This thesis examines the mechanisms that couple the monthly-averaged
atmospheric boundary layer (ABL) to open-ocean sea surface temperature (SST)
perturbations on scales of 50-500 km. The observed positive correlation between
surface wind speed anomalies and SST anomalies is successfully simulated using
the Weather Research and Forecasting (WRF) model.
In numerical...
Transition phenomena commonly occur in nature. These arise
either due to structural or behavioral changes in the medium. Examples
for these abound in all applied sciences and to mention a few
of these, we have, boundary layer, elastic-plastic deformation, and
shocks. The present work is devoted to the study of...
Atmospheric boundary layers become stably stratified at night over land when the surface becomes colder than the air layer above. In stable nocturnal boundary layers (SNBL), turbulence becomes weak and intermittent, terrain-induced phenomena such as drainage currents or gravity-waves emerge and the surface heterogeneity is enhanced. Because of their complexity...
Detailed current profiles between the sediment-water interface
and 20 cm above it reveal a viscous sublayer in the bottom boundary
layer on the Oregon continental shelf. Data from three field experiments
are used to test fundamental assumptions about boundary layer
flow in the ocean. The first study, discussed in Chapter...
A baroclinic, convective mixed-layer was modeled, using
water, in a laboratory convection tank identical to that
used in the free convection study of Deardorff and Willis
(1985). Baroclinicity and mean-flow shearing were achieved
by tilting the tank by an angle of 1O⁰. The resulting
mechanical-production rate of turbulence kinetic energy...
Simple models of transpiration, e.g., the Penman-Monteith equation, treat atmospheric conditions as driving variables. In fact, transpiration modifies temperature and humidity throughout the convective boundary layer, creating feedbacks that stabilize the water use of vegetation. This thesis concentrates on the new empirical relationships proposed by Monteith (1995), for developing simple...
This study concentrates on analysis of LongEZ aircraft data taken offshore of the Atlantic Coast of the United States. Due to the land structure of the region, it was possible to isolate the effect of narrow land on air as it flows offshore. The narrow land (Outer Banks) separates inland...
A two-scale approach for the turbulent mixing of momentum in an unstable stratified boundary layer is proposed in an attempt to eliminate existing inconsistencies between parameterized mixing of heat and momentum. The parameterization of the large eddy stress is suitable for simple boundary layer models where computational efficiency is important....
Eight years (1980-87) of twice-daily high-resolution radiosonde data from a tropical mid-Pacific island station are analyzed to generate time series of the planetary boundary layer (PBL) top pressure, an ageostrophic parameter (related to the divergence), and a parameter of mean PBL specific humidity. Sample spectra of these time series are...
An analytical two-layer model consisting of a time-dependent stratified
boundary layer topped by stratified free flow is developed in order
to study atmospheric boundary layer production of vertical motion. To
avoid use of a constant eddy viscosity, the boundary layer equations are
layer-integrated over a fixed depth, and surface stress...
The influence of boundary layer pumping on an externally-forced
synoptic-scale flow is examined. The results follow earlier theories of
stratified incompressible Boussinesq flow. These theories state that
the spin-down time scale and the penetration depth of the influence of
boundary layer pumping are inversely proportional to the stratification
and directly...
An eigenvector analysis of the velocity-temperature correlation
matrix is applied to clear-air turbulence measured by aircraft in the
Bora. The eigenvectors are identified with the main eddies of the
turbulence. This study attempts to infer the three-dimensional
structure of these eddies. The results are compared with turbulent
structures in the...
The numerical modeling of motions in the atmosphere's
planetary boundary layer (PBL) is a challenging task. In
general, the boundary layer interacts with both the overlying
atmosphere and the underlying land or water surface
in a complex manner. Random turbulence is also present in
the PBL which precludes exact prediction...
The influence of irregular terrain on the evolution of the daytime
planetary boundary layer (PBL) and meso-β scale dry circulations is
studied using two three-dimensional hydrostatic σ-coordinate models
with different approaches for the PBL parameterizations; the 4-layer
model uses the mixed-layer (bulk-layer) approach, while the 7-layer
model adopts the eddy-diffusivity...
Four buoyant plumes were produced within a laboratory convectively
mixed layer from a source height of about z[subscript s] = 0.15 h,
where h is the height of the convectively mixed layer. The
projected images of these plumes in the X-Z plane were analyzed
using a densitometer (photomultiplier tube) to...
High resolution data of moisture, temperature and wind velocity
collected by aircraft during the 1975 Air Mass Transformation
Experiment (ANTEX '75) provide information for detailed investigations
of the phenomena occurring at the top of a cloud-topped mixed
layer.
Joint frequency diagrams of humidity and temperature reveal that
for parts of...
The very stable boundary layer is a region of the atmosphere typified by large
vertical gradients of temperature and momentum. Analysis of very stable atmospheric
flows is complicated by the presence of nonlinear interactions among gravity waves, shear-driven
overturning circulations, two-dimensional vortical modes and intermittent turbulence
in various stages of...
A shallow convection scheme is derived from several data sets
(BOMEX, GATE, AMTEX, BLX83) and developed for the OSU 1-D boundary
layer model. Results of the model structure and characteristics of
the saturation point (SP) profile are compared against the constant
cloud diffusivity scheme of Tiedtke (1983) and the ECMWF...
A time dependent model of the shallow, tropical convective boundary layer is
developed and tested. To simplify the treatment of thermodynamic processes and
return to first principles of physics, conserved quantities of entropy and total
water density are used as primary model variables. In addition, a new shallow
cumulus parameterization...
Weak-wind flow in the nocturnal boundary is one of the most poorly understood problems in the field of meteorology. The understanding of weak-wind flows is essential for the improvement of regulatory dispersion models which are currently rendered invalid under weak-wind conditions and stable stratification. Recently there have been increased efforts...
The Generation IV Very High Temperature Reactor (VHTR) design is being actively
studied in various countries for application due to its inherent passive safe design,
higher thermal efficiencies, and proposed capability of providing high temperature
process heat. The pebble bed core is one of two core designs used in gas...
Predominant models for predicting rates of sediment transport face acute shortcomings when applied to coastal boundary layers. This is due to a neglect of the web of stochastic variables governing the rate of sediment dislodgement. While stochastic models do exist, the parametric extent of their validity tends to be limited,...
Sisson's formally exact series solution for momentum, heat and
mass transfer in steady two-dimensional or axi-symmetrical constant-property,
laminar boundary layer flow was examined. A new series
was proposed for the boundary condition accounting for the mass
transfer at the surface of the body on which the boundary layer is
formed....
An investigation was made to test the method of Head on the
flow about a circular cylinder with suction. The method of Head is an
approximate method of obtaining solutions to the boundary layer equations.
The method was adapted to the digital computer to facilitate
performing the calculations, and a...
Precision irrigation has made spatially explicit water management a reality. However, detailed knowledge about the spatially variable evapotranspiration is often unavailable. One example location where we can begin to understand the impact of spatial variability on evapotranspiration is at the field edge, which contains a sharp discontinuity in surface conditions....
A thermal infrared (TIR) camera is used to remotely sense the foliage temperature in a mountain valley. The foliage temperature is used as a proxy for air temperature and can be used to study and map the dynamics of the nocturnal, weak-wind boundary layer in this valley. All radiative flux...
Linkages between land use and its influence on the atmosphere have been a long-standing research area. For example, what is the impact of irrigated agriculture on downwind rainfall? Global-scale models show that moisture recycling is an important source of water for inland regions around the world, but they do not...
Lower atmospheric flux measurements are a difficult subset of atmospheric data to accurately collect. The interplay of cost, precision, specialty, resolution and repeatability compound an already difficult experimental problem. In response to this, a new, novel instrumentation approach to measuring within the atmospheric boundary layer (ABL) is introduced.
The combination...