Observation Analysis and Application Evaluation of Wind Profile Radar to Diagnosing the Boundary Layer of Landing Typhoon

Abstract

The feasibility of wind profile radar in typhoon observation is investigated with 6 cases including Feng-wong(1422), Chan-hom(1509), Nepartak(1601), Meranti(1614), Megi(1617), and Lekima(1909) during 2014 to 2019. Thirty-four groups datasets, including the Airda 3000 boundary layer wind profile radar, GPS balloon sounding and PARSIVEL laser precipitation data are analyzed.Preliminary analysis show that 30 out of 34 datasets satisfy the prerequisite condition of greater than 80% data completion. The average wind speed standard deviation of these 30 datasets is about 3.64 m·s-1 and the average difference is 4.67 m·s-1. Furthermore, 19 out of the 34 datasets achieve good results (standard deviation less than 4 m·s-1) when the observation by wind profile radar and sounding agree well above 250 m altitude, though they overlap less below that altitude. The sounding wind speed is observed to be much smaller than the wind profile radar data for altitudes below 250 m, which is possibly caused by the fact that sounding accelerates from stationary to consistent with environmental winds below 250 m altitude in typhoon environment, or by the disturbance in lower atmosphere of wind profile radar. Thus, ignoring the lowest 250 m altitude, the standard deviation of wind profile radar and balloon sounding decrease remarkably. This may imply that wind profile radar has high feasibility in boundary layer from 250 m altitude to the layer top under typhoon environment. In addition, data with lower validity are always located in the region which is about more than 200 km away from typhoon center, while the distribution of high validity data observation show no obvious pattern and locates from typhoon center to the outer region. There is also no significant relationship found between data validity and precipitation intensity. These may imply that wind profile radar have great potential under the condition of heavy precipitation and severe wind. The analysis of data with lower validity indicates that the distribution of humidity in typhoon and local disturbance cause uneven wind in the radar detection beam. In addition, because the coastal areas of Zhejiang and Fujian are mostly hilly terrain, the low-level circulation structure of typhoon is destroyed by terrain, which may also be one cause for the poor match of horizontal wind speed.Despite the limited data, wind profile radar shows a very hopeful potential and high validity in the observation and diagnosis of boundary layer even in severe convective weather environment such as typhoon inner core region.

Keywords

• wind profile radar
• typhoon observation experiment
• structure of typhoon boundary layer