“Places around the equator and those at latitude 60N are dominated by low pressure belts.
Yet the weather and heat transfer processes in the two regions are very different.The weather in the equatorial region is often unchanging while that along latitude 60’N is variable.” Briefly describe the formation of low pressure belts in the two regions.
Explain the different weather patterns in the two regions with reference to atmospheric circulation and movement of air masses. Discuss the heat transfer processes which take place in the atmosphere in the two regions.Illustrate your answer with examples from the two regions. The two low pressure belts found at the equator and at 60N are called equatorial low pressure belt and the temperate low pressure zone.
Though both are low pressure systems, their weather and heat transfer processes are very different. Their diversion can be viewed under The equatorial zones are distinguished by a hot and wet climate all year round, yet the temperate zones are typified by less stable areas. The temperature difference between the equator and the poles generates a circulation system which redistributes heat from low latitudes to high latitudes.The rising and sinking of air at different parts of the earth formed by these circulation cells form low-pressure zones and high-pressure zones respectively. Low pressure develops when air rises. A major zone of low pressure exists at the equator, where the sunlight heats the Earth’s surface and air in contact with it, causing it to rise, thus forming this low pressure region. The temperate low pressure belt, on the other hand, is formed by collision with cold polar air.
The descending air in the subtropical belt travels towards the higher latitudes, delivering warm air masses to the temperate regions.Here they collide with cold polar air and the warm air is forced to rise, developing a zone of low pressure. The temperate low-pressure zone is therefore cyclonic in nature which effectively explains its relative instability compared to the equatorial regions. For example, London, being located at 51N, is always surrounded by rain and intermittent sunshine. Though both regions are characterized by a low pressure system, the two zones’ characteristics are quite distinct in terms of atmospheric circulation and movement of air masses as their formation processes are deviating.Much of the equatorial belt experiences hot and humid weather. There is abundant rainfall due to the active vertical uplift of air that takes place there, and during certain periods, thunderstorms occur as well.
As the belt receives considerable sunshine and excessive rainfall, it provides an ideal growing ground for vegetation. The region consists of the Amazon Basin in Brazil, the Congo Basin in West Africa and Indonesia where luxuriant vegetation is found. At about 60N, there is another belt of cyclonic low pressure arising from the convergence of cold polar wind and warm subtropical westerly.Cyclonic depressions are formed upon the collision of the two zones, in this case, the North Atlantic and North Pacific in the Northern Hemisphere. They are characterized by relatively mild, moist winds that tend to bring frequent rain and snow. The precipitation often develop along warm and cold fronts, where cold air from the polar forces the warm, moist air of the westerlies to rise, which, on cooling , releases the moisture as clouds, and finally falling as rain and snow. Atmospheric Circulation is the large-scale movement of air, and the means by which thermal energy is distributed on the surface of the Earth.
The atmospheric circulation and the movement of air masses vary as well due to the different formation processes and the nature of the two low pressure belts. Atmospheric circulation refers to the large-scale movement of air and the means by which thermal energy is distributed on the surface of the earth. Due to the earth’s rotation, airflow is deflected by an angle in a different direction in Northern and Southern Hemispheres. This is called the Coriolis force which describes the east-west directions of air movement deflection caused by the earth’s rotation.At the equator, air movement is light and air from the subtropical zones in the Northern and Southern Hemispheres converges in a zone called the “Inter-Tropical Convergence Zone” (ITCZ). The “Northeast Trades” and “Southeast Trades” are the low latitude wind belts formed over the oceans. During the summer, the ITCZ in the Northern Hemisphere is shifted to the north of the equator, and due to the Coriolis force, the Southeast Trade winds are deflected to the right over the equator region and causing the “Southwest Monsoons”.
These wind movements contribute to the prolonged wet season in India and Southeast Asia n the summer months of April to September, resulting in the large disparity of climate characteristics of the two regions though both being low pressure belts. Heat transfer processes at the equatorial region and the temperate regions are of course not the same. Convection is the dominant heat transfer process at the equatorial region. Convective heat and mass transfer take place by convection cells. Air is continuously heated by the strong insolation received at the equator; this body of hot air expands and rises, and eventually is replaced by colder air.As the hot air reaches a point of condensation, the fluid begins to descend. As it descends, it warms again the cycle repeats itself.
This kind of heat transfer process is characterized by thunderstorms and heavy rain, causing an extremely unstable weather condition. Areas such as the Amazon Rainforest receive sufficient rainfall which allows it to flourish continuously and all around the year. In the temperate region on the other hand, the amount of insolation is less than the tropical.Thought the changes in these regions between summer and winter should be generally moderate, rather than extreme hot or cold, the presence of super continents, like Asia and America, gives rise to the strong effect of continentality causing the variations between summer and winter to be extreme. To conclude, the weather and heat transfer processes in the two regions are very different though both the equatorial region and the area around 60’N are low pressure areas. The weather in the equatorial region is often unchanging while that along latitude 60’N is variable.