Spatial Analysis of the Relationship of the Borneo Vortex Phenomenon to Rain in West Borneo

In November, December, January, and February throughout the year there is a phenomenon of the Borneo Vortex in the Northwest of Kalimantan Island to the southern part of the South China Sea. This phenomenon is formed continuously and is often associated with heavy rains and floods. Several previous studies have stated that there is an influence of the Borneo Vortex on atmospheric dynamics and changes in the amount of rainfall in certain regions. This study identifies and maps the relationship of the Borneo Vortex to rainfall to determine the influence of the Borneo Vortex in each region of West Kalimantan. The results showed that the highest frequency of the Borneo Vortex occurred in December at 32.6%. The relationship of the Borneo Vortex event to rain is determined by the value of the determination coefficient which is then tested F to select a significant value. IDW interpolation with power values of 1 to 4 was used to spatially analyze the relationship between the Borneo Vortex and rain in West Kalimantan. The results showed that the influence of the Borneo Vortex event on rainy days was more evenly distributed for the West Kalimantan region with medium criteria as many as 127 sub-districts or 75.6%, while the effect on rainfall with low, medium, and high threshold criteria was 60%, 35.4%, and 4.6%, respectively. The high criteria are more dominant in the northern and southern regions of West Kalimantan.