Climatic trends over tropics of Africa, A case of the Pra River Basin in Ghana

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Abstract The likelihood of changing trends in climatic time series over the Pra River Basin in Ghana was examined. Trend analyses were carried out on monthly, seasonal, and annual timescales for temperature and rainfall from 1950 to 2010. The use of Modified Mann–Kendall, Sen’s slope and Pettit tests revealed warming trends over the Pra River Basin. Maximum and Minimum annual temperature time series revealed a statistically significant increasing trend over 60% of the stations with Sen’s slopes varying from 0.006 to 0.035 oC/yr. Monthly temperature extremes revealed a statistically significant increasing trend over 80% of the stations. Seasonality revealed both increasing and decreasing trends for both dry and wet seasons, while annual rainfall experienced a decreasing trend in four out of the five stations with only one station being statistically significant at a 0.05 level. Both dry and wet season rainfall experienced statistically significant decreasing trends for all stations except one at 0.05 level. Strong downward trends in rainfall were observed for the dry season while weak downward trends were observed for the wet season. Moreover, increasing change points ranging between 0.76°C– 0.93°C on average were experienced mostly for TMAX around the mid-1960s through to the early 1980s. While decreasing change points within a range of between − 0.99°C and − 0.61°C on average were also observed for TMIN around the late 1950s through to the mid-1970s.

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