ANALYSIS OF COLD SURGE AND BORNEO VORTEX BY POTENTIAL VORTICITY

• Main Author: FATRIA ANDARINI (NIM 12809008), DITA
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/20037
• Institution: Institut Teknologi Bandung

Borneo Vortex is a cyclonic circulation in the west of Kalimantan that occurs due to the convergence between northeast winds with local topography. Borneo vortex is related to cold surge, which is a cold air from high pressure in Asia to south and east over the oceans in Indonesia in Asian Winter Monsoon. Cold surge enhanced the Borneo Vortex intensity. But there is not enough explanation about it yet. In this research, potential vorticity is used to analyze the presence of Borneo Vortex and influence of cold surge to Borneo Vortex’s formation. The hypothesis in this study is that potential vorticity advection of cold surge from mid latitude enhanced the intensity of Borneo Vortex. In this research, the analysis of vorticity potential in isentropic surface is conducted using the NCEP/NCAR Reanalysis data in pressure level. Analysis of potential vorticity anomaly is used to examine the presence of a Borneo Vortex and the effect of cold surge to Borneo Vortex,including a case study of Borneo Vortex and cold surge and composite of all of each events (Borneo Vortex days, cold surge days, and Borneo Vortex and cold surge days). <br /> <br /> <br /> According to the analysis of potential vorticity anomaly, the presence of Borneo Vortex begins with a system in tropic, which is indicated by a positive potential vorticity anomaly in Borneo. The maximum positive potential vorticity anomaly indicates the presence of Borneo Vortex. In cold surge days, there are advection of positive potential vorticity anomalies to equator. Meanwhile in cold surge and Borneo Vortex days, positive vorticity potential anomaly rises because the positive vorticity potential anomaly from north is increased. The rise of positive vorticity potential anomaly in Kalimantan does not indirectly come from cold surge advection, but from the positive vorticity potential anomaly in west of Philipines and Indian ocean which is connected with positive potential vorticity anomaly from north.