Evaluation of error components in rainfall retrieval from collocated commercial microwave links

Abstract. Opportunistic rainfall sensing using commercial microwave links (CMLs) operating in telecommunication networks has the potential to complement conventional rainfall monitoring, however, the diversity of sensors and their errors are difficult to handle. This analysis empirically evaluates errors of CML observations that manifest discrepancies between collocated sensors without reference rainfall measurements. Collocated CMLs are evaluated as independent rainfall sensors, which enable us to assess the effect of hardware homogeneity and measurement consistency using CML observations at twelve sites within a real telecommunication network in Prague. The evaluation considers 33 rainfall events distinguishing between stratiform and convective rainfall type in the period 2014 and 2016, monitored in 1-min temporal resolution. Collocated CMLs of identical and different frequencies are evaluated, and different rainfall types are discussed. The collocated commercial microwave links are in excellent agreement. The inherent error of rain-induced attenuation for paired independent commercial microwave links is 0.4 dB. The high correlation of the rainfall intensity measurements between the collocated sensors was obtained in a range between 0.96 and 0.99, and the root mean square error ranges between 0.4 mm h⁻¹ and 1.7 mm h⁻¹. This confirms homogeneous behaviour of the hardware in a real network. Therefore, the data of CMLs of the same characteristics can be processed with identi-cal parameters for rainfall retrieval models.