第八届青年地学论坛

precipitation and disastrous flooding over the Yangtze River basin. Monitoring and prediction of the intraseasonal variation
of Meiyu is crucial for disaster prevention and mitigation. Here, we proposed two sets of novel indices for Meiyu real-time
monitoring and prediction based on the compound zonal displacements of the South Asia high (SAH) and the western
Pacific subtropical high (WPH) at 10–30-day and 30–60-day period, respectively. For the 10–30-day period of Meiyu, the
zonal displacement of the SAH is associated with a mid-latitude Eurasian Rossby wave train, whereas the WPH is related
to the second mode of the boreal summer intraseasonal oscillation. On the 30–60-day timescale, the zonal displacement of
the SAH and the WPH are both associated with the first mode of the boreal summer intraseasonal oscillation. The subtle
differences in zonal displacement of the SAH and the WPH determine eight type configurations, corresponding to distinct
influences on Meiyu. Meiyu intraseasonal variation can be well reconstructed by using the relationship between these two
indices and rainfall anomalies pattern over China. Given that the ECMWF S2S model is more skillful in forecasting upperand
lower-level circulation than in directly forecasting precipitation, a hybrid dynamical–statistical model is conducted to
subseasonal prediction of Meiyu using the ECMWF model forecast indices. The hybrid model outperforms the ECMWF
model in subseasonal prediction of the Meiyu variation at 17–40-day lead times.

Meiyu · South Asia high · Western Pacific subtropical high · Subseasonal monitoring and prediction · Hybrid dynamical–statistical model