Topography Effect on Sea Breeze Front Initiated Rainfall on Summer Period in North Halmahera Vina Sabrina(a*), Nurjanna Joko Trilaksono(b), and Donaldi Sukma Permana(c)
1) Study Program of Earth Science,Faculty of Earth Science and Technology, Bandung Institute of Technology, Bandung, Indonesia
2) Indonesian Agency for Meteorology Climatology and Geophysics
Abstract
There are rain events that occur during the dry season in the North Halmahera region. This is thought to be due to the influence of local-scale weather phenomena that can cause rain during this period. The most dominant local scale weather phenomenon affecting weather dynamics in coastal areas is sea breeze circulation. Topographic variations can affect the strength of sea breeze, on the other hand the complexity of the coastline also impacts the propagation of sea breeze fronts. The existence of a sea breeze front can potentially produce rain clouds. In previous studies, it is known that the interaction of sea breeze front and topography can increase the intensity of rainfall in the mountain areas. This study will analyze the climatological conditions of the North Halmahera region to prove that local-scale weather phenomena are strong enough to produce rainfall in that period, then analyze the output of the WRF InaNWP BMKG model to explore the relationship between topography, sea breeze front propagation and rainfall so as to reveal the dynamics of the process when rain occurs in that period, the final stage is to verify using the eyeball and RMSE method to measure the model^s skill in predicting the weather. The results showed that climatological conditions in the period were not dominated by global and regional scale weather phenomena, but SST had enough potential to produce water vapor for convective cloud formation. The model output shows that strong convection occurs during the day and produces rain in the afternoon. This is due to the low level convergence of sea breeze circulation that combines with mountain flow from topographic effects in the northern part of Halmahera so that in the northern region the intensity of rainfall produced is greatest due to the influence of topography. The verification results show that the WRF model is able to reveal the dynamics of the rainfall process resulting from topographic effects on the sea breeze front but still underestimates the rainfall intensity compared to observations.
