On the proportion of upward flashes to lightning research towers

We compare in this paper direct measurements obtained at the Towers on Mount San Salvatore (Switzerland) and the Gaisberg Tower (Austria). They are situated in similar topographical environments but in different lightning activity zones. Direct measurements of lightning currents on these towers have revealed a major difference in terms of the number of downward flashes. While Berger and co-workers obtained a significant number of downward flashes, more recent observations on the Gaisberg and Peissenberg Towers were essentially composed of upward flashes. We use in this paper a new method to estimate the proportion of upward/downward flashes to a given tower, based on the data from lightning location systems. The analysis using the proposed method explains the discrepancy in terms of the measured number of downward flashes in Gaisberg Tower and in Monte San Salvatore Tower.