Introduction to Ocean Sciences

Chapter 9: Ocean-Atmosphere Interactions

Guide to Reading and Learning

Chapter 9 provides a description of the intimate interactions between ocean and atmospheric processes. These interactions are critical in controlling the Earth’s climate and weather and are an important key to predicting the climate change that may result from human enhancement of the greenhouse effect. For this reason, ocean–atmosphere interactions are now the central focus of a very large proportion of all ocean sciences research.

At the beginning of the chapter we learn how water evaporated into the atmosphere lowers the density of the air and causes it to rise, and how this water vapor is released when the reduced pressure at altitude cools the air. You may have known that this process causes rainfall and gives us our freshwater resources. However, did you know that heat transferred from the oceans to the atmosphere by this route is the principal source of energy that drives wind and weather systems in our atmosphere? Did you know that heat transferred from warm tropical oceans to higher latitudes and onto land is critical in maintaining the atmospheric temperature range within a relatively small range on the Earth and enabling life as we know it to develop and populate the entire globe?

The entire midsection of this chapter is devoted to describing how ocean–atmosphere interactions control the regional climates found on the Earth. First, we learn how these interactions set up distinct latitudinal bands within which there are consistent conditions of cloud cover, rain, or snowfall, and persistent climatic wind speeds and directions. To understand this, you must first learn the essentials of the Coriolis effect and geostrophic flow. A full understanding of these concepts is very difficult to attain, as it requires that you look at the world in a completely different way. To us, the Earth’s spinning motion is not noticeable because we are fixed to the solid Earth. However, moving air and water are not fixed to the solid Earth and they try to move in straight lines in three-dimensional space. As a result, they do not appear to flow in straight lines over the Earth surface from our rotating observation point. Do not despair if you cannot understand these concepts fully. Most scientists only understand them through complicated mathematics, so you are not alone. As long as you accept and learn the “Essential to Know” bullets associated with these two concepts, you will be able to apply them properly to understand how the air in the atmosphere and, in the next chapter, the water in the oceans, moves in response to heat and water transfers between the oceans and atmosphere.

After we have learned the basics of climate winds and rainfall and of how they change with the seasons, the chapter turns to one of the most important and fascinating ocean–atmosphere interactions: interannual oscillations. The best known and most important of these is El Niño, or the El Niño Southern Oscillation (ENSO) as scientist now call it. This oscillation is responsible for sometimes-dramatic changes in climate that can last many months and cause droughts, floods, collapses of populations of fish and other marine species, and a host of other effects throughout almost the entire world. The mechanism of El Niño is discussed in this chapter. However, a full understanding of El Niño requires concepts that are covered in Chapters 10 and 11. Also, the section on the effects of El Niño contains information that can be more fully understood after concepts discussed in Chapters 14–16 have been learned. I strongly suggest that that you read and learn about El Niño here but that you return to this section several times as you learn concepts in other chapters that can enhance your understanding of El Niño and its effects. This need to cross-reference concepts is yet another example of the interdisciplinary and interrelated nature of ocean sciences.

At the end of this chapter, we include a sampling of the local and short term changes that make up our weather as opposed to the long-term average climate. The hurricanes, extratropical cyclones, land and sea breezes, and the island effect included in this section are the weather events and features that are very closely linked to the transfers of heat and water vapor between the oceans and atmosphere that dramatically affect the weather, especially in coastal regions.

Make frequent visits to the Internet as you read Chapter 9. There are literally hundreds of Web sites that provide maps and data on weather and climate.

Chapter 9 Essential to Know 

Critical Concepts used in this chapter

CC.1, CC.3, CC.4, CC.5, CC.8, CC.9, CC.10, CC.11, CC.12, CC.13

9.1 The Atmosphere

  • Earth’s climate (average conditions for prior years) and weather (conditions at a specific time and place) are both dependent on the distribution of heat and water vapor in the atmosphere, and the oceans play a major role in these distributions
  • The oceans contain many times more heat energy than the atmosphere because the total mass of ocean water is more than 200 times that of the atmospheric gases, and water has a much higher heat capacity than air.
  • Gases are highly compressible. Even small increases in pressure produce a substantial reduction in volume
  • Pressure decreases rapidly with altitude in the atmosphere, so gases expand with altitude and density is reduced. The atmosphere is therefore steeply stratified and the density-driven vertical motions of air masses are limited to only a few kilometers above the Earth’s surface.

Atmospheric Structure

  • The atmosphere is separated into three distinct zones: the troposphere, between the Earth’s surface and between about 10 and 18 kilometers in altitude, with the stratosphere and the mesosphere at higher altitudes.

Ozone Depletion

  • Ozone depletion is caused by chlorofluorocarbons that diffuse upward to the ozone layer (located in the stratosphere) after they are released in the lower atmosphere.
  • Depletion is concentrated over the poles and in winter, as supercold ice crystals apparently aid the depletion.
  • Ozone depletion increased rapidly from the 1970s to the 1990s but chlorofluorocarbons are now banned and ozone depletion is expected to disappear within several decades.

9.2 Water Vapor in the Atmosphere

  • Vertical and horizontal air mass movements that occur primarily in the troposphere are the cause of the Earth’s weather and control its climate.

Water Vapor and Air Density

  • Adding water vapor to air by evaporation reduces the air’s density and causes it to rise because water molecules are heavier than the molecules of air gases they displace.
  • Saturation vapor pressure (the maximum concentration of water vapor in air) increases rapidly with rising temperature within the range of temperatures found in the atmosphere..
  • Water vapor is continuously added to the atmosphere by evaporation of water from the ocean surface.  The water vapor is transported in the atmosphere, and then condensed into precipitation.

Water Vapor, Convection, and Condensation

  • Warm, moist air rises, and because it expands as pressure is reduced with altitude and the heat energy of its molecules is spread in a larger volume, its temperature drops. This is adiabatic cooling.
  • Water vapor saturation pressure is reduced as air cools.
  • Water vapor in air precipitates when the water vapor saturation pressure is exceeded. However, air may become supersaturated before water condenses, as the water vapor molecules are separated in the air and it takes time before clusters can form to provide the nuclei for raindrops.
  • Latent heat carried into the atmosphere with the evaporated water is released to the atmosphere when the water vapor condenses.
  • Atmospheric convection cells are formed when warm, moist air rises, cools, loses its water vapor, becomes more dense, and sinks.

9.3 Water and Heat Budgets

  • Averaged over the entire planet and periods of time, the amounts of heat and water vapor that enter the atmosphere must equal the amounts that are removed.

Water Budget

  • The amount of water evaporated from the oceans annually is enough to cover the entire globe about 1 m deep.
  • Approximately 93% of water evaporated to the atmosphere is evaporated from the oceans but only 71% of the total precipitation (rain and snow) falls on the oceans.
  • The remaining 22% of water evaporated from the oceans falls on land and provides our freshwater resources.

Heat Budget

  • The Earth’s global heat budget is balanced so that the energy received in solar radiation is equal to the longer wavelength energy radiated back to space. Any imbalance in this relationship would cause climate to warm or cool.
  • Solar energy is partially reflected and partially absorbed by atmospheric gases, clouds, oceans, and land. These all reradiate some of this heat energy but the heat budget is complicated because heat energy can be transferred between land or oceans, and the atmosphere by conduction of sensible heat across the surface and by transfer of latent heat by water vapor. Also, reradiated heat can be absorbed by atmospheric gases and absorbed or reflected by clouds.
  • About 50% of the solar energy reaching the Earth is absorbed by the oceans but a major portion of this energy is then transferred to the atmosphere by evaporation as latent heat of water. This is the mechanism responsible for moderating the Earth’s climate differences between the polar and equatorial regions.

Latitudinal Imbalance in the Earth’s Radiation

  • Because the sun’s rays are spread over a greater surface area near the poles than at the equator, more heat per unit area is absorbed by the land and oceans in the tropics that in polar regions. However, the amount of heat radiated to space per unit area is about the same at all latitudes.
  • In tropical latitudes, solar heat reaching the Earth’s surface slightly exceeds heat radiated back to space. In high latitudes, heat radiated to space slightly exceeds the solar heat that reaches the Earth’s surface.
  • Heat is transported from tropical latitudes to polar regions by the latent heat of water vapor transported through the atmosphere and by the sensible heat transported by ocean currents. Ocean transport is more important near the equator and atmospheric transport is more important near the poles.

9.4 Climatic Winds

  • Winds are extremely variable day to day at any location but if we average these winds over many days and months we find a consistent pattern of winds that blow in different directions at different latitudes. These are called climatic winds.

Climatic Winds on a Nonrotating Earth 

  • On a nonrotating Earth, warm, moist air would rise at the equator; flow to the polar regions, cooling as it flowed; sink in the polar regions; and flow back to the equator. Surface winds would blow from poles to the equator.

Climatic Winds and the Coriolis Effect

  • Because the Earth rotates, moving air (and water masses) are deflected by the Coriolis effect.
  • Warm, wet air that rises at the equator moves toward higher latitudes at altitude. Initially, near the equator, there is little or no Coriolis deflection. However, as the air moves further north it is deflected progressively to the east until at about 30o N or S it is flowing directly west to east. By this time, it has cooled and lost most of its water vapor so it sinks back to the surface and turns back toward the equator to complete the convection cell. As the air flows toward the equator it is deflected by the Coriolis effect progressively to the west. However, as it nears the equator the Coriolis effect becomes smaller and the air continues to flow from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere with little further deflection. This is the Hadley cell and the ground-level winds are the trade winds.
  • This pattern is repeated in two additional convection cells between the Hadley cell and the poles.
  • In the Ferrel cells in mid-latitudes, ground-level air flows northward but is deflected to the west. These winds are the westerly winds
  • The third cell in each hemisphere is a polar cell near the poles.
  • Atmospheric upwelling and downwelling areas are regions where winds are light. At upwelling areas clouds and rain are abundant, whereas at downwelling areas there is little or no rainfall.
  • Atmospheric upwelling occurs at the equator and between the Ferrel and polar cells. Atmospheric downwelling occurs between the Hadley cells and Ferrel cells at around 30o latitude and at the poles.
  • The region near the equator between the Northern Hemisphere and Southern Hemisphere Hadley cells is called the intertropical convergence zone (ITCZ).
  • The region between the Ferrel cells and the polar cells is called the polar front. Fast-moving jet streams flow west to east in the upper troposphere above the polar front.

Seasonal Variations

  • The locations of the atmospheric convection cells migrate north and south seasonally as the tilt of the Earth’s axis causes the angle of the sun to the equator to change as the Earth moves around the sun.
  • Northern Hemisphere summer solstice occurs when the sun is directly overhead at its farthest north, June 21 or 22. Southern Hemisphere summer solstice (Northern Hemisphere winter solstice) is December 21 or 22. The spring and autumn equinoxes, when the sun is directly overhead at the equator, are March 20 or 21 and September 20 or 21, respectively.
  • Land masses interfere with and modify the convection cell pattern, including the location of the ITCZ.
  • Because ocean water has a high heat capacity compared to land, convection cells migrate farther north and south seasonally over the continents than they do over the oceans.
  • When the convection cells are moved north and south as the seasons change, climate temperatures follow, but with a time lag due to the time it takes for the sun to heat up the land or ocean. This is the reason why many Northern Hemisphere mid-and high-latitude areas have their warmest weather in August and their coldest in February, rather than at the solstices in June or December.
  • The time lag is greater over the oceans because more solar energy is needed to warm the oceans due to water’s high heat capacity.

Monsoons

  • Modification of the convection cells is greatest over the large land mass of Asia and this is the cause of the monsoons. Warm, moist air is drawn northward across the Indian Ocean into Asia in northern summer, when solar heating over Asia is intense and a strong low-pressure zone is formed. In northern winter, a strong high-pressure zone is formed over Asia, and cool, dry air moves south from Asia over the Indian Ocean.

9.5 Climate and Ocean-Surface Water Properties 

  • Ocean-surface water temperature and salinity are controlled primarily by solar radiation and heat and water transfers between the atmosphere and oceans.

Ocean-Surface Temperatures

  • Ocean-surface water temperatures generally decrease from the equator to the poles but there are modifications to this pattern due to ocean currents and upwelling.
  • There is a band of colder water across the equator on the eastern side of the Pacific Ocean where there is a divergence and cold water is upwelled. A weaker but similar band occurs in the Atlantic Ocean but upwelling is suppressed by the monsoons in the Indian Ocean.
  • Warmer water extends further poleward on the west sides of each ocean as a result of warm surface currents that flow poleward in these locations.
  • In mid- and low-latitudes, ocean-surface temperature bands shift north and south in response to seasonal changes in the sun’s angle but in polar regions temperatures are buffered by ice and do not change significantly with the seasons.

Ocean Surface Salinity

  • The distribution of salinity in ocean surface waters is related to the locations of the atmospheric convection cells.
  • Salinity is low in regions where precipitation exceeds evaporation and high when the opposite is true.
  • Surface water salinity is generally lower at the equator and in high latitudes.
  • Surface water salinity is higher in the subtropical Atlantic Ocean than in the other oceans because the trade winds can carry evaporated water from the Atlantic to the Pacific across the narrow neck of Central America. The westerlies do not transport evaporated water from the Pacific to the Atlantic Oceans due to the wide continents and mountain chains in the Americas at westerly wind latitudes.

9.6 Interannual Climate Variations

  • Interannual variations in regional climate occur in a number of areas, including the North Atlantic Ocean, the tropical Pacific Ocean, the North Pacific Ocean, the Indian Ocean, and the Arctic Ocean and may exist in other areas..
  • The oscillations are generally related to small variations in ocean surface temperature that occur in large areas of the ocean.
  • These oscillations, especially El Niño, can cause climate to change periodically between warm and cold and wet and dry winters throughout North America and elsewhere.

El Niño and the Southern Oscillation

  • El Niño is a complex oscillation that involves both oceans and atmosphere in the tropical Pacific Ocean. This oscillation can affect climate and cause floods, droughts, severe wave erosion, and many other effects throughout the Pacific Ocean region and even in other parts of the world.
  • The El Niño oscillation takes place when warm surface water, driven westward by the trade winds in the tropical Pacific, flows back to the east along the equator, where it is not deflected by the Coriolis effect. The warm water flows over the normally cold nutrient-rich water found in a band across the equatorial Pacific and in the area off Peru. The loss of nutrient-rich water drastically reduces phytoplankton productivity and eliminates food supplies for higher organisms.

Symptoms of El Niño

  • El Niño has occurred periodically, generally every 3–5 years, since as long ago as 1726.
  • The first sign of El Niño has historically been an increase in the temperature of the normally cold surface water in the upwelling zone off Peru.
  • When the cold water disappears, phytoplankton production is drastically reduced and the massive anchovy populations of the region collapse.
  • El Niño usually begins in December around Christmas and is generally gone by the following April but varies in intensity and duration.

El Niño/Southern Oscillation Sequence

  • In normal conditions, the trade winds pile-up warm surface waters toward the western side of the Pacific Ocean, and upwelling occurs in the equatorial band on the eastern side near Peru. Atmospheric pressure is high near Peru and it is low near Indonesia due to evaporation from the warmer water in this area.
  • The El Niño Southern Oscillation begins when the Peruvian high-pressure system weakens, which causes the southeast trade winds to weaken.
  • With normal persistent trade winds, the sea surface near Indonesia is elevated compared to the sea surface near Peru and this elevation is balanced by the atmospheric pressure difference between the two areas.
  • When the trade winds weaken, warm surface water begins to flow eastward across the pacific from Indonesia toward Peru. Because the flow is west to east at the equator, this flow, which resembles a long-wavelength wave, is not deflected by the Coriolis effect.
  • When the warm surface water flow reaches the upwelling area near Peru, the warm surface water shuts down the upwelling and an El Niño begins.
  • El Niño usually persists for about three months, until the trade winds have strengthened again and moved the warm surface water back to the west.
  • Sometimes the oscillation “overshoots” and a La Niña forms in which the Peruvian upwelling and the atmospheric pressure difference between Peru and Indonesia both become much stronger than usual.

Effects of El Niño

  • El Niño affects the climate of very large areas of the globe.
  • The principal effects include lower atmospheric pressure, more rainfall, and flooding in Peru, and higher atmospheric pressure and droughts in Indonesia and Australia.
  • A strong El Niño can cause droughts in Australia, India, Indonesia, Central America, west-central South America, Africa, and Central Europe and excessive rainfall in California, the East Coast of the United States and parts of South America, Britain, France, and the Arabian peninsula
  • El Niño produces an increase in the number and intensity of hurricanes in the Pacific Ocean but a reduction in the number and intensity of hurricanes in the Atlantic Ocean.
  • El Niño has major effect on marine ecosystems, causing the entire upwelling ecosystem near Peru to collapse, coral reefs to be stressed and die in the central Pacific, and warm water species to be found much further north than usual.

Modeling El Niño     

  • Because El Niño has such widespread and severe effect on climate, ocean scientists have deployed numerous instruments in and on the equatorial Pacific Ocean and have developed very sophisticated computer models in an attempt to provide a forecasting ability.
  • These models can now predict the onset of an El Niño with reasonable accuracy several months ahead of its appearance in the waters off Peru.
  • However, the models cannot predict the strength of an El Niño reliably until after the oscillation has already begun because the severity appears to be related to the timing of another oscillation that causes burst of stronger winds periodically at about 30-day intervals. If these bursts occur at exactly the right time after the El Niño sequence has begun, they can apparently accelerate the warm water wave as it starts to move west to east across the Pacific and, if this occurs, the El Niño is much stronger than the models would otherwise predict.

Other Oscillations

  • The North Atlantic Oscillation is a periodic change in the relative strengths of the atmospheric low-pressure zone near Iceland and the subtropical high-pressure zone near the Azores. The shift affects climate in Europe and primary production in North Atlantic Ocean ecosystems.
  • The Pacific Decadal Oscillation (PDO) has two modes, one in which the sea surface temperature in the northwest Pacific Ocean is relatively warm while the region from Canada to California and Hawaii are relatively cool, and another in which the relative temperatures are reversed. The PDO has major effects on the climate of North America, especially the location of the jet stream and the storms that follow the jet stream track, moving rainfall either to the north to Canada and Washington or more southerly to California, but also the temperatures and rainfall across the United States.

Climate Chaos?

  • Many physical and biological characteristics of the Pacific Ocean marine ecosystems have been monitored extensively for several decades.
  • Analysis of these records reveals that these ecosystems experienced phase shifts corresponding to switches in the PDO in most of these parameters between 1976 and 1977 and between 1988 and 1999.
  • For some species, the analysis showed that populations or indexes of health, such a breeding success, increased or decreased when the PDO switched one way and then returned to their previous value when the PDO switched back. However many such indices either increased at both switches or decreased at both switches.
  • This data indicates that oscillations such as the PDO may be agents of chaotic step changes in ecosystems and that ecosystems are much more variable and unpredictable that was previously thought.

9.7 Land–Ocean–Atmosphere Interactions

  • Landmasses interact with atmospheric convection cell circulation
  • Landmasses, especially mountain ranges, may block or steer air masses.
  • Land has a much lower heat capacity than water so land warms and cools during the day–night cycle much more than the oceans does. The temperature differential between land and ocean causes heat to be transferred locally by winds at and near the land–ocean boundary
  • These interactions can take place on a wide range of time and space scales affecting both regional and long-term climate and local weather events and conditions.

9.8 Global Climate Zones

  • Climate is defined by factors including the average annual temperature, seasonal and daily temperature range, extent and persistence of cloud cover, and seasonal and annual rainfall.
  • Climate varies with latitude, proximity to the oceans, and location and orientation of mountain ranges.

Ocean Climate Zones

  • Over the oceans, climate zones are arranged in generally latitudinal bands closely correlated with the ocean surface water temperatures and the atmospheric wind belts, convergences, and divergences.

Land Climate Zones

  • Land climate zones are more complicated that ocean climate zones.
  • Areas of the continents that are far from the oceans have much larger ranges of temperatures, both daily and seasonally, than coastal climates.
  • The moderating influence of the ocean on climate is reduced in locations where the climatic winds blow predominantly from the center of the continent toward the coast (e.g. the northeast United States).
  • Coastal climates are also affected by ocean currents. For example, the warm Gulf Stream gives Scandinavia a much milder climate than Alaska although they are at about the same latitude.
  • The moderating influence of the oceans can also be blocked by mountain chains aligned parallel to the coast. For example, the moderating influence reaches much further into Europe from the Atlantic Ocean than it does into North or South America, where mountain ranges block the climatic winds flowing from the Pacific Ocean.
  • Rainfall rates are also influenced by proximity to the oceans and by mountains. Water vapor carried from the oceans can reach far inland unless it encoutners mountain ranges. Mountains cause the air to rise and most of water vapor to fall as rain or snow on the ocean side of the range.

9.9 Weather Systems

  • Weather systems are chaotic and therefore cannot be predicted with any degree of certainly. Weather predictions will always be less accurate and will need to be more generalization the further ahead in time these predictions are made..

High- and Low-Pressure Zones

  • Weather systems are formed where areas of low or high atmospheric pressure are formed due to differential solar heating or evaporation.
  • Winds blowing in the Northern Hemisphere are deflected to flow counterclockwise around low-pressure zones and clockwise around high-pressure zones. The opposite is true in the Southern Hemisphere.
  • Winds near the Earth’s surface all flow in near-geostrophic balance so their strength and direction can be estimated from a barometric chart (map of air pressure). Wave heights and directions can also be forecast from these charts because the direction, fetch, and speed of the winds can all be estimated.

Hurricanes

  • Hurricanes form over the subtropical oceans where water temperature is high enough (generally above 26oC) to provide large energy inputs to a low-pressure system through evaporation, and where the Coriolis effect is sufficiently strong to cause the inflowing air to be deflected to flow around the low-pressure zone.
  • In these conditions the winds can be deflected to flow geostrophically around the low-pressure system, the low-pressure zone can intensify, and hurricane winds and circulation can develop and form a cloudless eye.
  • The winds move warm, moist air toward the low-pressure zone and the air mass gains more heat energy from the enhanced evaporation of wind blowing over warn water. As the air flows inward and is deflected to flow geostrophically it also rises in a spiral fashion, drawing more air in behind it and further intensifying the winds and circulation.
  • Most damage and deaths attributed to hurricanes come from storm surges. A storm surge is surface ocean water pushed ahead of the storm by winds and causes flooding as it raises sea level on the coast. Further damage is caused by wind waves on the elevated surface. The winds and storm surge are greatest in the northeast quadrant of the hurricane, not directly in the path of the eye.
  • Hurricanes form in all the tropical oceans but are called other names such as cyclones and typhoons in some regions. Hurricanes are rare in the South Atlantic and eastern tropical Pacific Ocean, as the surface water is generally slightly cooler in these regions.
  • There appears to be a long-term cycle (approximately 30 years) of increased and diminished hurricane activity. The late twentieth century was a time of relatively low activity, but we have now entered what is expected to be the more active part of the cycle.  Hurricane intensity and strength, at least in the Atlantic, are expected to be higher for some decades than they were in the 1990s.
  • It is of great concern that hurricane frequency and intensity may be increased and hurricanes may form and maintain their strength at higher latitudes as a result of the increase of ocean surface water temperatures due to the enhanced greenhouse effect, but the extent of any such effect is not known.

Extratropical Cyclones

  • Extratropical cyclones, which are similar to hurricanes, can develop when a wave develops on the front between the Ferrel cell and the polar cell. These storms can be much larger in area than hurricanes and can sustain winds that are almost as high.

9.10 Local Weather Effects

Land and Sea Breezes

  • Because of the difference in heat capacity between ocean water and land, sea breezes are formed on coastlines during the day when solar heating on the continent causes air to rise and be replaced by air drawn in over the water.
  • Land breezes form during the night and early morning when the land cools more than the ocean surface water and cold dense air flows out from the land over the ocean.

Coastal Fog

  • Coastal fogs form where sea breezes draw warm, moist air from offshore across cold nearshore waters onto the land.

The Island and Mountain Effect 

  • Islands and mountain chains cause air to rise then cool adiabatically, and the water vapor to condense as air rises up the windward side of a mountain.
  • Once over a mountain the air mass descends, warms, and water condensation stops. Thus, the windward side of a mountain has high rainfall and the leeward side is arid.

 

Critical Concept Reminders:

CC.1 Density and Layering in Fluids (pp. 200, 203, 207, 217, 223)

  • Fluids, including the oceans and atmosphere, are arranged in layers sorted by their density. Air density can be reduced by increasing its temperature, and by increasing its concentration of water vapor causing the air to rise. This is the principal source of energy for Earth’s weather. To read CC1 go to page 2CC.

CC.3 Convection and Convection Cells (pp. 203, 207)

  • Evaporation or warming at the sea surface decreases the density of the surface air mass and causes it to rise. The rising air mass cools by adiabatic expansion, and eventually loses water vapor by condensation, which increases temperature as latent heat is released. As air continues to rise, adiabatic expansion and radiative heat loss then cool the air and increase its density so that it sinks. These processes form the atmospheric convection cells that control Earth’s climate. To read CC3 go to page 10CC.

CC.4 Particle Size, Sinking, Deposition, and Resuspension (p. 203)

  • Suspended particles (either in ocean water or in the atmosphere) sink at rates primarily determined by particle size: large particles sink faster than small particles. This applies to water droplets in the atmosphere. The smallest droplets sink very slowly and form the clouds, while larger droplets fall as rain. To read CC4 go to page 12CC.

CC.5 Transfer and Storage of Heat by Water (pp. 209, 223, 224)

  • Water’s high heat capacity allows large amounts of heat to be stored in the oceans and released to the atmosphere without much change of ocean water temperature. Water’s high latent heat of vaporization allows large amounts of heat to be transferred to the atmosphere in water vapor and then transported elsewhere. Water’s high latent heat of fusion allows ice to act as a heat buffer reducing climate extremes in high latitude regions. To read CC5 go to page 15CC.

CC.8Residence Time (p. 202)

  • The residence time is the average length of time that molecules of contaminants such as chlorofluorocarbons spend in the atmosphere before being decomposed or removed in precipitation or dust. Long residence time allows such contaminants to diffuse upwards into the ozone layer in the upper atmosphere. To read CC8 go to page 19CC.

CC.9 The Global Greenhouse Effect (pp. 200, 203, 204, 205)

  • The oceans and atmosphere are both important in studies of the greenhouse effect, as heat, carbon dioxide and other greenhouse gases are exchanged between atmosphere and oceans at the sea surface. The oceans store large amounts of heat, and larger quantities of carbon dioxide both in solution and as carbonates. To read CC9 go to page 22CC.

CC.10Modeling (pp. 205, 220, 221)

  • The complex interactions between the oceans and atmosphere that control Earth’s climate and affect the fate of Greenhouse gases can best be studied by using mathematical models, many of which are extremely complex and require massive computing resources. To read CC10 go to page 26CC.

CC.11Chaos (pp. 205, 221, 222, 226)

  • The nonlinear nature of ocean-atmosphere interactions makes at least part of this system behave in sometimes unpredictable ways and makes it possible for climate and ecological changes to occur in rapid, unpredictable jumps from one set of conditions to a completely different set of conditions. To read CC11 go to page 28CC.

CC.12 The Coriolis Effect (pp. 207, 219, 226)

  • Water and air masses move freely over the Earth and ocean surface while objects on the Earth’s surface, including the solid Earth itself, are constrained to move with the Earth in its rotation. This causes moving water or air masses to appear to follow curving paths across the Earth’s surface. The apparent deflection, called the Coriolis Effect, is to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. The effect is at a maximum at the poles, and is reduced at lower latitudes, becoming zero at the equator. To read CC12 go to page 32CC.

CC.13 Geostrophic Flow (pp. 218, 226, 227)

  • Air and water masses flowing on horizontal pressure gradients are deflected by the Coriolis effect until they flow across the gradient such that the pressure gradient force and Coriolis effect are balanced, a condition called geostrophic flow. This causes ocean currents and winds to flow around high and low pressure regions in near circular paths. The familiar rotating cloud formations of weather systems seen on satellite images are formed by air masses flowing geostrophically. To read CC13 go to page 43CC.

 

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