Considering local network characteristics and environmental conditions improves rainfall estimates from commercial microwave links in Sri Lanka

<p>To improve rainfall monitoring from Commercial Microwave Links (CMLs) in a (sub)tropical climate, we adjust several parameters in the open-source R package RAINLINK that is used to retrieve rainfall rates from signal attenuation in cellular telecommunication networks.</p><p>These parameters related to local CML network characteristics (lower frequencies, longer link paths, quasi-linear <em>k-R</em> relation) and to environmental conditions (large spatial rainfall variability, convective rainfall) are considered to improve rainfall estimations across Sri Lanka. The analysis is based on data from ~1100 link paths for a 3-4 month period. The resulting rainfall depth maps are validated with multiple rain gauges across Sri Lanka at the hourly and daily time scale, and compared with space-borne weather radar data.&#160;</p><p>Until now, the majority of efforts to provide rainfall estimates from CMLs have focused on temperate climates, in Western Europe, where there generally is good coverage from weather radars and a fairly dense network of rain gauges. However, the greatest potential for this &#8216;opportunistic&#8217; source of rainfall estimation lies in those regions that lack traditional surface rainfall observations, most notably low- to middle income countries, and mountainous areas, where rain gauges are scarce or poorly maintained, and weather radars are largely unavailable.</p><p>With this study we further highlight the potential for CMLs to provide high-resolution space-time rainfall observations in the tropics for use in a wide range of hydrometeorological applications, such as forecasting rainfall-induced natural hazards (flash floods, landslides) and validating satellite rainfall products.</p>