Two and a half years of country-wide rainfall maps using radio links from commercial cellular telecommunication networks

Abstract

Although rainfall estimation employing microwave links from cellular telecommunication networks is recognized as a new promising measurement technique, its potential for long‐term large‐scale operational rainfall monitoring remains to be demonstrated. This study contributes to this endeavor by deriving a continuous series of rainfall maps from a large 2.5 year microwave link data set of, on average, 3383 links (2044 link paths) covering Netherlands (∼3.5 × 104 km2), a midlatitude country (∼5°E, ∼52°N) with a temperate climate. Maps are extensively verified against an independent gauge‐adjusted radar rainfall data set for different temporal (15 min, 1 h, 1 day, 1 month) and spatial (0.9, 74 km2) scales. The usefulness of different steps in the rainfall retrieval algorithm, i.e., a wet‐dry classification method and a filter to remove outliers, is systematically assessed. A novel dew filter is developed to correct for dew‐induced wet antenna attenuation, which, although a relative underestimation of 6% to 9% is found, generally yields good results. The microwave link rainfall estimation technique performs well for the summer months (June, July, August), even outperforming interpolation of automatic rain gauge data (with a density of ∼1 gauge per 1000 km2), but large deviations are found for the winter months (December, January, February). These deviations are generally expected to be related to frozen or melting precipitation. Hence, our results show the potential of commercial microwave links for long‐term large‐scale operational rainfall monitoring.

Rainfall retrieval with commercial microwave links in São Paulo, Brazil

“…The (climatological) yearly accumulated rainfall is 1441 mm. Overeem et al (2016b) report winter time issues in rainfall estimates from CML, i.e. solid and melting precipitation.…”

“…The spatiotemporal resolution of rainfall estimates from CML varies from seconds to minutes, and from hundreds of meters to tens of kilometers. For instance, Messer et al (2012), and Overeem et al (2016b) , and 0.1 to 2.1 km per km 2 , respectively. Fencl et al (2015), and Messer et al (2012) provide 1-min rainfall estimates, whereas 1-s retrievals are obtained by Chwala et al (2016), and Doumounia et al (2014).…”

“…CML rainfall estimates are more representative of rainfall at the ground surface than those offered by satellites and/or weather radars. Networks of CML are more dense than gauge networks given their worldwide deployment 15 for telecommunication purposes (Overeem et al, 2016b;Kidd et al, 2017). This worldwide spread of CML potentially offers rainfall estimates in places where rain gauges are scarce or poorly maintained, or where ground-based weather radars are not yet deployed or cannot be afforded.…”

“…Most of the recent studies concerning rainfall retrieval from CML have focused on temperate and Mediterranean climates, e.g., Overeem et al (2016b); Messer and Sendik (2015). Thus, our evaluation is one of the first which focuses on a subtropical climate, complementing the study of Doumounia et al (2014), which focused on a semi-arid climate.…”

An urban microwave link rainfall measurement campaign

“…In typical operational settings larger 20 temporal measurement intervals such as 15 minutes are common (e.g. Overeem, et al, 2016b). In order to illustrate the performance of a basic algorithm without any sort of correction at this resolution, Fig.…”