Truncated Gamma Drop Size Distribution Models for Rain Attenuation in Singapore

Abstract-Rain drop size distributions (DSD) are measured with disdrometers at five different climatic locations in the Indian tropical region. The distribution of drop size is assumed to be lognormal to model the rain attenuation in the frequency range of 10-100 GHz. The rain attenuation is estimated assuming single scattering of spherical rain drops. Different attenuation characteristics are observed for different regions due to the dependency of DSD on climatic conditions. A comparison shows that significant differences between ITU-R model and DSD derived values occur at high frequency and at high rain rates for different regions. At frequencies below 30 GHz, the ITU-R model matches well with the DSD generated values up to 30 mm/h rain rate but differ above that. The results will be helpful in understanding the pattern of rain attenuation variation and designing the systems at EHF bands in the tropical region.

Section: Introductionmentioning

confidence: 99%

RAIN ATTENUATION MODELING IN THE 10-100 GHz FREQUENCY USING DROP SIZE DISTRIBUTIONS FOR DIFFERENT CLIMATIC ZONES IN TROPICAL INDIA

Das¹,

Maitra²,

Shukla³

2010

“…The two distributions are the lognormal and modified gamma functions. The general expression to describe the rain rate, R, (in mm/hr) from the distrometer is given in [15]:…”

Section: Dsd Models With the Methods Of Moments (Mom)mentioning

confidence: 99%

“…The Laws and Parsons [10] and Marshall and Palmer [11] are based on the exponential distribution, and generally used in temperate regions. The other two, Lognormal and modified gamma distributions, are peculiar to tropical and sub-tropical regions [12][13][14][15][16]. Researchers from Brazil [14], India [17], Malaysia [18], and Nigeria [19,20], all from the tropical regions, have employed the latter two distribution functions to model the raindrop size for all kinds of rainfall characteristics in their respective regions.…”

Section: Introductionmentioning

confidence: 99%

Obtaining Raindrop Size Model Using Method of Moment and Its Applications for South Africa Radio Systems

Malinga¹,

Owolawi²

2013

Abstract-In this paper, the Raindrop Size Distribution (DSD) modeling and analysis are presented.Drop sizes are classified into different rain types, namely: drizzle, widespread, shower and thunderstorm. The gamma and Lognormal distribution models are employed using the method of moments estimator, considering the third, fourth and sixth order moments. The results are compared with the existing raindrop size distribution models such as the three parameter lognormal distribution proposed by Ajayi and his colleagues and Singapore's modified gamma and Lognormal models. This is then followed by the implementation of the proposed raindrop size distribution models on the computation of the specific rain attenuation. Finally, the paper suggests a suitable raindrop size distribution model for the region with its expressions. The proposed models are very useful for the determination of rain attenuation for terrestrial and satellite systems.

“…The actual parameters for each rain rate are shown in Table 5. The corresponding values of N T , µ ln , and σ ln , for the lognormal distribution, using the MoM, are: The gamma distribution parameters using the method of moments are determined as follows [10,14]:…”

Section: Methods Of Moments For Raindrop Size Distributionmentioning

confidence: 99%

“…The gamma distributions used are those obtained from [17] for Indonesia, and [14,21] for Singapore. The corresponding coefficients are shown in Table 7 and Table 8.…”

Section: Comparison With Other Tropical Raindrop Size Distributionsmentioning

confidence: 99%

Raindrop Size Distribution Modeling for Radio Link Design Along the Eastern Coast of South Africa

Afullo¹

2011

Abstract-A study of the raindrop size distribution along the eastern coast of South Africa (Durban) is presented. The Biweight kernel estimator based on distometer measurement is used to determine the best estimate of the measured raindrop size probability distribution function (pdf). The best kernel estimator, which results in the lowest integral square error (ISE), is used to measure the closeness of the estimated lognormal and gamma pdf of raindrop size to the measured raindrop size distribution. It is established that the optimised lognormal pdf slightly outperforms the optimised gamma pdf in terms of the mean ISE and the RMSE values, with mean ISE values of 0.026 for lognormal and 0.04 for gamma distributions, respectively, and corresponding mean RMSE values of 0.073 and 0.081, respectively. The method-of-moments gamma and lognormal distributions are observed to be worse estimators of the measured pdf than the two optimized distributions. The N (D) distributions using the optimised lognormal and gamma distributions for the region are compared with those for different tropical regions, namely, India, Singapore, Nigeria, Indonesia, and Brazil. While the Indian lognormal N (D) model gives the highest peak for low raindrop sizes for all rain rates, Durban's gamma and lognormal models exhibit the widest raindrop size spread over all rain rates ranging from 1-120 mm/h. Finally, the specific attenuation due to rain using the Durban models are compared against the ITU-R models and actual measurements over a 19.5 GHz LOS link; the results indicate a need for further work involving both distrometer and radio link measurements for rain rates exceeding 30 mm/h in the eastern coast of South Africa.