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A study of the relationship between ageostrophy and dynamical periodicities of the tropical Pacific Boundary LayerMcCandlish, Cole B. 28 April 1994 (has links)
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 calculated along with a spectra for nighttime outgoing
longwave radiation (OLR) data (centered at a gridpoint near the island station)
and compared in order to investigate the relationship between the ageostrophy
and dynamical phenomena of the tropical Pacific.
Methods of boundary layer top diagnosis are compared. Data derived methods
include temperature inversion detection, humidity jump detection, and wind shear
detection. The model based diagnosis method uses a Richardson number scheme.
Comparisons between data derived methods and model based methods show good
agreement. Correlation coefficients for comparisons are all above 0.91.
In each sample spectra, the dominant peak corresponds to the frequency of
the annual cycle. With an estimated annual cycle removed from each of the
time series the nighttime (12 GMT) sample spectra for PBL top pressure shows
a peak at a frequency that corresponds to the 30-60 day Intraseasonal Oscillation
(ISO). Removal of an estimated annual cycle was unsuccessful for the daytime (0
GMT) sample spectra for PBL top pressure, PBL mean specific humidity, and the
ageostrophic parameter. Sample spectra of the ageostrophic parameter show peaks
in the ISO frequency range for both 12 GMT and 0 GMT even before removal
of the annual cycle was attempted. The ISO range peaks remained in the 12
GMT ageostrophic parameter spectrum when the annual cycle was successfully
removed.
The nighttime OLR spectrum is dominated by the annual cycle peak and its
harmonics. The OLR spectrum also shows a significant peak in the ISO range
of periods. Removal of an estimated annual cycle intensifies the peak in the ISO
range.
The ageostrophic parameter time series is compared to the results of an EOF
analysis performed on the same 8 years of radiosonde humidity measurements.
The first three EOF modes of specific humidity give sample spectra which are
dominated by the annual cycle. With the annual cycle removed the sample spectra
of the first and third EOF modes of specific humidity both show significant peaks
in the ISO frequency range, while the second EOF mode sample spectrum is
dominated by two peaks at frequencies corresponding to periods of approximately
4 and 5 months.
The presence of common frequencies in the ISO range of the power spectra
of the ageostrophic parameter (a measure of divergence), the nighttime OLR (a
measure of deep convection), the nighttime planetary boundary layer top, and the
first EOF mode of specific humidity, lends support to theories that relate the ISO
to the interaction of dynamics and moist processes. / Graduation date: 1995
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Seasonal variation of wind gustiness in a portion of the Columbia GorgeBaker, Robert W. 16 June 1976 (has links)
The seasonal variation of wind speed fluctuations is studied at
four locations in The Dalles area of the Columbia River Gorge.
Three of the sites are located in or near the valley floor while the
fourth site is on top of a 900 m (3000 ft) ridge just north of The Dalles.
The speed fluctuations or gustiness at these sites varies with terrain
roughness, wind speed, and atmospheric stability.
Due to the channelling effects of the Gorge, wind flow in The
Dalles area is predominantly upriver or downriver. Strongest winds
occur from the west at all four of the sites that were analyzed.
Highest gustiness values occurred at the Martin Marietta site
located near the rugged foothills of the eastern slopes of the Cascade
Mountain Range. Moderate gustiness values were common at KCIV
located on the top of the ridge north of The Dalles and at the D.C.
Test Site surrounded by rolling hills. Smoothest flow was found along
the relatively level valley floor at The Dalles Dam.
Gustiness in relation to wind speed varied at all four sites.
Gustiness values increased with speed through the moderate speed
range at KCIV while gustiness decreased with speed at The Dalles
Dam and the Martin Marietta site. No distinct relationship was found
at the D.C. Test Site.
At KCIV changes in gustiness are directly related to the amount
of solar insolation and hence the atmospheric stability. Gustiness
values were highest during the summer and daytime values were
greater than those at night during both winter and summer. In contrast,
at the other three sites near or on the valley floor no distinct
relationship between the stability variations and the changes in gustiness
could be found. Results indicated that the gustiness values
during the winter at these three locations exceeded those during the
summer. It appears that the unstable nature of the post frontal
wintertime air mass is responsible for the strong and turbulent
northwest flow.
Although moderate speed fluctuations were common at KCIV,
this site is the most appealing of the four locations for wind power
generation due to the persistency of moderately strong winds during
both summer and winter. Least attractive of the four sites is Martin
Marietta where high gustiness values along with weak winter winds
provide little usable wind energy. / Graduation date: 1977
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Analysis of surface wind stress and ocean circulations simulated by general circulation modelsLee, Sheng-wei 01 July 1982 (has links)
Graduation date: 1983
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The influence of cross-winds on the performance of natural draft dry-cooling towers /Du Preez, Abraham Francois. January 1992 (has links)
Dissertation (Ph. D.)--University of Stellenbosch, 1992. / Bibliography. Also available via the Internet.
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Quantitative uncertainty of chemical plume transport in low wind speeds using measured field data and stochastic modeling /Wannberg, Veronica Elaine, January 2008 (has links) (PDF)
Thesis (M.S.)--Brigham Young University. Dept. of Civil and Environmental Engineering, 2008. / Includes bibliographical references (p. 51-54).
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Wind scatterometry with improved ambiguity selection and rain modeling /Draper, David, January 2003 (has links) (PDF)
Thesis (Ph. D.)--Brigham Young University. Dept. of Electrical and Computer Engineering, 2003. / Includes bibliographical references (p. 231-237).
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Time series analysis of meteorological data: wind speed and direction彭運佳, Pang, Wan-kai. January 1993 (has links)
published_or_final_version / abstract / toc / Statistics / Master / Master of Philosophy
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Tidal winds in the upper atmosphere.De Beco, Jean-Paul. January 1970 (has links)
No description available.
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Wind-driven circulation : impact of a surface velocity dependent wind stressDuhaut, Thomas H. A. January 2006 (has links)
The use of an ocean surface velocity dependent wind stress is examined in the context of a 3-layer double-gyre quasigeostrophic wind-driven ocean circulation model. The new wind stress formulation results in a large reduction of the power input by the wind into the oceanic circulation. This wind stress is proportional to a quadratic function of Ua--u o, where Ua is the wind at 10m above the ocean surface and uo is the ocean surface current. Because the winds are typically faster than the ocean currents, the impact of the ocean surface velocity on the wind stress itself is relatively small. However, the power input is found to be greatly reduced with the new formulation. This is shown by simple scaling argument and numerical simulations in a square basin. Our results suggest that the wind power input may be as much as 35% smaller than is typically assumed. / The ocean current signature is clearly visible in the scatterometer-derived wind stress fields. We argue that because the actual ocean velocity differs from the modeled ocean velocities, care must be taken in directly applying scatterometer-derived wind stress products to the ocean circulation models. This is not to say that the scatterometer-derived wind stress is not useful. Clearly the great spatial and temporal coverage make these data sets invaluable. Our point is that it is better to separate the atmospheric and oceanic contribution to the stresses. / Finally, the new wind stress decreases the sensitivity of the solution to the (poorly known) bottom friction coefficient. The dependence of the circulation strength on different values of bottom friction is examined under the standard and the new wind stress forcing for two topographic configurations. A flat bottom and a meridional ridge case are studied. In the flat bottom case, the new wind stress leads to a significant reduction of the sensitivity to the bottom friction parameter, implying that inertial runaway occurs for smaller values of bottom friction coefficient. The ridge case also gives similar results. In the case of the ridge and the new wind stress formulation, no real inertial runaway regime has been found over the range of parameters explored.
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Statistical downscaling prediction of sea surface winds over the global oceanSun, Cangjie 28 August 2012 (has links)
The statistical prediction of local sea surface winds at a number of locations over
the global ocean (Northeast Pacific, Northwest Atlantic and Pacific, tropical Pacific
and Atlantic) is investigated using a surface wind statistical downscaling model based
on multiple linear regression. The predictands (mean and standard deviation of both
vector wind components and wind speed) calculated from ocean buoy observations on
daily, weekly and monthly temporal scales are regressed on upper level predictor fields
(derived from zonal wind, meridional wind, wind speed, and air temperature) from
reanalysis products. The predictor fields are subject to a combined Empirical Orthogonal
Function (EOF) analysis before entering the regression model. It is found that
in general the mean vector wind components are more predictable than mean wind
speed in the North Pacific and Atlantic, while in the tropical Pacific and Atlantic the
difference in predictive skill between mean vector wind components and wind speed is
not substantial. The predictability of wind speed relative to vector wind components
is interpreted by an idealized Gaussian model of wind speed probability density function,
which indicates that the wind speed is more sensitive to the standard deviations
(which generally are not well predicted) than to the means of vector wind component
in the midlatitude region and vice versa in the tropical region. This sensitivity of
wind speed statistics to those of vector wind components can be characterized by a
simple scalar quantity theta=arctan(mu/sigma) (in which mu is the magnitude of average vector
wind and sigma is the isotropic standard deviation of the vector winds). The quantity theta
is found to be dependent on season, geographic location and averaging timescale of
wind statistics.
While the idealized probability model does a good job of characterizing month-to-month
variations in the mean wind speed based on those of the vector wind statistics,
month-to-month variations in the standard deviation of speed are not well modelled.
A series of Monte Carlo experiments demonstrates that the inconsistency in the characterization
of wind speed standard deviation is the result of differences of sampling
variability between the vector wind and wind speed statistics. / Graduate
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