Gradient height and velocity profile during typhoons

Abstract Velocity profile and gradient height have been objects of main concerns in the study of wind engineering for a long time. For normal (non-typhoon) conditions, the shape of the wind profile as well as the gradient height have been well established for different types of terrain. However during severe tropic cyclones and typhoons such information is still insufficient. This paper tries to answer the two questions (1. Is there a gradient height during typhoons; and if so what is its value? 2. How does the velocity vary with height during typhoons?) by analysising the past twenty years typhoon data. Both the upper level wind data from radar sounding and the surface anemometer wind records have been studied. Result of the analysis shows that the gradient height during typhoons is very low; it is only about half the expected value for monsoon winds. Wind profiles for mean and gust wind have also been established. The finding is found to compare favourable with results obtained by Hong Kong Royal Observatory.