The Spatio-Temporal Variability of Rainfall over the Agro-Ecological Zones of Ghana
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Date
2019-07-26
Journal Title
Journal ISSN
Volume Title
Publisher
Atmospheric and Climate Sciences
Abstract
Rainfall variability plays an important role in many socio-economic activities
such as food security, livelihood and farming in Ghana. Rainfall impact studies are thus very crucial for proper management of these key sectors of the
country. This paper examines the seasonal and annual rainfall variability in
the four agro-ecological zones of Ghana from the CHIRPS V2 rainfall time
series spanning a period of 1981-2015. The rainfall indices were computed
with the aid of the FClimDex package whereas the trends of these indices
were further tested using the Mann Kendall trend test. The results show good
agreement (r ≥ 0.7) between CHIRPS V2 and gauge in almost all portions of
country although high biases were observed especially in DJF season over
parts of the Northeastern (NE) portions of the country. The mean seasonal
rainfall climatology over the country is observed to be in the range of 20 - 80
mm, 60 - 200 mm, 100 - 220 mm and 40 - 180 mm in DJF, MAM, JJA and
SON seasons respectively with high intensities of rainfall dominating Southwestern portions of the country. The trend analysis revealed positive trends of
consecutive dry days in the Transition, Forest and Coastal zones and negative
trends in the Savannah zone of the country. Decreasing trends of consecutive
wet days are observed over the Savannah, Transition and Coastal zones whereas increasing trends dominate the Forest zone. Savannah, Forest and Transition zones show weak increasing trends of the number of heavy rainfall days
whilst weak decreasing trends are observed over the Coastal zone of the country. Similarly, weak increasing trends of the number of very heavy rainfall days
are observed over all the agro-ecological zones except in the Transition zone.
It is observed that the annual wet day rainfall total has increasing trend in the
Savannah and Forest zones of the country whereas decreasing trends cover
the remainder of the zones. The trends of these indices in the agro-ecological
zones were all significant at a significant value of 0.05. This paper assessed the
performance of the CHIRPS V2 rainfall data over the region and reports on the biases in seasonal rainfall amounts which are limited in previous studies.
These findings have adverse impacts on rain-fed agricultural practices, water
resource management and food security over the country.
Description
An article published by Atmospheric and Climate Sciences, 2019, 9, 527-544 and available at DOI: 10.4236/acs.2019.93034
Keywords
Rainfall, Variability, Trends, Agro-Ecological Zones, Ghana
Citation
Atmospheric and Climate Sciences, 2019, 9, 527-544