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On the maximum vertical extent of convective cloudsUnknown Date (has links)
"An attempt is made to examine the credibility and explore the implications of the reports of convective clouds to extreme heights which have been indicated by radar in recent years. The extreme cases have not been verified by independent observations and it is shown that inherent limitations in radar observations of convective cloud heights are such as to raise serious doubts in regard to the accuracy of many of the extreme echo heights which have been reported"--Abstract. / Typescript. / "Scientific report to the U.S. Navy Weather Research Facility, Norfolk, Virginia, under contract N189-50775A." / "15 April 1962." / Includes bibliographical references (leaves 32-34).
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A study of positive cloud-to-ground lightning flashes in mesoscale convective systemsLu, Chungu 05 August 1988 (has links)
This study is mainly concentrated on examining the positive cloud-to-ground
lightning activity associated with Mesoscale Convective Systems. Six MCS events
which occurred during the O.K. PRE-STORM program in 1985 are studied. Data
indicating the location and polarity of the cloud-to-ground lightning flashes from a
lightning location network are analyzed in conjunction with the low-level echo
patterns as obtained from radar. Spatial and temporal characteristics of positive
cloud-to-ground flashes are identified from the data analysis. For all cases
examined, positive cloud-to-ground flashes were found most commonly in the
stratiform regions of the MCSs examined, and their frequency tended to peak
during the later stages of the storm lifecycle.
Two mechanisms responsible for the occurrence of positive cloud-to-ground
lightning flashes with the above spatial and temporal characteristics are discussed.
Based on the laboratory results, a 1-D charge generation model is developed. The
model results show that in-situ charging is unlikely to be the dominant
mechanism for charge generation in the stratiform region under normal
atmospheric conditions. Sensitivity studies show, however, that in-situ charging
processes strongly depend upon the liquid water, graupel and snow contents in the
cloud. Under favorable atmospheric conditions, in-situ charging may lead to a
significant charge generation. Hence, we cannot completely dismiss in-situ
charging mechanism. Analysis of wind fields from dual-Doppler radar in
combination with vertical profile of electric fields indicates that charge advection
from the convective region to the stratiform region of MCSs may be a potential
mechanism responsible for the occurrence of positive cloud-to-ground lightning
flashes in the stratiform region. / Graduation date: 1989
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Numerical analysis of convective storm development over Maldives : a thesis submitted in fulfilment of the requirements for the degree of Masters [i.e. Master] of Science in Geography at the University of Canterbury /Shareef, Ali. January 2009 (has links)
Thesis (M. Sc.)--University of Canterbury, 2009. / Typescript (photocopy). Includes bibliographical references (p. 109-120). Also available via the World Wide Web.
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The lifting condensation level and its relation to convective cloud baseWilde, Nicholas Paul. January 1984 (has links)
Thesis (M.S.)--University of Wisconsin--Madison, 1984. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 153-162).
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An investigation of warm-season cloud patterns and related precipitation across Maryland and the Delmarva PeninsulaHyre, Heather Richelle 01 May 2010 (has links)
Surface heterogeneities cause differential heating that can generate mesoscale convective boundaries, sometimes leading to cloud development and enhanced localized precipitation. A preferred cloud pattern has been identified across Maryland and the Delmarva Peninsula region from 1998-2006 through the detection of cumuliform clouds on days when synoptic-scale forcing is weak. Hourly visible Geostationary Operational Environmental Satellite (GOES) imagery data are used to identify convective cloud masses. This allows quantitative description of the frequency and spatiotemporal extent of the clouds, helping forecasters gain insight into when and where they are likely to develop. Despite the inability to determine the underlying causes of the distinct cloud pattern, primarily due to the complex land cover, results indicate that the land receives significantly higher average total cloud cover than the Chesapeake Bay with Delaware receiving the highest average total cloud cover per state. Average total precipitation amounts follow this same trend on synoptically-weak days.
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An observational study of the energetics and dynamical aspects of GATE cloud clustersWang, Jough-tai 21 November 1986 (has links)
Thermodynamical and dynamical aspects of tropical cloud
clusters are studied using data from the GARP Atlantic Tropical
Experiment (GATE). The data set used in this study is a
three-dimensional gridded set of upper-air analyses constructed by
Ooyama and Chu (Hurricane Research Division, AOML/NOAA and
SSEC-University of Wisconsin) for wind data and Esbensen (Oregon
State University) for thermodynamic data. The energy and momentum
budgets are estimated on the scale of large cloud clusters.
A strong upper-tropospheric heat source and middle-tropospheric
drying are characteristic features of the mature stage
of the observed cloud clusters. The heat source, moisture sink and
the virtual heat flux for cloud clusters are larger than the
corresponding quantities from GATE easterly-wave composites. The
surface precipitation estimates produced from the vertically
integrated moisture budget are consistent with direct observations.
From the momentum budget study, the following conclusions are
drawn concerning the cumulus momentum effects. In the growing
stage, the mesoscale and cumulus scale effect tends to: 1) provide
a vertically integrated net sink for westerly momentum around the
cluster center; 2) induce a convergent circulation in the lower
layer. In the mature stage, the effects are to: 1) induce a
divergent circulation in the upper layer and maintain a vorticity
couplet pattern; 2) maintain a weak convergent circulation in the
lower layer; and 3) cause a relatively weak easterly acceleration
in the upper layer at the center. A hypothesis is postulated to
illustrate the convective dynamical effects.
A simple barotropic non-divergent model was constructed to
investigate the large-scale response to the hypothesized cumulus
momentum forcing similar to that found in the GATE cloud-cluster
momentum budget. The numerical results show that the cumulus
momentum forcing is a plausible kinetic energy source for the
mesoscale wavenumber spectrum. The sporadic nature of the
convective mass flux does not have a significant effect on the
large-scale dynamical response for physically realistic parameters
in a barotropic non-divergent dynamical system. / Graduation date: 1987
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Effects of aerosols on deep convective cumulus cloudsFan, Jiwen 15 May 2009 (has links)
This work investigates the effects of anthropogenic aerosols on deep convective clouds and the associated radiative forcing in the Houston area. The Goddard Cumulus Ensemble model (GCE) coupled with a spectral-bin microphysics is employed to investigate the aerosol effects on clouds and precipitation. First, aerosol indirect effects on clouds are separately investigated under different aerosol compositions, concentrations and size distributions. Then, an updated GCE model coupled with the radiative transfer and land surface processes is employed to investigate the aerosol radiative effects on deep convective clouds. The cloud microphysical and macrophysical properties change considerably with the aerosol properties. With varying the aerosol composition from only (NH4)2SO4, (NH4)2SO4 with soluble organics, to (NH4)2SO4 with slightly soluble organics, the number of activated aerosols decreases gradually, leading to a decrease in the cloud droplet number concentration (CDNC) and an increase in the droplet size. Ice processes are more sensitive to the changes of aerosol chemical properties than the warm rain processes. The most noticeable effect of increasing aerosol number concentrations is an increase of CDNC and cloud water content but a decrease in droplet size. It is indicated that the aerosol indirect effect on deep convection is more pronounced in relatively clean air than in heavily polluted air. The aerosol effects on clouds are strongly dependent on RH: the effect is very significant in humid air. Aerosol radiative effects (ARE) on clouds are very pronounced for mid-visible single-scattering albedo (SSA) of 0.85. Relative to the case without the ARE, cloud fraction and optical depth decrease by about 18% and 20%, respectively. The daytime-mean direct forcing is about 2.2 W m-2 at the TOA and -17.4 W m-2 at the surface. The semi-direct forcing is positive, about 10 and 11.2 W m-2 at the TOA and surface, respectively. Aerosol direct and semi-direct effects are very sensitive to SSA. The cloud fraction, optical depth, convective strength, and precipitation decrease with the increase of absorption, resulting from a more stable atmosphere due to enhanced surface cooling and atmospheric heating.
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Effects of aerosols on deep convective cumulus cloudsFan, Jiwen 15 May 2009 (has links)
This work investigates the effects of anthropogenic aerosols on deep convective clouds and the associated radiative forcing in the Houston area. The Goddard Cumulus Ensemble model (GCE) coupled with a spectral-bin microphysics is employed to investigate the aerosol effects on clouds and precipitation. First, aerosol indirect effects on clouds are separately investigated under different aerosol compositions, concentrations and size distributions. Then, an updated GCE model coupled with the radiative transfer and land surface processes is employed to investigate the aerosol radiative effects on deep convective clouds. The cloud microphysical and macrophysical properties change considerably with the aerosol properties. With varying the aerosol composition from only (NH4)2SO4, (NH4)2SO4 with soluble organics, to (NH4)2SO4 with slightly soluble organics, the number of activated aerosols decreases gradually, leading to a decrease in the cloud droplet number concentration (CDNC) and an increase in the droplet size. Ice processes are more sensitive to the changes of aerosol chemical properties than the warm rain processes. The most noticeable effect of increasing aerosol number concentrations is an increase of CDNC and cloud water content but a decrease in droplet size. It is indicated that the aerosol indirect effect on deep convection is more pronounced in relatively clean air than in heavily polluted air. The aerosol effects on clouds are strongly dependent on RH: the effect is very significant in humid air. Aerosol radiative effects (ARE) on clouds are very pronounced for mid-visible single-scattering albedo (SSA) of 0.85. Relative to the case without the ARE, cloud fraction and optical depth decrease by about 18% and 20%, respectively. The daytime-mean direct forcing is about 2.2 W m-2 at the TOA and -17.4 W m-2 at the surface. The semi-direct forcing is positive, about 10 and 11.2 W m-2 at the TOA and surface, respectively. Aerosol direct and semi-direct effects are very sensitive to SSA. The cloud fraction, optical depth, convective strength, and precipitation decrease with the increase of absorption, resulting from a more stable atmosphere due to enhanced surface cooling and atmospheric heating.
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Simulations of the sulphur chemistry of a convective cloudRakowsky, Ademar R. January 1986 (has links)
No description available.
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A three dimensional cloud chemistry model / / A 3 dimensional cloud chemistry model.Tremblay, André, 1948- January 1985 (has links)
No description available.
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