Determination of the Coefficients "a" and "b" of the K-R Relationship for Accurate Measurement of Water Quantity Using Cellular Links in Burkina Faso

Abstract

Electromagnetic waves emitted between antennas interact with the atmosphere, undergoing absorption, scattering, and emission processes. Previous studies have shown that the relationship between specific attenuation (K) due to rain of these microwaves and the precipitation rate (R) can be modeled by an empirical power law. The coefficients "a" and "b" of this relationship, linking microwave signal attenuation to precipitation rate, vary depending on frequency, temperature, raindrop size distribution, and other parameters. Thus, it is crucial to obtain data adapted to specific geographical and environmental conditions for accurate rainfall rate assessment. In this study, we determined for the first time in Burkina Faso, the values of "a" and "b" using data from a disdrometer installed in Nazinga. These Data were collected from October 1, 2016, to September 26, 2017, over a period of about one year. These values were used in the relationship to determine rainfall rates. The Pearson correlation coefficient between the different series of values of the rain is over 0.9.  A comparison of the cumulative rainfall rates determined with the data from a rain gauge at Bobo Dioulasso airport was made. There is a perfect correlation between the values determined in Nazinga and those of Doumounia et al., 2019 with bias values ranging between -3,31 and 0.61 depending on the frequency value and its polarization. The discrepancy between the series of values and those of the rain gauge highlights the need to take local conditions into account when determining the values of "a" and "b" for a better determination of rainfall rates.