SIMULASI NUMERIK MEKANISME TURBULENSI DEKAT AWAN KONVEKTIF

Abstract

Intisari Turbulensi yang dialami oleh pesawat komersial rute Jakarta-Medan telah dilaporkan mengalami Clear Air Turbulence (CAT) di atas Sumatera Utara pada tanggal 24 Oktober 2017. Namun berdasarkan data citra satelit Himawari dari Badan Meteorologi, Klimatologi, dan Geofisika (BMKG) Indonesia menyebutkan bahwa di sekitar lokasi turbulensi terdapat awan kumulonimbus. Penelitian ini memanfaatkan model WRF-ARW dengan resolusi spasial dan temporal tinggi untuk mengetahui secara detail proses yang terjadi pada awan konvektif penyebab Near Cloud Turbulence (NCT). Turbulensi tersebut disebabkan oleh bilangan Richardson rendah yang terbentuk di wilayah udara jernih (clear air) yang berjarak 300-700 m di atas puncak awan dan diperkuat dengan adanya Turbulensi Energi Kinetik (TKE) mencapai 4,4 m2 / s2 dan geser angin vertikal (VWS) oleh arus keluar awan konvektif.  Abstract Turbulence encountered by commercial aircraft Jakarta-Medan routes has been reported that experienced Clear Air Turbulence (CAT) over North Sumatra on October 24th, 2017. However, based on Himawari satellite imagery data produced by Agency for Meteorology, Climatology, and Geophysics (BMKG), Indonesia stated that there was a cumulonimbus cloud around the turbulence location. This study utilizes WRF-ARW models with a high spatial and temporal resolution to find out in detail the processes that occur in convective clouds causing Near Cloud Turbulence (NCT). The turbulence was caused by a low Richardson number formed in the clear-air area, which has a distance of 300 - 700 m above the cloud top and reinforced by the existence of Turbulence Kinetic Energy (TKE) reaching 4,4 m2/s2 and vertical wind shear (VWS) by deep convection’s outflow.