The Interaction Relationship Between Tropical Cyclone Genesis And Surrounding Environment Fields

Based on NCEP/NCAR1°×1°gridded analyses data per6hours and the best track data from JTWC, the temporal and spatial distribution as well as the value of the divergent wind surrounding118tropical cyclones in the range of100°E to180°E in the northern hemisphere from May to September in2004to2010was statistically analyzed. TCs can be divided into seven types according to different influence systems, and the first four categories take more than91.5%of the total number, which are1) cross-equatorial flow type;2) cross-equatorial flow and subtropical high equal type;3) strong cross-equatorial flow and weak subtropical high type;4) subtropical high type. The strong cross-equatorial flow and weak subtropical high type is more likely located in the south and east of the other types, as the cross-equatorial flow and subtropical high equal type is located in the north and east.Centered on TC, within500kilometers away from the closed vortex of the new TCs at950hPa is affected by subtropical high in the first quadrant, subtropical high and continental high in the second quadrant, cross-equatorial flow in the third quadrant and the fourth quadrant is mostly affected by cross-equatorial flow and seldom affected by subtropical high. The rigeional average divergent wind varies from0.6to1.6m·s-1in the first quadrant, from0.6to0.9m·s-1in the second quadrant, from0.4to4.1m·s-1in the third quandrant and varies from0.9to3.0m·s-1in the forth quandrant at950hPa. The effect intensity of cross-equatorial flow varies in the range of1.8～4.3m·s-1and the effect intensity of subtropical high varies in the range of1.2～1.8m·s-1.As for200hPa, the rigeional average divergent wind varies from2to3.2m·s-1in the first quadrant, from1.1to3m·s-1in the second quadrant, from0.4to4.8m-s-1in the third quandrant and varies from1.2to3.8m·s-1in the forth quandrant. The divergent wind of TC has an effect on subtropical high with the intensity varies from2.1～3.8m·s-1and also has an effect on cross-equatorial flow with the intensity varies from3.4-5.7m·s-1.The upper layer divergent wind of TC is1.5m·s-1stronger than the lower layer divergent wind of the surrounding systems. In addition, the divergent wind at the upper layer is1m·s-1stronger than the lower layer in the second and the fourth quandrant,1.5m·s-1stronger in first quandrant and equal to the lower layer in the third quandrant. Rigional average U dimention of the divergent wind at the lower layer is mostly less than1m·s-1, but V dimention varies in different types and the strongest V dimention is over3m·s-1. Rigional average U dimention of the divergent wind at the upper layer varies from0.3to2m·s-1and V dimention varies from0.1to4.6m·s-1.By conducting both the control test and sensitivity test on TC0704we know that another new TC will still generate in few days after removing the TC, which also proves the surrounding systems play an important role in TC genesis as well as the impact on sunrrounding systems by TCs.