Characteristics of environmental fields and asymmetric precipitation at different stages of typhoon Khanun intensification

Using multi-source observational data,the study analyzes the environmental fields and the asymmetric precipitation characteristics during different intensification associated related stages of typhoon Khanun.The study compared and analyzed the environmental field characteristics of typhoon intensity changes at different stages from aspects such as sea surface temperature near the typhoon,evolution of upper-level and low-level circulations,moisture transport,and vertical wind shear.The results indicate that high sea surface temperatures near the typhoon center,dual outflows in the upper levels,continuous supply of summer monsoon moisture,and relatively small vertical wind shear between high and low levels provide favorable conditions for the rapid intensification of the typhoon.Generally,during the intensification process,there are conditions such as deteriorating sea surface temperatures,reduced upper-level outflow channels,disrupted moisture transport pathways,and increased vertical wind shear throughout the atmospheric layer.During the rapid intensification stage,periodic convective bursts occur within the typhoon's inner core region,with deep convection propagating from the downshear side to the upshear side.The convective region contracts toward the typhoon center.In contrast,during the general intensification stage,convective activity remains consistently on the left side of the environmental vertical wind shear,which is closely related to the asymmetric distribution of dynamic and thermal fields near the typhoon center.