Abstract
Rain plays a major impairment factor for propagation of electromagnetic waves in atmosphere for systems operating at frequencies above 10 GHz. Several effects are noted such as depolarization, scintillation, interference due to scattering and extra attenuation which seems to increase with frequency. To mitigate its effect in satellite communication, knowledge of local rainfall statistics is necessary which act as milestone for design of radio link. Rain attenuation is best visualize by the 1-min rainfall rate statistic but the measurement of this rain rate distribution is rare on a worldwide basis and observation of rain rate are done with longer integration times typically 30 min or more. In this paper, efforts have been made to develop model that can convert rain rate complementary cumulative distribution function to shorter integration times. The average relative error margin of about 5, 14, 43, 71 and 115 % are noted for 5 to 1-, 10 to 1-, 20 to 1, 30 to 1- and 60 to 1-min respectively from ITU-R P.837-6 method which have been analyzed in further section of this article. The empirical natures of conversion methods as such Segal method, Burgueno’s method, Chebil and Rahman method and Logarithmic model are studied along with the proposed new model that seems to be applicable in derivation of 1-min rain rate of the South Korea rain rate statistics. International Telecommunication Union-Radio communication Sector (ITU-R) has developed a recommendation ITU-R P.837-6 that enables the user to estimate the local 1-min rainfall rate statistical distribution which is compared with calculated 1-min rain rate distribution from experimental 1-min rainfall accumulation. Unfortunately, ITU-R P.837-6 estimated 1-min values show greater error percentages. In order to get better approximation of local 1-min rain rate estimation, a novel method is proposed and it’s efficiency have been compared with rainfall rate statistics obtained from nine different locations in the South Korea.
Highlights
Due to increased congestion of communication spectrum below 10 GHz, there is an increasing need for the use of the short centimeter and millimeter wave parts of the spectrum in both terrestrial and satellite communication paths
Rainfall data is effectively recorded by Korea Meteorological Administration (KMA), a central governmental organization of the Republic of Korea under the Ministry of Environment (MOE), which has developed a digital system for accurate measurement of 1-min rainfall amount since 2004 through the use of Tipping bucket rain gauge over several sites some of which are shown in Fig. 1 with the intensity to develop the South Korea’s own numerical prediction model
In order to better visualize the 1-min rain rate distribution data against International Telecommunication Union-Radio communication Sector (ITU-R) P.837-6 (2012) predicted values for several time percentage over the nine sites in the South Korea at equiprobable exceedance probability (0.001 ≤ P ≤ 0.1 %), CCDFs of rain rate are plotted which are shown from Figs. 4a–c, 5a, b
Summary
Due to increased congestion of communication spectrum below 10 GHz, there is an increasing need for the use of the short centimeter and millimeter wave parts of the spectrum in both terrestrial and satellite communication paths. Rainfall data of longer integration time relatively on hourly basis is readily available, 5or 10-min accumulation data are recorded by several weather services, but 1-min accumulation interval data is available from only special observations at a few locations Under this scenario, derivation of model for statistical distribution of short time interval requires the limited number of available observation to be combined in order to provide statistically valid empirical distribution function (Crane 1996). The rain rate characteristic of the South Korea was studied to predict 1-min rain rate statistic in Jung et al (2008), which was based on the 2 years of rain events. With three years of rainfall data, a conversion method for rainfall rate with various integration time was proposed (Lee et al 1994) base on linear and logarithmic approach. A model for rain drop size distribution (Park et al 2002), was introduced which describe extended gamma distribution function
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