云南省褐飞虱早期迁入虫源及其发生大气背景分析

为了探明我国西南稻区褐飞虱早期迁入种群的虫源地,为后期预测和防治提供依据,通过对2007—2016年云南植保站4—5月份褐飞虱虫情进行分析,选取出云南省勐海、芒市、江城、师宗、麻栗坡、广南6个代表性站点,利用WRF-FlexPart耦合模式对2013年、2015年和2016年这些站点的早期迁入峰进行了数值模拟,得到近年来云南省褐飞虱早期迁入虫源的虫源地。选取了2013年褐飞虱早期迁入量较大的迁入峰进行了大气背景分析,结合峰期影响褐飞虱迁飞的大气动力场、温度场和相对湿度场,探讨了影响云南省褐飞虱早期迁入的大气背景。研究结果表明:(1)近年来云南省褐飞虱迁入的虫源主要来自缅甸,部分来自老挝和泰国,少数来自越南,还有极少量来自孟加拉国。(2)这一时期,当释放高度分别为1500、2000 m时,褐飞虱的迁飞高度分别集中在2216 m和2489 m,平均迁飞高度分别是2167、2454 m,从不同释放高度回推的褐飞虱迁飞高度的起伏趋势具有较好的一致性,表明模式能较好地反映系统性垂直气流和下垫面起伏对其上层三维流场和种群迁飞的影响。(3)选取2013年5月22—26日发生在云南勐海、麻栗坡和广南的一次典型褐飞虱迁入过程,分析了大气背景场对褐飞虱迁飞的影响,结果显示:受印缅低压控制或影响,高空从境外虫源区至云南降虫区有西南水平气流作为种群输送动力;温场在降虫区东北侧有"低温屏障墙"存在,阻止了种群的继续北迁;垂直速度场上虫源区有上升气流促使种群起飞迁出,降虫区有下沉气流促使种群降落;弱降水形成的拖曳下沉气流对降虫也十分有利;相对湿度场对此次迁飞过程不形成任何胁迫。

Source identification and meteorological analyses of the early immigration of Nilaparvata lugens into Yunnan Province, China

Ten-year observational data for the brown plant hopper (BPH), Nilaparvata lugens (Stål) at six plant-protection monitoring stations in Yunnan Province are presented to determine the sources of BPH, at the time of their early immigration into the rice-planting areas of Southwestern China, in April and May from 2007 to 2016. The six stations included in the study were Mangshi, Menghai,Jiangcheng, Shizong, Malipo, and Guangnan. These observational analyses were then used to provide scientific evidence in support of the migration predictions for BPH and measures for its prevention. The Flexible Particle Dispersion (Flexpart) model driven by the Weather Research and Forecast Model (WRF) outputs was used to simulate the early immigration peaks observed at these stations in 2013, 2015, and 2016 and then identify their sources. A detailed analysis of the data obtained for 2013 was conducted to determine the atmospheric dynamics, temperature, and relative humidity conditions during the early immigration of BPH in Yunnan Province. The BPH that had early immigration in Yunnan Province in these years were mainly from Myanmar, partly from Laos and Thailand, a few from Vietnam, and very few from Bangladesh. The prevailing (average) migration heights of BPH at 2216 m (2167 m) and 2489 m (2454 m) corresponded to the release heights of 1500 m and 2000 m, respectively. Good agreement between the model backward trajectories and the BPH migrating heights indicates that the model was able to capture the impact of systematic vertical airflows and the complex underlying surface on group migrations. A typical case study of an immigration event of BPH observed in Menghai, Malipo, and Guangnan in Yunnan Province from May 22nd to 26th in 2013 further demonstrates that the immigration of BPH from abroad at upper levels into Yunnan Province was mainly driven by the southwest prevailing winds associated with the Indo-Burma low pressure system; the low-temperature zone was a barrier preventing continuous northward migration over the Northeast landing areas of the BPH; and the BPH migration behaviors were highly associated with vertical motions. While the updraft was responsible for the taking-off and moving out, the downdrafts corresponded to BPH descent; the dragging effect of subsidence associated with weak rainfall was favorable this descent, whereas the relative humidity field had limited impact on the migration of BPH populations during this event.