A comparison among four different retrieval methods for ice-cloud properties using data from CloudSat, CALIPSO, and MODIS

The A-Train constellation of satellites provides a new capability to measure vertical cloud profiles that leads to more detailed information on ice-cloud microphysical properties than has been possible up to now. A variational radar–lidar ice-cloud retrieval algorithm (VarCloud) takes advantage of the complementary nature of the CloudSat radar and Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) lidar to provide a seamless retrieval of ice water content, effective radius, and extinction coefficient from the thinnest cirrus (seen only by the lidar) to the thickest ice cloud (penetrated only by the radar). In this paper, several versions of the VarCloud retrieval are compared with the CloudSat standard ice-only retrieval of ice water content, two empirical formulas that derive ice water content from radar reflectivity and temperature, and retrievals of vertically integrated properties from the Moderate Resolution Imaging Spectroradiometer (MODIS) radiometer. The retrieved variables typically agree to within a factor of 2, on average, and most of the differences can be explained by the different microphysical assumptions. For example, the ice water content comparison illustrates the sensitivity of the retrievals to assumed ice particle shape. If ice particles are modeled as oblate spheroids rather than spheres for radar scattering then the retrieved ice water content is reduced by on average 50% in clouds with a reflectivity factor larger than 0 dBZ. VarCloud retrieves optical depths that are on average a factor-of-2 lower than those from MODIS, which can be explained by the different assumptions on particle mass and area; if VarCloud mimics the MODIS assumptions then better agreement is found in effective radius and optical depth is overestimated. MODIS predicts the mean vertically integrated ice water content to be around a factor-of-3 lower than that from VarCloud for the same retrievals, however, because the MODIS algorithm assumes that its retrieved effective radius (which is mostly representative of cloud top) is constant throughout the depth of the cloud. These comparisons highlight the need to refine microphysical assumptions in all retrieval algorithms and also for future studies to compare not only the mean values but also the full probability density function

Doping driven structural distortion in the bilayer iridate (Sr1−x_{1-x}Lax_x)3_3Ir2_2O7_7

Neutron single crystal diffraction and rotational anisotropy optical second harmonic generation data are presented resolving the nature of the structural distortion realized in electron-doped (Sr$_{1-x}$La$_x$)$_3$Ir$_2$O$_7$ with $x=0.035$ and $x=0.071$. Once electrons are introduced into the bilayer spin-orbit assisted Mott insulator Sr$_3$Ir$_2$O$_7$, previous studies have identified the appearance of a low temperature structural distortion and have suggested the presence of a competing electronic instability in the phase diagram of this material. Our measurements resolve a lowering of the structural symmetry from monoclinic $C2/c$ to monoclinic $P2_1/c$ and the creation of two unique Ir sites within the chemical unit cell as the lattice distorts below a critical temperature $T_S$. Details regarding the modifications to oxygen octahedral rotations and tilting through the transition are discussed as well as the evolution of the low temperature distorted lattice as a function of carrier substitution.Comment: 8 pages, 4 figure

A Study of the Perceptions of Female Displaced Workers in a Community College Regarding Their Educational Expectations and Barriers to Their Achievement.

Adult women enter or reenter college for a variety of reasons, one of which is because of the loss of a job and the need to retrain for reentry into the workforce. The purpose of this phenomenological study was to investigate the actual experiences of female displaced workers entering community college, as compared with their initial expectations as adult learners. Data were collected through interviews with 23 displaced workers age 25 or older who were either enrolled in or had graduated from an associate of applied science degree program at Northeast State Technical Community. Interview transcripts were analyzed using Glaser and Strauss’s (1967) constant comparative method. Achieving particular grades, obtaining a degree, and being able to get a job were the primary ways in which the participants initially defined success. In addition, they attributed the success they achieved to the encouragement and support of their teachers, their families, and their peers as well as to their faith and personal dedication and determination. The barriers they encountered included dispositional, situational, and institutional barriers. Furthermore, they found their initial fears of not fitting in and of being too old to learn to be without merit. While they had underestimated the amount and level of difficulty of the work that would be involved, they had also underestimated their own abilities. Recommendations for future practice included conducting annual orientation sessions for faculty; semester reviews of course offerings and instructional delivery formats; and a series of 10, one-hour workshops, provided at the beginning of each semester, to help alleviate the fears that were consistently expressed. Additional qualitative and quantitative research was also recommended

High power operation of an X-band gyrotwistron

We report the first experimental verification of a gyrotwistron amplifier. The device utilized a single 9.858 GHz, TE011 cavity, a heavily attenuated drift tube, and a long tapered output waveguide section. With a 440 kV, 200-245 A, 1 μs electron beam and a sharply tapered axial magnetic field, peak powers above 21 MW were achieved with a gain near 24 dB. Performance was limited by competition from a fundamental TE11 mode. A multimode code was developed to analyze this system, and simulations were in good agreement with the experiment

On Generating Gravity Waves with Matter and Electromagnetic Waves

If a homogeneous plane light-like shell collides head-on with a homogeneous plane electromagnetic shock wave having a step-function profile then no backscattered gravitational waves are produced. We demonstrate, by explicit calculation, that if the matter is accompanied by a homogeneous plane electromagnetic shock wave with a step-function profile then backscattered gravitational waves appear after the collision.Comment: Latex file, 15 pages, accepted for publication in Physical Review

Explaining Risk to Clients: An Advisory Perspective

To illustrate how advisors explain risk to clients, we map our view of current advisory practice, with particular emphasis on risk management, to our view of the current mosaic of planning paradigms. We then apply that information to identify questions for further discussion and research. We conclude there has been an evolution in advisory practice from a focus on product, to policy, and now increasingly to process, with communication about risk remaining central throughout