Gaps Between the Transmission and Reception of Information on Rainfall Amounts

Abstract

In weather forecasts, the intensity of rainfall is often expressed either as a quantitative value – the amount of rainfall per hour – or using qualitative language such as “heavy rain.” To date, however, there has been no research into the extent of rainfall that is assumed by information receivers when presented with these qualitative terms. Thus, the present study examines the correspondence between rainfall evaluation and expressions using a rainfall generator. The large-scale rainfall experiment facility owned by the National Research Institute for Earth Science and Disaster Resilience was used to generate rainfall of 60, 180, and 300 mm h-1, and 21 experiment participants experienced this rainfall without knowing the rainfall amounts. Following this, the participants were asked to give feedback using a scale that correlated numerical expressions of rainfall amounts per hour with 10 language expressions such as “heavy rain” and “downpour.” The results revealed that rainfall rates of 60, 180, and 300 mm h-1 were evaluated by the participants as 135, 223, and 311 mm h-1, respectively. The 10 language expressions were felt to be stronger than the official criteria outlined by the Japan Meteorological Agency. In addition, there was no statistical significance among several expressions, suggesting that the qualitative language used to describe different rainfall amounts by information senders were not distinguished by information receivers.