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 in CML observations that manifest discrepancies between collocated sensors without reference to rainfall measurements. Collocated CMLs are evaluated as independent rainfall sensors and enable us to assess the effect of hardware homogeneity and measurement consistency using CML observations at 12 sites within a real telecommunication network in Prague. The evaluation considers 33 rainfall events distinguishing between stratiform and convective rainfall types in the period of 2014–2016, monitored at 1 min temporal resolution. Collocated CMLs of identical and different frequencies are evaluated, and different rainfall types are discussed. The collocated CMLs are in excellent agreement. The inherent error in rain-induced attenuation for paired independent CMLs is 0.4 dB. The high correlation of the rainfall intensity measurements between the collocated sensors was obtained in a range of 0.96 to 0.99, and the root mean square error ranges from 0.4 to 1.7 mm h−1. This confirms the homogeneous behaviour of the hardware in a real network. Therefore, the data of CMLs of the same characteristics can be processed with identical parameters for rainfall retrieval models.