Harmattan

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Harmattan haze surrounding Abuja National Mosque in Abuja MosqueinAbuja.jpg
Harmattan haze surrounding Abuja National Mosque in Abuja

The Harmattan is a season in the West African subcontinent, which occurs between the end of November and the middle of March. It is characterized by the dry [1] and dusty northeasterly trade wind, of the same name, which blows from the Sahara Desert over West Africa into the Gulf of Guinea. [2] The name is related to the word haramata in the Twi language. [3] The temperature is cold [1] in most places, but can also be hot [4] in certain places, depending on local circumstances. [5]

A season is a division of the year marked by changes in weather, ecology, and amount of daylight. On Earth, seasons result from Earth's orbit around the Sun and Earth's axial tilt relative to the ecliptic plane. In temperate and polar regions, the seasons are marked by changes in the intensity of sunlight that reaches the Earth's surface, variations of which may cause animals to undergo hibernation or to migrate, and plants to be dormant. Various cultures define the number and nature of seasons based on regional variations.

West Africa westernmost region of the African continent

West Africa is the westernmost region of Africa. The United Nations defines Western Africa as the 16 countries of Benin, Burkina Faso, Cape Verde, The Gambia, Ghana, Guinea, Guinea-Bissau, Ivory Coast, Liberia, Mali, Mauritania, Niger, Nigeria, Senegal, Sierra Leone and Togo, as well as the United Kingdom Overseas Territory of Saint Helena, Ascension and Tristan da Cunha. The population of West Africa is estimated at about 362 million people as of 2016, and at 381,981,000 as of 2017, to which 189,672,000 are female, and 192,309,000 male.

Gulf of Guinea The northeasternmost part of the tropical Atlantic Ocean between Cape Lopez in Gabon, north and west to Cape Palmas in Liberia

The Gulf of Guinea is the northeasternmost part of the tropical Atlantic Ocean between Cape Lopez in Gabon, north and west to Cape Palmas in Liberia. The intersection of the Equator and Prime Meridian is in the gulf.

Contents

The Harmattan blows during the dry season, which occurs during the lowest-sun months. In this season the subtropical ridge of high pressure stays over the central Sahara Desert and the low-pressure Intertropical Convergence Zone (ITCZ) stays over the Gulf of Guinea. On its passage over the Sahara, the harmattan picks up fine dust and sand particles (between 0.5 and 10 microns).

Intertropical Convergence Zone

The Intertropical Convergence Zone (ITCZ), known by sailors as the doldrums or the calms, is the area encircling Earth near the Equator, where the northeast and southeast trade winds converge.

Effects

The Harmattan season differs from winter, because it is characterized by cold, dry, dust-laden wind, and also wide fluctuations in the ambient temperatures of the day and night. Temperatures can easily be as low as 9 °C (48 °F) all day, but sometimes in the afternoon the temperature can also soar to as high as 30 °C (86 °F), while the relative humidity drops under 10%.

Winter one of the Earths four temperate seasons, occurring between autumn and spring

Winter is the coldest season of the year in polar and temperate zones. It occurs after autumn and before spring in each year. Winter is caused by the axis of the Earth in that hemisphere being oriented away from the Sun. Different cultures define different dates as the start of winter, and some use a definition based on weather. When it is winter in the Northern Hemisphere, it is summer in the Southern Hemisphere, and vice versa. In many regions, winter is associated with snow and freezing temperatures. The moment of winter solstice is when the Sun's elevation with respect to the North or South Pole is at its most negative value. The day on which this occurs has the shortest day and the longest night, with day length increasing and night length decreasing as the season progresses after the solstice. The earliest sunset and latest sunrise dates outside the polar regions differ from the date of the winter solstice, however, and these depend on latitude, due to the variation in the solar day throughout the year caused by the Earth's elliptical orbit.

Relative humidity

Relative humidity (RH) is the ratio of the partial pressure of water vapor to the equilibrium vapor pressure of water at a given temperature. Relative humidity depends on temperature and the pressure of the system of interest. The same amount of water vapor results in higher relative humidity in cool air than warm air. A related parameter is that of dewpoint.

Harmattan haze over Ho, Ghana Ho, Ghana.JPG
Harmattan haze over Ho, Ghana

The air is particularly dry and desiccating when the Harmattan blows over the region. [1] The Harmattan brings desert-like weather conditions: it lowers the humidity, dissipates cloud cover, prevents rainfall formation and sometimes creates big clouds of dust which can result in dust storms or sandstorms.[ citation needed ] The wind can increase fire risk [6] and cause severe crop damage. [7] The interaction of the Harmattan with monsoon winds can cause tornadoes. [2]

Dust storm meteorological phenomenon common in arid and semi-arid regions

A dust storm is a meteorological phenomenon common in arid and semi-arid regions. Dust storms arise when a gust front or other strong wind blows loose sand and dirt from a dry surface. Fine particles are transported by saltation and suspension, a process that moves soil from one place and deposits it in another.

Monsoon seasonal changes in atmospheric circulation and precipitation associated with the asymmetric heating of land and sea

Monsoon is traditionally defined as a seasonal reversing wind accompanied by corresponding changes in precipitation, but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with the asymmetric heating of land and sea. Usually, the term monsoon is used to refer to the rainy phase of a seasonally changing pattern, although technically there is also a dry phase. The term is sometimes incorrectly used for locally heavy but short-term rains, although these rains meet the dictionary definition of monsoon.

Harmattan haze

In some countries in West Africa, the heavy amount of dust in the air can severely limit visibility and block the sun for several days, [8] comparable to a heavy fog. This effect is known as the Harmattan haze. It costs airlines millions of dollars in cancelled and diverted flights each year. [9] [10] When the haze is weak, the skies are clear. [11] [12] The dry air can break the trunks of trees growing in the region. [13]

Fog atmospheric phenomenon

Fog is a visible aerosol consisting of tiny water droplets or ice crystals suspended in the air at or near the Earth's surface. Fog can be considered a type of low-lying cloud, usually resembling stratus, and is heavily influenced by nearby bodies of water, topography, and wind conditions. In turn, fog has affected many human activities, such as shipping, travel, and warfare.

Health

Humidity drops to as low as 15%, which can result in spontaneous nosebleeds for some people. [7] Other health effects on humans may include conditions of the skin (dryness of the skin), eyes, and respiratory system, including aggravation of asthma. [14]

Asthma long-term disease involving poor airflow in the lungs

Asthma is a common long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm. Symptoms include episodes of wheezing, coughing, chest tightness, and shortness of breath. These may occur a few times a day or a few times per week. Depending on the person, they may become worse at night or with exercise.

See also

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The chergui or sharqi is the name of a continental easterly or southeasterly wind which blows on the southernmost part of Morocco, a hot and dry wind coming from the Sahara Desert. This wind can be compared with the sirocco, a very hot and very dry desert wind. The Arabic word means "coming from the east", as the chergui emanates from the desert east of the Atlas Mountains. This is a rain shadow wind as it falls down after passing over the top of the mountain range as a very hot and dry air into the coastal plains area towards the Atlantic ocean, which brings soaring temperatures typical of the desert, often over 40 °C (104 °F) and can even turn around 48 °C (118.4 °F) during the day at summertime and the relative humidity is extremely low, nearly always below 15%. The chergui can also more rarely blow at wintertime, and is responsible of a warm, sunny and dry weather.

References

  1. 1 2 3 Minka, Ndazo Salka; Ayo, Joseph (2014). "Influence of cold–dry (harmattan) season on colonic temperature and the development of pulmonary hypertension in broiler chickens, and the modulating effect of ascorbic acid". Open Access Animal Physiology: 1. doi:10.2147/OAAP.S51741.
  2. 1 2 "Harmattan". Encyclopædia Britannica. Retrieved 22 July 2015.
  3. "Harmattan". Merriam-Webster.com. Merriam-Webster. 2012.
  4. Climate and Land Degradation ( ISBN   3540724370, 2007): "At the southern fringe of the Sahara Desert, a special dry and hot wind, locally termed Harmattan, occurs."
  5. Geographical Review (1919): "Knox writes of this wind : The Harmattan is experienced as a wind which blows, especially in the months of December, January, and February, from the NE. and is a hot wind in some localities and a cold wind in others, according to circumstances."
  6. "Harmattan: Behold A Season". Leadership (Nigerian newspaper). 13 December 2014.
  7. 1 2 Terazono, Emiko; Blas, Javier (January 19, 2012). "Saharan wind stirs cocoa market". Financial Times. Retrieved January 28, 2012.
  8. "Tuareg unrest". BBC, via Temoust. 2007-09-07. Archived from the original on 2007-12-30. Retrieved 2007-10-08.
  9. This Day: Nigerian Civil Aviation warns pilots, airlines of Harmattan haze
  10. Valdmanis, Richard (2012-02-08). "Giant dust cloud chokes west Africa". Reuters. Retrieved 2012-02-09.
  11. "As harmattan finally hits Lagos". Vanaguard. 16 December 2014. Retrieved 11 October 2015.
  12. "The Climate Of Nigeria". The Library of Congress Studies. Retrieved 11 October 2015.
  13. "The North American Review, Volume 42". 1836. p. 213.
  14. Anuforo, Emeka; Chukwu, Lilian (20 January 2015). "Coping With Health Hazards of Harmattan Haze". Rivers State News.