page_title: Climate of Argentina
section_title: Atmospheric Circulation
hierarchical_section_title: Climate of Argentina / Factors that influence the climate / Atmospheric Circulation
caption_attribution_description: Weather maps showing the usual position of weather system around the southern part of South America.
context_page_description: The climate of Argentina is a vastly complex subject, as the vast size of the country and wide variation in altitude make for a wide range of climate types. Summers are the warmest and wettest season in most of the country except in most of Patagonia where it is the driest season. Winters are normally mild in the north, cool in the center and cold in the southern parts experiencing frequent frost and snow. Because southern parts of the country are moderated by the surrounding oceans, the cold is less intense and prolonged than areas at similar latitudes in the northern hemisphere. Spring and autumn are transition seasons that generally feature mild weather.
  Many regions have different, often contrasting, microclimates. In general, northern parts of the country are characterized by hot, humid, rainy summers and mild winters with periodic droughts. Mesopotamia, in the northeast is characterized by high temperatures and abundant precipitation throughout the year with droughts being uncommon. West of this lies the Chaco region, which is the warmest region in Argentina.
context_section_description: The South Atlantic High and the South Pacific High both influence the pattern of winds and precipitations 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. The formation a cold front associated with it moves to the northeast owing to the topographic barrier that the Andes forms. The passage of the cold front to the northeast leads to the movement of the high pressure system from the South Pacific Ocean into the southern tip of South America. All of these conditions lead to strong anticyclogenesis to the east of the Andes and thus, the high pressure system intensifies as it enters southern Argentina. When both the high pressure system (over southern Argentina) and low pressure system strengthen, it creates a very strong pressure gradient that draws cold air from the south, strengthening southerly winds. 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) that draw this cold air northwards, which is driven by this pressure gradient. Cold air can move northwards until 18ᵒS when the blocking effect of the Andes is smaller due to a change in its orientation. 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 c
caption: Weather map showing the usual position of weather systems around the southern part of South America.
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