热带气旋（TC）的强度预报是TC预报业务中相对落后并亟待解决的一个重要问题。本项目拟针对西北太平洋海域，对影响TC强度变化的一类大尺度环境因子,即对流层高层环境流场的作用及其与TC强度变化的关系开展分析和研究。通过统计最近几十年TC与高空环流的相互作用，揭示西北太平洋海域该现象的气候特征及其与TC强度变化的关系，总结归纳出相应高层环流的流型特征，找到有利于TC增强的高空环流型；通过对典型个例的诊断分析和大样本的统计分析，揭示高空环流如何与其他影响TC强度变化的因子（如海温和垂直风切变等）相互配置，共同影响TC强度变化。最后，构造一个定量表征高空环流对TC强度变化影响的水平平面指标，旨在将研究结果应用到实际中，为西北太平洋地区TC强度变化的预测提供客观的参考依据。

The forecast of the intensity change of a tropical cyclone (TC) is still a challenging task in TC research community nowadays, and therefore requires more attention to find a possible solution. The present study is going to investigate the relationship between upper-tropospheric environmental flow, one of the factors that influencing TC's intensity, and the intensity change of the TCs over the western North Pacific. Through statistical analysis of TC-upper level flow interaction, the climatology of interaction over the western North Pacific is to be revealed in detail. Flow patterns which are most favorable for TC's intensification will be identified though exploring all the samples. The combining effects of upper-level flow and other environmental factors (such as sea surface temperature and vertical wind shear) on TC's intensity change will also be investigated through typical-case diagnosis as well as statistical analysis. Finally, an horizontal index representing the possible influence of upper-tropospheric environmental flow will be constructed. This index could provide useful information and aid the intensity forecast of TCs over the western North Pacific.