Five sets of model sensitivity experiments are conducted to investigate the influence of tropical cyclone （TC） genesis location and atmospheric circulation on interannual variability of TC intensity in the western North Pacific （WNP）. In each experiment, bogus TCs are placed at different initial locations, and simulations are conducted with identical initial and boundary conditions. In the first three experiments, the specified atmospheric and SST conditions represent the mean conditions of E1 Nifio, La Nifia, and neutral years. The other two experiments are conducted with the specified atmospheric conditions of E1 Nifio and La Nifia years but with SSTs exchanged. The model results suggest that TCs generated in the southeastern WNP incurred more favorable environmental conditions for development than TCs generated elsewhere. The different TC intensities between E1 Nifio and La Nifia years are caused by difference in TC genesis location and low-level vorticity （VOR）. VOR plays a significant role in the intensities of TCs with the same genesis locations between E1 Nifio and La Nina years.
