Comparison between Leonid meteor shower observations during 1998–2000

Observations for the Leonid meteor shower from the Gaomeigu station of Yunnan Observatory during 1998–2000 are analyzed in this paper. We introduce a new statistical quantity zenithal hourly mass rates (ZHMR) to deal with the mass flow of a meteoroid stream. The variations of r, ZHR and ZHMR are given. During our observations, ZHMR had often a value of the order of 10−6–10−3 g/km2 h. The variation of r may be more strong and frequent in 1998 than in 1999, but in most cases, it was about 2.0. Interesting phenomena like filamentary structure was observed in ZHR and mass influx profiles. In our observations, the filamentary structure has no periodic variation. In general, the ZHMR and ZHR would show different behaviour and go to their maximum at different times. The ZHMR may become a new statistic to support comparisons between different observers, and might be a more useful quantity for predictions. In 1999, the dust trails of 4- and 5-revolution (rev) seem to leave nothing at the exact predicted time. At most, we estimate the ZHR introduced solely by the 4-rev. trail should not be over 50.