Spelling suggestions: "subject:"main dnd rainfall"" "subject:"main dnd ainfall""
311 |
Preliminary processing and evaluation of radar measurements in satellite-path propagation researchFriberg, Carol Diane 15 November 2013 (has links)
Rain and other precipitation cause attenuation and depolarization of high frequency satellite signals. Some characteristics of rain can be measured by dual-polarized radar. These characteristics can then be used to predict the effects of the rain on satellite-path propagation.
This thesis describes briefly the theory of radar and satellite link measurements. Methods for calibrating the equipment and deriving actual experimental values from measured power are presented in detail. A set of computer programs to approximately predict radar and link values from measured rain rate are developed. Predicted and measured values may then be compared by a researcher to evaluate system operation and assess the importance of the event data. A discussion of the use of sampled data and these comparisons concludes the report. / Master of Science
|
312 |
Contaminant removal from impervious pavements and its relationship with raindrop impact energy, cumulative kinetic energy of rainfall events, and rainwater pHAngelotti, Robert W. January 1985 (has links)
The relationships between contaminant removal from impervious pavements and raindrop impact energy, cumulative kinetic energy of rainfall events, and rainwater fit were evaluated. A commercial urban area was chosen to perform simulated rainfall experiments. The runoff from these experiments was collected and analyzed for total suspended solids, volatile suspended solids, total Kjeldahl nitrogen, soluble Kjeldahl nitrogen, oxidized nitrogen, ammonia, ortho-phosphate, total phosphorus, soluble phosphorus, total lead and total zinc. Raindrop impact energy, rainfall intensity, rainfall duration, and rainwater pH were factors which were varied to examine their effect on contaminant wash-off phenomena. The present exponential decay theory of contaminant removal was verified and modified to incorporate the cumulative kinetic energy of rainfall events. An empirical model for contaminant removal was also developed. Data showed that both raindrop impact energy and cumulative storm energy had significant effects on contaminant removal. Contaminant wash-off was found to be independent of rainwater pH except for solids removal at low rain intensities. Additional results indicated that there is a "threshold impact energy" necessary before significant removal of contaminants associated with insoluble material can occur. The kinetic energy attributed to surface runoff overflow was found to be very important in the mechanisms responsible for contaminant removal at high rainfall intensities. / M.S.
|
313 |
A compendium of Virginia hydrologyYang, Yung-Chi 27 April 2010 (has links)
Engineers engaged in watersupply or power projects are often faced with the problem of dealing the adequency of the supply, as well as that of the extremes of flow on which the safety of hydraulic structures depends. / Master of Science
|
314 |
Millimeter wave scattering by rain in an antenna's near fieldBarksdale, Harry January 1988 (has links)
One of the important considerations in radio link analysis is the signal degradation that accompanies rainfall in a link’s path. Random scattering by rain can adversely affect a propagating wave in two ways. First, it results in attenuation and depolarization of the coherent field which is associated with the forward propagating wave. ln addition to this, random scattering gives rise to an incoherent field component that can further degrade the signal in a manner similar to multipath.
This dissertation presents an analysis of the coherent and incoherent effects of rain scatter at millimeter-wave frequencies. Within it, the scattering properties of individual spherical and non-spherical are quantified. Spherical raindrops are treated using the Mie theory and non-spherical ones analyzed with Waterman’s Extended Boundary Condition Method. Computed values of forward scattering amplitudes and scattering cross-sections for both spherical and non-spherical raindrops at 80, 45, 70 and 90 GHz are presented; the computer programs used to obtain the scattering data are also provided. Following the analysis of individual raindrops scatterers, the Foldy·Lax Twersky integral equations for coherent field and incoherent intensity are used to derive the coherent and incoherent outputs of a generic radio receiver. In doing so, the effects of scattering in an antenna’s far-field and radiating near field (Fresnel Region) are analyzed. Through this analysis, it is shown that the expected system outputs are essentially the same in either case.
Using the computed raindrop scattering parameters and models developed for the coherent and Incoherent system outputs, specific cases are Iooked at for 30, 45, 70 and 90 GHz operation and theoretical data presented. The data consists of the predicted attenuation and Isolation of the coherent signal and the ratio of coherent to Incoherent power In the presence of rain. From the latter it Is found that during heavy rainfall, the Incoherent effects can be appreciable and should be taken into account. / Ph. D.
|
315 |
Spatial variability of surface rainfall and its impact on radar retrievalDatta, Saswati 01 April 2001 (has links)
No description available.
|
316 |
An algorithm for identifying rain contaminated ocean wind vector cells in a hurricane environment using the seawinds scatterometer on quikSCATDevan, Vinod 01 July 2001 (has links)
No description available.
|
317 |
Improving the Reliability of Compartmental Models: Case of Conceptual Hydrologic Rainfall-Runoff ModelsSorooshian, Soroosh, Gupta, Vijai Kumar 08 1900 (has links)
No description available.
|
318 |
CALIBRATION OF RAINFALL-RUNOFF MODELS USING GRADIENT-BASED ALGORITHMS AND ANALYTIC DERIVATIVESHendrickson, Jene Diane, Sorooshian, Soroosh 05 1900 (has links)
In the past, derivative-based optimization algorithms have not
frequently been used to calibrate conceptual rainfall -riff (CRR)
models, partially due to difficulties associated with obtaining the
required derivatives. This research applies a recently- developed
technique of analytically computing derivatives of a CRR model to a
complex, widely -used CRR model. The resulting least squares response
surface was found to contain numerous discontinuities in the surface
and derivatives. However, the surface and its derivatives were found
to be everywhere finite, permitting the use of derivative -based
optimization algorithms. Finite difference numeric derivatives were
computed and found to be virtually identical to analytic derivatives.
A comparison was made between gradient (Newton- Raphsoz) and
direct (pattern search) optimization algorithms. The pattern search
algorithm was found to be more robust. The lower robustness of the
Newton-Raphsoi algorithm was thought to be due to discontinuities and a
rough texture of the response surface.
|
319 |
Temporal distribution of storm rainfall on the Witwatersrand and its effect on peak flows.Cross, Anthony Leighton January 1991 (has links)
A project report submitted to the Faculty of
Engineering, University of the Witwatersrand,
Johannesburg, in partial fulfilment of the requirements
for the degree Of Master Of Science in Engineering. / The temporal distribution of rainfall can have a
significant effect on peak runoff, especially so in the
small catchments that are typical of the Witwatersrand.
This report investigates the shape of the natural
hyetoraph and its use in the analysis of peak runoff.
It describes the climatology of the sub-continent and
rain-producing systems. Then more specifically,
aspects of rainfall over Johannesburg are discussed.
Some Of the more commonly-used temporal distributions
of rainfall are reviewed and the relationship between
intensity-time distributions and mass curves is
illustrated.
Mass curves are derived using data from a rain gauge in
Norwood, Johannesburg. The data is analysed with the
assistance of a computer program and classified into
quartiles. The quartiles are further analysed in an
attempt to define their characteristics in greater
detail.
The mass curves are used wIth a hydrological model to
generate hydrographs. The values of runoff peaks are
found to be comparable with those obtained using
currently accepted temporal rainfall distributions. / AC 2018
|
320 |
The dynamics and energetics of tropical-temperature troughs over Southern AfricaD'Abreton, Peter Charles January 1992 (has links)
Water vapour content and transport over southern Africa and adjacent oceans
are examined. Early summer rainfall over the northern and central interior of
South Africa tends to be associated with baroclinic controls whereas late-summer
rainfall is barotropic in origin. This is reflected in the northwesterly water vapour
transport from an Atlantic Ocean source by middle and upper tropospheric
westerly waves in early summer. A thermally indirect Ferrel cell, indicated-from
energetics, COpIU1nSthe· temperate nature of the early-summer atmosphere over
southern Africa. Late summer water vapour transport, in contrast, is strongly
from the tropics, with' a reduced eddy component, indicating an important
tropical control on late SUmmerrainfall especially in terms of fluctuations in the
position of the ascending limb of .the Walker cell Over southern Africa. The
Hadley cell is of importance to the late summer rainfall in that dry (wet) years
are associated with an anomalous cell OVereastern (central) South Africa such
that low level vapour transport is southerly (northerly). The anticyclone over the
eastern parts of southern Africa, coupled with. a trough over the interior
(especially at the 700 hPa pressure level), is important for the introduction of
water vapour over the subcontinent in wet and dry years and for
tropical-temperate trough case studies. Water vapour source regions differ from
early summer (Atlantic Ocean) to late summer (Indian Ocean), which reflects the
temperate. control on early and the tropical control on late summer circulation.
The convergence of water vapour over southern Africa in wet years and during
tropical-temperate troughs is not only important for cloud formation and
precipitation, but also for latent heat release associated with convergent water
vapour. Diabatic heating decreases the stability of the tropical atmosphere
thereby resulting in increased vertical motion. It also forces an anomalous Badley
circulation during wet late summers and tropical-temperate trough .cases as a
result of complex energy transformations. Heating increases eddy available
potential energy which is converted to zonal available potential energy by a
thermally indirect circulation found in the tropics. The zonal potential energy is
then converted to kinetic energy by the thermally direct Badley cell. Water
vapour and its variations are thus important for the precipitation, heating and
SUbsequent energy of the subtropical southern African atmosphere, / GR 2017
|
Page generated in 0.0774 seconds