahead of the young squall line. Analyses show that the wake depression is not a uniform, stagnant feature behind the mesohigh but has embedded small-scale features, a distinct lifecycle and can undergo rapid intensification. The wake depression also is related to some aspects of the squall line's precipitation pattern. The low consistently "hugs" the back edge of the stratiform precipitation and is observed to split into two separate lows as the convective line splits. Additionally, the wake depression is a hydrostatic response to a layer of warm, dry air (produced by subsidence) found just above the surface. It is suggested that the wake depression is in part a surface manifestation of forced subsidence by the descending rear inflow jet.Sponsored by the National Science Foundation - ATM-8507961

The Hidden Nuclear Spectrum of the Luminous IRAS Source FSC10214++4724

Optical spectropolarimetry of the luminous IRAS source FSC10214$+$4724 (z$=2.286$) reveals that the strong (\twid17\%) linear polarization detected by Lawrence \etal\/ is shared by both the narrow UV emission lines and the underlying continuum. This observation and the brightness of the source rule out synchrotron emission and dichroic extinction by dust as the polarizing mechanism, leaving scattering as the only plausible cause of the polarized emission. The narrowness of the lines requires that the scatterers be dust grains or cool ($<1.6\times$10$^4$~K) electrons. We can recover the spectrum that is incident on the scattering medium provided we make some reasonable assumptions regarding the source geometry. The scattered UV spectrum has a power law index $\alpha$~ of $-1.2 \pm 0.6$ ($F_\nu\propto\nu^\alpha$), steeper than what would be expected from a young burst of star formation, but similar to many AGN.Comment: 10 pages, with figure, uuencoded postscript Institute for Advanced Study number AST 94/1

Flexible correction processes in social judgment: implications for persuasion

Journal ArticleTwo experiments were conducted to examine correction for perceived bias in persuasion situations. Study 1 showed that, although a manipulation of source likability had an impact on attitudes when no instruction to remove bias was present, when people were asked to remove any bias from their judgments, the effect of the source likability manipulation disappeared. The fact that the correction instruction did not increase the impact of an argument quality manipulation on attitudes suggested that effort aimed at correction is conceptually distinct from effort aimed at processing a message in general. Study 2 showed that a correction for source likability took place under low elaboration conditions--where a manipulation of source likability had an impact when no correction instructions were provided, and under high elaboration conditions--where a manipulation of source likability had no impact when no correction instructions were provided. In the high elaboration conditions, correcting for an impact that was not actually present led a dislikable source to be more influential than a likable source

Constraints on the initial mass, age and lifetime of Saturn's rings from viscous evolutions that include pollution and transport due to micrometeoroid bombardment

The Cassini spacecraft provided key measurements during its more than twelve year mission that constrain the absolute age of Saturn's rings. These include the extrinsic micrometeoroid flux at Saturn, the volume fraction of non-icy pollutants in the rings, and a measurement of the ring mass. These observations taken together limit the ring exposure age to be < a few 100 Myr if the flux was persistent over that time (Kempf et al., 2023). In addition, Cassini observations during the Grand Finale further indicate the rings are losing mass (Hsu et al., 2018; Waite et al., 2018) suggesting the rings are ephemeral as well. In a companion paper (Durisen and Estrada, 2023), we show that the effects of micrometeoroid bombardment and ballistic transport of their impact ejecta can account for these loss rates for reasonable parameter choices. In this paper, we conduct numerical simulations of an evolving ring in a systematic way in order to determine initial conditions that are consistent with these observations.Comment: 31 pages, 19 figures, 2 tables, Published in Icaru