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A two-dimensional omega equation for the 1000-700 MB layer with diabatic heating,Ferrentino, Peter S. January 1966 (has links)
Thesis (M.S.) - U.S. Naval Postgraduate School, 1966. / Bibliography: leaves 57-[58].
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Effects of baroclinicity on storm divergence and stratiform rain in a precipitating subtropical regionHopper, Jr., Larry John 15 May 2009 (has links)
Divergence structures associated with the spectrum of precipitating systems in
the subtropics and midlatitudes are not well documented. A mesoscale model (MM5) is
employed to quantify the relative importance different baroclinic environments have on
divergence profiles for common storm types in southeast Texas, a subtropical region.
Divergence profiles averaged over a 100 x 100 nested grid with 3-km grid spacing are
calculated from the model-derived wind fields for each storm. The divergence profiles
simulated for selected storms are consistent with those calculated from an S-band radar
using the velocity-azimuth display (VAD) technique.
Divergence profiles from well-modeled storms vary in magnitude and structure
across the spectrum of baroclinicities and storm types common in southeast Texas.
Barotropic storms more characteristic of the Tropics generate the most elevated
divergence (and thus diabatic heating) structures with the largest magnitudes. As the
degree of baroclinicity increases, stratiform area fractions increase while the levels of
non-divergence (LNDs) decrease. However, some weakly baroclinic storms contain
stratiform area fractions and divergence profiles with magnitudes and LNDs that are similar to barotropic storms, despite having lower tropopause heights and less deep
convection. Additional convection forms after the passage of some of the modeled
barotropic and weakly baroclinic storms that contain elevated divergence signatures,
circumstantially suggesting that heating at upper-levels may cause diabatic feedbacks
that help drive regions of persistent convection in the subtropics.
Applying a two-dimensional stratiform-convective separation algorithm to MM5
reflectivity data generates realistic stratiform and convective divergence signals.
Stratiform regions in barotropic storms contain thicker, more elevated mid-level
convergence structures with larger magnitudes than strongly baroclinic storms, while
weakly baroclinic storms have LNDs that fall somewhere in between with magnitudes
similar to barotropic storms. Divergence profiles within convective regions typically
become more elevated as baroclinicity decreases, although variations in magnitude are
less coherent. These simulations suggest that MM5 adequately captures mass field
perturbations within convective and stratiform regions, the latter of which produces
diabatic feedbacks capable of generating additional convection. As a result, future
research determining the climatological dynamic response caused by divergence profiles
in MM5 may be feasible.
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Photodissociation Dynamics of Halogen Oxide SpeciesDooley, Kristin S. 2009 May 1900 (has links)
The focus of this dissertation is the study of the photodissociation dynamics of
halogen oxide species (XO, X = Cl, Br, I). These radical species are known to be
important in stratospheric and tropospheric ozone depletion cycles. They are also useful
benchmark systems for the comparison to current theoretical methods where they
provide insight into the dynamics occurring beyond the Franck-Condon region. These
systems are studied using velocity map ion imaging, a technique that measures velocity
and angular information simultaneously. Photofragment species are state-selectively
ionized for detection using 2+1 REMPI (Resonance Enhanced Multi-Photon Ionization).
The instrumentation employs a molecular beam of the XO radicals formed using
pyrolitic and photolytic methods.
The current work involves the measurement of fundamental physical constants of
the XO species. The bond dissociation energy of IO is measured. Vibrational level
dependent correlated final state branching ratios of the predissociation of the A(^2 II_3/2)
state of ClO and BrO are reported, and comparison to theoretical methods is discussed.
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Observed Characteristics of Clouds and Precipitating Systems Associated with the Tropical Circulation in Global Models and ReanalysesStachnik, Justin Paul 03 October 2013 (has links)
This dissertation presents a series of work related to the representation of the Hadley circulation (HC) in atmospheric reanalyses and general circulation models (GCMs), with connections to the underlying tropical and subtropical cloud systems that comprise the mean meridional circulation. An intercomparison of eight atmospheric reanalyses showed that significant variability exists in the mean state for HC intensity, with less variability in HC width. Ensemble trends were broadly consistent with previous work and suggest a strengthening and widening of the tropical circulation over the last 30 years.
Composite profiles of the apparent heat source and moisture sink were calculated for the International Satellite Cloud Climatology Project (ISCCP) cloud regimes using sounding observations from 10 field campaigns. Distinct heating profiles were determined for each ISCCP cloud regime, ranging from strong, upper-tropospheric heating for mesoscale convective systems to integrated cooling for populations associated with marine stratus and stratocumulus clouds. The derived profiles were generally similar over land and ocean with the notable exception of the fair-weather cumulus regime, which leads to some uncertainty in the mid- and upper-level reconstruction of subtropical heating.
An instrument simulator indicated that low-latitude cloud properties from the NASA MERRA reanalysis qualitatively matched the distributions of cloud-top pressure and optical thickness in the ISCCP data, though the tallest and thickest clouds were missing from the reanalysis. Simulator results were sensitive to the choice of cloud overlap parameterization and the reanalysis consistently underpredicted the observed cloud fractions for all regimes. The vertical velocity, temperature, and moisture for each regime in MERRA largely matched observations from previous studies, suggesting that the dynamic and thermodynamic properties of the cloud regimes are well captured by the reanalysis.
Finally, HC interannual variability was examined as a function of the observed frequency of the ISCCP cloud regimes. The strongest HC overturning events were attributed to an El Niño response in the central Pacific Ocean in addition to links between the intensity and position of the Pacific ITCZ. The ISCCP regime describing the most vigorous and organized convection contributed the most towards the total anomalous heating during HC extremes, despite an overall low frequency of occurrence. Idealized GCM simulations forced with the observed three-dimensional diabatic heating from ISCCP data produced too strong a HC with some improvement in other fields. Overall, much progress has been made regarding the links between low-latitude cloud systems and the HC, though future work will continue to address the upscale feedbacks of regional cloud variations upon the tropical circulation.
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The 23-26 September 2012 UK floods : influence of diabatic processes and upper-level forcing on cyclone developmentHardy, Sam January 2017 (has links)
The thesis comprises two separate journal articles that together form a coherent body of work. In this thesis, the key physical processes responsible for the 23-26 September 2012 UK floods are investigated using a case study approach. The cyclone responsible for the floods developed near the Azores on 20¬-22 September following the interaction between an equatorward-moving potential vorticity (PV) streamer and tropical storm Nadine. Convectively-driven latent heat release associated with the developing cyclone reduced upper-level PV and resulted in the fracture of the PV streamer into a discrete anomaly as the cyclone intensified. In Paper 1, convection-permitting model simulations and diabatic heating rate and PV tendency calculations along trajectories demonstrate that deposition heating strongly reduced upper-level PV in the vicinity of the PV streamer, contributing to its fracture into a discrete anomaly. The cyclone deepened further over the UK on 23-26 September, ahead of a second upper-level PV anomaly. In Paper 2, sensitivity simulations of the storm are presented. PV inversion is used to modify the strength and position of the PV anomaly in the initial conditions and to examine whether the event could have been even more extreme with different upper-level forcing. Results show that quasigeostrophic forcing for ascent ahead of the PV anomaly contributed to the maintenance of the rainfall band over the UK. Counterintuitively however, strengthening the upper-level forcing produced a shallower cyclone with lower rainfall totals. Instead of moving eastward over the UK to interact with the cyclone, the strengthened anomaly rotated cyclonically around a large-scale trough over Iceland, resulting in a fragmented rainfall band. The counterintuitive results suggest that the verifying analysis represents almost the highest-impact scenario possible for this flooding event.
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Dynamics and organisation of precipitation bands in the midlatitudesNorris, Jesse Michael January 2014 (has links)
The thesis is presented in alternative format, meaning that the results of the thesis take the form of three journal articles, each telling a distinct story within the subject matter, but collectively highlighting the sensitivity of bands to frictional and diabatic processes. Paper 1 is an idealised-modelling study with the Weather Research and Forecasting (WRF) model, in which moist baroclinic waves are simulated from an initial zonally uniform mid-latitude jet on an f-plane at 20-km grid spacing, and the sensitivity of the resulting precipitation bands is explored. Paper 2 employs further WRF idealised-baroclinic-wave simulations and takes a simulation from Paper 1, after the cold front has formed, as the initial condition. A nested domain at 4-km grid spacing is inserted when this simulation is re-initialised to invesigate the sensitivity of finer-scale precipitation cores along the surface cold front. In both Papers 1 and 2, friction and latent-heat release enhance multiple banding at the two distinct horizontal scales, while surface fluxes hinder multiple banding. Paper 3 studies post-frontal snowbands over the English Channel and Irish Sea during extreme cold-air outbreaks in the winters of 2009-10 and 2010-11, via a climatology of precipitation-radar, sounding, and SST data, and real-data WRF sensitivity simulations of one such band over the English Channel. The observational and modelling results show that strong winds and large differential heat fluxes between land and sea were necessary to generate banded precipitation. Coastal orography and the land-sea frictional contrast aided the morphology of bands, but banded precipitation did still form in the absence of these influences in the sensitivity simulations. These three studies and the thesis as a whole highlight the role of frictional and diabatic processes in modifying various types of precipitation bands within baroclinic waves, and in generating bands that would otherwise not exist.
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Development of wavefunction theory for the excited states of π-conjugated molecular aggregates and its application / π共役分子集合体の励起状態に対する波動関数理論の開発と応用Nishio, Soichiro 24 November 2023 (has links)
京都大学 / 新制・課程博士 / 博士(理学) / 甲第24964号 / 理博第4989号 / 新制||理||1712(附属図書館) / 京都大学大学院理学研究科化学専攻 / (主査)准教授 倉重 佑輝, 教授 渡邊 一也, 教授 林 重彦 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM
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A Numerical Model for Nonadiabatic Transitions in MoleculesAgrawal, Devanshu 01 May 2014 (has links)
In molecules, electronic state transitions can occur via quantum coupling of the states. If the coupling is due to the kinetic energy of the molecular nuclei, then electronic transitions are best represented in the adiabatic frame. If the coupling is instead facilitated through the potential energy of the nuclei, then electronic transitions are better represented in the diabatic frame. In our study, we modeled these latter transitions, called ``nonadiabatic transitions.'' For one nuclear degree of freedom, we modeled the de-excitation of a diatomic molecule. For two nuclear degrees of freedom, we modeled the de-excitation of an ethane-like molecule undergoing cis-trans isomerization. For both cases, we studied the dependence of the de-excitation on the nuclear configuration and potential energy of the molecule.
We constructed a numerical model to solve the time-dependent Schr\"{o}dinger Equation for two coupled wave functions. Our algorithm takes full advantage of the sparseness of the numerical system, leading to a final set of equations that is solved recursively using nothing more than the Tridiagonal Algorithm.
We observed that the most effective de-excitation occurred when the molecule transitioned from a stable equilibrium configuration to an unstable equilibrium configuration. This same mechanism is known to drive fast electronic transitions in the adiabatic frame. We concluded that while the adiabatic and diabatic frames are strongly opposed physically, the mathematical mechanism driving electronic transitions in the two frames is in some sense the same.
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The Vertical Structure of Tangential Winds in Tropical Cyclones: Observations, Theory, and Numerical SimulationsStern, Daniel Philip 01 July 2010 (has links)
The vertical structure of the tangential wind field in tropical cyclones is investigated through observations, theory, and numerical simulations. First, a dataset of Doppler radar wind swaths obtained from NOAA/AOML/HRD is used to create azimuthal mean tangential wind fields for 7 storms on 17 different days. Three conventional wisdoms of vertical structure are reexamined: the outward slope of the Radius of Maximum Winds (RMW) decreases with increasing intensity, the slope increases with the size of the RMW, and the RMW is a surface of constant absolute angular momentum (M). The slopes of the RMW and of M surfaces are objectively determined. The slopes are found to increase linearly with the size of the low-level RMW, and to be independent of the intensity of the storm. While the RMW is approximately an M surface, M systematically decreases with height along the RMW. The steady-state analytical theory of Emanuel (1986) is shown to make specific predictions regarding the vertical structure of tropical cyclones. It is found that in this model, the slope of the RMW is a linear function of its size and is independent of intensity, and that the RMW is almost exactly an M surface. A simple time-dependent model which is governed by the same assumptions as the analytical theory yields the same results. Idealized hurricane simulations are conducted using the Weather Research and Forecasting (WRF) model. The assumptions of Emanuel's theory, slantwise moist neutrality and thermal wind balance, are both found to be violated. Nevertheless, the vertical structure of the wind field itself is generally well predicted by the theory. The percentage rate at which the winds decay with height is found to be nearly independent of both size and intensity, in agreement with observations and theory. Deviations from this decay profile are shown to be due to gradient wind imbalance. The slope of the RMW increases linearly with its size, but is systematically too large compared to observations. Also in contrast to observations, M generally increases with height along the RMW.
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Progress Towards the Fast Transport of a 87Rb Bose-Einstein CondensateMize, Margaret G. 26 July 2022 (has links)
No description available.
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