Ghana - Climate

The climate is tropical. Climate forecast and climate change scenarios for the country predict a more severe and frequent pattern of drought and flood events. The eastern coastal belt is warm and comparatively dry; the southwest corner, hot and humid; and the north, hot and dry. There are two distinct rainy seasons in the south--May-June and August-September; in the north, the rainy seasons tend to merge. A dry, northeasterly wind, the Harmattan, blows in January and February. Annual rainfall in the coastal zone averages 83 centimeters (33 in.).

Bounded on the South by the Atlantic Ocean and on the West by La Cote d”ivoire, the East by Togo and the North by Burkina Faso, Ghana is a tropical country. The South Western part is located within the warm wet forest zone similar to the Amazon. Accra, the capital, is located in the dry equatorial cones. Kumasi is in the wet savanna. It lies between 4° and 11 ° North at the equator and has a coastline of 540 km.

Northern Ghana has a range season from about April to October. The rest, of the year is hot and dry, with temperatures up to about 38°C. In Southern Ghana the rains last from April to June and again from September to October. Generally temperatures are between 21 – 31°C. The rains are usually restricted to specific times each day during the rainy season; they are not continuous throughout the day.

The country's warm, humid climate has an annual mean temperature between 26°G and 29°C. Variations in the principal elements of temperature, rainfall, and humidity that govern the climate are influenced by the movement and interaction of the dry tropical continental air mass, or the harmattan, which blows from the northeast across the Sahara, and the opposing tropical maritime or moist equatorial system. The cycle of the seasons follows the apparent movement of the sun back and forth across the equator.

During summer in the northern hemisphere, a warm and moist maritime air mass intensifies and pushes northward across the country. A low-pressure belt, or intertropical front, in the airmass brings warm air, rain, and prevailing winds from the southwest. As the sun returns south across the equator, the dry, dusty, tropical continental front, or harmattan, prevails.

Climatic conditions across the country are hardly uniform. The Kwahu Plateau, which marks the northernmost extent of the forest area, also serves as an important climatic divide. To its north, two distinct seasons occur. The harmattan season, with its dry, hot days and relatively cool nights from November to late March or April, is followed by a wet period that reaches its peak in late August or September. To the south and southwest of the Kwahu Plateau, where the annual mean rainfall from north to south ranges from 1,250 millimeters to 2,150 millimeters, four separate seasons occur. Heavy rains fall from about April through late June. After a relatively short dry period in August, another rainy season begins in September and lasts through November, before the longer harmattan season sets in to complete the cycle.

The extent of drought and rainfall varies across the country. To the south of the Kwahu Plateau, the heaviest rains occur in the Axim area in the southwest corner of Ghana. Farther to the north, Kumasi receives an average annual rainfall of about 1,400 millimeters, while Tamale in the drier northern savanna receives rainfall of 1,000 millimeters per year. From Takoradi eastward to the Accra Plains, including the lower Volta region, rainfall averages only 750 millimeters to 1,000 millimeters a year.

Temperatures are usually high at all times of the year throughout the country. At higher elevations, temperatures are more comfortable. In the far north, temperature highs of 31°C are common. The southern part of the country is characterized by generally humid conditions. This is particularly so during the night, when 95 to 100 percent humidity is possible. Humid conditions also prevail in the northern section of the country during the rainy season. During the harmattan season, however, humidity drops as low as 25 percent in the north.

Historical data for Ghana from the year 1961 to 2000 clearly shows a progressive rise in temperature and decrease in mean annual rainfall in all the six agro-ecological zones in the country. Climate change is manifested in Ghana through: (i) rising temperatures, (ii) declining rainfall totals and increased variability, (iii) rising sea levels and (iv) high incidence of weather extremes and disasters. The average annual temperature has increased 1°C in the last 30 years. Based on this data, some estimate that temperature will continue to rise, while rainfall is also predicted to decrease in all agro-ecological zones.

The major challenges in all zones are weather extremes such as flooding, droughts and high temperatures. In the Transitional zone, the projected trends that are most likely to pose the major problem are the early termination of rainfall which is likely to convert the current bi-modal regime to a uni-modal one. Historical analysis has indicated that, rainfall variability may be the single largest component of rainfall changes affecting all agro-ecological zones in Ghana.

Ghana’s economy relies heavily on climate sensitive sectors mainly on agriculture, energy and forestry. About 70% of the population depends directly or indirectly on agriculture (fisheries, crop and animal farming etc.) and forest sector for both timber and non timber forest products. Any anomaly in the climate therefore tends to affect the economy of Ghana, particularly the vulnerable.

The limited use of irrigation facilities and high dependence on unfavorable climatic conditions for the realisation of good harvest tend to introduce huge instability in the standards of living of the people. The percentage of cultivated land under irrigation in Ghana is 0.89%. This is equivalent to 23,657 hectares. Consequently, majority of Ghanaians, who live in the rural areas and thrive mainly on rain-fed farming in rural communities, become disproportionately vulnerable since they are most exposed to hazards such as bush fires, flooding and droughts and are least capable of adapting to such hazards.

In the Transition zone for instance, the short dry spell (July and August) which is crucial for preparing the land for the second crop is increasingly becoming wetter and the short rainy season terminating early. There is a progression toward a uni-modal regime for the transitional zone with serious consequences for rain-fed agriculture. In the Forest zones, reductions in rainfall are reported to be about 20% which is far larger than the 10% reduction in the Transition and Savannah to the north. The major challenge in the forest however, is that the reduction permeates the entire rainfall regime.