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Mesopotamia

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Humid Chaco

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Arid Chaco

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Northwest Argentina

 * Causes of droughts in Northwest Argentina
 * Precipitation climatology in Northwest Argentina
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 * Description for La Rioja and Catamarca
 * Climate description for Quebrada de Humahuaca
 * Climate for arid valleys in NOA
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 * Climate of Tucuman province
 * Recursos Hídricos de la Puna, Valles y Bolsones Áridos del Noroeste Argentino

Patagonia

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 * Trees in Patagonia
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Floods

 * Diseases related to flooding
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 * Flooding risks

Droughts

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Climate Change in Argentina

 * Cómo afecta el cambio climático a la Argentina from La Nacion
 * Cambio climático: cómo afecta ya a la Argentina from Clarin
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 * Regional Climate Change in Southern South America Part I
 * Regional Climate Change in Southern South America Part II

Floods in Buenos Aires

 * Wind tide in the Rio de la Plata Estuary: Meteorological Conditions
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 * El Niño no tiene la culpa: Vulnerabilidad de en el noreste Argentino
 * Managing Disaster Risk in Emerging Economies
 * Inundaciones en el Area Metropolitana de Buenos Aires

Vietnam

 * Variations of surface temperature and rainfall in Vietnam from 1971 to 2010
 * Influence of the Pacific and Indian Ocean climate drivers on the rainfall in Vietnam
 * Interannual Variation of the Fall Rainfall in Central Vietnam
 * Changes in the autumn precipitation and tropical cyclone activity over Central Vietnam and its East Sea
 * Interannual Variation of the Late Fall Rainfall in Central Vietnam
 * Collaborative Effects of Cold Surge and Tropical Depression–Type Disturbance on Heavy Rainfall in Central Vietnam
 * Regional trends in early-monsoon rainfall over Vietnam and CCSM4 attribution
 * [iopscience.iop.org/article/10.1088/1748-9326/10/2/024008/meta Decadal oscillation of autumn precipitation in Central Vietnam modulated by the East Pacific–North Pacific (EP–NP) teleconnection]

Geographic factors
There are four main types of climate in Argentina: warm, moderate, arid and cold in which the extension of the country along with its relief features determines the different varieties in the main climate types. The most important geographical factors that influence the climate of Argentina are latitude, elevation, and distance from the sea. With Argentina extending from 22oS to 55oS, there are differences in the amount of incoming solar radiation and the amount of daylight received in each season, which affects temperature. Thus, temperatures decrease from north to south due to the differences in latitudes.

Although the centre and the eastern parts of the country are mostly flat, the west is mountainous. Both the Andes and Sierras Pampeanas affect the climate of Argentina, leading to differences in temperature, pressure, and spatial distribution of precipitation depending on the topography and altitude. Here, the Andes exert an important influence on the climate. Owing to the higher altitudes of the Andes north of 40oS, they completely block the normal westerly flow, preventing low pressure systems containing moisture from the Pacific Ocean from coming in. Thus, much of Argentina north of 40oS is dominated by wind circulation patterns from the South Atlantic High. South of 40oS, the Andes are lower in altitude, allowing much of Patagonia to be dominated by westerly winds and air masses from the Pacific Ocean. However, the north–south orientation of the Andes creates a barrier for humid air masses originating from the Pacific Ocean. This is because they force these air masses upwards, cooling adiabactically. Most of the moisture is dropped on the Chilean side, causing abundant precipitation and cloudiness while on the Argentine side, the air warms adiabatically, causing it to become drier as it descends. Thus, an extensive rain–shadow is present in much of Patagonia, causing it to receive very little precipitation. The Sierras Pampeanas influences the climate on a much smaller scale than the Andes.

Distance from the sea is another important geographic factor. Owing to the shape of the country, the close proximity to the ocean means that most of the country, excluding the north is moderated by the surrounding oceans, leading to lower thermal amplitudes than comparable latitudes in the northern hemisphere. The two main currents that impact the climate of Argentina are the Brazil Current from the north and the Malvinas Current from the south (a branch of the Antarctic Circumpolar Current). The Brazil Current transports warm subtropical waters southwards while the Malvinas Current transports cold, subantarctic waters northwards. The Malvinas Current cools the coastal areas, particularly during winter when the current is more stronger. Thus, coastal areas of the Pampas have cooler summers and a longer frost period owing to the cold Malvinas Current. As well, it is the main factor in making Tierra del Fuego more colder than at comparable latitudes in the northern hemisphere in Europe since it is influenced by the cold Malvinas Current rather than the warm North Atlantic Current.

Atmospheric Circulation
The South Atlantic High and the South Pacific High both influence the pattern of winds in Argentina. Owing to the greater high of the Andes at latitudes north of 40oS, much of Argentina is dominated by wind circulation patterns from the South Atlantic High. The South Atlantic High transports moisture from the Atlantic Ocean to Argentina. This occurs throughout the year due to the atmospheric pressure being lower on land than in the ocean. Much of the north and central parts of the country are affected by the South Atlantic High, with a strong influence in the eastern parts than in the west. This is due to the eastern parts being more frequently affected by the South Atlantic High, causing precipitation to decrease westwards.

Throughout the year, the South Pacific High influences the climate by bringing cold, moist air masses originating from Patagonia. During the most intense cold waves, they form when a transient high pressure system located in the South Pacific Ocean moves eastwards to the southern tip of South America. As it begins to move, this high pressure system strengthens the South Pacific High and is forced to move southwards to south of 40oS where the Andes are shorter in height. As well, an upper level ridge forms over the South Pacific Ocean along with an upper level trough extending from subtropical latitudes to the South Atlantic Ocean. At the same time, a low pressure system forms over the South Atlantic Ocean which eventually strengthens. This low pressure system that forms over the South Atlantic Ocean forms a cold front associated with it that moves to the northeast owing to the topographic barrier that the Andes forms. The passage of the cold front to the northeast from the low pressure system leads to the movement of the high pressure system from the South Pacific Ocean into the southern tip of South America. Because of these conditions in conjunction with the presence of the upper level ridge over the South Pacific, the upper level trough, and the topographic barrier of the Andes, this favours strong anticyclogenesis to the east of the Andes and thus, the high pressure system intensifies as it enters southern Argentina. When the high pressure system starts to develop over Southern Argentina along with the development of the low pressure system over the South Atlantic, this generates a pressure gradient that draws winds from the south/southwest, drawing cold air from the south that are a factor in strengthening the high pressure system. When both the high pressure system and low pressure system strengthen, it creates a very strong pressure gradient that draws cold air from the south, strengthening southerly winds.<ref name= Owing to the topographic barrier of the Andes, it forces and channels the cold air to accumulate on the eastern side of the Andes. This generates an ageostropic component from the south (due to a reduction in the Coriolis force caused by accumulation of cold air on the eastern side of the Andes), which is driven by the pressure gradient, drawing cold air from the south northwards to the eastern side of the Andes. Cold air can move northwards until 18oS when the blocking effect of the Andes is smaller due to a change in its orientation. Thus, the Andes reinforce the southerly flow of cold air northwards by channeling it to the east. Overall, these conditions results in the coldest temperatures due to the cold masses from high latitudes being pulled northwards. A weaker cold wave occurs when the South Pacific High remains over the ocean and does not have a migratory high pressure system originating from the South Pacific High that moves east of the Andes (it builds over the Andes). Although this occurs throughout the year, during winters, it leads to cold temperatures while during summer, it leads to strong and deep convections. These convections are responsible for about 50% of summer precipitation south of 25oS.

The Chaco Low is a semi–permanent low pressure system situated east of the Andes that is approximately located between 20oS and 30oS during summer (displaced to the north in winter). It is stronger in the summer than in winter due to a combination of high insolation, dry surface conditions, and southward displacement of the South Atlantic and South Pacific High (this makes it difficult for cold fronts to enter at lower latitudes). The Chaco Low interacts with the South Atlantic High, generating a pressure gradient that draws moist air from the northeast to coastal and central regions of Argentina. It also forces easterly winds from the Amazon basin to move southward, which is reinforced by the funneling effect from both the Andes and the Brazilian Plateau. The Chaco Low brings large amounts of moisture that favour the development of convective thunderstorms during summer, reaching as far south as 35oS. This movement of air from the north owing to the interaction between the Chaco Low and the South Atlantic high is the strongest in summer when the Chaco Low is at its strongest. These winds bring hot, humid tropical air from the north. Sustained and intense winds from the north are responsible for severe weather events such as heat waves and severe convection. During winter, the Chaco Low weakens as a result of lower insolation. This is partly responsible for the decrease in winter precipitation over much of Argentina (in addition to northward displacement of westerlies) due to a weaker transport of air masses from the tropics. This excludes areas south of 40oS where it is dominated by westerlies.

El Niño and La Niña
The El Niño–Southern Oscillation leads to changes in the atmospheric circulation patterns (also known as teleconnections). Although the exact mechanisms are unknown, the impacts of the changes in atmospheric circulation patterns caused by the El Niño–Southern Oscillation are more clearly observed in the more humid eastern parts of the country (between Uruguay and southern Brazil). During El Niño events, precipitation is more higher than normal while during La Niña events, precipitation is lower than normal in the Pampas. In general, El Niño tends to increase precipitation during late spring and summer, particularly in the north. The impacts of La Niña in the eastern parts of the country (northeast and the Pampas) are observed in winter where precipitation is lower. In Northwest Argentina, El Niño events are associated with a strong reduction in rainfall during summer. In contrast, La Niña events increase precipitation in northwest Argentina. In the central–western parts of Patagonia, spring precipitation tends to be lower during La Niña events and higher during El Niño events. Summer precipitation exhibits an opposite pattern where La Niña years involve wetter summers while El Niño years featuring drier summers. On the Andes in central western Argentina, precipitation is higher during El Niño year.

In general, La Niña events are associated with lower temperatures (particularly colder winters) in the Pampas. During winter, frosts are more common during La Niña events compared to El Niño events. This is due to a stronger southerly flow during La Niña events caused by a higher concentration of high pressure systems in the South Pacific and an increase in cyclonic activity (more low pressure systems) in the South Atlantic. This creates conditions that are favourable for bringing cold air from the south, particularly when there is a formation of a high pressure system over Patagonia (associated with the passage of a front) that is responsible for bringing cold air from the south. Thus, invasions of cold air from the south are more common during La Niña events. In contrast, warm spells in the Pampas and northern parts of the country are more intense and frequent during El Niño events. This is due to stronger westerly winds south of 40oS, leading to less frequent incursions of cold air from the south while enhancing winds from the north that bring in warm air. Although La Niña events lead to colder winters with more frequent incursions of cold air in both the north and central parts of the country, it leads to more frequent and intense warm spells in the last months of the year. In other regions, El Niño events lead to more frequent and intense warm spells in Northwest Argentina (during autumn), northeast Argentina (during spring) and central Argentina (during summer). Cold air anomalies arising from El Niño events are observed during spring and are the result of an increase in rainfall that lead to reductions in insolation. For the southern parts of the country, El Niño events are associated with more intense and frequent cold spells during the coldest months. In summer, El Niño events are associated with warmer summer temperatures in the southern parts of the country.

Antarctic Oscillation
The Antarctic Oscillation, also known as the Southern Hemisphere Annular Mode is the main factor in tropospheric circulation variability south of 20oS and is characterized by pressure anomalies with one situated in the Antarctic and one situated in a band at around 40–50oS around the globe. It mainly affects middle and high latitudes in the Southern Hemisphere. It is characterized by the north–south displacement of the westerly wind belt that circle around Antarctica. Such variation in the position of the westerly wind belt affects the intensity and position of cold fronts and mid latitude storm systems and is partly responsible for variation in precipitation in the southern parts of Argentina. The Antarctic Oscillation is characterized by two phases: a positive and a negative phase. A positive phase is when the westerly wind belt is displaced to the south. The positive phase occurs when there is increased surface pressure over the southern parts of the South American continent and decreased pressure in Antarctica. This results in stronger westerly winds in the southern parts of the country while preventing cold fronts from penetrating inland, producing more stable conditions. Furthermore, the positive phase leads to warmer conditions south of 40oS, particularly during the summer in areas between 40–60oS. Precipitation is lower due to less frontal and orographic precipitation resulting from reduced westerly wind flow between 40–60OS. Opposite conditions occur in the negative phase when the westerly wind belt is shifted equatorward. Cold fronts moving northwards from the south penetrate more frequently, leading to more precipitation and cooler temperatures during the negative phase. The major effect of negative phase of the Antarctic Oscillation occurs in spring when it increases precipitation over southeastern South America.

Indian Ocean Dipole
The Indian Ocean Dipole is an atmospheric–oceanic phenomenon characterized by differences in sea surface temperatures between the eastern and western sections of the tropical Indian Ocean. Similar to the Antarctic Oscillation, the Indian Ocean Dipole is characterized by two phases: a positive and a negative phase. In the positive phase, the eastern section of the tropical Indian Ocean is cooler (lower sea surface temperature) and the western section is warmer than normal (higher sea surface temperature). On the other hand, the negative phase is characterized by warmer sea surface temperatures on the eastern section and cooler sea surface temperatures on the western section of the tropical Indian Ocean. Studies have shown that the Indian Ocean Dipole is partly responsible for variations in precipitation in Argentina and South America in general. During a positive phase, precipitation is higher in the Río de la Plata Basin due to teleconnections.

Seasons
Most of Canada has four seasons: Winter, Spring, Summer, Autumn and Fall, all featuring different weather conditions.

Winter
Canada has one of the most severe winter weather in the world. In most places, winters are very cold with temperatures that are normally below 0 C. Snow covers the ground from December to March or April in most places. The causes for the very cold winters in much of Canada is due to the high latitudes over much of the country along with a flat topography east of the Rocky Mountains, which allows cold Arctic air from the north to travel south and east unimpeded, bringing very cold conditions to much of the country.

Despite this, temperatures during winter vary considerably in different parts of the country. Areas close to a large body of water are much warmer than inland areas. The coastal areas in British Columbia have the mildest winters owing to the moderating influence of the warm Pacific Ocean. Temperatures rarely drop below -20 C. On the Atlantic coast, the moderating influence of the Atlantic Ocean is less pronounced than the Pacific Ocean due to the predominant winds being from the land rather than the ocean and is not influenced by the warm Atlantic Ocean currents. In the case that the winds come from the Atlantic Ocean, the Maritimes experience milder temperatures during the winter season. Away from coastal areas, temperatures generally decrease as latitude and/or altitude increases with the coldest areas being in the mountain valleys of Yukon and Ellesmere Island. Generally, the interior plains and the north experience extremely cold weather during winter. Although cold temperatures predominate in winter, warm periods are very common, lasting from a few hours to a week in which the warming is gradual and the cooling is sudden and rapid.

Precipitation varies widely across the country during winter. In the Pacific coast of British Columbia, precipitation is high during winter months due to being in the path of low pressure systems (in summer, these low pressure systems move north, resulting in summer being drier). As well, with the predominant wind being from the west which carries a series of upper troughs and rides in the upper air flow, winters are when the upper troughs are at their strongest. Thus, winters in British Columbia are characterized by high cloud cover and precipitation, which is further enhanced by orographic precipitation, resulting in copious amounts of precipitation to fall on the west coast and mountainous areas on the windward slopes during winter. Having the most mildest winters in Canada, snowfall is lighter than inland areas due to the Pacific Ocean making the air too warm to allow for large quantities of snow to fall. Thus, precipitation is likely to fall in the form of rain rather than snow during winters on the Pacific coast. At higher altitudes, orographic precipitation leads to very high snowfall with certain areas in Western Cordillera such as the Coast and Rocky Mountains of British Columbia and the St. Elias Mountains in the Yukon receiving more than 1,000 cm of snowfall per year. In the interior plains and the North, winters are dry with snowfall being light due to the air being cold and dry. These areas receive the lowest amount of snow in the country. In Ontario, Quebec and the Maritimes, the milder winters compared to the interior plains results in the air being less dry causing winter precipitation to be similar to summer precipitation. With the exception of the west coast, snow cover is continuous with much of precipitation during winter falling as snow. Freezing precipitation can fall in any parts of the country.