Spatial variability of annual rainfall in East Java Regions: application of histogram and normal QQ-Plot

Abstract

This research aims to analyse the spatial variability of annual rainfall. Daily rainfall data from 936 rain-gauges in East Java regions are used as the primary input. The average annual rainfall and the maximum annual rainfall are obtained from the daily rainfall data. Research procedures consist of data pre-treatment, ESDA, interpolation, and interpretation. Histogram and QQ-Plot were used to describe the spatial variability of annual rainfall in each sub-region. Next, an IDW interpolation method was used to create a thematic map of the annual rainfall. The results showed that local spatial variability of rainfall could be visualised more detail for each sub-region using histogram and QQ-Plot. The thematic map showed that the distribution of average annual rainfall in the region range from 1000 mm/year up more than 3000 mm/year. Maximum annual rainfall range between 2,100 mm/year up to 4,500 mm/year. The result also shows the positive correlation between the altitude of the rain-gauge and local annual rainfall received.