Spatial and Temporal Analysis of Rainfall and Temperature Extreme Indices in Tanzania

Ladislaus B Chang’A,Hashim K Ng’Ongolo,Habiba I Mtongor,Philbert M Luhunga,Agnes L Kijazi

doi:10.4236/acs.2017.74038

Abstract

Climate extreme indices in Tanzania for the period 1961-2015 are analyzed us-ing quality controlled daily rainfall, maximum and minimum temperatures data. RClimdex and National Climate Monitoring Products (NCMP) software developed by the commission for climatology of the World Meteorological Organization (WMO) were used for the computation of the indices at the respective stations at monthly and annual time scales. The trends of the extreme indices averaged over the country were computed and tested for statistical significance. Results showed a widespread statistical significant increase in temperature extremes consistent with global warming patterns. On average, the annual timescale indicate that mean temperature anomaly has increased by 0.69°C, mean percentage of warm days has increased by 9.37%, and mean percentage of warm nights has increased by 12.05%. Mean percentage of cold days and nights have decreased by 7.64% and 10.00% respectively. A non-statistical significance decreasing trends in rainfall is depicted in large parts of the country. Increasing trend in percentage of warm days and warm nights is mostly depicted over the eastern parts of the country including areas around Kilimanjaro, Dar-es-Salaam, Zanzibar, Mtwara, and Mbeya regions. Some parts of the Lake Victoria Basin are also characterized by increasing trend of warm days and warm nights. However, non-statistical significant decreasing trends in the percentage of warm days and warm nights are depicted in the western parts of the country including Tabora and Kigoma regions and western side of the lake Victoria. These results indicate a clear dipole pattern in temperature dynamics between the eastern side of the country mainly influenced by the Indian Ocean and the western side of the country largely influenced by the moist Congo air mass associated with westerly winds. The results also indicate that days and nights are both getting warmer, though, the warming trend is much faster in the minimum temperature than maximum temperature.

Highlights

Hydro-meteorological related disasters, from climate extremes are responsible for about 90% of all global natural disasters [1]
The annual timescale indicate that mean temperature anomaly has increased by 0.69 ̊C, mean percentage of warm days has increased by 9.37%, and mean percentage of warm nights has increased by 12.05%
The results describe the sign, magnitudes and significance of the trends in mean temperature anomaly, percentage of warm days, percentage of warm nights, percentage of cold days, percentage of cold nights, rainfall anomaly and Standardized Precipitation Index

Summary

Introduction

Hydro-meteorological related disasters, from climate extremes are responsible for about 90% of all global natural disasters [1]. The frequency and magnitude of climate extremes including droughts, floods and heat waves have been found to increase on global scale, and have significantly contributed to the loss of life and properties and severe infrastructure damages in various parts of the world [5] [6] [7]. Over the last few decades most parts of Tanzania have experienced an increased incidence of extreme climatic events, floods and droughts that have been associated with severe socio-economic and ecological implications. The country has experienced severe and recurrent droughts, which have caused devastating impacts, in agriculture, water, energy and livestock sectors, and paralyzing socio-economic activities and development. The most recent devastating droughts include those of 2003, 2005, 2011, 2014 and 2016 [10]

Methods

Results

Conclusion