Rainfall Changes in the Northern Region of Aceh
Ahmad Farhan (a*), Muhammad Syukri (b), Saumi Syahreza (b), Taufan Hidayat (c)

a) Graduate School of Mathematics and Applied Science, Syiah Kuala University, Banda Aceh, 23111, Indonesia
*Email: farhan[at]usk.ac.id
b) Department of Physics, Faculty of Mathematics and Natural Sciences, Syiah Kuala University, Banda Aceh, 23111, Indonesia
c) Department of Agrotechnology, Faculty of Agriculture, Syiah Kuala University, Darussalam, Banda Aceh 23111, Indonesia

Abstract

Abstract. The Northern Region of Aceh (Aceh Bagian Utara) is located at the northern tip of Sumatra Island, with coordinates bordered by the Indian Ocean to the west and the Malacca Strait to the north. Previous studies reported that rainfall (RF) during the 2010-2019 period increased compared to the 2000-2009 period. However, these studies did not explain whether this increase is significant or when the change began. This study aims to address these questions. Rainfall data for a 30 year period (1995-2024) were obtained from the Sultan Iskandar Muda Meteorological Station and the Aceh Climatology Station. The data were analyzed using various statistical methods, allowing for comparison of the results from each method. The analysis revealed that the data were not normally distributed, and therefore, non-parametric statistical methods were used for further analysis. The Mann-Kendall test yielded a Z value of -0.018, which is within the acceptance region of Ho, indicating that no significant trend in rainfall changes was found. Robust regression resulted in a trend line equation with a relatively small slope, with a coefficient of determination 0.3676. The 5-year Moving Average graph shows a slight increase in rainfall after 2012. However, this increase is not strong enough to be considered a permanent trend. Based on the three analytical approaches, it is concluded that no significant trend in annual rainfall increase or decrease was observed in the Northern Region of Aceh during the period of 1995-2024. The observed annual fluctuations are more influenced by natural atmospheric variability, such as extreme ENSO and IOD events, and other equatorial atmospheric instabilities, making it impossible to definitively determine when the increase in rainfall began.

Keywords: Climate Change, ENSO, IOD, Mitigation, Adaptation, Mann-Kendall

Topic: Energy and Environmental Physics