The central belt of the planet got its name equatorial due to its location on both sides of the equator from 5-8 degrees north to 4-11 degrees south latitude.
Eternal summer
Bounded by subequatorial belts, the equatorial belt consists of three areas:
- Continent South America: Amazon River Lowlands;
- Mainland Africa: equatorial part; Gulf of Guinea;
- Part of the Great Sunda Islands and the nearest water area.
Equatorial latitudes simultaneously cover areas of both parts of the world, with the same climatic conditions in both the Northern and Southern hemispheres.
Equatorial air mass formation
The amount of heat that the sun gives to the earth's surface is one of the main factors affecting the climate of any corner on Earth. The degree of heating of the planet's surface depends on the angle at which the sun's rays fall on it. The closer to the equator, the more the Earth's surface warms up, therefore, the temperature of ground air increases.
On the territory of the equatorial belt, the angle of incidence of the sun's rays is the highest, therefore, the average annual air temperature in the regions of the equatorial belt is +26 degrees with slight differences. The air masses of the equatorial belt, when heated, rise and create an upward movement of air currents.
A zone of low atmospheric pressure is formed near the Earth’s surface - the equatorial depression. The heated and moist air rising up becomes saturated and cools there. As a result of thermal conversion, many cumulus clouds are collected, precipitated in the form of rain.
The air masses of the equatorial belt formed in the depression zone always have a high temperature. Humidity in this area is also increased.
This is the unique equatorial climatic zone. The characteristics of air masses are always similar. Since they form in a zone of low atmospheric pressure over land and the ocean, scientists do not divide them into marine and continental subtypes of climate.
Features of the air masses
The dominant air masses of the equatorial belt form the equatorial type of climate, which is characterized by:
- High constant air temperature from 24 0 to 28 0 with insignificant differences during the year with a difference of 2-3 0 . The change of seasons takes place imperceptibly, summer dominates all year round. The average temperature in the equatorial belt does not change throughout the year.
- An abundance of precipitation with two precipitation maxima corresponding to the zenith position of the Sun, and two minima during solstices. It rains, but unevenly.
- The mode of precipitation in the equatorial belt and their amount falling over the year differs for different regions of the equatorial belt.
A typical equatorial climate is characteristic of the Western Amazon and the Congo Basin. In the Congo Basin, the amount of precipitation that fell during the year is 1200-1500 mm, in some places 2000 mm per year. The area of the Amazonian lowland is significantly larger than the Congo Basin, the air masses of the equatorial belt are formed more intensively. The annual amount of precipitation reaches 2000-3000 mm. This is many times higher than the annual rate.
Equatorial Climate Belt: Climate Characteristic
The western part of the Andes and the north of the Guinean coast are characterized by the most abundant precipitation, their amount can exceed 5000 mm per year, in some places up to 10000 mm per year. Such an abundance of precipitation is affected by a strong counterflow between the trade winds of the north and south. In these areas, summer maximum precipitation is expressed.
The mode of precipitation in the equatorial belt varies significantly from season to season. A dry period is either absent or lasts one to two months. The large difference in summer and winter rainfall in these regions is due to the dry and dusty West African trade wind of Harmatan. From late November to early March, he blows from the Sahara towards the Gulf of Guinea.
Equatorial belt: climate forming winds
Precipitation is directly related to the intra-tropical zone of trade winds convergence, the zone where the convergence of air currents is observed. The convergence zone stretches along the equator, coincides with the zone of low atmospheric pressure and is located most of the year north of the equator. In seasons, the occurring displacements of the convergence zone are accompanied by changes most noticeable in the Indian Ocean basin.
Here the trade winds are replaced by monsoons. Sustainable winds, depending on the season, change their direction. The strength of the wind can change: from weak to become barrage. In this zone, most of all tropical cyclones form. Tropical latitudes are characterized by high atmospheric pressure.
Trade winds and monsoons
They form air streams that rush into the low pressure zone - to the equator. Due to the rotation of the Earth, the northeast trade wind near the equator takes the north direction, and the southeast trade wind takes the south. When meeting, they form a calm - windless strip. Trade winds are weak air currents blowing along the equator all year round, they are the most stable winds on the planet.
Thus, after equinox days, maximum precipitation falls in the equatorial zone. A slight decrease in precipitation is observed after solstice days. Over the earth's surface, heated by the sun's rays, an accumulation of clouds forms. It usually rains in the afternoon, accompanied by thunderstorms. Downpours and thunderstorms over the sea occur at night, this is the difference between the marine and continental climate.
There is so much atmospheric precipitation that moisture does not have time to evaporate. The value of relative humidity is kept at 80-95%. Excess moisture swamps the soil, contributing to the growth of impassable multi-tier equatorial forests. Western monsoons constantly blow over the moist forests of equatorial latitudes in summer and eastern monsoons in winter, Guinean monsoon and Indonesia monsoon in Africa.