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Assess the role of the global atmospheric circulation in the rainfall patterns in the tropics.[20]

Based on what we have discussed today, please deliberate over the various factors and come up with your overarching argument. In your argument statement, you should:

Answer the question directly

Provide the main reason why you argue in that manner

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The global atmospheric circulation plays a large part in the rainfall patterns in the tropics, and might as well be the most significant factor influencing them. The global atmospheric circulation, comprising of the Hadley cells and the ITCZ on the global scale, followed by ENSO and monsoons on a regional scale, is a system comprising of numerous processes driven by winds and their movement. The location and seasonal movement of the Hadley cells and the ITCZ all but determine a region's likely climatic type, and their subsequent rainfall patterns. Monsoons are formed from how winds carry moisture from oceans onto land, and ENSO's origins are much guided by the presence, absence, or even reversal of the trade winds across the Pacific's surface. Local, non climatic factors like topography, local heating and continentality alter the main influences of the global atmospheric circulation to create unique climatic conditions on a smaller scale.

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Global atmospheric circulation comprises of the Hadley cells and the positioning of the ITCZ. It is most important in determining the broad distribution of rainfall in the tropics. Rainfall in the tropics is generally due to convectional rain. Air circulation within the Hadley cell from regions of high humidity at the ITCZ further poleward thus determine the general proportion of annual convectional rainfall in the tropics.

Other factors like monsoon winds carry humid or dry air onto continental regions, varying across the year. However, precipitation from monsoon rains mainly augments rainfall by affecting temporal variations of rainfall and has a regional effect. The total annual rainfall is still controlled by the extent of influence of the ITCZ. The ENSO affects coastal regions, and topological factors like mountain barriers bring orographic rain, but these factors act on a small scale with a regional and local effect respectively.

TL;DR
ITCZ: General annual rainfall (Evaporation, convectional)
Monsoon: Temporal variations + Regional, not main
ENSO: Regional, not main
Topography: Local, not main

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The global atmospheric circulation (GAC) could be the most influential in affecting and influencing the rainfall pattern in the tropics. The GAC mainly comprises of the Hadley cells as well as the ITCZ that affects the rainfall patterns in a global scale. The Hadley cell is a large scale atmosphere thermally-direct convection cell that is found in the tropics, in which air rises near the equator and sinks at the mid latitudes, while the ITCZ refers to the a line of clouds that shifts throughout the year based on the location of the overhead sun.
However, there may also be other factors that can influence the rainfall pattern in the tropics, such as monsoons that affects rainfall patterns on a regional scale due to the establishment of high and low pressure zones that drives the movement of winds that carry moisture. Finally on a smaller more localised scale, there are also factors such as local heating when a certain area is heated up more than its surroundings, resulting in differential heating of the ground, further leading on to the formation of cumulonimbus clouds, bringing rainfall.

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ATQ:
The global atmospheric circulation is the most important factor in controlling the rainfall patterns in the tropics, consisting of the Hadley cells. The seasonal migration of the Intertropical Convergence Zone (ITCZ), an area of low pressure within the Hadley cell, contributes to the rainfall patterns and distribution in the tropics. Therefore, the role of the global atmospheric circulation is to regulate rainfall patterns through the ITCZ.

Due to the high levels of insolation received at the tropical latitudes, heated air rises with high moisture content, condensing at dew point temperature to form cumulonimbus clouds that bring convectional rain to areas directly under the ITCZ. As a result, the ITCZ and global atmospheric circulation are the main determinants of rainfall in the tropics on a global scale.

Why:
Regional factors like monsoons and ENSO are less significant as monsoon winds are seasonal and only affect certain climatic regions (mainly Am climates). ENSO is also less significant as it's centred on the equatorial Pacific and doesn't have the same scale of impact as the global atmospheric circulation.

Local factors like topography local heating and continentality are also less significant as topography mainly influences orographic rainfall, which occurs on a very small scale, only on the windward side of orographic barriers. Continentality and local heating are also micro-scale factors which are not the main determinant of rainfall patterns in the tropics.

Main reason:
Global atmospheric circulations affects the rainfall patterns in the tropics on the largest spacial scale.

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Among the various factors affecting rainfall patterns in the tropics, the global atmospheric circulation without a doubt has the greatest impact. Being a macro-scale factor, it naturally sets the conditions for many of the other factors. In the context of the tropics, it is made up of the movement of the Hadley cell, which determines the broad distribution of rainfall by controlling the positioning of the ITCZ and STHP, in turn causing different areas to experience high and low rainfall simultaneously. Where the ITCZ is over, rainfall is high due to the intense insolation leading to the formation of clouds, which cause rainfall. On the other hand, areas in the STHP experience low rainfall as high pressure is created by the sinking air, inhibiting cloud formation.

On a regional scale, monsoon winds can lead to variations in rainfall patterns (i.e. Wet and dry seasons) when different areas experience different temperatures, which lead to the movement of trade winds that carry moisture and cause rainfall. However, monsoons are primarily caused by the shift in the ITCZ, thus the global atmospheric circulation has a direct impact on monsoons.

On a local scale, orographic rainfall is caused by the topography of specific areas, such as the presence of mountains. Areas with such topographic features tend to experience more orographic rain than those without, thus causing rainfall patterns to emerge. However, this factor acts on an extremely small scale and is incomparable to the global atmospheric circulation in producing rainfall patterns.

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The Global Atmospheric Circulation (GAC) is the most significant determinant of rainfall patterns in the tropics. On a global scale, the GAC constitutes the Hadley Cell, the seasonal migration of the Inter-Tropical Convergence Zone (ITCZ), and the Subtropical High Pressure belts (STHP). Areas directly below the ITCZ receive high levels of rainfall due to intense insolation. At the same time, areas at the STHP experience a lack of rain due to the persistently sinking air mass which inhibits cloud formation. As such, rainfall in the different regions of the tropics is highly influenced by GAC.

On the other hand, regional factors have a less significant impact on rainfall patterns in the tropics. Regional factors include the El Nino Southern Oscillation (ENSO), which is centered on the equatorial Pacific, and monsoon winds. Monsoons are the seasonal reversal of surface winds and the ENSO refers to a change in pattern between sea-level pressures. Thus, both factors vary in occurrence according to the season and their impacts are limited to specific regions. Therefore, the influence of regional factors on rainfall patterns in the tropics is less significant.

Local factors may also contribute to rainfall patterns. For example, the topography of certain areas may bring about orographic rainfall. Areas with topographical features such as mountains or other large landforms tend to experience more frequent events of orographic rainfall. However, this factor acts on a much smaller scale than the GAC, and its effects are relatively less significant.

Since the GAC acts on the largest scale, it is the most important factor influencing rainfall patterns in the tropics.

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ATQ: Global atmospheric circulation has the largest influence on precipitation patters in the Tropics.
Global atmospheric circulation: Tricellular model(Hadley, Ferrel and Polar cells) + coriolis effects impact on wind direction.
Context: Tropics-narrow down to the Hadley cell(Tropic of Cancer, Capricorn and the Equator)
Types of climates: tropical humid and tropical arid
Hadley Cell:
-heating causes air to rise at the equator, aloft air travels polewards
-movement of air at the surface of the earth from the Tropics to the equator(HP-LP)
-formation of the ITCZ
-how the movement of the sun causes the itcz to shift throughout the year, resulting in differing rainfall patterns
-northeast and southwest monsoons, Indian and African monsoons.

Argument:
-based on the scale of impact of global atmospheric circulation in comparison to other factors such as continentality(localised to places that are far away from water bodies)
-GAC: influences precipitation in ALL the tropical areas, regardless of their continentality or topography.

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The global atmospheric circulation has the greatest and most significant impacts on the rainfall pattern in the tropics among other factors , the scale and extensiveness of atmospheric circulation is no doubt the most overarching of the alll the factors , which includes the hadley cells and the ITCZ on the global scale . The Hadley cell and ITCZ are what determines where clouds as welll as the climatic characteristics of the region , which has a direct impacts over many of the seasonal events such as monsoons and typical rainfall in the tropics , these processes are are what drives the important trade winds which will significantly impact rainfall patterns in the tropics .

However , this is not to say that regional air circluation does not impact rainfall in the tropics . events such as the ENSO will impact the trade winds in the pacific ocean , which also help yo drive moisture towards the tropics which help to influence rainfall.

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The global atmospheric circulation plays a significant role in influencing the rainfall patterns in the tropics, comprising the Hadley cells and Intertropical Convergence zone (ITCZ). (Description of what global atmospheric circulation is)

Firstly, the global atm circulation influences the rainfall on a macro scale. (Describe Hadley and ITCZ + compare A and B climate)
However though the gac influences tropics in a macro scale, there are also other factors influencing different parts of the tropics.

Monsoon influences precipitation in a regional scale (country vs other countries). (description of Asian monsoon and African monsoon). However rainfall patterns within countries also vary.

Continentality varies the rainfall patterns within a country. (Describe maritime effect vs continental effect).

All in all, many factors ranging from the global to local scale affects the rainfall patterns and thus it is an interconnected system.

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The global atmospheric circulation, plays a large role in the rainfall patterns in the tropics. It consists of the Hadley cells which is where the ITCZ is situated. The Hadley Cells are located in the tropics where high levels of insolation is received, causing the heated air saturated with moisture to condense at dew point, forming cumulonimbus clouds leading to convectional rain. Therefore, rain occurs frequently in the tropics. However, regional factors such as ENSO centered on locations surrounding the Pacific Ocean brings about rain to mainly the Am climates. Monsoon winds caused by the shift in the ICTZ causes the distinguishable wet and dry seasons.  Local factors like orographic rainfall on the winward side, caused by topography local heating, operate on  micro-scale.

Therefore, all factors play an important role in the rainfall patterns in the tropics although the global atmospheric circulation is of most significant. The scale at which it operates is the largest and most extensive, with the local factors operating on the smallest degree

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The global atmospheric circulation is the most important in influencing rainfall patterns in the tropics, through the Hadley cells and the shifting of the Inter Tropical Convergence Zone (ITCZ). In the tropics (30 degrees North and South of the equator), convectional rain usually falls consistently throughout the year as the tropics is within ITCZ all year round. It is the most crucial as it operates on a global scale and affects rainfall in all regions within the tropics.

On a regional level, El Nino Southern Oscillation (ENSO) and monsoon winds help influence the intensity and availability of rainfall. In the Pacific region, ENSO will influence the dry and wet seasons of the western and eastern Pacific landmass whereas monsoon winds such as the North-east and South-west monsoon will influence the amount of rainfall India receives (more rain during South-west monsoon due to the moisture-laden south-westerly winds passing over the Indian Ocean, and no rain during the North-east monsoon due to the north-easterly winds that pass over landmasses of Central Asia before reaching India). However, ENSO and monsoon winds tend to only affect the rainfall patterns of coastal areas surrounding it (eg. Pacific Ocean, Indian Ocean) and do not have a very significant impact on rainfall in inland tropical areas unlike Global Air Circulation.

In addition, local factors like topography can also contribute to shaping rainfall patterns. For example, tropical areas with topographic features like mountains or hills experience orographic rain more frequently, even in arid climates. This is because the moist air is forced to rise over the landmass and this causes the air to reach dew point temperature and form clouds on the windward side of the mountain, where rain falls. However, this factor only affects areas on a small scale i.e. regions with high altitude topographic features and do not affect the rainfall patterns of the tropics generally.

To recapitulate, Global Air Circulation is still the most crucial feature in influencing rainfall pattern in the tropics as it acts on the largest scale of the three factors and affects all regions in the tropics generally.