Sun - Earth interaction: a review

Both the Sun and the Earth are sources of heat that power an interconnected set of dynamic systems (lithosphere, hydrosphere & cryosphere, atmosphere, biosphere).

Within the Sun, heat is transferred by radiation and convection, which involves circulation of hydrogen ions. Within the Earth heat is transferred by conduction and convection, which involves circulation of silicates in the mantle and the crust, and by the circulation of iron in the liquid outer core. On the surface of the Earth and the atmosphere, heat emanating largely from the Sun is transferred by convection, which involving the circulation of water and carbon. Both the Sun and the Earth and their atmospheres are layered. Both systems evolve and change.

Layered Bodies

The Sun is composed largely of hydrogen (75%) and helium (25%), and minor amounts of carbon, nitrogen, and argon. The layers of the Sun are the core, radiative zone, and convective zone. The layers of the Sun's atmosphere are the photosphere (6000 degrees C), chromosphere (20,000�C) and the corona (1,000,000�C). We see the photosphere (Fig. 1). The Sun's radius is about 109 times that of the Earth. The Sun fuels itself by fusion of hydrogen to form helium. It releases gamma rays and neutrinos at the core, where the temperature is 15,000,000�C, and the density is10 times that of gold. The Sun ejects solar wind (charged particles) and emits electromagnetic radiation (gamma ray, X-ray, ultraviolet ray, visible light, infrared, radio wave).

The abundant elements of the whole Earth are iron (34.8%), oxygen (29.3%), silicon (14.7%), magnesium (11.3%), sulfur (3.3%), nickel (2.4%), calcium (1.4%), and aluminum (1.2%). After the Earth was whacked, 4.5 billion years ago, by a giant meteorite, the lithosphere was a fast-acting dynamic engine. That impact caused the Earth to be layered and to liberated heat in the process, as well as to issue gases. Some of those gases form the atmosphere, others condensed to form oceans (part of the hydrosphere) that partly froze into ice to form the cryosphere, and all interacted to generate the biosphere. Though not as active as before, the Earth is still a dynamic engine, as evidenced by plate tectonic movements. The dynamism of the Earth continues because the heat acquired 4.5 billion years ago is not exhausted, and because heat is evolved during radioactive disintegration. The layers of the Earth are the inner core, the outer core, mantle, and crust (Fig. 2). The composition of the crust is oxygen (45.2%), silicon (27.8%), aluminum (8.5%), iron (5.8%), Calcium (5.06%), Magnesium (2.7%), sodium (2.32%), and potassium (1.65%).

The Earth's crust and the topmost mantle form the lithosphere, the rock layer that lies over a moldable layer called the asthenosphere. The Earth's lithosphere is analogous to the hard shell of an egg, which can be segmented. Each segment of the lithosphere is called a plate, and the boundary separating neighboring plates is a plate boundary. Plates move about as a result of heat redistribution within the Earth. Powered by the heat from within the Earth, and the redistribution of that heat by convection, neighboring plates of the lithosphere move in one of three ways. Neighboring plates move away from each other at divergent plate boundaries. At convergent plate boundaries, neighboring plates move toward each other and collide. In contrast, at transform plate boundaries, neighboring plates slide alongside each other (Fig. 3). Earthquakes and volcanoes are preferentially located at plate boundaries (Fig. 4), and at hotspots. Volcanoes bring molten rock from below and issue gasses, including greenhouse gases to the atmosphere. Volcanoes also eject ashes into the sky, which reflect the Sun's heat back to space. Sulfur dioxide issued by volcanoes serves as aerosol for condensation of water and formation of rain. Large volcanic eruptions and supervolcanoes can bring about earth cooling for some time, though the greenhouse gasses may takeover warming effects subsequently.

New lithosphere is added at divergent plate boundaries, whereas old oceanic lithosphere is destroyed at convergent boundaries. Continents break apart by plate divergence and ocean basins are formed as continents drift apart, whilst old oceans are closed up as continents collide. The distribution of continents and oceans of the restless Earth over vast geologic time may cause the Earth to become an "icehouse" or "hothouse".   Oceanic circulation patterns change as do the oceans, and bring about different climates. As continents collide, mountain ranges, such as the Himalayas, rise to lofty heights only to be weathered and eroded, during which time carbon dioxide is removed from the atmosphere, as carbon bearing minerals form sedimentary rocks, e.g., limestone which become buried. Eventually this results in "icehouse" condition for the globe. However, the "ice house" conditions of globe have to do with the transit of the solar system across the spiral arm of the Milky Way Galaxy, while the "hot house" conditions represent times when the solar system is transiting between the spiral arms (Sheviv and Veizer, 2003, See Table 1)

Heat transference by convection beneath the lithosphere, exerts tension and compression on the lithosphere, which are stored as strain energy in rocks. When the stored strain energy in the rocks exceeds the yield strength of the rocks, the rocks rapture, and the strain energy is released in the form of earthquake (seismic wave), which travel at different speeds through different rocks depending on the rigidity and density of rocks. The exact place at which a rock raptures is called the focus of an earthquake, whereas the epicenter of an earthquake is located on the surface directly above the focus (Fig. 5). Earthquakes waves travel through the body of the Earth in two ways, which are called P-wave and S-wave. Waves that travel by pushing particles to and fro, on the line of propagation of the wave are P-waves. Waves that travel by pushing particle perpendicular to the Propagation direction of the wave are S-waves. S-waves do not travel through liquid. Both P and S- waves are slowed why they pass through the moldable asthenosphere. Hence, geologists determine the layering of the Earth from earthquake study.

The Earth's atmosphere is composed of nitrogen and oxygen, and is layered (Fig. 6) into the troposphere (temperature decreases with elevation), stratosphere (temperature increases with elevation), mesosphere (temperature decreases with elevation), and ionosphere (temperature increases with elevation). The Earth's ocean has dissolved ions mostly of sodium, chlorine and the sulfate ion. The ocean is layered (Fig. 7) into an upper, middle (200 to 1000 meters below surface) and lower part. The middle layer has different names, depending on the property of the ocean by which it is identified, e.g., thermocline (showing rapid change in temperature), halocline (showing rapid change in salinity), pycnocline (showing rapid change in density) or the oxygen minimum zone. Yet another mode of vertical layering of the ocean is produced by thermohaline circulation. Here, cold surface waters sink and move horizontally (advect) segregated by their differences in density (Fig. 8).


In the Sun, different convection cells move charged particles from the boundary of the radiative-convective zones (tachocline) to the top of the convection zone and back down to the tachocline. The convecting cells of charged particles generate magnetism. Magnetic lines become twisted as a result of the differential rotation of the Sun. The Sun rotates on the average once every 27 days, faster (every 24 days) at the equator and slower (every 30 days) at the poles. Strong magnetic lines break through the Sun's surface outward at the umbra only to re-enter the Sun at the penumbra. These constitute a couplet of sunspot, which are dark (3700�C) zones compared to the environment (6000�C). Solar flare and wind result from Sun's magnetic field moving out into its atmosphere as it loops through the umbra and penumbra. The umbra and penumbra are parallel to the Sun's equator. The sunspots begin near the Sun's poles and move toward the equator, sunspot activity (intensity or number of sunspots) has a period of about 11 years (Fig. 9). Though overall radiation changes only by about 0.1%, ultraviolet radiation increases by 10 to 20 % during intense sunspot activity.

The Earth behaves as though there is a bar magnet at its center (Fig. 10). The magnetism is about 0.04 gauss compared to that of the Sun, which is 3000 gauss. The Earth has a magnetosphere (Fig. 11)that lies beyond the ionosphere. Usually the magnetosphere is pear shaped as it gets compressed (300 km wide) on the Sun side and stretched (30000 km) on the night side of the Earth. The magnetosphere shields the Earth from incoming solar wind, and that is why the Sun side of the magnetosphere is compressed. Solar particles that seep through the Earth's magnetosphere are trapped at two Van Allen Belts, doughnut shaped belts, 3000 km and 20,000 km above the surface of the Earth (Fig. 11). The upper belt traps electrons, whilst the lower belt traps protons. Because magnetic lines of force crowed at the poles and intersect the atmosphere, charged particles of the Van Allen Belts escape from the belts and collide with molecules of the atmosphere over the poles causing the atmosphere to glow (aurora borealis).

Origin of the Earth's Atmosphere:

The Earth's initial atmosphere resulted from bombardment of the Earth by a Mars-size meteorite, about 4.5 billion years ago. That impact melted the Earth, created the Moon, tilted the Earth's rotation axis, and evolved gases, which made up the early atmosphere. Subsequent volcanic activity replenishes the atmosphere with gases. The gasses that are evolved from the Earth are rich in water vapor, carbondioxide, carbon monoxide, etc., but do not have free oxygen. Hence, the early atmosphere of the Earth was quite different in composition from the current one, which is made of 79% nitrogen, and 21 % oxygen, with minor amounts of water vapor (0.1 to 3%), argon (0.9%), and carbon dioxide (0.03%). As a result of the abundance of greenhouse gases, the early atmosphere was quite hot, about 300�C, compared to the current temperature of 21�C. The atmospheric composition and heat changed subsequent to the appearance of bundles of DNA molecules, cyanobacteria, or blue green algae. These organisms are called autotrophs because they produce their food, whereas other organisms that evolved later are grazers, or flesh eaters. As shown by the process in Equation 1, autotrophs remove from the environment carbondioxide and give off oxygen as they make their food, glucose (C6H12O6).

6CO2 + 6 H2O + energy = C6H12O6 + 6O2                               Equation 1.

The energy used by these autotrophs (Equation 1) may come from the chemical breakdown of methane, in which case the process is called chemosynthesis, or the energy may come from sunlight in which case the process is called photosynthesis. After millions of years, the unicellular bundles of DNA (Prokaryotes) developed a nucleus surrounded by cytoplasm and evolved to Eukaryotes. Since cyanobacteria that matted the sea bottom produced large amounts of oxygen ancient shallow seas became places at which iron oxide was deposited. The cyanobacteria mats later changed to chert (silicon dioxide rock), and huge deposits of alternating chert and iron oxide formed banded iron formations (BIF) that serve as sources of iron for humans. Where the algal mats were replaced by calcium carbonate, corrugated layers of carbonate rock called stromatolites were formed. Formation of calcium carbonate also removes carbon dioxide from the atmosphere. The composition of atmosphere changed as carbon dioxide was removed from it and oxygen given to it. Besides reducing the water vapor content of the atmosphere, the oceans serve as sinks for carbondioxide gas, more gas sinking as temperatures become colder. Hence, the reduction of greenhouse gas corresponds to reduction of the temperature of the atmosphere, though it is difficult to establish causal relationship.

By 540 million years ago, the oceans were teaming with life that evolved from an initial cyanobacterium. Yet, the organisms were not skeletal, as we do not find macroscopic body fossils of the Precambrian. At the turn of the Silurian, enough ozone (molecule composed of three atoms of oxygen) that could absorb ultraviolet radiation was developed in the stratosphere. With the reduction of ultraviolet radiation that reached the surface of the Earth, plants began to colonize the land by the Devonian. Vascular plants that invaded the land eventually contributed to "icehouse" condition of the globe. Their roots speeded weathering, which resulted in incorporation carbon dioxide in new minerals, and the plants removed carbon dioxide during photosynthesis, which was not recycled to the atmosphere because the lignin in these plants does not oxide (Berner, 2001).

The heat budget: When the sun shines on Earth, part of it is reflected back by the outer atmosphere to space, part of it is absorbed by the atmosphere, and part by the surface of the Earth. Both those quantities of heat that are absorbed by the Earth and the atmosphere are irradiated back to space, so that the total amount of heat that comes to the Earth equals that which goes out from the Earth and its atmosphere. This balance between the incoming and outgoing heat is called the heat budget.

Though the heat budget is balanced, the amount of Sun's heat received by a unit area in the tropics is smaller than the heat received by the same size of area in the polar regions. The difference in such insulation is because the sun strikes the tropics at high angles, whilst the angle of incidence of sun's ray at high latitudes is at a lower angle (Fig. 12).   Whilst the tropics are regions of net heat gain, the high latitudes are places of net heat loss (Fig. 12). Consequently, oceans at high latitudes are frozen into ice. Frozen water (cryosphere) has a higher albedo effect; it reflects back sun's light more effectively. Hence, heat within the troposphere will have to be redistributed by the movement of air molecules, between the polar and equatorial regions. Likewise the oceans will be set in motion.

Layering of the Atmosphere

The gaseous content of the atmosphere is replenished by volcanic eruption (contribution from the lithosphere). Those gases that are held to the Earth by gravity make up the atmosphere. Accordingly, the lower part of the atmosphere has the highest concentration of gaseous molecules. It is also in the lower part of the atmosphere, the troposphere, that heat is transferred by convection.

Troposphere: Radiated from the Sun, white light passes through the Earth's atmosphere and is absorbed by that Earth's surface. It is reradiated as infrared (longer wavelength, and less energetic) ray, most of which is absorbed by greenhouse gases (water vapor and carbondioxide), to keep the troposphere fairly warm. However, the temperature decreases with elevation within the troposphere.

Insolation places a difference in temperature along the Earth's surface from the Equator to the poles. The vertical and horizontal differences of temperature within the troposphere result in heat transference by convection. This fact together with the coriolis effect, which arises from the rotation of the Earth, result in three tropospheric convection cells called the Hadley, Farrel, and Polar cells (Fig. 13), with attendant surface winds called easterly trade winds, westerlies, and easterly polar winds, respectively.

Stratosphere: Interaction of solar ultraviolet radiation with molecules in the stratosphere

result in the formation of an ozone-rich layer. The process imparts heat to the stratosphere, so that the temperature increases with elevation within the stratosphere. Because the amount of ultraviolet radiation is increased 10 to 20% during high sunspot activity, some scientists have proposed that variation in pressure gradient within the stratosphere might cause variation in pressures within the underlying troposphere and affect climate that way. During the "Mini Ice Age", 1600 to 1800 AD, sunspot activity was minimal to nonexistent, at a period also called the Maunder Minimum. Some scientists suggest that low sunspot activity, which corresponds to low amount of ultraviolet radiation, might correspond to climate cooling, though the jury is still out on this one. Some scientists have actually proposed a linkage between sunspot activity and El Nino events.

Mesosphere: This is a layer through which temperature decrease with elevation. The air density is minimal, though it is sufficient to cause drag on satellite motion.

Ionosphere or thermosphere: In this layer gamma rays and ultraviolet radiation strip electrons from molecules, so that it is a zone of ionized molecules. Temperature increases with elevation in this layer. Radio waves are reflected back to Earth thereby enabling communication.

The hydrologic cycle: The structure of water molecules is such that two hydrogen atoms are closer to one side, resulting in the positive side, leaving the other side to have a net negative charge (Fig. 16). Hence, water molecule is dipolar (has two molecules), with its oxygen and hydrogen ions being held together by strong covalent bonds. Neighboring water molecules are held by week hydrogen bonds. When sunlight strikes water, water molecules may vibrate, which is measured as temperature rise (sensible heat), or the energy may be used to break up hydrogen bonds (latent heat). The latent heat of fusion (changing ice to water) is 80 calories per gram, whereas the latent heat of vaporization (change of water to vapor) is 540 calories (Fig. 15). 1 calorie is the amount of heat required to raise the temperature of 1 gram of water by 1�C.

The hydrologic cycle involves the cycling of water from oceans to the atmosphere then over and through land back to the ocean (Fig. 16). It redistributes heat on the surface of the Earth. Latent heat of vaporization is removed from oceans by evaporation and released to the atmosphere as water is condensed and rain precipitates. Likewise, plant transpiration, which is the opposite of the photosynthetic reaction (Equation 1), releases heat to the atmosphere. Rain that falls on land rushes down slope as surface run off, through rivers, and through underground flow back to plants and the oceans, and the cycle repeats.

Sea breeze and Monsoon: The ocean has high heat capacity, i.e., temperature may not change with added heat because part of Sun's heat is used to breakup hydrogen bonds. In contrast, compared to the ocean, the land warms during the day (low air pressure) and gets colder during the night (high pressure). Wind blows from high to low pressure. Consequently, there is sea breeze with attendant sea spray during the day and land breeze during the night (Fig. 17).   Mountains that obstruct sea breeze commonly have precipitation of rain on the windward side and rain-shadow deserts on the lee side (orographic effect).

The monsoon are analogous to sea breeze and land breeze, but on a larger scale, because they also are a result of the tilted axis of the Earth that produce the annual four seasons (winter, spring, summer, fall), and the migration of the Inter Tropical Convergent Zone (ITCZ) across the Equator (Fig.18). The monsoons were first described in the northern Indian Ocean. During the summer, June, July, August, the land gets hotter than the oceans, the ITCZ shifts north of the Equator, and wet winds blow from the ocean to the land. During the winter, dry winds blow from land toward the ocean. These alternating landward and seaward blowing winds constitute the monsoons. There appears to be a teleconnection between the Indian monsoons and the climate in the equatorial eastern Pacific. According to Gilbert (1924) drought in India corresponds to weak values of the Southern Oscillators (air pressure difference between Tahiti and Australia). Weak or negative SO Index corresponds to an El Nino event, and is now referred to an El Nino Southern Oscillator (ENSO). ENSO corresponds to the period when warm water sloshes from Australia across the eastern Pacific to the Peruvian coast, yet another way by which more heat from the ocean is released to the atmosphere.

Surface Ocean Circulation:

The surface water of oceans circulates (Fig. 19) and redistributes heat. It is initiated by wind circulation, but maintained as geostrophic current. Important ideas to describe here include knowledge of wind circulation pattern, coriolis deflection, net water transport toward centers of circulation patterns, and a balance between pressure gradient and coriolis deflection that results in a geostrophic current.

Coriolis Effect: Looking from space down the North Pole is analogous to viewing a west-to-east rotating merry go round (Fig. 20). If a person from the center of the merry go round (the North Pole) threw a ball at a straight line to the periphery of the merry go round (the Equator), the ball appears to curve to the right. This is a consequence of the rotation of the merry go round, or the Earth. In the Northern Hemisphere (NH) moving currents are deflected to the right. In the Southern Hemisphere (SH), they are deflected to the left.

Wind patterns: Were the Earth covered by ocean, and it was not rotating, hot air would rise at the Equator, diverge and move aloft toward the poles, cool and descend at the poles, and return on the surface of the Earth to the Equator. Two circulation cells over the whole Earth would have redistributed heat by convection. However, the Earth rotates, from west to east, resulting in deflection of current to the right in the Northern hemisphere, and to the left in the Southern Hemisphere. The deflection of current due to the rotation of the Earth is called coriolis deflection. The net result of coriolis deflection is to subdivide circulation cells into 6 wind circulation cells, 3 in the Northern Hemisphere, and the other 3 in the Southern Hemisphere (Fig. 13). From the Equator to the poles these cells are called the Hadley, Farrel, and Polar, and the corresponding surface winds are trade winds or easterlies, westerlies, and polar easterlies. In tropical areas, air rises, releases moisture, and yields rain. Over 30� latitude, where cold air descends, air molecules are held in the compressed air, so that this latitude is the location of the great deserts of the world.

Between the Trade winds are the doldrums, or the Inter Tropical Convergent Zone (ITCZ). The ITCZ is the "heat equator". The ITCZ (Fig. 20) shifts across the equator in accordance with the location of the Sun over the Earth, which has a tilted spin axis. Moreover, presence of land, most of it located in the Northern Hemisphere, affects the wind circulation. It results generally in low-pressure area over the subtropical land, and generally high pressure over subtropical oceans. These results in initiating surface water circulation gyres around the subtropical highs. The gyres circulate around high-pressure areas clockwise in the Northern Hemisphere, and counterclockwise in the Southern Hemisphere. Essentially, the trade winds and the westerlies drag surface ocean water until they are deflected by continental edges and complete the circulation.

In tropical zones low-pressure areas above waters as hot as 27� C become centers of clockwise movement in the NH, and counterclockwise movement in the SH. These "heat chimneys" by which the ocean releases heat to the atmosphere are called hurricanes (Fig. 23), typhoons or cyclones, and propagate east to west over tropical seas, until they hit cooler land areas at which they die.

Ekman spiral: As winds move over the ocean, they cause water molecules of the ocean to move likewise. The surface ocean water will move at 45� to the east of the wind in the Northern Hemisphere, and to the west of the wind in the Southern Hemisphere. Each successfully lower water layer will likewise be deflected and a spiral motion appears. This is the Ekman spiral (Fig. 22). The spiral dies below 200 meters beneath surface water, at the start of the pycnocline. The net transport of surface water ends up being at 90� to the right of the wind in the Northern Hemisphere, and to the left of the wind in the Southern Hemisphere. This net water transport direction is called the Ekman transport.

Role of Ekman Transport: Ekman transport moves surface water at 90� and away from the wind direction. The following are consequences of that transport.

  1. In circulation gyres, Ekman transport piles the water toward the center of the gyres. Water flows down hill (due to pressure gradient effect) from the centers of the gyres but will be defected by the coriolis effect. In time the pressure gradient effect will be counter balanced by the coriolis effect and a geostrophic current will circulate around the gyres (Fig. 23).
  2. To counter the piling of water at the center of gyres, the water sinks or downwells by depressing the thermocline.   Moreover, the places from which surface water has moved will be replaced by upwelling (Fig. 24)of deep, cold and nutrition rich water. Upwelling is present on the east side of tropical oceans, and at the Equator.

The vertical movements of ocean water explained by using Ekman transport are also a means of redistribution of heat. Vertical transport of ocean water is also achieved by thermohaline circulation,

Thermohaline Circulation: Cold, salty, and dense waters sink and move laterally at depth. As waters from different parts of the subpolar part of the ocean sink, one layer of cold water moves beneath another. For example, in the Atlantic Ocean, the Antarctic bottom water (AABW) flows northward beneath the south following North Atlantic bottom water (NABW), which in turn is overlain by southward flowing North Atlantic deep water (NADW). In turn, this is overlain by Mediterranean water, North Atlantic, and Central Atlantic waters (Fig. 25).

Global Conveyor Belt: Thermohaline and surface water circulation combine to form a giant circulation belt (Fig. 26) that redistributes heat. Salty and cold water of the North Atlantic sinks, and advects at depth. Sinking of cold water from the South Atlantic further pushes the deep water to move to the Indian and Pacific Ocean at which the water upwells. Surface waters are imported from to the North Atlantic Ocean from the Indian Ocean and the North Pacific Ocean on the surface and exported at depth from the North Atlantic to the Indian and North Pacific oceans, and the cycle is repeated

Back and forth movement of warm surface water across eastern Pacific: Yet another method by which the ocean releases heat to the atmosphere is by covering the equatorial eastern Pacific with warm water during EL Nino events. During El Nino events (Fig. 27), 1) sea level pressure (SLP) increases in the east, 2) sea temperature rises in the east, 3) phytoplanktons and other aquatic organisms of the Peruvian coast are killed, 4) an internal wave, the Kelvin wave that propagates through the thermocline has arrived at the Peruvian shelf, and has depressed the thermocline there. The 30 to 40 meter amplitude of the Kelvin wave generates 10 to 15 cm waves on the surface, which can be traced by altimetry. 5) The Southern Oscillation Index (SOI), the difference between air pressure in Tahiti and Darwin is low or is negative, and trade wind flow is slackened or reversed. 6) The equatorial Walker air circulation cell has been broken in two cells (Fig. 28) and rain has shifted from Australia to the middle of the equatorial Pacific. 7) The northern jet stream has been perturbed such that it is pulled to low latitude at the latitude of coastal California, whilst it is pushed to higher latitudes at latitude of Florida.

In non -El Nino conditions, warm water is more restricted to the western portion of the eastern Pacific, near Indonesia and Australia. At this condition, which is the most common case, 1) SLP is highest in the west, and the surface of the ocean water slopes to the east (Fig. 29), 2) sea temperature rises in the west, 3) phytoplnktons and other aquatic organisms abound in the coastal waters of Peru, 4) weak Rossby waves move from east to west on the thermocline, which declines to the west, 5) The SOI is quite positive and strong trade winds blow from east to west, 6) The equatorial Walker cell leads to air rising over eastern Australia with associated rainfall (Fig. 28), 7) The jet stream perturbation is more subdued.

Each of the seven parameters described above can be measured and used as proxies for predicting the onslaught of El Nino, the period during which the ocean warms the atmosphere, and serious weather effects, such as flood, forest fires, drought, and disease are imposed in different parts of the world. The parameters may be measured either directly on the surface and depth of ocean, or recorded by detectors the signals of which are collected by satellites and beamed to data collection stations.  

The cause for the back and forth movement of warm water over the equatorial eastern Pacific is a subject of current research. Some scientists have proposed that the atmospheric phenomena initiate the oceanic phenomena. Others have suggested that the oceanic phenomena trigger the atmospheric oscillation. Irrespective of which phenomena come first, it is likely that it is the heat of the Sun that sets the El Nino Southern Oscillator (ENSO) as a coupled ocean-atmosphere phenomenon.

There are inbuilt instabilities during a non-El Nino condition. At the same elevation, warm water is present in near Australia, whilst cold water is present near Peru. This causes a gravitation -potential-surface instability, which has to be accounted for by gravity related perturbation or waves. The Hadley, Farrel, and Polar cells are essentially meridian (north-south oriented), whilst the Walker cell is equatorial (east-west oriented), and quite large during non El Nino conditions. This condition should cause perturbations in the tropospheric airflow, including in the upper tropospheric jet stream region. The Jet stream in the upper troposphere is likely affected by stratospheric pressure variations that result from increased heat absorption during periods of high sunspot activities.