972 research outputs found
Analysis Of A Parallel Stratiform Mesoscale Convective System During The Midlatitude Continental Convective Clouds Experiment
During the Midlatitude Continental Convective Clouds Experiment, a PS MCS traversed north-central Oklahoma on 11 May 2011. In-situ measurements of the stratiform precipitation region were obtained from six horizontal flight legs flow by the University of North Dakota Citation II Weather Research Aircraft in conjunction with measurements collected using a multitude of ground-based radars and a dense balloon sounding network specifically set up for the MC3E project. Winds were nearly unidirectional south-southwesterly over Oklahoma and southern Kansas, which created the parallel stratiform characteristics. Gamma functions were fit to ten-second averaged two-dimensional cloud probe spectra. Comparisons of N0, μ, and λ with values from McFarquhar et al. (2007) show the microphysical processes in the parallel stratiform region are similar to those in trailing stratiform regions. The similarities between the 11 May 2011 PS MCS and the simulated one from Parker (2007) show that basic kinematic features of these events are understood
Investigating Evaporation Of Melting Ice Particles Within A Bin Melting Layer Model
Single column models have been used to help develop algorithms for remote sensing retrievals. Assumptions in the single-column models may affect the assumptions of the remote sensing retrievals. Studies of the melting layer that use single column models often assume environments that are near or at water saturation. This study investigates the effects of evaporation upon melting particles to determine whether the assumption of negligible mass loss still holds within subsaturated melting layers. A single column, melting layer model is modified to include the effects of sublimation and evaporation upon the particles. Other changes to the model include switching the order in which the model loops over particle sizes and model layers; including a particle sedimentation scheme; adding aggregation, accretion, and collision and coalescence processes; allowing environmental variables such as the water vapor diffusivity and the Schmidt number to vary with the changes in the environment; adding explicitly calculated particle temperature, changing the particle terminal velocity parameterization; and using a newly-derived effective density-dimensional relationship for use in particle mass calculations.
Simulations of idealized melting layer environments show that significant mass loss due to evaporation during melting is possible within subsaturated environments. Short melting distances, accelerating particle fall speeds, and short melting times help constrain the amount of mass lost due to evaporation while melting is occurring, even in subsaturated profiles. Sublimation prior to melting can also be a significant source of mass loss. The trends shown on the particle scale also appear in the bulk distribution parameters such as rainfall rate and ice water content.
Simulations incorporating observed melting layer environments show that significant mass loss due to evaporation during the melting process is possible under certain environmental conditions. A profile such as the first melting layer profile on 10 May 2011 from the Midlatitude Continental Convective Clouds Experiment (MC3E) that is neither too saturated nor too subsaturated is possible and shows considerable mass loss for all particle sizes. Most melting layer profiles sampled during MC3E were too saturated for more than a dozen or two of the smallest particle sizes to experience significant mass loss. The aggregation, accretion, and collision and coalescence processes also countered significant mass loss at the largest particles sizes because these particles are efficient at collecting smaller particles due to their relative large sweep-out area.
From these results, it appears that the assumption of negligible mass loss due to evaporation while melting is occurring is not always valid. Studies that use large, low-density snowflakes and high RH environments can safely use the assumption of negligible mass loss. Studies that use small ice particles or low RH environments (RH less than about 80%) cannot use the assumption of negligible mass loss due to evaporation. Retrieval algorithms may be overestimating surface precipitation rates and intensities in subsaturated environments due to the assumptions of negligible mass loss while melting and near-saturated melting layer environments
GDP per Capita Differentials between Nations: Patterns and Models
Seit den 70er Jahren erscheint die Welteinkommensverteilung zwischen den Nationen polarisiert in arm und reich. Dieses Phänomen kann theoretisch mithilfe des Solow Wachstumsmodells erklärt werden. Der Nachweis wurde auf drei Arten geführt. Als erstes wurde graphisch gezeigt, dass Änderungen der Annahmen bezüglich der Sparquote, des Bevölkerungswachstums sowie der Sparquote des Humankapital im erweiterten Solow Wachstumsmodell zu Bipolarität führen können. Die zweite Vorgehensweise war analytisch: eine endogene Sparquote wurde in das Solow Wachstumsmodell eingefügt, für welches dann die Gleichgewichte bestimmt wurden. Es konnte gezeigt werden, dass es zur Polarisierung kommt. Schließlich wurde ein empirisch determiniertes Solow Wachstumsmodell formuliert. Die Sparquote sowie die Bevölkerungswachstumsrate wurden mithilfe von Regressionen geschätzt und in das Modell integriert. Hieraus wurden anschließend die Gleichgewichte bestimmt
XRBcats: Galactic High Mass X-ray Binary Catalogue
We present a new catalogue of the high-mass X-ray binaries (HMXBs) in the
Galaxy improving upon the most recent such catalogue. We include new HMXBs
discovered since aforementioned publication and revise the classification for
several objects previously considered HMXBs or candidates. The catalogue
includes both basic information such as source names, coordinates, types, and
more detailed data such as distance and X-ray luminosity estimates, binary
system parameters and other characteristic properties of 169 HMXBs, together
with appropriate references to the literature. Finding charts in several bands
from infra-red to hard X-rays are also included for each object. The aim of
this catalogue is to provide the reader a list of all currently known Galactic
HMXBs with some basic information on both compact objects and non-degenerate
counterpart properties (where available). We also include objects tentatively
classified as HXMBs in the literature and give a brief motivation for the
classifcation in each relevant case. The catalogue is compiled based on a
search of known HMXBs and candidates in all commonly available databases and
literature published before 31 October 2022. Relevant properties in the optical
and other bands were collected for all objects either from the literature or
using the data provided by large-scale surveys. In the later case, the
counterparts in each individual survey were found by cross-correlating
positions of identified HMXBs with relevant databases. An up-to date catalogue
of Galactic HMXBs is presented to facilitate research in this area. An attempt
was made to collect a larger set of relevant HMXB properties in a more uniform
way compared to previously published works.Comment: 10 pages, 2 figures, submitted to A&A. For auxillary files, see
http://astro.uni-tuebingen.de/~xrbcat
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