Part of a series on |
Weather |
---|
Weatherportal |
The Harmattan is a season in West Africa that occurs between the end of November and the middle of March. It is characterized by the dry and dusty northeasterly trade wind, of the same name, which blows from the Sahara over West Africa into the Gulf of Guinea. [1] The name is related to the word haramata in the Twi language. [2] The temperature is cold mostly at night in some places but can be very hot in certain places during daytime. generally, temperature differences can also depend on local circumstances. [3]
The Harmattan blows during the dry season, which occurs during the months with the lowest sun. In this season, the subtropical ridge of high pressure stays over the central Sahara and the low-pressure Intertropical Convergence Zone (ITCZ) stays over the Gulf of Guinea. On its passage over the Sahara, the Harmattan picks fine dust and sand particles (between 0.5 and 10 microns). It is also known as the "doctor wind", because of its invigorating dryness compared with humid tropical air.
This season differs from winter because it is characterized by cold, dry, [4] 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 5%. It can also be hot in some regions, like in the Sahara. [5]
The air is particularly dry and desiccating when the Harmattan blows over the region. [4] 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. [1]
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] The extreme dryness of the air may cause branches of trees to die. [12]
A 2024 study found that dust carried by the Harmattan increases infant and child mortality, as well as has persistent adverse health impacts on surviving children. [13]
Humidity can drop lower than 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), dried or chapped lips, eyes, and respiratory system, including aggravation of asthma. [14]
Cape Verde is a group of arid Atlantic islands which are home to distinct communities of plants, birds, and reptiles. The islands constitute the unique Cape Verde Islands dry forests ecoregion, according to the World Wildlife Fund.
Nigeria is a country in West Africa. It shares land borders with the Republic of Benin to the west, Chad and Cameroon to the east, and Niger to the north. Its coast lies on the Gulf of Guinea in the south and it borders Lake Chad to the northeast. Notable geographical features in Nigeria include the Adamawa Plateau, Mambilla Plateau, Jos Plateau, Obudu Plateau, the Niger River, Benue River, and Niger Delta.
Western Sahara is a territory in Northern Africa, bordered by the North Atlantic Ocean, Morocco proper, Algeria, and Mauritania. Geographic coordinates: 24°30′N13°00′W
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 affects many human activities, such as shipping, travel, and warfare.
The Santa Ana winds are strong, extremely dry downslope winds that originate inland and affect coastal Southern California and northern Baja California. They originate from cool, dry high-pressure air masses in the Great Basin.
In meteorology, an air mass is a volume of air defined by its temperature and humidity. Air masses cover many hundreds or thousands of square miles, and adapt to the characteristics of the surface below them. They are classified according to latitude and their continental or maritime source regions. Colder air masses are termed polar or arctic, while warmer air masses are deemed tropical. Continental and superior air masses are dry, while maritime and monsoon air masses are moist. Weather fronts separate air masses with different density characteristics. Once an air mass moves away from its source region, underlying vegetation and water bodies can quickly modify its character. Classification schemes tackle an air mass's characteristics, as well as modification.
A Foehn or Föhn, is a type of dry, relatively warm, downslope wind that occurs in the lee of a mountain range. It is a rain shadow wind that results from the subsequent adiabatic warming of air that has dropped most of its moisture on windward slopes. As a consequence of the different adiabatic lapse rates of moist and dry air, the air on the leeward slopes becomes warmer than equivalent elevations on the windward slopes.
A high-pressure area, high, or anticyclone, is an area near the surface of a planet where the atmospheric pressure is greater than the pressure in the surrounding regions. Highs are middle-scale meteorological features that result from interplays between the relatively larger-scale dynamics of an entire planet's atmospheric circulation.
Weather lore is the body of informal folklore related to the prediction of the weather and its greater meaning.
The trade winds or easterlies are permanent east-to-west prevailing winds that flow in the Earth's equatorial region. The trade winds blow mainly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere, strengthening during the winter and when the Arctic oscillation is in its warm phase. Trade winds have been used by captains of sailing ships to cross the world's oceans for centuries. They enabled European colonization of the Americas, and trade routes to become established across the Atlantic Ocean and the Pacific Ocean.
Desert ecology is the study of interactions between both biotic and abiotic components of desert environments. A desert ecosystem is defined by interactions between organisms, the climate in which they live, and any other non-living influences on the habitat. Deserts are arid regions that are generally associated with warm temperatures; however, cold deserts also exist. Deserts can be found in every continent, with the largest deserts located in Antarctica, the Arctic, Northern Africa, and the Middle East.
The Loo is a strong, dusty, gusty, hot and dry summer wind from the west which blows over the Indo-Gangetic Plain region of North India and Pakistan. It is especially strong in the months of May and June. Due to its very high temperatures, exposure to it often leads to fatal heatstrokes.
The Saharan air layer (SAL) is an extremely hot, dry, and sometimes dust-laden layer of the atmosphere that often overlies the cooler, more humid surface air of the Atlantic Ocean. It carries upwards of 60 million tonnes of dust annually over the ocean and the Americas. This annual phenomenon sometimes cools the ocean and suppresses Atlantic tropical cyclogenesis.
The climate of Delhi is an overlap between monsoon-influenced humid subtropical and semi-arid, with high variation between summer and winter temperatures and precipitation. Delhi's version of a humid subtropical climate is markedly different from many other humid subtropical cities such as São Paulo, Houston, and Brisbane in that the city features dust storms and wildfire haze due to its semi-arid climate.
Albania has a variety of climate systems. With its coastline facing the Adriatic and Ionian seas in the Mediterranean sea, its highlands backed upon the elevated Balkan landmass, and the entire country lying at a latitude subject to a variety of weather patterns during the winter and summer seasons, however it has a high number of climatic regions for such a small area. The coastal lowlands have typically mediterranean climate while the highlands have a continental climate. In both the lowlands and the interior, the weather varies markedly from north to south.
A desert is a landscape where little precipitation occurs and, consequently, living conditions create unique biomes and ecosystems. The lack of vegetation exposes the unprotected surface of the ground to denudation. About one-third of the land surface of the Earth is arid or semi-arid. This includes much of the polar regions, where little precipitation occurs, and which are sometimes called polar deserts or "cold deserts". Deserts can be classified by the amount of precipitation that falls, by the temperature that prevails, by the causes of desertification or by their geographical location.
Khamsin, chamsin or hamsin, more commonly known in Egypt as khamaseen, is a dry, hot, sandy local wind affecting Egypt and the Levant; similar winds, blowing in other parts of North Africa, the Arabian Peninsula and the entire Mediterranean basin, have different local names, such as bad-i-sad-o-bist roz in Iran and Afghanistan, haboob in the Sudan, aajej in southern Morocco, ghibli in Tunis, harmattan in the western Maghreb, africo in Italy, sirocco which blows in winter over much of the Middle East, and simoom.
This glossary of meteorology is a list of terms and concepts relevant to meteorology and atmospheric science, their sub-disciplines, and related fields.
The climate of Nigeria is mostly tropical. Nigeria has three distinct climatic zones, two seasons, and an average temperature ranging between 21 °C and 35 °C. Two major elements determine the temperature in Nigeria: the altitude of the sun and the atmosphere's transparency. Its rainfall is mediated by three distinct conditions including convectional, frontal, and orographical determinants. Statistics from the World Bank Group showed Nigeria's annual temperature and rainfall variations, the nation's highest average annual mean temperature was 28.1 °C in 1938, while its wettest year was 1957 with an annual mean rainfall of 1,441.45mm.
At the southern fringe of the Sahara Desert, a special dry and hot wind, locally termed Harmattan, occurs.