Abstract:

To clarify the source regions and atmospheric driving mechanisms of the catastrophic migration events of rice planthoppers in northwestern Guangxi, this study conducted backward trajectory simulations for the peak migration days of rice planthoppers in 2008 using the HYSPLIT 5.0 trajectory model, combined with comprehensive analyses of concurrent meteorological factors such as atmospheric dynamic fields, temperature and humidity fields, and precipitation. The results indicate: (1) Among the six major migration peaks with over 100,000 rice planthoppers being caught per trap in northwestern Guangxi rice-growing areas, the primary sources were the rice-growing regions along the Yunnan-Myanmar border and the northern rice-growing areas of the Indo-China Peninsula. (2) Cluster analysis of backward trajectories for 161 catastrophic peak days revealed three key migration pathways for the catastrophic migration of rice planthoppers in northwestern Guangxi in 2008: the southwest monsoon pathway from Yunnan-Myanmar to the Yunnan-Guizhou Plateau, the cross-border monsoon pathway from the Indo-China Peninsula to river valleys, and the lowland monsoon pathway from the You River to the Hongshui River. Among these, southerly pathways accounted for 86.8% of the total trajectories, constituting the dominant migration route. (3) The southerly warm and moist airflow originating from the Bay of Bengal and the South China Sea at the 850 hPa level served as the primary transport carrier for rice planthopper migration. The high-altitude humid environment formed by rapid temperature recovery and sustained moisture transport during the 2008 spring provided favorable conditions for the migration process. (4) The frequency and volume of rice planthopper migration peaks were significantly correlated with the number of rainy days at night, and increased precipitation duration and intensity would exacerbate migration risks. Additionally, subsiding airflow was a critical dynamic factor contributing to the concentrated landing of rice planthoppers. The results of this study showed that the primary sources of the catastrophic migration of rice planthoppers in northwestern Guangxi in 2008 originated from foreign rice-growing regions in Yunnan-Myanmar and the Indo-China Peninsula, entering through three atmospheric pathways coupled with terrain and monsoon circulation; the migration process was primarily driven by the transport of southerly warm and moist airflow at the 850 hPa level and promoted by abnormal hydrothermal conditions in spring; while nocturnal precipitation and subsiding airflow in the destination areas were key triggers for the concentrated landing of the insect populations.

Key words: rice planthopper, migratory trajectory, source population characteristics, climate anomalies, HYSPLIT simulation, catastrophic invasion, northwestern Guangxi region