Harmattan is a season that is observed in the Western African nations of the African continent. It occurs in-between the end of November and the middle of March month. It is a dry season with typical characteristics of a dry and dusty season. The season is brought over by the northeasterly trade wind which is also named the Harmattan and it blows from the Sahara desert over West Africa and moves into the Gulf of Guinea. Depending on the local circumstances the temperature during harmattan can range from cold in most places to hot in certain regions.
Characteristics of the Harmattan
The harmattan season brought in by the dry and dusty northeasterly trade wind occurs during the months of the lowest sun i.e. from the months of November to January with the highest during the period of December. During this season the subtropical ridge stays over the central region of the Saharan desert and there the low-pressure Intertropical Convergence Zone (ITCZ) stays over the Gulf of Guinea. While passing over the Sahara the Harmattan wind picks up the fine dust and sand particles which becomes the typical characteristic of the Harmattan season. The wind flow during the winter season of the Harmattan is given in the below picture:
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The language from which the harmattan meaning is derived is the Twi language, a dialect of Akan language spoken in southern and central Ghana. The name has become so popular that the harmattan meaning has become synonymous with the particular season as in the case of monsoon and winter. Due to its strong dryness, as compared to the humid tropical air, the trade wind is also known as “doctor wind”.
The season is particularly different from the winter season as it is prominently associated with cold, dry, dust-laden wind and wide fluctuations in the room temperatures of the day and the night. For example, during the entire day, the temperature may remain as low as 9℃ but during the afternoon it can rise up to 30℃ with relative humidity dropping below 5%. Also, it is not cold in all regions but in some regions of the Sahara, the weather will be hot for the Harmattan season. It is well established that the air of Harmattan is dry and desiccating.
It is known for the desert-like conditions because of the following characteristics: lowering of the humidity, dissipation of cloud cover, prevention of rainfall and sometimes the creation of big clouds of dust that lead to the occurrence of desert storms or sandstorms. The fire risk increases because of the dry wind of the Harmattan season anc can also cause severe damage to the crops in all the regions where the season is prevalent. The interaction of the Harmattan with the monsoon winds can cause tornadoes.
Effects of the Harmattan Haze
An effect known as the Harmattan Haze is quite prevalent in some countries of West Africa, with a heavy amount of dust present in the air. It can severely lead to the limitation of visibility and block the sun for several days, comparable to heavy fog. Because of this, there is a loss of millions of dollars to airlines because of the cancellations and diversions of the flights each year. When the haze gets weak and the sky gets clearer because of the extreme dryness of the air the trees will begin to die. Two distinct images of the Harmattan haze at two different places is shown below:
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The drop in humidity below 15% can/might result in spontaneous nosebleeds for some of the people. There are also other health effects on the people caused by the Harmattan. They include conditions like dryness of the skin, dried or chapped lips, eyes, and respiratory problems. This season is also adverse for people suffering from asthma because it can cause aggravation of asthma.