Kinematics and thermodynamics of a midlatitude, continental mesoscale convective system and its mesoscale vortex

Also issued as author's dissertation (Ph.D.) -- Colorado State University, 2001.Includes bibliographical references.The author examines a mesoscale convective system (MCS) and the mesoscale convective vortex (MCV) it generated. The MCS, which comprised a leading convective line and trailing stratiform region, traversed Kansas and Oklahoma on 1 August 1996, passing through the NOAA Wind Profiler Network, as well as four sites from which soundings were being taken every three hours during a field project. The unusually rich data set permitted study of the MCS and MCV over nine hours on scales between those of operational rawinsondes and Doppler radars. The author used a spatial bandpass filter to divide observed wind into synoptic and mesoscale components. The environment-relative, mesoscale wind contained an up- and downdraft and divergent outflows in the lower and upper troposphere. The mesoscale wind was asymmetric about the MCS, consistent with studies of gravity waves generated by heating typical of that in many MCSs. According to a scale-discriminating vorticity budget, both the synoptic and mesoscale winds contributed to the prominent resolved sources of vorticity in the MCV: tilting and convergence. Unresolved sources were also large. The author speculates that an abrupt change in the main source of vorticity in an MCV may appear as an abrupt change in its altitude of maximum vorticity. Distributions of temperature and humidity in the MCS were consistent with its mesoscale circulations. In the terminus of the mesoscale downdraft, advection of drier, potentially warmer air exceeded humidifying and cooling from rain, so profiles of temperature and dewpoint exhibit onion and double-onion patterns. The mesoscale updraft was approximately saturated with a moist adiabatic lapse rate. Mesoscale drafts. and convective drafts vertically mixed the troposphere, partially homogenizing equivalent potential temperature. The MCV contained a column of high potential vorticity in the middle troposphere, with a cold core below the freezing level and a warm core above-a pattern characteristic of profiles of heating by stratiform regions. The cold core was 2 km too shall w to be in pure gradient balance with wind in the MCV. Ongoing forcing during the observed lifetime of the MCV may have prevented it from achieving balance, even if that was its tendency.Sponsored by the National Science Foundation under grants ATM-0071371 and ATM-9618684; and NASA grant NCCS-288

Surface pressure transients in mesoscale convective systems

Spring 1996.Also issued as author's thesis (M.S.) -- Colorado State University, 1996.Includes bibliographical references.For decades meteorologists have observed that mesoscale convective systems (MCSs) increase surface pressure beneath and immediately behind their leading cumulonimbi ( the mesohigh) and reduce surface pressure at the rear edge of their anvils (the wake low). By enhancing coarse surface pressure observations of 12 PRE-STORM MCSs, I exposed transitory highs and lows living within mesohighs and wake lows. I propose that these transients are the more elemental MCS surface pressure perturbations; mesohighs and wake lows are merely temporal and spatial envelopes of transients. Moreover, existing theories of mesohigh and wake low origins readily apply to the ephemeral transients. A quasi-Lagrangian analysis of 92 transients produced five primary results. First, as the MCSs matured, the difference between each complex's transitory highs' mean pressure and transitory lows' mean pressure increased in 78% of the conclusive cases. Second, there is no clear evidence that transitory highs consistently strengthened before their partner transitory lows. Third, transient paths reflect MCSs' occasional. symmetric-to-asymmetric metamorphoses. Fourth, composites of the time-evolution of the numbers and apparent sizes of transients partially support theories of MCS upscale evolution. Fifth, composite transient numbers and apparent sizes vary almost identically with time in a pattern that closely resembles the fluctuation of stratiform and convective volumetric rain rates of MCSs studied by McAnelly and Cotton (1992).Sponsored by the National Science Foundation ATM-9313716

DO METEOROLOGISTS SUPPRESS THUNDERSTORMS? Radar-Derived Statics and the Behavior of Moist Convection

Most meteorologists are acquainted with the no- tion of a weather hole—that is, a place that receives less exciting weather than does its surroundings. Exciting weather takes many forms, but when people use the term weather hole, they tend to mean a place that thunderstorms often barely miss, or near which approaching storms often dissipate. For this paper, that is the meaning we adopt. In our experience, many meteorologists and lay weather enthusiasts genuinely believe that they live in weather holes, and this belief, almost without fail, seems to stem from countless hours spent gazing at displays of radar reflectivity. We have generally presumed that such people simply relish thunderstorms, are memorably disappointed whenever storms miss them, and erroneously conclude that their locations are subject to some kind of meteorologic disfavor. The recent availability of multiple years\u27 worth of national radar composites from the Weather Surveillance Radar-1988 Doppler (WSR-88D) network makes it possible to address objectively, if not definitively, whether meteorologists appear to live in weather holes and whether such an appearance is physical or artificial

Partial joint processing with efficient backhauling using particle swarm optimization

In cellular communication systems with frequency reuse factor of one, user terminals (UT) at the cell-edge are prone to intercell interference. Joint processing is one of the coordinated multipoint transmission techniques proposed to mitigate this interference. In the case of centralized joint processing, the channel state information fed back by the users need to be available at the central coordination node for precoding. The precoding weights (with the user data) need to be available at the corresponding base stations to serve the UTs. These increase the backhaul traffic. In this article, partial joint processing (PJP) is considered as a general framework that allows reducing the amount of required feedback. However, it is difficult to achieve a corresponding reduction on the backhaul related to the precoding weights, when a linear zero forcing beamforming technique is used. In this work, particle swarm optimization is proposed as a tool to design the precoding weights under feedback and backhaul constraints related to PJP. The precoder obtained with the objective of weighted interference minimization allows some multiuser interference in the system, and it is shown to improve the sum rate by 66% compared to a conventional zero forcing approach, for those users experiencing low signal to interference plus noise ratio

IRF4 and BATF are critical for CD8(+) T-cell function following infection with LCMV.

CD8(+) T-cell functions are critical for preventing chronic viral infections by eliminating infected cells. For healthy immune responses, beneficial destruction of infected cells must be balanced against immunopathology resulting from collateral damage to tissues. These processes are regulated by factors controlling CD8(+) T-cell function, which are still incompletely understood. Here, we show that the interferon regulatory factor 4 (IRF4) and its cooperating binding partner B-cell-activating transcription factor (BATF) are necessary for sustained CD8(+) T-cell effector function. Although Irf4(-/-) CD8(+) T cells were initially capable of proliferation, IRF4 deficiency resulted in limited CD8(+) T-cell responses after infection with the lymphocytic choriomeningitis virus. Consequently, Irf4(-/-) mice established chronic infections, but were protected from fatal immunopathology. Absence of BATF also resulted in reduced CD8(+) T-cell function, limited immunopathology, and promotion of viral persistence. These data identify the transcription factors IRF4 and BATF as major regulators of antiviral cytotoxic T-cell immunity

THE MATERHORN: Unraveling the Intricacies of Mountain Weather

Emerging application areas such as air pollution in megacities, wind energy, urban security, and operation of unmanned aerial vehicles have intensified scientific and societal interest in mountain meteorology. To address scientific needs and help improve the prediction of mountain weather, the U.S. Department of Defense has funded a research effort—the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) Program—that draws the expertise of a multidisciplinary, multi-institutional, and multinational group of researchers. The program has four principal thrusts, encompassing modeling, experimental, technology, and parameterization components, directed at diagnosing model deficiencies and critical knowledge gaps, conducting experimental studies, and developing tools for model improvements. The access to the Granite Mountain Atmospheric Sciences Testbed of the U.S. Army Dugway Proving Ground, as well as to a suite of conventional and novel high-end airborne and surface measurement platforms, has provided an unprecedented opportunity to investigate phenomena of time scales from a few seconds to a few days, covering spatial extents of tens of kilometers down to millimeters. This article provides an overview of the MATERHORN and a glimpse at its initial findings. Orographic forcing creates a multitude of time-dependent submesoscale phenomena that contribute to the variability of mountain weather at mesoscale. The nexus of predictions by mesoscale model ensembles and observations are described, identifying opportunities for further improvements in mountain weather forecasting

DO METEOROLOGISTS SUPPRESS THUNDERSTORMS? Radar-Derived Statistics and the Behavior of Moist Convection

Most meteorologists are acquainted with the notion of a weather hole—that is, a place that receives less exciting weather than does its surroundings. Exciting weather takes many forms, but when people use the term weather hole, they tend to mean a place that thunderstorms often barely miss, or near which approaching storms often dissipate. For this paper, that is the meaning we adopt. In our experience, many meteorologists and lay weather enthusiasts genuinely believe that they live in weather holes, and this belief, almost without fail, seems to stem from countless hours spent gazing at displays of radar reflectivity. We have generally pre- sumed that such people simply relish thunderstorms, are memorably disappointed whenever storms miss them, and erroneously conclude that their locations are subject to some kind of meteorologic disfavor. The recent availability of multiple years\u27 worth of national radar composites from the Weather Surveillance Radar-1988 Doppler (WSR-88D) network makes it possible to address objectively, if not definitively, whether meteorologists appear to live in weather holes and whether such an appearance is physical or artificial

Evaluation of Urban Canopy Models against Near-Surface Measurements in Houston during a Strong Frontal Passage

Urban canopy models (UCMs) in mesoscale numerical weather prediction models need evaluation to understand biases in urban environments under a range of conditions. The authors evaluate a new drag formula in the Weather Research and Forecasting (WRF) model’s multilayer UCM, the Building Effect Parameterization combined with the Building Energy Model (BEP+BEM), against both in-situ measurements in the urban environment as well as simulations with a simple bulk scheme and BEP+BEM using the old drag formula. The new drag formula varies with building packing density, while the old drag formula is constant. The case study is a strong cold frontal passage that occurred in Houston during the winter of 2017, causing high winds. It is found that both BEP+BEM simulations have lower peak wind speeds, consistent with near-surface measurements, while the bulk simulation has winds that are too strong. The constant-drag BEP+BEM simulation has a near-zero wind speed bias, while the new-drag simulation has a negative bias. Although the focus is on the impact of drag on the urban wind speeds, both BEP+BEM simulations have larger negative biases in the near-surface temperature than the bulk-scheme simulation. Reasons for the different performances are discussed