Markov chain analysis of the rainfall patterns of five geographical locations in the south eastern coast of Ghana

Meshach Tettey,Daniel A Abaye,Francis T Oduro,David Adedia

doi:10.1186/s40322-017-0042-6

Abstract

This study develops an objective rainfall pattern assessment through Markov chain analysis using daily rainfall data from 1980 to 2010, a period of 30 years, for five cities or towns along the south eastern coastal belt of Ghana; Cape Coast, Accra, Akuse, Akatsi and Keta. Transition matrices were computed for each town and each month using the conditional probability of rain or no rain on a particular day given that it rained or did not rain on the previous day. The steady state transition matrices and the steady state probability vectors were also computed for each town and each month. It was found that, the rainy or dry season pattern observed using the monthly steady state rainfall vectors tended to reflect the monthly rainfall time series trajectory. Overall, the probability of rain on any day was low to average: Keta 0.227, Akuse 0.382, Accra 0.467, Cape Coast, 0.50 and Akatsi 0.50. In particular, for Accra, the rainy season was observed to be in the months of May to June and September to October. We also determined that the probability of rainfall generally tended to increase from east to west along the south eastern coast of Ghana.

Highlights

Global warming has been confirmed to be affecting regional and continental rainfall patterns of the world, with the recorded evidence showing that there is an increase in precipitation in Canada, northern Europe and northern Russia, while vast areas of sub-Saharan Africa, southern India and South-East Asia are becoming dryer (Groisman et al 2005; Kharin et al 2005; Westral et al 2013; Fletcher et al 2015)
A preliminary look at the rainfall data collected over the 30-year period (1980–2010) in the five geographical locations, Cape Coast, Accra, Akuse, Akatsi and Keta in south eastern coast of Ghana indicates that the rainfall pattern is not evenly distributed
It was determined that a Markov chain analysis classifies this pattern

Summary

Introduction

Global warming has been confirmed to be affecting regional and continental rainfall patterns of the world, with the recorded evidence showing that there is an increase in precipitation in Canada, northern Europe and northern Russia, while vast areas of sub-Saharan Africa, southern India and South-East Asia are becoming dryer (Groisman et al 2005; Kharin et al 2005; Westral et al 2013; Fletcher et al 2015). Until the beginning of the twenty-first Century, there was little observable evidence to support this interference. In their seminal work, von Storch and Zwiers (1999) analysed two data-sets of global rainfall patterns covering the years 1925 to 1999. Their work concluded that, over the 75-year period under study, global warming ‘contributed significantly’ to increases in precipitation in the northern hemisphere’s mid-latitudes, a region between 40° and 70° north. The northern hemisphere’s tropics and subtropics, a region spanning from the Equator to 30° north, became drier. These trends have since been confirmed by many other reports Torrential rains have continued to deluge locations in these drier zones including Accra, Ghana’s capital creating floods

Methods

Results

Conclusion