Variability in Rainfall, Temperature and Relative Humidity at Bahir Dar City Areas, Ethiopia

Abstract

This study was conducted to assess change in rainfall, temperature and relative humidity at Bahir Dar city in relation to global climate change. The study focused on analyzing changes in meteorological data, specifically temperature, rainfall and relative humidity. Bahir Dar city was selected due to its proximity to Lake Tana and its rapid urbanization over the past few decades. Debre Markos city (with no lake nearby) was selected for comparison, to assess the thermal inertia effect of the lake on Bahir Dar. The assessments in this study showed that Bahir Dar city has experienced mean temperature change of about 0.4 oC per decade, which is higher than the global average (0.08 oC per decade) and a decrease in rainfall of about 30 mm per decade. Monotonic increment of minimum temperature (0.60 oC decade-1) surpassed that of maximum temperature (0.25 oC per decade) and this was further confirmed by a decrease in change of diurnal temperature range of -0.34 oC per decade. The increase in temperature at Bahir Dar over the global average is attributed to rapid urbanization (urban heat island effect). Comparison between Bahir Dar and Debre Markos showed slight influence of thermal inertia of the lake on Bahir Dar’s minimum temperature. Greater lake effect was observed with the change in relative humidity, which showed a reduction of only 0.4% per decade at Bahir Dar compared to 3.8% at Debre Markos. The cyclic pattern of temperature clearly manifested the long cycle of Pacific Decadal Oscillation (PDO) while the short cycle PDO was slightly subdued perhaps due to the local effect. Rainfall cycle modestly followed the pattern of the Sahel.