Correlation of rain dropsize distribution with rain rate derived from disdrometers and rain gauge networks in Southern Africa.
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Date
2011
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Abstract
Natural phenomena such as rainfall are responsible for communication service disruption, leading
to severe outages and bandwidth inefficiency in both terrestrial and satellite systems, especially
above 10 GHz. Rainfall attenuation is a source of concern to radio engineers in link budgeting and
is primarily related to the rainfall mechanism of absorption and scattering of millimetric signal
energy. Therefore, the study of rainfall microstructure can serve as a veritable means of optimizing
network parameters for the design and deployment of millimetric and microwave links. Rainfall
rate and rainfall drop-size are two microstructural parameters essential for the appropriate
estimation of local rainfall attenuation. There are several existing analytical and empirical models
for the prediction of rainfall attenuation and their performances largely depend on regional and
climatic characteristics of interest. In this study, the thrust is to establish the most appropriate
models in South African areas for rainfall rate and rainfall drop-size.
Statistical analysis is derived from disdrometer measurements sampled at one-minute interval over
a period of two years in Durban, a subtropical site in South Africa. The measurements are further
categorized according to temporal rainfall regimes: drizzle, widespread, shower and thunderstorm.
The analysis is modified to develop statistical and empirical models for rainfall rate using gamma,
lognormal, Moupfouma and other ITU-R compliant models for the control site.
Additionally, rain drop-size distribution (DSD) parameters are developed from the modified
gamma, lognormal, negative exponential and Weibull models. The spherical droplet assumption is
used to estimate the scattering parameters for frequencies between 2 GHz and 1000 GHz using the
disdrometer diameter ranges. The resulting proposed DSD models are used, alongside the scattering
parameters, for the prediction and estimation of rainfall attenuation.
Finally, the study employs correlation and regression techniques to extend the results to other
locations in South Africa. The cumulative density function analysis of rainfall parameters is applied
for the selected locations to obtain their equivalent models for rainfall rate and rainfall DSD
required for the estimation of rainfall attenuation.
Description
Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2011.
Keywords
Rain and rainfall--South Africa--Measurement., Raindrops--Size., Millimetre wave communication systems., Microwave communication systems--South Africa., Theses--Electronic engineering.