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|Title: ||Variabilities in Rainfall Onset, Cessation and Length of Rainy Season for the Various Agro-Ecological Zones of Ghana|
|Authors: ||Amekudzi, L.K.|
Asare, Ernest O.
Codjoe, Samuel N. A.
|Keywords: ||onset and cessation|
|Issue Date: ||Jun-2015|
|Citation: ||Climate, 2015, 3, 416-434|
|Abstract: ||Abstract: This paper examines the onset and cessation dates of the rainy season over Ghana
using rain gauge data from the Ghana Meteorological Agency (GMet) over the period of
1970–2012. The onset and cessation dates were determined from cumulative curves using
the number of rainy days and rainfall amount. In addition, the inter-annual variability of
the onset and cessation dates for each climatic zone was assessed using wavelet analysis.
A clear distinction between the rainfall characteristics and the length of the rainy season in
the various climatic zones is discussed. The forest and coastal zones in the south had their
rainfall onset from the second and third dekads of March. The onset dates of the transition
zone were from the second dekad of March to the third dekad of April. Late onset, which
starts from the second dekad of April to the first dekad of May, was associated with the
savannah zone. The rainfall cessation dates in the forest zone were in the third dekad of
October to the first dekad of November, and the length of the rainy season was within
225–240 days. The cessation dates of the coastal zone were within the second and third
dekad of October, and the length of rainy season was within 210–220 days. Furthermore, the
transition zone had cessation dates in the second to third dekad of October, and the length
Climate 2015, 3 417
of the rainy season was within 170–225 days. Lastly, the savannah zone had cessation dates
within the third dekad of September to the first dekad of October, and the length of rainy
season was within 140–180 days. The bias in the rainfall onset, cessation and length of
the rainy season was less than 10 days across the entire country, and the root mean square
error (RMSE) was in the range of 5–25 days. These findings demonstrate that the onset
derived from the cumulative rainfall amount and the rainy days are in consistent agreement.
The wavelet power spectrum and its significant peaks showed evidence of variability in the
rainfall onset and cessation dates across the country. The coastal and forest zones showed
2–8- and 2–4-year band variability in the onsets and cessations, whereas the onset and
cessation variability of the transition and savannah zones were within 2–4 and 4–8 years.
This result has adverse effects on rain-fed agricultural practices, disease control, water
resource management, socio-economic activities and food security in Ghana.|
|Description: ||This article is published in Climate, and also available at doi:10.3390/cli3020416.|
|Appears in Collections:||College of Science|
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