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Tel Aviv University (2018)

On the use of commercial microwave links for rainfall profile estimation in semi-arid areas

Raich Roi

Titre : On the use of commercial microwave links for rainfall profile estimation in semi-arid areas

Auteur : Raich Roi

Etablissement de soutenance : Tel Aviv University

Grade : Master of Science (MS) Engineering 2018

Résumé
Over the past decade, the rain-induced-attenuation over Commercial Microwave Links (CMLs) has been the source of many studies, and is part of an on-going research of precipitation estimation based on the Received Signal Level (RSL) measurements. While the common practice for precipitation estimation involves the usage of rain gauges and weather radars, a novel method was suggested by Messer et al. in 2006, involving existing CMLs used in the backhaul communication links, for the sake of precipitation monitoring. Both rain gauges and CML measurements have been proven as good and trustworthy methods for liquid precipitation (i.e. rainfall) monitoring. Radar systems, on the other hand, can detect other types of precipitation as well. However, radar systems are known for accuracy issues when measuring near-ground precipitation in the distance. In addition, when monitoring rain rates in semi-arid regions and when measuring precipitation at an arid region, precipitation particles, rain, or snow flakes, may evaporate before reaching the ground. This evaporation is regarded as the Virga phenomenon and is occurring naturally when the air below the cloud is relatively dry, and will continue until humidity below the base of the cloud is high enough to decrease the evaporation and then, the precipitation will reach the ground. This work suggests, for the first time, a method for profiling the vertical rain-rates in arid areas using a combination of several radar beams, which observe at different heights above ground along with the cellular links in order to achieve more accurate Above Ground Level (AGL) rain-rates where the Virga may affect the radar measurements of rain. This is done by estimating the cloud base level and the rain rate at the cloud base level. In addition, an approach for quantitating the Virga phenomena, using CMLs will be introduced. Moreover, so far, most of the studies of using CMLs for rain rate estimation were tested for non-arid regions, where the Drop Size Distribution (DSD) of rain may be often quite different than the DSD in arid regions. This work, will discuss a calibration procedure for the Power-Law relation, in regard to arid areas. In this work we also validate our result by testing it on two events in a semiarid location in south-eastern Israel.

Mots clés : Signal detection Radar meteorology Rain and rainfall — Forecasting Signal processing עיבוד אותות גשמים — חיזוי רדאר מטראולוגי גילוי אותות

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