Spatial and temporal change of rainfall pattern in east coast of North Sumatera

The North Sumatera rainfall area is classified as equatorial type, which characterized by two peaks of maximum rainfall for each year and distribute evenly through the year with maximum 1 dry month. However, the occurrence of rainfall below normal in the period of January-April in 2014-2016 shows that there has been a change in rainfall patterns that can be caused by climate change. This paper aims to identify changes in rainfall patterns on the east coast of North Sumatera spatially and temporally. Over 16 years (1999-2014) monthly and annual rainfall data series in 74 locations along east coast of North Sumatera are selected for identifying the rainfall pattern change. The data was taken from private rain gauge and North Sumatra Agency for Meteorology, Climatology, and Geophysics (BMKG), which located along the east coast of North Sumatera. The observation on annual rainfall shows changes in rainfall patterns in the study sites would occur every 5-7 years. The occurrence of La Nina and El Nino also give a part on the change of annual rainfall pattern.