A STUDY OF LOW-LEVEL WIND SHEAR (LLWS) AT SOEKARNO-HATTA INTERNATIONAL AIRPORT DURING 2015-2019 USING DOPPLER WEATHER RADAR DATA

• Main Author: Ratnasari, Yesi
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/64868
• Institution: Institut Teknologi Bandung

Low level wind shear (LLWS) is a type of wind shear that occurs between surfaces up to 487,7 m (1600 feet). This phenomenon is extremely hazardous to aircraft, especially during takeoff and landing. However, due to the nature of the phenomenon, it is still impossible to make predictions (small scale, high variability, and short duration). As a result, understanding trigger factors becomes critical in issuing early warnings. These trigger factors differ by region and will affect the frequency characteristics of events. During 2015-2019 pilots have reported 146 LLWS incidents at Soekarno-Hatta International airport. The triggering circumstances in each case, however, are unknown. In this study, the factors considered as triggers are convective clouds, sea breeze front (SBF), and land breeze front (LBF). This study aims to analyze the dominant trigger factors and the frequency characteristics of events of the LLWS, both spatially and temporally. The data used were pilot reports (PIREP), Doppler weather radar, and automated weather observing system (AWOS) from 2015 to 2019. There are three main stages to this research. First, identifying the case by translating the PIREP codes. Second, analyzing the trigger factors and the intensity of each case using three radar products and AWOS gusty data. Third, analyzing the dominant trigger factors and frequency characteristics of events both spatially and temporally using statistical processing. The result shows that the dominant trigger factors of LLWS are convective clouds both single and multicell along with patterns of gust front (GF) and/or microburst (MBA). Clouds dominated from the south of the airport are associated with strong convection during the day as well as the rest of the convection process at night from mountainous and highland regions. This is supported by maximum fluctuations of the frequency of events in December-January-February (DJF) (seasonal) and forms a semidiurnal pattern with two peaks (07.00 – 09.00 UTC and 14.00 – 16.00 UTC) (diurnal). In term of spatial, LLWS often occurs on 25L runways with an average intensity of 10,12 m / s (19,68 kt).