Vertical Velocity Characteristics of Hurricanes Based on Dropsondes Data
Based on observational data collected by dropsondes,this paper analyzed the distribution characteristics of hurricanes'vertical velocity in the lower atmospheric layer(within 3 km of the ground).The results show that smaller vertical velocity(<2 m·s-1)exhibited no significant difference in distribution with height in the near-center region(R/RMW≤5,where Rrepresents the distance between the dropsonde and the center of the hurricane,and RMW denotes the maximum wind speed radius of the hurricane),the far-center region(5≤R/RMW<10)and outside-hurricane region(R/RMW≥10).However,the frequency of positive values of larger vertical velocity(≥2 m·s-1)in the near-center region was the highest,significantly exceeding that in the far-center and outside-hurricane regions.Conversely,the frequency of negative values in the outside-hurricane region was the highest,significantly exceeding that in the near-center and far-center regions.In the near-center region of hurricanes,the frequency of updrafts decreased with the increase in height,while the frequency of downdrafts increased.In the far-center and outside-hurricane regions,the intensity and proportion of vertical velocity did not change obviously with height.The intensity and proportion of updrafts in the near-center region increased with hurricane intensity,while the median velocity and proportion of vertical velocity in the far-center and outside-hurricane regions showed little change with hurricane intensity.Moreover,it is found that the updrafts in hurricanes can exceed 10 m·s-1,usually in the normalized radius of 1-2.5,and the maximum wind speed of the hurricane should reach 50 m·s-1.
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