Analysis of localized rainfall by using grid observation data of automatic weather station in Bandung basin case studies 28 February and 9 March 2017

Abstract

On 28 February and 9 March 2017, there has been flooding in different areas of the Bandung Basin. Flood on 28 February 2017 occurred in the southern part of Bandung Basin, while flood on 9 March 2017 only occurred in the northern part of Bandung Basin. The floods were caused by heavy rainfall in each region. Allegedly the rain that occurred in the region is a localized rain. Localized rain means rain only occurs in one area whereas other areas do not rain. In this study, an analysis of the localized rain is based on observational data grid and convective cloud distribution that produces rain. The data grid is based on Automatic Weather Station (AWS) network data located in the Bandung Basin. Ordinary kriging is an interpolation method chosen to create a data grid and produce grid data with a spatial resolution of 0.025 ° × 0.025 ° and its temporal resolution of 10 minutes with available data that is from January to March 2017. Spread of rain in the Bandung Basin can be seen clearly using grid of observational data that have been made and found the existence of localized rain events in this region. Results from the grid of rain data indicate if the rain on 28 February 2017 occurred at different times between the northern and southern part of Bandung Basin. The rain began to occur first in the northern part of Bandung at 12:10 local time (LT). Further rain recorded at Dayeuhkolot station located in the middle of the Bandung Basin at 14:00 LT. While in the southern part of Bandung basin, the rain started measuring at 16.00 LT. Rain in the Bandung Basin on 28 February 2017 is not only produced by a single convective cloud that moves, but there are three convective clouds that produce rain in the Bandung Basin. A convective cloud originated from the Bandung Basin itself and two other convective clouds originated from areas outside the Bandung Basin. Wide rain coverage is the result of the merger of the three convective clouds. While the rain that occurred on 9 March 2017 only occurred in the northern part of Bandung. The rain began measuring in Lembang and Dagopakar at 17:10 LT. Rain is generated by convective clouds that grow outside the northern part of Bandung Basin to enter the Bandung Basin. By knowing the area of rain distribution, can also know which region gets the highest rain intensity. It is important to know the extent of the distribution of rain, especially for areas that have flood risk as a form of disaster mitigation so as to reduce the losses incurred.