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Rainfall and the tropical climate dominate the tropical rain belt, which oscillates from the northern to the southern tropics over the course of the year, roughly following the solar equator. The tropical rain belt is an area of active rain that is positioned mostly around the tropics. [1]
The reason the rain belt is situated near the tropics can be attributed to the fact that the Sun's radiation is strongest near the equator, which is located in the middle of the tropics. This solar radiation generates large amounts of heat near the equator. [1] [2] This causes the air at ground level in the tropics to warm up. Because hot air is less dense than cold air, the hot air rises into the upper levels of the atmosphere, cooling as it rises. [1]
However, cooler air cannot hold as much moisture as hot air, so when the air rises and cools, its water condenses, forming clouds which cause rain in the form of thunderstorms and rain showers.
The tropical rain belt is located along the equator, but they will extend out to the Tropic of Cancer, which is the 23.5 north latitude, as well as the Tropic of Capricorn, which is the 23.5 south latitude. [1] It moves north in the Northern hemisphere summer and south in the Northern hemisphere winter, following the thermal equator where temperatures are highest at each point in the year. It is a manifestation of the Intertropical Convergence Zone. [3]
The tropical rain belt lies in the southern hemisphere of the Indian ocean and western Pacific ocean roughly from October to March, and during this time the northern tropics experience a dry season in which precipitation is very rare, and days are typically hot and sunny throughout. From April to September, the rain belt lies in the northern hemisphere, and a wet season occurs there, while the southern tropics experience their dry season.
The rain belt reaches roughly as far north as the Tropic of Cancer and as far south as the Tropic of Capricorn in the western Pacific Ocean. Its variation in the Western Hemisphere is minimal, roughly between the equator and the 15th parallel north latitude. Near these latitudes, there is one wet season and one dry season annually. On the equator, there are two wet and two dry seasons as the rain belt passes over twice a year, one moving north and one moving south. Between the tropics and the equator, locations may experience both a short wet and a long wet season. Local geography may substantially modify these climate patterns.
As the earth warms, the rain belt is projected to move north of the current position. [4] Recent climate change can be attributed to rising carbon dioxide concentrations in the atmosphere; caused by the burning of fossil fuels. The correlation between the concentration of carbon dioxide in the atmosphere and average global temperature is undeniably direct, meaning that as more carbon dioxide is released into the atmosphere, the temperature of the Earth is expected to rise as well. [5] Even though the Earth is warming as a whole entity, the Northern Hemisphere is warming faster than the Southern because of melting Arctic sea ice. [6]
As the Northern Hemisphere warms, a temperature gradient is established between the Northern and Southern hemispheres. [6] The warmer temperatures in the Northern parts of the tropics foster an environment more conducive to the development of moisture. The additional moisture is met with a low-level atmosphere that is cooler because the warm air has risen to the higher levels of the atmosphere. [6]
This scenario leads to increased precipitation and is a fundament behind the idea that the rain belt is moving north. [6] The contrast in temperature is only a part of the entire process that is driving the tropical rain belt northward. [6] Another factor that influences the tropical rain belt is ocean circulation. Ocean Overturning Circulation is a process that involves ocean circulation between the Antarctic and Arctic regions. [7]
Dargan Frierson explains that in this process, the Northern Hemisphere receives more heat than the Southern because the overturning circulation brings more heat into the Northern Hemisphere as opposed to the Southern. He also states that as a result, the extra heat is transferred to the tropical regions in the Northern Hemisphere, causing warm ocean water to be situated in the northern tropics. [7] This warm ocean water is what eventually generates rain and thunderstorms, and because there is more warm water in the northern tropics, it is obvious that the tropical rain belt is moving northward. [7] Due to global climate change, the circulation of ocean currents and ocean temperatures might adjust in favor of pushing the belt further north into the region of oscillation. [7]
However, there is also the possibility that climate change will slow down ocean currents and circulation, which can change the present-day dynamic and send the rain belt to the south. [7] Therefore, ocean circulation, ocean temperature, and the temperature of the earth are all attributing to the movement of the tropical rain belt. It is evident that the trend is northward and the belt is currently situated in the northern tropics, but the possibility of southward movement does exist. [7] The northward movement does affect many countries and crops because the tropical rain belt is essential to food production in areas that rely on heavy precipitation.
The tropical regions will be affected most by the northward movement of the rain. The banana and coffee crops in Guatemala and Indonesia will become compromised by the loss of precipitation. [4] In addition, the effects of a drier climate in Mexico could push the Mexican desert into southern portions of Texas, New Mexico and other areas in the southern U.S. [4] Areas in the Middle East, Western America, and the Amazon rainforest risk the possibility of becoming drier and less humid. [6] In contrast, the northward trend could bring more rain to areas in Asia already exposed to monsoons. [6]
An increase of moisture in monsoon prone areas could be catastrophic as massive floods could follow the large amounts of rain added to preexisting rain from monsoons. [6] Using geographical information, it is possible that the northward movement of the rain belt is already evident because of droughts in the western US, Syria and northern China. [6] Although the possible adversarial effects of the movement can be devastating, the northward movement of the rain belt could bring an increase of rain to areas that have been decimated by droughts, which could prove to be very beneficial. [4]
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.
The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at 23°26′10.3″ (or 23.43619°) N and the Tropic of Capricorn in the Southern Hemisphere at 23°26′10.3″ (or 23.43619°) S. The tropics are also referred to as the tropical zone and the torrid zone.
The Tropic of Capricorn is the circle of latitude that contains the subsolar point at the December solstice. It is thus the southernmost latitude where the Sun can be seen directly overhead. It also reaches 90 degrees below the horizon at solar midnight on the June Solstice. Its northern equivalent is the Tropic of Cancer.
The horse latitudes are the latitudes about 30 degrees north and south of the Equator. They are characterized by sunny skies, calm winds, and very little precipitation. They are also known as subtropical ridges or highs. It is a high-pressure area at the divergence of trade winds and the westerlies.
In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls from clouds due to gravitational pull. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. Precipitation occurs when a portion of the atmosphere becomes saturated with water vapor, so that the water condenses and "precipitates" or falls. Thus, fog and mist are not precipitation but colloids, because the water vapor does not condense sufficiently to precipitate. Two processes, possibly acting together, can lead to air becoming saturated: cooling the air or adding water vapor to the air. Precipitation forms as smaller droplets coalesce via collision with other rain drops or ice crystals within a cloud. Short, intense periods of rain in scattered locations are called showers.
Physical oceanography is the study of physical conditions and physical processes within the ocean, especially the motions and physical properties of ocean waters.
The subtropical zones or subtropics are geographical and climate zones to the north and south of the tropics. Geographically part of the temperate zones of both hemispheres, they cover the middle latitudes from 23°26′10.3″ (or 23.43619°) to approximately 35° north and south. The horse latitudes lie within this range.
The Intertropical Convergence Zone, known by sailors as the doldrums or the calms because of its monotonous windless weather, is the area where the northeast and the southeast trade winds converge. It encircles Earth near the thermal equator though its specific position varies seasonally. When it lies near the geographic Equator, it is called the near-equatorial trough. Where the ITCZ is drawn into and merges with a monsoonal circulation, it is sometimes referred to as a monsoon trough, a usage that is more common in Australia and parts of Asia.
Atmospheric circulation is the large-scale movement of air and together with ocean circulation is the means by which thermal energy is redistributed on the surface of the Earth. The Earth's atmospheric circulation varies from year to year, but the large-scale structure of its circulation remains fairly constant. The smaller-scale weather systems – mid-latitude depressions, or tropical convective cells – occur chaotically, and long-range weather predictions of those cannot be made beyond ten days in practice, or a month in theory.
The dry season is a yearly period of low rainfall, especially in the tropics. The weather in the tropics is dominated by the tropical rain belt, which moves from the northern to the southern tropics and back over the course of the year. The temperate counterpart to the tropical dry season is summer or winter.
The Madden–Julian oscillation (MJO) is the largest element of the intraseasonal variability in the tropical atmosphere. It was discovered in 1971 by Roland Madden and Paul Julian of the American National Center for Atmospheric Research (NCAR). It is a large-scale coupling between atmospheric circulation and tropical deep atmospheric convection. Unlike a standing pattern like the El Niño–Southern Oscillation (ENSO), the Madden–Julian oscillation is a traveling pattern that propagates eastward, at approximately 4 to 8 m/s, through the atmosphere above the warm parts of the Indian and Pacific oceans. This overall circulation pattern manifests itself most clearly as anomalous rainfall.
The geography of South America contains many diverse regions and climates. Geographically, South America is generally considered a continent forming the southern portion of the landmass of the Americas, south and east of the Colombia–Panama border by most authorities, or south and east of the Panama Canal by some. South and North America are sometimes considered a single continent or supercontinent, while constituent regions are infrequently considered subcontinents.
The Hadley cell, also known as the Hadley circulation, is a global-scale tropical atmospheric circulation that features air rising near the equator, flowing poleward near the tropopause at a height of 12–15 km (7.5–9.3 mi) above the Earth's surface, cooling and descending in the subtropics at around 25 degrees latitude, and then returning equatorward near the surface. It is a thermally direct circulation within the troposphere that emerges due to differences in insolation and heating between the tropics and the subtropics. On a yearly average, the circulation is characterized by a circulation cell on each side of the equator. The Southern Hemisphere Hadley cell is slightly stronger on average than its northern counterpart, extending slightly beyond the equator into the Northern Hemisphere. During the summer and winter months, the Hadley circulation is dominated by a single, cross-equatorial cell with air rising in the summer hemisphere and sinking in the winter hemisphere. Analogous circulations may occur in extraterrestrial atmospheres, such as on Venus and Mars.
Earth rainfall climatology Is the study of rainfall, a sub-field of meteorology. Formally, a wider study includes water falling as ice crystals, i.e. hail, sleet, snow. The aim of rainfall climatology is to measure, understand and predict rain distribution across different regions of planet Earth, a factor of air pressure, humidity, topography, cloud type and raindrop size, via direct measurement and remote sensing data acquisition. Current technologies accurately predict rainfall 3–4 days in advance using numerical weather prediction. Geostationary orbiting satellites gather IR and visual wavelength data to measure realtime localised rainfall by estimating cloud albedo, water content, and the corresponding probability of rain.
A cold-core low, also known as an upper level low or cold-core cyclone, is a cyclone aloft which has an associated cold pool of air residing at high altitude within the Earth's troposphere, without a frontal structure. It is a low pressure system that strengthens with height in accordance with the thermal wind relationship. If a weak surface circulation forms in response to such a feature at subtropical latitudes of the eastern north Pacific or north Indian oceans, it is called a subtropical cyclone. Cloud cover and rainfall mainly occurs with these systems during the day.
The climate of Africa is a range of climates such as the equatorial climate, the tropical wet and dry climate, the tropical monsoon climate, the semi-arid climate, the desert climate, the humid subtropical climate, and the subtropical highland climate. Temperate climates are rare across the continent except at very high elevations and along the fringes. In fact, the climate of Africa is more variable by rainfall amount than by temperatures, which are consistently high. African deserts are the sunniest and the driest parts of the continent, owing to the prevailing presence of the subtropical ridge with subsiding, hot, dry air masses. Africa holds many heat-related records: the continent has the hottest extended region year-round, the areas with the hottest summer climate, the highest sunshine duration, and more.
The climate of Asia is dry across its southwestern region, with dry across much of the interior. Some of the largest daily temperature ranges on Earth occur in the western part of Asia. The monsoon circulation dominates across the southern and eastern regions, due to the Himalayas forcing the formation of a thermal low which draws in moisture during the summer. The southwestern region of the continent experiences low relief as a result of the subtropical high pressure belt; they are hot in summer, warm to cool in winter, and may snow at higher altitudes. Siberia is one of the coldest places in the Northern Hemisphere, and can act as a source of arctic air mass for North America. The most active place on Earth for tropical cyclone activity lies northeast of the Philippines and south of Japan, and the phase of the El Nino-Southern Oscillation modulates where in Asia landfall is more likely to occur. Many parts of Asia are being impacted by climate change.
The Monsoon of South Asia is among several geographically distributed global monsoons. It affects the Indian subcontinent, where it is one of the oldest and most anticipated weather phenomena and an economically important pattern every year from June through September, but it is only partly understood and notoriously difficult to predict. Several theories have been proposed to explain the origin, process, strength, variability, distribution, and general vagaries of the monsoon, but understanding and predictability are still evolving.
There are a number of explanations of the asymmetry of the Intertropical Convergence Zone (ITCZ), known by sailors as the Doldrums.
The Pangean megamonsoon refers to the theory that the supercontinent Pangea experienced a distinct seasonal reversal of winds, which resulted in extreme transitions between dry and wet periods throughout the year. Pangea was a conglomeration of all the global continental land masses, which lasted from the late Carboniferous to the mid-Jurassic. The megamonsoon intensified as the continents continued to shift toward one another and reached its maximum strength in the Triassic, when the continental surface area of Pangea was at its peak.
