Analysis On The Influence Of The Landfalling Typhoon In The Catastrophic Immigrations Of Nilaparvata Lugens (Stal)

Brown planthoppers(BPH),Nilaparvata lugens(stal) is a kind of immigration pest. It’s happened in the rice every year,and there is more BPH in the south area than in the north aera.Since the1970s,BPH outbroke in China on a large scale,and it become the top pest to harm rice production in our country,and so millions of rice area was harmed.BPH may outbreak by many environment factors,and the agricultural environment, meteorological background and geographic conditions are the most important element among these factors.BPH mainly occurs in the eastern part of our country, and this region is influenced seriously by typhoon.And so the study that is on the effect of the typhoon in the catastrophic immigrations of BPH is particularly important.In order to clarify the statistical pattern that the landfalling strong tropical cyclones influenced on the catastrophic immigrations of rice brown planthopper,Nilaparvata lugens(stal) in China,in this paper,the data of the landfalling strong tropical cyclones in China and the lighting catches of BPH covered the main Chinese rice-growing regions from1979to2008were collected and analyzed under the assistance of ArcGIS9.3,a software of geographic information system.The results were followed as:(1) In China, there were220strong tropical cyclones passed through the main rice-growing regions and466great events of BPH’s immigration occurred in30years from1979to2008.73in220landfalling strong tropical cyclones resulted into the occurrence of BPH’s catastrphic immigration events directly and147in220landfalling strong tropical cyclones produced the indirect effect on the immigrations.(2) The numbers of the landfalling strong tropical cyclones were various in different years during1979to2008and their influence was not alike in the BPH’s migrations northward and southward of these years.In30years,the landfalling strong tropical cyclones had brought more obvious influence on the migrations in1980,1981,2005,2006and2007.The influence was the most obvious in2007and all of7landfalling strong tropical cyclones produced the remarkable impact on the catastrophic immigrations of BPH’s populations. The effect of the landfalling strong tropical cyclones on the immigration northward of BPH’s populations was the most serious in2006and the influence on the immigration southward was the most remarkable in2005.(3) In these years,there were the most of landfalling strong tropical cyclones occurred in July,August and September of a year as well as the great events of BPH’s immigration occurred most frequently in the same months.The landfalling strong tropical cyclones had played an more important role on the catastrophic immigration of BPH’s populations in the three months than the other months of a year.(4) The analysis on the spatial distribution of the landfalling strong tropical cyclones and BPH’s immigration events for the different provinces displayed that the BPH’s immigrations in the main rice-growing regions of the Southeastern China had been influenced by the landfalling strong tropical cyclones and the impact was different with the change of the spatial probability distribution of the landfalling strong tropical cyclones passed through these regions.The most serious influence of the landfalling strong tropical cyclones on the BPH’s immigrations occurred in Guangdong Province and Fujian Province of China.(5)The statistical results indicated that a suitable insect source is an indispensable condition of the catastrophic immigrations of BPH when a landfalling strong tropical cyclone influenced on a rice-growing region. The atmospheric background of the typical north,south,and blended immigrations were simulated and analyzed objectively by WRF(Weather Research and Forecasting Model),the daily re-analyzed meteorological data in the Northern Hemisphere and daily rainfall data of753stations from1961to2010that provided by meteorological information center of China meteorological administration.And BPH’s migration trajectory was simulated by the software of Hysplit.The results showed that:(1)the most important atmospheric circulation factor that controlled and influenced BPH is the allocation of typhoons systems with other weather systems and the evolution of typhoon systems with time on850hPa isobaric surface.(2)The air streams of the horizontal wind field on the850hPa could be used to describe the main migration directions of the BPH populations.In the immigration,the air streams from the south in the east of typhoon were conducive to BPH flying to the north,and the air streams from the north in the weat of typhoon were conductive to BPH flying to the south.(3)The updraft in votex area of typhoon is favourable for BPH takeoff;the typhoon system peripheral gale area with strong sinking airflow had a very important role of BPH’s landing.(4)Precipitation plays a very important dynamic stress role to BPH’s landing,but BPH did not land in the strongest precipitation area of typhoon system,and BPH landed in the weak precipitation area with strong sinking airflow of typhoon system,and if there was no strong sinking airflow,the strong precipitation would lead to a large number of BPH’s landing.(5)On the850hPa,the migration trajectory of BPH was influenced by the horizontal wind field absolutely.