Abstract
When monitoring rain rates by weather radar in semi-arid regions and when measuring precipitation at an arid region; precipitation particles, rain, or snowflakes may evaporate before reaching the ground. This evaporation is regarded as the Virga phenomenon and may cause a false representation of the precipitation amount that actually reaches the ground. The Virga occurs naturally when the air below the cloud is relatively dry, and continues until humidity below the base of the cloud is high enough to decrease the evaporation. This paper suggests a method of combining near ground Commercial Microwave Links (CMLs) attenuation measurements, in conjunction with data from several weather radar beams, observing different heights, in order to produce estimates of the vertical profile of the rain-rate values and of the Cloud Base level (ClB). We propose an estimation method and demonstrate it using real-data measurements of two major storm events in the dead-sea area. We verify the validity of the estimation near ground by comparing the results with Rain Gauges’ (RGs) actual measurements in addition to comparing the estimated ClB with real ClB observations of a nearby weather station. While the storm events selected indeed show great evaporation, the suggested method provides excellent results, with a correlation of up to 0.9615, when correlated with real measurements of RGs of two storms from 2014 to 2016.
Highlights
The attenuation recorded at Commercial Microwave Links (CMLs), due to precipitation, produced many studies for over more than a decade while continuing to be the source of new research in the field of precipitation estimation, and rain estimation in particular, based on Received SignalLevel (RSL) measurements
As CMLs are widespread with high density, and cover long areas mainly across lengths of 1–30 km, in this paper we suggest a method of profiling vertical rain-rates in arid areas using a combination of several radar beams, observing at different heights, along with cellular links, in order to achieve more accurate above-ground level rain-rates where the Virga may affect the radar measurements of rain, while verifying the suggested method on two cases of storms in the semi-arid zone of Israel where the Virga phenomenon, i.e., the evaporation of rain was of significance
The location of southern Israel was selected for our experiment site, as this region is of semi-arid nature, and can enable the occurrence of the Virga phenomenon
Summary
The attenuation recorded at Commercial Microwave Links (CMLs), due to precipitation, produced many studies for over more than a decade while continuing to be the source of new research in the field of precipitation estimation, and rain estimation in particular, based on Received SignalLevel (RSL) measurements. The rain-induced-attenuation of the transmission signal over CMNs links, is calculated as the Transmitted Signal Level (TSL) at the first base station of the link after deducting the RSL in the opposite side of the CML, and after removal of a base zero-level; it was shown to be directly connected to the amount of rain per unit of time in the CML’s path by the Power-Law relation [1] Based on this Power-Law relation, the ongoing study has produced many methods, for rainfall monitoring, such as but not limited to, rainfall estimation [2,3,4], rain detection [5,6], and rainfall mapping [7,8].
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