The climate system consists of the atmosphere, lithosphere, hydrosphere, and biosphere. The atmosphere plays a crucial role in the process of climate formation. Different regions of the planet have different amounts of precipitation. Some of the regions are dry and some are humid. Such mechanisms as well as hot and cold streams, winds, and latitude influence the amount of precipitation in tropics and temperate latitudes.
In the atmospheric conditions, heat exchange is characterized by the complex processes of generating, transmission, transfer, and heat loss in most important system of the Earth – its atmosphere. Direct solar radiation transmitted through the atmosphere and diffused radiation partially reflected from it heat the upper layers of both soil and water. The Earth’s surface emits invisible infrared radiation that, for the most part, is absorbed by the atmosphere and heats. The atmosphere emits infrared radiation, the most part of which is absorbed by the Earth’s surface. At the same time, terrestrial and atmospheric radiations are continuously emitted into space. Together with the reflected solar radiation, these radiations balance the inflow of solar radiation to the Earth. Part of the radiant energy goes into heating of the planet’s surface and atmosphere.
In addition to the heat exchange by radiation, between the surface and the atmosphere, there is an exchange of heat by conduction. In the transfer of heat within the atmosphere, mixing of air in the vertical direction plays an important role. A considerable part of the heat input to the Earth’s surface is expended in heating the water. In condensation of water vapor, heat is released in the atmosphere, which is used to heat air. John Oliver (2008) states that “Practically all precipitation results from the adiabatic cooling of ascending moist airmasses” (p. 577). The essential process of heat exchange is a horizontal transfer of heat by air currents.
Between the atmosphere and the surface of the planet, there is a constant hydrologic cycle. Moisture evaporates from the water surface, soil, and vegetation into the atmosphere. Large amounts of heat from the soil and the upper layers of water are spent on this process. Under real conditions, water vapor is condensed in the atmosphere (Oliver, 2008). Thereby, clouds and fogs emerge. Precipitation falling from the clouds balances the evaporation in general for the entire globe. The amount of rainfall and their distribution in space and time determine the characteristics of vegetation and agriculture. The hydrological regime of water bodies depends on the distribution of rainfall and their variability. The freezing of the soil and the regime of continuous permafrost are associated with the snow depth.
Due to the uneven heating of the planet by the sun and distribution of precipitation on the Earth’s surface, the climate of the planet is highly diverse. The amount of rainfall depends on the latitude, the general circulation of the atmosphere and associated processes, and the relief. These days, tropics are characterized by excessive precipitation. Precipitation in this area is mainly associated with the intertropical convergence zone that is located just north of the equator (Oliver, 2008). Seasonal displacements of the zone to the north and south in some areas lead to the formation of two peaks of rainfall during the year, and they are separated by drier periods. Every day, thousands of thunderstorms form over the wet tropics. Between them, the sun shines at full strength. In tropics, there are permanent storms causing floods and monsoons causing hurricanes with the squally wind. Scientists have found that because of the global warming, the Earth’s climate zone can literally go under the water. The increase in the average temperature of the planet by one degree will lead to the increase in the amount of precipitation in the equatorial region by 10% immediately (Nicholson, 2011). This, in turn, will cause catastrophic devastating floods in the fairly densely populated areas. Compared with other regions, the tropics accustomed to abundant rainfall respond to the climate change in a different way. Scientists state that the tropical region is more sensitive to global warming than other regions worldwide. Greenhouse effect leads to the rise of temperature in the atmosphere (Nicholson, 2011). In turn, this fact leads to the increase in humidity in the tropical region. The global warming threatens with catastrophic flooding in the densely populated areas of the equator.
Average annual precipitation at temperate latitudes is usually less than 500 mm but more than 250 mm (Nicholson, 2011). As for the development of steppe vegetation in the conditions of higher temperatures more rainfall is necessary, the latitude and high-altitude position of the area determine climate changes. For the climate of this zone, there are no general regularities of the distribution of rainfall throughout the year. For example, in areas bordering the subtropics with dry summer, there is maximum precipitation in winter. However, in the areas adjacent to the areas of humid continental climate, rains fall mainly in summer. Cyclones of temperate latitudes bring the majority of winter precipitation that often falls as snow and that can be accompanied by strong winds (Nicholson, 2011). Summer thunderstorms often come with hail. The amount of rainfall varies greatly from year to year. It is also associated with the changes of the global climate.
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The trade winds influence the low rainfall in the tropical regions (Nicholson, 2011). They are dry winds. Thus, in the area of their development, precipitation is low. In both hemispheres near the subtropical high, deserts are located due to the lack of rainfall. Dryness of these regions is determined by the trade winds that blow from the land, the downward movement of the air near the subtropical barometric maximum, and cold currents passing the coast. As a result, the air is dry and the rainfall is scarce.
The tropical region is represented by tropical rainforests, dry tropical forests, and savannas. Savannah is a zonal type of landscape of tropical and subequatorial climatic zones. This natural area is clearly expressed by the change of wet and dry seasons with consistently high air temperatures – between 15°C to + 32°C (Nicholson, 2011). With the increasing distance from the equator, the period of the wet season reduces from 8-9 months to 2-3 and rainfall – from 2000 up to 250 mm per year (Nicholson, 2011). In these areas, precipitation is intermittent and changeable. Since this region lies entirely in the tropics, in each individual place, the sun is at its zenith twice a year. Most of the rain falls at that time because the areas of the intertropical convergence and related humid conditions are shifted to the north and to the south with the sun twice during the year. Alternating dry seasons come from the fact that the rainless area of high pressure associated with deserts comes to the savannah region. Dry tropical forests are forests that receive less precipitation than tropical rainforests. Dry forests tend to have a dry season and a rainy season (Nicholson, 2011). Although there is a sufficient amount of precipitation to support the growth of vegetation on the proper level, the trees must be able to withstand long periods of drought.
Atmospheric precipitation on the earth’s surface is extremely unevenly distributed. Some areas suffer from the excess moisture while others – from its lack. The highest rainfall around the globe should be expected in the areas where the atmospheric humidity is high and where there are conditions for the raising and the cooling of air. However, these days, due to the global climate changes, many regions suffer from the excessive rains or prolonged droughts.