Effects of Low-Frequency Oscillation at Different Latitudes on Summer Precipitation in Flood and Drought Years in Southern China

Based on the daily precipitation data from 753 meteorological stations provided by National Meteorological Information Center (China) and reanalysis NCEP/NCAR ERA5 during period 1980 to 2020, low-frequency (LF) characteristics of typical summer flood drought years in southern China their relation LF atmospheric circulation at different latitudes are compared analyzed, extended-range forecasting signals given. The results show that: (a) In both years, is controlled 10–20 day oscillation (quasi-biweekly oscillation, QBWO); (b) convection active but convective center southward vertical meridional stronger. key systems 500 hPa height field include “two ridges one trough” “+”, “−”, “+” East Asia Pacific (EAP) teleconnection wave train mid-high Eurasia. However, more westward than Subtropical High stronger extensive, with significant extension; (c) (drought) there northerly then westerly (central westerly) dry-cold, northeasterly wet-cold, southwesterly (none), southeasterly (including southerly across equator) wet-warm water vapor channels. sources dry wet cold air located near Novaya Zemlya (the eastern West Siberian Plain), Yellow Sea, Bohai Sea (Sea Japan). Additionally, Arabian Bay Bengal, western Ocean, sea area northeastern Australia Ocean northern Australia); (d) predictive outgoing longwave radiation (OLR) appear −11 days, while −9 days. There eastward propagation only spread years.