STATISTICAL CLASSIFICATION AND CHARACTERISTICS ANALYSIS OF BINARY TROPICAL CYCLONES OVER THE WESTERN NORTH PACIFIC OCEAN SUMMER: CONTRASTIVE ANALYSIS FOR ACTIVE AND INACTIVE YEARS OF TROPICAL CYCLONES

Using the 1949-2007 western North Pacific tropical cyclones (TCs) best-track data archived at the Shanghai Typhoon Institute of China Meteorological Administration for the western North Pacific from 1949 to 2007, both the characteristics of binary and multiple TCs and samples of interactions among TCs and multi-TCs are identified and statistically analyzed. According to the various features of individual TC tracks and interacting tracks, seven distinct types are proposed to describe the binary system of TCs and their interaction samples. The mean trajectories of the west and east component of binary TCs in each type are obtained using a new cluster analysis technique. These types are then analyzed in terms of landfall process, occurrence seasonality, coexistent lifetime, especially the large-scale patterns of atmospheric circulation. Finally, typical steering flows and conceptual models of the binary TCs at different phases are established based on six-hourly flow maps of the binary system and the averages are determined of the mean steering flow of ten representative binary TCs. Then, typical steering flows and conceptual models at the beginning, middle and final phase in each type are established to describe the large-scale circulation patterns of the binary system interaction types.