First Implementation of CML-Based Rainfall Estimation in Türkiye: Focus on İstanbul

 

Rainfall detection and monitoring rely heavily on ground observation stations, meteorological radars, and microwave/infrared sensors onboard satellite platforms. However, the irregular distribution of observation stations, radar limitations due to ground clutter and topographic blockage, and the low spatial and temporal resolutions of polar-orbiting satellites—which carry the microwave sensors providing direct precipitation data—complicate rainfall tracking in urban areas during flash floods. To overcome these limitations, there is growing interest in approaches that utilize signal attenuation data from Commercial Microwave Links (CML) within telecommunication networks. Rain-induced attenuation on these CML signals provides critical information for estimating precipitation type and intensity.

This study aims to perform the first CML-based high-resolution rainfall estimation in Türkiye, focusing on İstanbul—a megacity with a population of 16 million, complex micro-climatic features, and high flood vulnerability. The methodological framework integrates signal data from thousands of CML lines operated by Vodafone Türkiye with a network of 45 rain gauges belonging to the Turkish State Meteorological Service (TSMS). The proposed model architecture includes wet-dry classification of signal data, dynamic correction of additional signal losses caused by antenna wetting (wet antenna effect), and optimization of the attenuation-rain rate relationship tailored to local precipitation characteristics. This paper presents the data processing infrastructure, station-based validation methods, and the potential contributions of this pioneering CML-based rainfall retrieval system to the urban hydro-meteorological monitoring capacity of İstanbul.

Keywords: Commercial Microwave Link (CML), Rainfall, İstanbul, Türkiye.