14.LONGITUDNAL AIR CIRCULATION.
This atmospheric motion is known as zonal overturning circulation. Longitudinal air circulation refers to the circulation of air between two longitudes over the suace of earth. like latitudinal air circulation, longitudinal air circulation also includes cells. Longitudinal circulation, however, is a result of the heat capacity of water, its absorptivity, and its mixing. Longitudinal circulation occurs because the temperature of water and land are different. at places where the temperature is high , warm air Rises, shift to colder region in the upper atmosphere,sinks after getting colder,some of important longitudinal cells having implications for global weather are as follows:
▪️Walker cell or Pacific ocean cell.
The Southern Hemisphere has a horizontal air circulation cell called as Walker Cell . The Walker cell plays an important role in global weather. It is entirely based on the Pacific Ocean cell and Rises on account of Mark differences in the surface temperature of Western Pacific coast of south.The Walker circulation is the result of a difference in surface pressure and temperature over the western and eastern tropical Pacific Ocean. Three conditions May arises in the Pacific Ocean cell.
- La Nada.
The term “lanada”or “neutral” conditions describe the phase where there is neither and El nion,nor La nina.The ENSO cycle primarily affects U.S. weather in the fall, winter and spring, and less so in the summer.
Description of Pacific Ocean cell during lanada conditions:
New remote sensing data from NASA’s Jason-2 satellite show near-normal sea- surface height conditions across the equatorial Pacific Ocean. Ocean water adjoining South America is called due to the presence of cold humboldt current, ocean water adjoining Asian Australia is comparatively warm full stop there is a high pressure belt and specific low pressure belt and western Pacific. When the surface wind blow from Eastern Pacific to Western Pacific. The wind get warm and rise up words. After reaching the upward atmosphere the wind start moving towards the Eastern Pacific the time they reached over Eastern Pacific they become cold enough to descend downwards.
🔸️ implifications of lanada conditions….
▪️ the surface wind drag the ocean water towards Western Pacific.as the level of ocean water is slightly higher which is nearly 60cm,in western pacific as compared to the level in
eastern pacific.
▪️ the drag that experience from the surface wind which results in the ocean current, which moves from east Pacific to Western Pacific.
▪️ upwelling refers to the rise in ocean water from the lower level on to the ocean surface levels full stop the continuous shift of ocean water towards Western Pacific facilitates upwelling currents in Eastern Pacific adjoining, the coast of South America ,facilitates are large biodiversity the coast of Peru in one of the largest fishing Grounds of the world.
2.”La Nina”.
La Nina is a climate pattern that describes the cooling of surface ocean water along the tropical west coast of South America. La Nina refers to the condition when the Humboldt current is usually colder . in other words, water adjoining the coast of south America are usually colder.
La Nina is considered to be the counterpart to El Nino, which is characterized by unusually warm ocean temperatures in the equatorial region of the Pacific Ocean. There Is a very high pressure belt in Eastern Pacific and low pressure belt in western Pacific. Asha result surface wind blow faster from Eastern Pacific to Western Pacific. 🔸️implications of La Nina conditions…. La Nina is considered to be the counterpart to El Nino, which is characterized by unusually warm ocean temperatures in the equatorial region of the Pacific Ocean. fast surface winds drag the ocean water towards Western Pacific . The level of ocean water is higher in western Pacific as compared to the level in Eastern Pacific.
▪️the area of the Pacific Ocean between the Tropic of Cancer and the Tropic of Capricorn. Unusually strong, eastward-moving trade winds and ocean currents bring this cold water to the surface the drag experienced from surface winds result in faster movement of the equatorial ocean current.
▪️ the warm Rising wind experience condensation over Western Pacific resulting in even heavier rainfall on the coast of Asia and Australia where as La Nina conditions are responsible for floods in Australia and Indonesia….
▪️ La Nina has positive impact over India monsoon as a result there is over supply of nutrients at the surface of oceans, leading to abundance of fishing.
▪️ the largest shift of ocean water towards Western Pacific facilitates strong upwelling current in Eastern Pacific the trade wind are a strong during La Nina as a result India receives surplus rainfall during lanada conditions.
3.”El Nino”.
El Niño is a climate phenomenon that occurs when a vast pool of water in the eastern tropical Pacific Ocean becomes abnormally warm. Under normal conditions, the warm water and the rains it drives are in the western Pacific. El Niño occurs every few years… it is a temporary replacement of a cold humboldt current by a warm current along the coast of peru in South America. These warm current become so intense that the surface water temperature rises at 10 degree Celsius.
🔸️ implications of El Nino conditions …
▪️warming of the central to eastern tropical Pacific Ocean, El Niño 2015-2016 is affecting more than 60 million people, particularly in eastern and southern Africa, the Horn of Africa, Latin America and the Caribbean, and the Asia-Pacific region. Warming of tropical Pacific water affects the Global pattern of pattern and wind system including the monsoon wind in the Indian Ocean.el nino weakness the Indian monsoon…
▪️ as a surface wind move from Australia towards South America. coast of Asia and Australia experience dry, descending winds. Northern Australia experience drought. Forest fire become common in Indonesia and Australia.
▪️ the warm Rising wind adjoining the coast of South America bring rainfall and even floods in Peru and other part of south america.this warming of tropical Pacific Water affects the Global pattern of pressure and wind systems, including the monsoon winds in the Indian Ocean. Elnino weakness the Indian monsoon.
▪️ the equatorial ocean current is replaced by the the equatorial counter current. The counter current moves the coast of Asia and Australia towards South America. The nutrient level in the upper layer of eastern Pacific Falls drastically comma leading to loss of biodiversity and reduction in fishing.
🔸️Indian ocean dipole.
Indian ocean dipole is defined as the difference in the sea surface temperature between the two equatorial area of Indian Ocean The western Indian Ocean and Eastern Indian Ocean..
Description
The Indian Ocean Dipole (IOD), also known as the Indian Niño, is an irregular oscillation of sea surface temperatures in which the western Indian Ocean becomes alternately warmer (positive phase) and then colder (negative phase) than the eastern part of the ocean. Periodic oscillation of sea surface temperatures from “positive” to “neutral” and the “negative” phase. This condition is is favourable for the Indian monsoon as it causes and Apparent barrier in the Eastern Indian Ocean and I diverts all the south westerly winds towards the Indian subcontinent.
🔸️Madden julian oscillation..
The Madden Julian oscillation is an oceanic- atmospheric phenomenon that affects Global weather activities.it is the major fluctuation in tropical weather on weekly to monthly timescales. The MJO can be characterised as an eastward moving ‘pulse’ of cloud and rainfall near the equator that typically recurs every 30 to 60 days. It is also known as ISO or intraseasonal oscillation… it amplitude or power is invariably large over warmer water of the Indian Ocean and relatively less over the cooler water of the Pacific Ocean. The transversing planetary scale phenomenon Travels across the equatorial region of the globe carrying a pluse of clouds and rain. During a normal monsoon season the amplitude lanada is less over the Pacific Ocean. In a year with El Nino, when the Pacific Ocean warms up MJO gains strength in the Pacific Ocean as well.
15.SEASONAL AND LOCAL WINDS.
The winds that change their direction with onsets of different seasons. These are hence called as Seasonal Winds. A monsoon is a type of seasonal wind in low-latitude climates that seasonally changes direction between winter and summer.
▪️MONSOON.
A monsoon is traditionally a seasonal reversing wind accompanied by corresponding changes in precipitation, but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with the asymmetric heating of land and sea. in other words wind that changes their direction with the change in season are called monsoon monsoon wind arises on account of differential heating of land and water. Differential heating of land and water arises because the specific heat capacity of water is higher than the specific heat capacity of land. As compared to the heat required by land to raise its temperature.
The major monsoon systems of the world consist of the West African and Asia-Australian monsoons. The inclusion of the North and South American monsoons with incomplete wind reversal has been debate.. land is colder than sea a low pressure belt emerges over sea and and thus wind blow from land to sea .these winds are dry and thus do not bring rainfall over land or sea…
▪️ sea and land Breeze.
A sea breeze or onshore breeze is any wind that blows from a large body of water toward or onto a landmass; it develops due to differences in air pressure created by the differing heat capacities of water and dry land. As such, sea breezes are more localised than prevailing winds. In coastal areas land is hotter than sea during the day due to differential heating. Where as sea is hotter than during the night. During the day sea breeze blow towards the land and reverse happens during night, when land breeze blow from land to sea. Wind is known by the direction from which it originates land breeze images from land and sea breeze images from sea. During the night fisher man go for fishing under the influence of land breeze and during day time, they came back to land under the influence of sea breeze.
