Pressure and Wind Systems PDF

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It is referred to as air or atmospheric pressure when the weight of a column of air contained in a unit area from the mean sea level to the top of the atmosphere is measured. The atmospheric pressure is measured in millibars, which are the smallest units of measurement. Approximately 1,013.2 milliba...

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Pressure and Wind Systems It is referred to as air or atmospheric pressure when the weight of a column of air contained in a unit area from the mean sea level to the top of the atmosphere is measured. The atmospheric pressure is measured in millibars, which are the smallest units of measurement. Approximately 1,013.2 millibars of average atmospheric pressure are measured at sea level. Because of gravity, the air near the surface is denser and has a higher pressure than the air above it. The air pressure is measured with the aid of a mercury barometer or an aneroid barometer, respectively. The pressure decreases as one rises in altitude. If you are at any elevation, the temperature varies from place to place, and this variation is the primary cause of air motion, i.e., wind that moves from highpressure areas to low-pressure areas, at any elevation. Distribution of Pressure on Earth’s Surface As with the horizontal distribution of temperature on the earth's surface, the horizontal distribution of air pressure on the earth's surface is closely related to the distribution of temperature because the same factors that influence temperature on the earth's surface also influence the horizontal distribution of pressure. The distribution of pressure on the earth's surface is influenced by several factors, the most important of which are the unequal distribution of insolation over the surface, differential heating of land and water, and differences in the albedo of the earth's surface. However, there is another factor that comes into play during the development of the pressure belt, and that is the Coriolis force, which is caused by the rotation of the earth. Pressure Belts A rotationally rotating earth with a uniform surface (in order to eliminate the effect of altitude on pressure, pressure is measured at any station after being reduced to sea level) has seven alternate low- and high-pressure belts on the earth's surface, which are based on the distribution pattern of surface pressure. In nature, these pressure belts do not last indefinitely. In accordance with the apparent movement of the sun, they oscillate. During the winter months in the northern hemisphere, they migrate southward, and during the summer months, they migrate northward. -

Equatorial low-pressure belt Subtropical high-pressure belt – Northern hemisphere Subtropical high-pressure belt – Southern hemisphere Subpolar low-pressure belt – Northern hemisphere Subpolar low-pressure belt – Southern hemisphere Polar high-pressure belt – Northern hemisphere Polar high-pressure belt – Southern hemisphere

Equatorial Low-Pressure Belt

It can be found between the latitudes of 10°N and 10°S. Because of the high insolation and convective rise of air, it is a thermally induced belt of cloud cover (updraft). This region experiences vertical clouds, such as Polar High cumulonimbus, with thunder and lightning, as well as afternoon showers between 2 and 4 p.m., followed by atmospheric stability and complete calmness after that. Because of the lack of air movement and the resulting generation of intense low pressure, this region is also referred to as the doldrums. According to popular belief, ships sailing through the doldrums can become stuck for several weeks if they do not have enough sail power to move forward. The zone of convergence of the N-E and S-E Trade winds is represented by this belt. Sub-Tropical High Pressure Belt It can be found between 25° and 35° latitudes in both the northern and southern hemispheres. It is a high-pressure zone that has been created dynamically. As a result of the mechanical force produced by air accumulated aloft, cold and dry air (downdraft) sinks to the ground, resulting in this condition. Upon entering the equatorial region, the air becomes heavier and descends, resulting in the air accumulation. The Coriolis force and the geostrophic effect are two factors that contribute to the accumulation of air. As a result of the warm and dry subsiding air, hot tropical deserts develop on the western sides of continents in this zone, preventing rain from accumulating there. Because of the frequent calms that occur in this area of high pressure, it is referred to as 'Horse Latitude.' While passing through this zone of calm, merchants transporting horses in their ships were required to discard some of the horses in order to lighten their ships, which was a common practise in ancient times. This is the reason why this zone is referred to as 'Horse Latitude."

Belt of Low Pressure in the Subpolar Polar Region It can be found along the 60° to 65° latitude line in both hemispheres. Despite the fact that it is a dynamically induced pressure belt, thermal factors cannot be overlooked. In meteorology, it is referred to as the convergence zone of warm and cold air masses. It is also referred to as the temperate convergence zone. The formation of fronts, as well as the development of temperate cyclones, as well as the frequent change in weather conditions, are common phenomena observed here. Belt of High Pressure in the Polar Regions It can be found near the poles between 75° and 90° latitude in both hemispheres, between 75° and 90° latitude in the northern hemisphere. Despite the fact that the pressure belt is caused by thermal convection, the importance of dynamic factors cannot be overlooked. The region is experiencing a subsidence of cold and dry air, which is causing the high

pressure to decrease. Because of the coriolis effect, the subsiding air is transformed into an anti-cyclone, which results in an outflow of air in the form of a hurricane. Buran is the name given to these gales in Siberia, while blizzard is used in North America. Pressure and Wind Patterns: January On the first of January, a powerful high-pressure system known as the Siberian high is positioned over the frozen landscape of northern Asia. Located over the chilled North American continent is a weaker version of the polar high. These cold anticyclones are composed of extremely dense air, which is responsible for the weight of the air columns. In fact, the highest recorded sea-level pressure, 1084 millibar (32.01 inches of mercury), was recorded in December 1968 at Agata, Siberia, and was the highest ever measured. The polar highs are prominent features of the winter circulation over the northern hemisphere's continents, particularly in the Arctic. As a result of subsidence within these air columns, clear skies and divergent surface flow are observed. The winds that result from this are referred to as polar easterlies....