Assessment of the quality of measurements from selected amateur rain gauges

At the Polish Institute of Meteorology and Water Management – National Research Institute (the Polish acronym: IMGW-PIB), experimental parallel measurements of daily precipitation totals were carried out from August 2021 – September 2022. Measurements were made with 5 types of amateur rain gauges (A – CliMET CM1016; B – TFA Dostmann 47.1008; C – TFA Dostmann 47.1000; D – Davis 6466 AeroCone Rain Collector; E – TFA Dostmann 47.3005.01) and a manual Hellmann rain gauge (H), which was taken as reference. The results showed that the most frequent differences in the rain gauges tested are very small differences (in daily rainfall totals Δ≤0.1 mm). They account for 63–86% of the days. On the other hand, large (1.0<Δ≤5.0 mm) and very large (Δ>5.0 mm) differences are most frequent in type D, respectively: 12% and 5% of days. This type, as the only one of the tested types, is characterised by the occurrence of days with very large differences with respect to rain gauge H. The tested rain gauges of the same type do not show the same sign of difference with respect to the reference rain gauge, as there are both negative and positive differences. The C type rain gauge shows the smallest average difference of daily precipitation totals against the H-type rain gauge (+0.04 mm). On the other hand, the average differences for types A and B are negative and amount to –0.1 and –0.2 mm, respectively. In contrast, the average difference for type D is +0.2 mm. Some amateur rain gauges perform better or similar to operationally used rain gauges of automatic networks. Types A, C and B can be used in voluntary networks with appropriate and continuous human supervision and their results used, as an additional source of information, for operational purposes at IMGW-PIB or other hydrological and meteorological services. The rain gauge D is useful only during warm season. Type E was not suitable for the conditions of the experiment for technical reasons.