草地贪夜蛾迁飞大气动力条件分析及过程模拟

Atmospheric Dynamics Analysis and Simulation of the Migration of Fall Armyworm

分析2019—2021年草地贪夜蛾在我国跨区域迁飞的大气环流形势和低层风动力条件,并选取北迁进入长江流域、北迁进入东北地区、秋季向南回迁以及冬季在冬繁区扩散4次典型天气过程,利用改进的HYSPLIT(Hybrid Single-particle Lagrangian Integrated Trajactory)模型模拟其迁飞轨迹和落点。结果表明:由于每年西北太平洋副热带高压强度、位置和西伸程度不同,西南气流强度也不同,影响草地贪夜蛾在我国的北迁进程,使其经过迁飞过渡区和到达北方玉米主产区的时间存在差异。选取4次天气过程模拟草地贪夜蛾的迁飞,其中3次过程模拟的草地贪夜蛾迁飞轨迹和降落区域得到实况监测的验证,但模型对2022年1月26—28日西南急流天气过程下草地贪夜蛾迁飞轨迹和降落区域的模拟在贵州西部和南部、福建出现错报。HYSPLIT模型对迁飞轨迹的模拟效果较好,但对迁飞距离、时长、落点的模拟上仍具有较大不确定性,未来需进一步结合雷达监测等手段改进优化模型,提高模拟预报准确率。

After the invasion of fall army worm(Spodoptera frugiperda)in China at the end of 2018 or at the beginning of 2019,it spreads rapidly and becomes a seasonal migrating pest that seriously threatens the maize production in China.The long-distance migration of adult fall armyworm is closely related to the seasonal changes of atmospheric circulation in East Asia.The atmospheric circulation and low layer wind dynamic condition that influence the migration of fall armyworm in 2019-2021 are analyzed,and 4 typical weather processes beneficial to the migration are selected to simulate the migration path and landing point with Hybrid Single-particle Lagrangian Integrated Trajactory(HYSPLIT)model.The results show that,during the northward migration of fall armyworm in spring and summer,the strength of the southwest airflow is different due to the varying strength,location and westward extension of the Northwestern Pacific subtropical high(WPSH)in each year,and therefore the low layer wind driving the migration of fall armyworm to transition region and main corn planting area is different.The earlier onset of the South China Sea summer monsoon in May of 2019 is conducive to the early migration from South China into the middle and lower reaches of the Yangtze.June is a key stage for the fall armyworm migration to northern summer maize area,and further spreading to the spring maize area in North China.The west ridge point positions of WPSH from June to July varies in different year,and leads to different northernmost landing position of the pests,which is attributed to the south airflow carrying fall armyworm on the western side of the WPSH.The dynamic conditions of low layer wind during August to September are different in 2019-2021,which vital to the migration to main spring maize producing areas in Northeast China.In 4 simulation cases,3-weather-process simulations are effectively monitored and verified,indicating the migration path and landing point of fall armyworm.However,in January of 2022,there are some misreports landing point in Guizhou and Fujian,though the southwest low level jet is favorable.HYSPLIT model is effective in the flight trajectory simulation,but it has some uncertainty in the migration distance,time and landing point due to biological characteristics,topography,microclimate,etc.In future,the simulation model should be improved by combination of real-time radar monitoring and other means.