A simple method to determine patterns of wet and dry seasons

Abstract

The objective of this paper is to describe a simple method to determine patterns of wet and dry seasons based on historical climate data. Here, the daily rainfall and evapotranspiration were used as input variables, each of which was accumulated over one year. The accumulated data was then estimated using a continuous equation in the form of a 6th order polynomial equation. Nets of the first derivate of the rainfall minus that of evapotranspiration were used to determine wet and dry periods. Here, the wet period occurs when the nets are positive, and the dry period occurs when the nets are negative. Later, algorithms were developed to point the start, end, and peak of, and to calculate the available rainwater in each period. The method was applied here to determine patterns of wet and dry seasons in Serang Regency, Banten Province, Indonesia. The climate data was collected from a local climate station managed by the National Agency for Meteorology, Climatology, and Geophysics from 1978 to 2018 (41 years). There were three wet periods and three dry periods. On average, the dry season started from 107±67 J-day to 263±113 J-day and was followed by the wet season till 121±57 J-day. In the dry season, the rainwater was deficit about -353 mm. Whereas, in the wet season, rainwater was surplus about 576 mm. And, in the whole season, the rainwater was surplus up to 223 mm, which may be conservable to anticipate water deficit in the dry season.