Characteristics of Meteorological Elements During Typhoon Kalmaegi Observed by Unmanned Aerial Vehicle

China is one of the countries where meteorological disasters happen frequently, and typhoon is one ofthe most serious disasters.Meteorological Observation Center of China Meteorological Administrationhave carried out typhoon observation experiment by unmanned aerial vehicle (UAV) in 2008.For the first time, UAV is used to observe typhoon Kalmaegion 18 July 2008, and it is a successfulfield campaign.The UAV sends back data and lands safely after the observation.The UAV flies directlytowards the typhon center and observes the temperature, relative humidity, pressure, wind direction andwind speed with onboard meteorological sensors.It takes almost 4 hours to observe the meteorological elements, the cruising altitude of UAV is 500 m and the nearest distance to typhoon center is about108.4 km.The meteorological elements such as air temperature, pressure, relative humidity, wind direction, wind speed and altitude are received successfully during the observation period.The UAV fliesthrough precipitation area, upwind area, strong convection and such serious flight environment.Thus aquasi-real-time observation system with the capability of flight observing, data collecting, processing anddistributing is established.The observation data reflects some basic characteristics of typhoon, showing that pressure and altitudehave good correlation (r=-0.98). Closer to the typhoon center, pressure is lower and wind speed ishigher.Gradients of temperature is about -1.02 ℃/100 m from ground to 300 m and about -0.46 ℃/100 m from 300 m to 500 m.The temperature varies largely with the height in the near surface layer, which shows that the ground surface has much influence on the temperature.During the observation period, the maximum wind velocity is about 22.3 m · s ^-1 with the average of about 15.1 m · s ^-1.Closer to the typhoon center, higher the relative humidity is.When the UAV arrives at the destination and returns, therelative humidity is 100%and after that it decreases.It can be concluded that when the relative humidity ishigh, UAV flies in the precipitation area.It also shows the waterproof performance of UAV is good, which ensures it fly normally in the precipitation weather.