Abstract. There is a growing interest in emerging opportunistic sensors for precipitation, motivated by the need to improve its quantitative estimates at the ground. The scope of this work is to present a preliminary assessment of the accuracy of commercial microwave link (CML) retrieved rainfall rates in Northern Italy. The CML product, obtained by the open-source RAINLINK software package, is evaluated on different scales (single link, 5 km×5 km grid, river basin) against the precipitation products operationally used at Arpae-SIMC, the regional weather service of Emilia-Romagna, in Northern Italy. The results of the 15 min single-link validation with nearby rain gauges show high variability, which can be caused by the complex physiography and precipitation patterns. Known sources of errors (e.g. the attenuation caused by the wetting of the antennas or random fluctuations in the baseline) are particularly hard to mitigate in these conditions without a specific calibration, which has not been implemented. However, hourly cumulated spatially interpolated CML rainfall maps, validated with respect to the established regional gauge-based reference, show similar performance (R2 of 0.46 and coefficient of variation, CV, of 0.78) to adjusted radar-based precipitation gridded products and better performance than satellite-based ones. Performance improves when basin-scale total precipitation amounts are considered (R2 of 0.83 and CV of 0.48). Avoiding regional-specific calibration therefore does not preclude the algorithm from working but has some limitations in probability of detection (POD) and accuracy. A widespread underestimation is evident at both the grid box scale (mean error of −0.26) and the basin scale (multiplicative bias of 0.7), while the number of false alarms is generally low and becomes even lower as link coverage increases. Also taking into account delays in the availability of the data (latency of 0.33 h for CML against 1 h for the adjusted radar and 24 h for the quality-controlled rain gauges), CML appears as a valuable data source in particular from a local operational framework perspective. Finally, results show complementary strengths for CMLs and radars, encouraging joint exploitation.

Abstract. There is a growing interest in emerging opportunistic sensors for precipitation estimates, motivated by the need to describe with detail precipitation structures. In this work a preliminary assessment of the accuracy of Commercial Microwave Links (CMLs) retrieved rainfall rates in northern Italy is presented. The CML product, obtained by the publicly available RAINLINK package, is evaluated at different scales (single link, 5 km x 5 km grid, river basin) against the precipitation products operationally used at Arpae-SIMC, the Regional Weather Service of Emilia-Romagna, in northern Italy. The results of the 15 min single-link validation with close-by raingauges show high variability, with influence of the area physiography and precipitation patterns and the impact of some known issues (e.g. melting layer). However, hourly cumulated spatially interpolated CML rainfall maps, validated with respect to the established regional gauge-based reference, show performances (R2 of 0.47 and CV of 0.77) which are very similar, when not even better, to satellite- and adjusted radar-based precipitation gridded products. This is especially true when basin-scale total precipitation amounts are considered (R2 of 0.85 and CV of 0.63). Taking into account also delays in the availability of the data (latency of 0.33 hours for CML against 1 hour for the adjusted radar and 24 h for the quality controlled raingauges), CMLs appear as a valuable data source in particular from a local operational framework perspective. A diffuse underestimation is evident at both grid box (Mean Error of −0.26) and basin scale (Multiplicative Bias of 0.7), while the number of false alarms is generally low and gets even lower as coverage increases. Finally, results show complementary strengths for CMLs and radars, encouraging a joint exploitation.

The paper by Fencl et al. addresses a topical and interesting matter, as extends known opportunistic precipitation sensing techniques to the more recent E band links. It highlights the new possibilities uncovered by the different frequencies and hardware and focuses on the consequent challenges. The authors give a complete picture of the subject from theory to application, preparing the ground for future studies. The article is therefore certainly valuable and of primary interest to the CML scientific community and AMT readers.

No abstract

No abstract