The use of an airborne lidar for mapping cirrus clouds in FIRE, phase 2

The Univ. of Washington (UW) and Georgia Tech have recently built a dual wavelength airborne lidar for operation on the UW's Convair C-131A research aircraft. This lidar was used in studying aerosols and clouds. These studies demonstrated the utility of airborne lidar in a variety of atmospheric research and prompt the suggestion that this facility be included in the next FIRE cirrus experiment. The vertically pointing airborne lidar would be used as a complement to ground based lidars. The airborne lidar would ensure extended coverage of IFO cases that develop upwind of the surface lidars or which miss the ground based lidars while still being the focus of satellite and aircraft in situ studies. The airborne lidar would help assure that cirrus clouds were simultaneously viewed by satellite, sampled by aircraft, and structurally characterized by lidar. System specifications are listed and a schematic is shown of the lidar system aboard the C-131A

Individual aerosol particles from biomass burning in southern Africa: 2. Compositions and aging of inorganic particles

Individual aerosol particles collected over southern Africa during the SAFARI 2000 field study were studied using transmission electron microscopy and field- emission scanning electron microscopy. The sizes, shapes, compositions, mixing states, surface coatings, and relative abundances of aerosol particles from biomass burning, in boundary layer hazes, and in the free troposphere were compared, with emphasis on aging and reactions of inorganic smoke particles. Potassium salts and organic particles were the predominant species in the smoke, and most were internally mixed. More KCl particles occur in young smoke, whereas more K2SO4 and KNO3 particles were present in aged smoke. This change indicates that with the aging of the smoke, KCl particles from the fires were converted to K2SO4 and KNO3 through reactions with sulfur- and nitrogen-bearing species from biomass burning as well as other sources. More soot was present in smoke from flaming grass fires than bush and wood fires, probably due to the predominance of flaming combustion in grass fires. The high abundance of organic particles and soluble salts can affect the hygroscopic properties of biomass- burning aerosols and therefore influence their role as cloud condensation nuclei. Particles from biomass burning were important constituents of the regional hazes

Spectral absorption of marine stratocumulus clouds derived from in situ cloud radiation measurements

A multiwavelength scanning radiometer was used to measure the angular distribution of scattered radiation deep within a cloud layer at discrete wavelengths between 0.5 and 2.3 microns. The relative angular distribution of the intensity field at each wavelength is used to determine the similarity parameter, and hence single scattering albedo, of the cloud at that wavelength using the diffusion domain method. In addition to the spectral similarity parameter, the analysis provides a good estimate of the optical thickness of the cloud beneath the aircraft. In addition to the radiation measurements, microphysical and thermodynamic measurements were obtained from which the expected similarity parameter spectrum was calculated using accepted values of the refractive index of liquid water and the transmission function of water vapor. An analysis is presented for the results obtained for a 50 km section of clean marine stratocumulus clouds on 10 July 1987. These observations were obtained off the coast of California from the University of Washington Convair C-131A aircraft as part of the First ISCCP Regional Experiment (FIRE). A comparison of the experimentally-derived similarity parameter spectrum with that expected theoretically from the cloud droplet size distribution measured simultaneously from the aircraft is presented. The measurements and theory are in very close agreement for this case of clean maritime clouds

How political elite leverage Twitter to polarize America

While social media has changed how humans use the internet, Twitter has drastically reformed how individuals worldwide receive their news. As news outlets fail to keep up with the rapid dissemination of information online, Twitter has become a sounding board for the political elite who leverage the platform\u27s immediacy and virality. This study, using Quantitative Ethnography\u27s Epistemic Network Analysis, seeks to determine if the political elite, specifically members of Congress, are leveraging Twitter to spread polarizing information to strengthen their base. In this study, extensive coding of select members of the 118th Congress was completed and compared to Voteview.com\u27s DW-Nominate polarization scores for each studied Member of Congress. The second question looks at Twitter\u27s algorithm. It seeks to determine if the algorithm gives preferential status to the political elite who use polarizing tweets to generate higher user engagement resulting in higher ad revenue. In the second research question, the study dives into the type of rhetoric used by Members of Congress to determine the key terms used in polarizing tweets that garner the highest engagement. Lastly, the study intends to determine if the political manipulation of Twitter users is problematic. A review of the former President Donald Trump and Former Brazilian President Jair Bolsonaro\u27s Twitter accounts are studied, coded, and imported into the Epistemic Network Analysis Web Tool to determine if these two leaders bear any responsibility for the subsequent insurrections that took place in Washington D.C. and Praça dos Três Poderes, Brazil. The study revealed that there is an immediate need for monitoring and potentially regulating social content as there is extensive use of highly polarizing language by the political elite that has brought with it harmful consequences

Cloud absorption properties as derived from airborne measurements of scattered radiation within clouds

Researchers briefly review the diffusion domain method for deriving the cloud similarity parameter and present preliminary analyses of the results thus far obtained. The presentation concentrates on the following points: (1) intercomparison of calibrated reflected intensities between the cloud absorption radiometer and the U.K. multispectral cloud radiometer; (2) quality control tests required to select those portions of an aircraft flight for which measurements are obtained within the diffusion domain; (3) case studies of the spectral similarity parameter of marine stratocumulus clouds; and comparisons of the experimentally-derived similarity parameter spectrum with that expected theoretically from the cloud droplet size distribution obtained from in situ observations

The random phase approximation applied to ice

Standard density functionals without van der Waals interactions yield an unsatisfactory description of ice phases, specifically, high density phases occurring under pressure are too unstable compared to the common low density phase I$_h$ observed at ambient conditions. Although the description is improved by using functionals that include van der Waals interactions, the errors in relative volumes remain sizable. Here we assess the random phase approximation (RPA) for the correlation energy and compare our results to experimental data as well as diffusion Monte Carlo data for ice. The RPA yields a very balanced description for all considered phases, approaching the accuracy of diffusion Monte Carlo in relative energies and volumes. This opens a route towards a concise description of molecular water phases on surfaces and in cavities

In situ measurements of ship tracks

It has long been known that cloud droplet concentrations are strongly influenced by cloud condensation nuclei (CCN) and that anthropogenic sources of pollution can affect CCN concentrations. More recently it has been suggested that CCN may play an important role in climate through their effect on cloud albedo. A interesting example of the effect of anthropogenic CCN on cloud albedo is the so-called 'ship track' phenomenon. Ship tracks were first observed in satellite imagery when the ship's emissions were evidently needed for the formation of a visible cloud. However, they appear more frequently in satellite imagery as modifications to existing stratus and stratocumulus clouds. The tracks are seen most clearly in satellite imagery by comparing the radiance at 3.7 microns with that at 0.63 and 11 microns. To account for the observed change in radiance, droplet concentrations must be high, and the mean size of the droplets small, in ship tracks. Researchers describe what they believe to be the first in situ measurements in what appears to have been a ship track

Use of a post-asynchronous online discussion assessment to enhance student critical thinking

Asynchronous online discussion (AOD) is used in many tertiary education courses, and assessing it has been shown to enhance critical thinking outcomes. There has, however, been debate on what should be assessed and how the assessment should be implemented. The most common form of assessment involves grading the individual discussion contributions, but it has been suggested that employing a culminating task based on the AOD may be effective. This preliminary study compared the effect on student critical thinking of two approaches to AOD assessment: using a post-AOD assessment, and assessing the discussion contributions themselves. The results, though tentative, showed that while both assessment approaches resulted in significant improvements in student critical thinking, there was no difference in the impact on critical thinking skills between using the post-AOD assessment and assessing the discussion contributions. This result suggests that the form of assessment used in an AOD may be less important than the fact that assessment is included. Interviews with students also provided some insight into ways in which they perceived the discussion environment had contributed to their critical thinking skills. The findings of this study pave the way for further research in this important area

Wide radio beams from γ-ray pulsars

We investigate the radio and γ-ray beaming properties of normal and millisecond pulsars (MSPs) by selecting two samples from the known populations. The first, Sample G, contains pulsars which are detectable in blind searches of γ-ray data from the Fermi Large Area Telescope. The second, Sample R, contains pulsars detectable in blind radio searches which have spin-down luminosities Ė>10^(34) erg s^(–1). We analyze the fraction of the γ-ray-selected Sample G which have detectable radio pulses and the fraction of the radio-selected Sample R which have detectable γ-ray pulses. Twenty of our 35 Sample G pulsars have already observed radio pulses. This rules out low-altitude polar-cap beaming models if, as is currently believed, γ-ray beams are generated in the outer magnetosphere and are very wide. We further find that, for the highest-Ė pulsars, the radio and γ-ray beams have comparable beaming factors, i.e., the beams cover similar regions of the sky as the star rotates. For lower-Ė γ-ray emitting pulsars, the radio beams have about half of the γ-ray sky coverage. These results suggest that, for high-Ė young and MSPs, the radio emission originates in wide beams from regions high in the pulsar magnetosphere, probably close to the null-charge surface and to the γ-ray emitting regions. Furthermore, it suggests that for these high-Ė pulsars, as in the γ-ray case, features in the radio profile represent caustics in the emission beam pattern