Geography Exam 2

Figure 3.2 will explain Conduction, Radiation and Convection- important concepts to understand heat transfer. The discussion on types of heat on page 73 is very important; make sensible heat is probably familiar to you but latent heat lies at the heart of heat transfer so pay particular attention to this concept.

(Figure 3.2): Heat-Transfer Process: Infrared energy RADIATES from the burner (fire) to the saucepan and the air. Energy CONDUCTS through the molecules of the pan and the handle. The water physically mixes, carrying heat energy by CONVECTION. Latent heat is the energy absorbed when liquid water changes to steam (water vapor). Heat energy can be transferred in a number of ways throughout Earth's atmosphere, land, and water bodies. RADIATION is the transfer of heat in electromagnetic waves, such as that from the Sun to the Earth or as that from a fire or a burner on the stove. The temperature of the object or substance determines the wavelength of radiation it emits; the hotter an object, the shorter the wavelengths that are emitted. Waves of radiation do not need to travel through a medium, such as air or water, in order to transfer heat. CONDUCTION is the molecule-to-molecule transfer of heat energy as it diffuses through a substance. As molecules warm, their vibration increases, causing collisions that produce motion in neighboring molecules, thus transferring heat from warmer to cooler material. An example is energy conducted through the handle of a pan on a kitchen stove. Different materials (gases, liquids, and solids) conduct sensible heat directionally from areas of higher temperature to those of lower temperature. This heat flow transfers energy through matter at varying rates, depending on the conductivity of the material- Earth's land surface is a better conductor than air; moist air is a slightly better conductor than dry air. Gases and liquids also transfer energy by CONVECTION, the transfer of heat by mixing or circulation. An example is a convection oven, in which a fan circulates heated air to uniformly cook food, or the movement of boiling water on a stove. In the atmosphere or in bodies of water, warmer (less dense) masses tend to rise, and cooler (more dense) masses tend to sink, establishing patterns of convection. This physical mixing usually involves a strong vertical motion. When horizontal motion dominates, the term advection applies. Heat always flows from areas of higher temperature into an area of lower temperature. Heat flow stops when the temperatures become equal. Two types of heat energy are important for understanding Earth-atmosphere energy budgets. SENSIBLE HEAT can be "sensed" by humans as temperature because it comes from the kinetic energy of molecular motion. LATENT HEAT ("hidden heat") is the energy gained or lost when a substance changes from one state to another- such as from water vapor to liquid water (gas to liquid) or from water to ice (liquid to solid). Latent heat transfer differs from sensible heat transfer in that as long as a physical change in state is taking place, the substance itself does not change temperature.

My lecture diverges from the text here-take your knowledge of the forces that initiate wind to page 121 and read under the heading Local Winds. If you can master winds at the local level I think it makes the Global scale understanding easier. Figure 4.15 and 4.17 will help you here

(Figure 4.15): Conditions for daytime valley breezes and nighttime mountain breezes. A) Day-time valley breezes: Warm air flows from the bottom up in the daytime. Valley air gains heat energy rapidly during the day. Valley slops are heated sooner during the day than valley floors. As the slopes heat up and warm the air above, this warm, less-dense air rises and creates an area of low pressure. By the afternoon, winds blow out of the valley in an upslope direction along this slight pressure gradient, causing a valley breeze. B) Nighttime mountain-breeze conditions. Cold air flows from the top down at nighttime. At night, heat is lost from the slopes, and the cooler air then subsides downslope in a mountain breeze.

Revisit the greenhouse effect which should be familiar to you by now but your understanding will be tested on November 3 of the concepts. Figures 3.7 and 3.8 and 3.9 may fill in some important gaps.

3.7 explanation is above^ (Figure 3.8): Energy effects of cloud types. a) Low, thick clouds lead to cloud-albedo forcing and atmospheric cooling. b) High, thin clouds lead to cloud-greenhouse forcing and atmospheric warming. (Figure 3.9): Jet contrails form contrail cirrus. Older contrails widen to form high, cirrus clouds, with an overall warming effect on Earth.

The discussion on Albedo and Reflection is very important to completing your knowledge of climatic conditions on the Planet. Check figure 3.6 out and become familiar with the albedo values shown.

A portion of arriving energy bounces directly back into space- this is REFLECTION. The reflective quality, or intrinsic brightness, of a surface is ALBEDO, an important control over the amount of insolation that reaches earth. We report albedo as the percentage of insolation that is reflected- 0% is total absorption; 100% is total reflectance. In terms of visible wavelengths, darker colored surfaces (such as asphalt) have lower albedos, and lighter colored surfaces (such as snow) have higher albedos. On water surfaces, the angle of the solar rays also affects albedo values: lower angles produce more reflection than do higher angles. In addition, smooth surfaces increase albedo, whereas rougher surfaces reduce it. Individual locations can experience highly variable albedo values during the year in response to changes in cloud and ground cover. Satellite date reveal that albedos average 19-38% for all surfaces between the tropics (23.5N to 23.5S latitude), whereas albedos for the polar regions may be as high as 80% as a result of ice and snow. Tropical forests with frequent cloud cover are characteristically low in albedo (15%), whereas generally cloudless deserts have higher albedos (35%). Earth and its atmosphere reflect 31% of all insolation when averaged over a year. The glow of earth's albedo, or the sunshine reflected off earth, is called earthshine. (Figure 3.6): Various Albedo Values. In general, light surfaces are more reflective than dark surfaces and thus have higher albedo values. Earth's albedo average: 31% Fresh Snow: 80-95% Water Bodies: 10-60% (varies with sun altitude) Moon: 6-8%

What term describes the "assimilation of radiation by molecules of matter and its conversion from one form of energy to another?" Reread page 73.

ABSORPTION. ABSORPTION is the assimilation of radiation by molecules of matter, converting the radiation from one form of energy to another. Solar energy is absorbed by land and water surfaces (about 45% of incoming insolation) as well as by atmospheric gases, dust, clouds, stratospheric ozone (together about 24% of incoming insolation). It is converted into either longwave radiation or chemical energy (the latter by plants, in photosynthesis). The process of absorption raises the temperature of the absorbing surface. The atmosphere does not absorb as much radiation as earth's surface because gases are selective about the wavelengths they absorb. For example, oxygen and ozone effectively absorb ultraviolet radiation in the stratosphere. None of the atmospheric gases absorbs the wavelengths of visible light, which pass through the atmosphere to earth as direct radiation. Several gases- water vapor and carbon dioxide, in particular- are good absorbers of longwave radiation emitted by earth. These gases absorb heat in the lower troposphere, a process that explains why earth's atmosphere is warmer at the surface, acting like a natural greenhouse.

Know air pressure and how we measure it; know what wind is and how we measure it. Pay very close attention to the concepts listed under Driving Forces within the Atmosphere. Master figures 4.6, 4.7, 4.8, 4.9.

Air pressure- the weight of the atmosphere described as force per unit area- is key to understanding wind. The molecules that constitute air create air pressure through their motion, size, and number, and this pressure is exerted on all surfaces in contact with air. The number of molecules and their motion are also the factors that determine the density and temperature of the air. Both pressure and density decrease with altitude in the atmosphere. The low density in the upper atmosphere means the molecules are far apart, making collisions between them less frequent and thereby reducing pressure. The subjective experience of 'thin air' at high altitudes is caused by the smaller amount of oxygen available to inhale (fewer air molecules means less oxygen). When air in the atmosphere is heated, molecular activity increases, and temperature rises. With increased activity, the spacing between molecules increases, so that density is reduced and air pressure decreases. Therefore, warmer air is less dense, or lighter, than colder air and exerts less pressure. Water vapor is has less mass than dry air. As water vapor in the air increases, density increases, so humid air exerts less pressure than dry air. The end result over earths surface is that warm, humid air is associated with low pressure and cold, dry air is associated with low pressure. Any instrument that measures air pressure is a barometer. Torricelli developed a MERCURY BAROMETER. A more compact barometer design, which works without a meter-long tube of mercury, is the ANEROID BAROMETER. Aneroid means 'using no liquid'. The aneroid barometer principle is simple: imagine a small chamber, partially emptied of air, that is sealed and connected to a mechanism attached to a needle on a dial. As the air pressure outside the chamber increases, it presses inward on the chamber; as the outside pressure decreases, it relieves the pressure on the chamber- in both cases causing changes in the chamber that move the needle. An aircraft altimeter is a type of aneroid barometer. WIND is generally the horizontal motion of air across Earth's surface. Within the boundary layer at the surface, turbulence adds wind updrafts and downdrafts and thus a vertical component to this definition. Differences in air pressure between one location and another produce wind. Winds two principal properties are speed and direction, both of which can be measured by simple instruments. An ANEMOMETER measures wind speed in kilometers per hour (kmph), miles per hour (mph), meters per second (mps), or knots. (A knot is a nautical mile per hour, covering one minute of Earth's arc in an hour, equivalent to 1.85 kmph, or 1.15 mph.) A WIND WAVE determines wind direction; the standard measurement is taken 10 m (33ft) above the ground to reduce the effects of local topography on wind direction. (Figure 4.6): The Coriolis Force- an apparent deflection. C) Distribution of the Coriolis Force on Earth. Apparent deflection is to the RIGHT in the NORTHERN HEMISPHERE and to the LEFT in the SOUTHER HEMISPHERE. Earth rotates EASTWARD. west to east. (Figure 4.7): Three Physical Forces that produce winds. A) PRESSURE GRADIENT. HIGH pressure TO LOW pressure. -HIGH is DESCENDING, DIVERGING (down and out). -LOW is ASCENDING, CONVERGING (up and in/together). B)Pressure Gradient + CORIOLIS FORCES (upper-level winds). Earth's roatation adds to the corilois force, giving a 'twist' to air movements. High pressure and low pressure areas develop a rotaty motion, and wind flowing between highs and lows flows parallel to isobars. -NORTHERN HEMISPHERE: From high to low, twists in an infinity sign motion. Infity sign starts from the H and flows over and dips down below the L and comes back over the top of the L back underneath the H, and continues the infinity sign. -SOUTHERN HEMISPHERE: opposite of Northern Hemisphere^. Infinity sign starts from the H like a northern hemisphere infinity sign, but instead of coming over the top to begin, goes underneath and comes over on top of the L and dips back down beneath the L and back over the top of the H to continue the infinity sign. C)Pressure Gradient+ Coriolis+ FRICTION FORCES (surface winds). -Surface friction adds a countering force to coriolis, producing winds that spiral out of a High-Pressure area and into a low pressure area. Surface winds cross isobars at an angle. (Isobars are "--" (like a wall; straight across)). Air flows into low pressure cyclones and turns to the left because of deflection to the right. ^ same concept as the corilois infinity sign in both Northern and Southern hemisphere. Except this time, they just go to the Low areas of pressure and don't necessarily come back to the high pressure. Don't make a complete infinity sign. (Figure 4.8): High-and low-pressure cells and associated wind movement. Surface winds spiraling clockwise out of the high pressure area toward the low pressure area, where winds spiral counter-clockwise into the low pressure area. ^Same concept as the Coriolis force and infinty sign. In the sense that in nothern hemisphere, begins in the H and flows over the H, dips below the L and comes back over the L and dips below the H. ^begins with the clockwise motion (H) and ends with counter-clockwise motion (L), but doesn't return back to the High pressure system in the infinity motion, rather, it ascends up in the sky and goes back to the H where it then descends down into the H to repeat the process. (Figure 4.9): Global Barometric Pressures for January and July. A) January average surface barometric pressures (millibars); dashed line marks the general location of the intertropical convergence zone (ITCZ). ITCZ begins at the 20S, below the equator and travels eastward, up along the equator and back down to 20S below the equator. B) July average surface barometric pressures. ITCZ begins at 20N, above the equator, travels down along the equator, makes it's way back up to 20N about 3/4 way across. Ends at about 25N, above the equator. Both have high pressures near the ITCZ, low pressure further North and South of the ITCZ. Closer the ITCZ is to the equator, the more allowance there is for areas of low pressure to be somewhat prevalent in the Northern hemisphere, this is indicated in the January averages, rather than the July averages, where the ITCZ begins more North at 20N and ends at 25N, both above the equator.

Refraction is a real mind blower you should be able to explain to me these related phenomena: creation of a rainbow, mirages, sunrise and sunset. Figures 3.4 and 3.5 will help.

As insolation enters the atmosphere, it passes from one medium to another, from virtually empty space into atmospheric gases. A change of medium also occurs when insolation passes from air into water. Such transitions subject the insolation to a change of speed, which also shifts its direction- this is the bending action of REFRACTION. In the same way, a crystal or prism refracts light passing through it, bending different wavelengths to different angles, separating the light into its component colors to display the spectrum. (Figure 3.4): A Rainbow. Raindrops- and in this photo, moisture droplets from the Niagara River- refract and reflect light to produce a primary rainbow. Note that in the primary rainbow the colors with the shortest wavelengths are on the inside and those with the longest wavelengths are on the outside. In the secondary bow, note that the color sequence is reversed because of an extra angle of reflection within each moisture droplet. A RAINBOW is created when visible light passes through raindrops and is refracted and reflected toward the observer at a precise angle. Another example of refraction is a MIRAGE, an image that appears near the horizon when light waves are refracted by layers of air at different temperatures (and consequently of different densities). (Figure 3.5): Sun Refraction. The distorted appearance of the sun as it sets over the ocean is produced by refraction of the sun's image in the atmosphere. Refraction produces the atmospheric distortion of the setting sun. When the sun is low in the sky, light must penetrate more air than when the sun is high; thus light is refracted through air layers of different densities on its way to the observer. This distortion means that we see the suns refracted image for 4 minutes before the sun actually peaks over the horizon in the morning and for about 4 minutes after the sun sets in the evening. The extra 8 minutes of daylight caused by refraction vary with atmospheric temperature, moisture, and pollutants.

What is the effect of clouds, and naturally injected aerosols such as volcanic gasses and tephra into the atmosphere? Do anthropogenic substances have the same effect as natural aerosols?

Clouds and aerosols are unpredictable factors in the tropospheric energy budget. The presence or absence of clouds may make a 75% difference in the amount of energy that reaches the surface. Clouds reflect shortwave insolation, so that less insolation reaches Earth's surface, and they absorb longwave radiation leaving earth. Longwave radiation trapped by an insulating cloud layer can create a warming of Earth's atmosphere as part of the greenhouse effect. (Figure 3.7) Effects of Clouds on Shortwave and Longwave Radiation. Clouds reflect and scatter shortwave radiation, returning a higher percentage to space. Clouds absorb and reradiate longwave radiation emitted by earth; some longwave energy is lost to space and some moves back toward earth's surface. Air pollutants from both natural and anthropogenic sources affect atmospheric albedo. Stratospheric aerosols from the 1991 eruption of Mount Pinatubo in the Philippines, resulted in an increase in global atmospheric albedo and a temporary average cooling of 0.5C (0.9F). Scientists have correlated similar cooling trends with other large volcanic eruptions throughout history. Industrial pollutants such as sulfate aerosols are today increasing the reflectivity of the atmosphere, cooling earth's surface. However, some aerosols (especially black carbon) readily absorb radiation and reradiate heat back toward Earth- with warming effects. Recent research indicates that black carbon, or soot, from human sources plays a more important role in recent global warming than previously thought. Ultimately, one cools and one warms.

Know the scenarios for El Niño, La Niña, ENSO

EL NINO- Southern Oscillation, warm phase (ENSO): weakened or reversed wind pattern, warm water dominates. Warm water all over pacific- tropical pacific ocean. weaker upwelling-blocked LA NINA, cool phase (ENSO): stronger trade wind pattern stronger upwelling lots of rain in western tropical pacific ocean cold water dominates in Normal Condition: Everything is balanced: cold and warm water, upwelling, winds, are balanced.

It is vital that you understand what we're talking about when we use the term "temperature" make sure you ferret out the meaning of the term on page 86. It is important to understand the logic behind the use of the three temperature scales in figure 3.13 the narrative will fill in the gaps.

Earlier, we discussed types of heat and mechanisms of heat transfer, such as conduction, convection, and radiation. Unlike heat, temperature is not a form of energy; however temperature is related to the amount of energy in a substance. TEMPERATURE is a measure of the average kinetic energy of individual molecules in matter. Thus, temperature is a measure of heat. Remember that heat always flows from matter at a higher temperature to matter at a lower temperature, and heat transfer usually results in a change in temperature. For example, when you jump into a cool lake, kinetic energy leaves your body and flows into the water, causing a transfer of heat and lowering of the temperature of your skin. Heat transfer can also occur without a change in temperature, when a substance changes state (as in latent heat transfer). The temperature at which atomic and molecular motion in matter completely stops is ABSOLUTE ZERO. This value on 3 commonly encountered temperature measuring scales is -273 celsius (C), -459.67 Fahrenheit (F), and 0 Kelvin (K). The Fahrenheit temperature scale, places the melting point of ice at 32 degrees F, separated by 180 subdivisions from the boiling point of water at 212 degrees F. Note that ice has only one melting point, but water has many freezing points, ranging from -32 down to -40 degrees F, depending on its purity, its volume, and certain conditions in the atmosphere. The Celsius scale, places the melting point of ice at 0 degrees Celsius and the boiling point of water at sea level at 100 degrees C. The scale divides into 100 degrees using a decimal system. The Kelvin scale, starts at absolute zero. The kelvin scale's melting point for ice is 273 K, and its boiling point of water is 373 K, 100 units higher. Therefore, the size of one Kelvin unit is the same size as one Celsius degree. Scientists often use this scale because its temperature readings are proportional to the actual kinetic energy in a material. Most countries use the Celsius scale to express temperature- the United States is an exception.

Revisit insolation on page 73 and be sure to understand why the sky is blue.

Earth's blue skies and red sunrises and sunsets are answered using a principle known as RAYLEIGH SCATTERING. This principle applies to radiation scattered by small gas molecules and relates the amount of scattering in the atmosphere to wavelengths of light- shorter wavelengths are scattered more, whereas longer wavelengths are scattered less. Blues and violets are the shorter wavelengths of visible light. According to the Rayleigh scattering principle, these wavelengths are scattered more than longer wavelengths such as orange or red. When we look at the sky with the sun overhead, we see the wavelengths that are scattered the most throughout the atmosphere. Although both blues and violets are scattered, our human eye perceives this color mix as blue, resulting in the common observation of a blue sky. The altitude of the sun determines the thickness of the atmosphere through which its rays must pass to reach an observer. Direct rays (from overhead) pass through less atmosphere and experience less scattering than do low, oblique-angle rays, which must travel farther through the atmosphere. When the sun is low on the horizon at sunrise or sunset, shorter wavelengths (blue and violet) are scattered out, leaving only the residual oranges and reds to reach our eyes.

CHAPTER 3 Understand the pathways that energy takes as it passes through the troposphere. You must understand the difference between incoming and outgoing energy- what is different between energy incoming to the Earth's surface and energy being radiated from objects on the Earth's surface back into space?

Figure (3.1): Energy gained and lost by Earth's surface and atmosphere includes incoming and reflected shortwave radiation, energy absorbed at Earth's surface, and outgoing long-wave radiation. For earth, energy income is INSOLATION, and energy expenditure is RADIATION to space, with an overall balance maintained by the two. Energy coming in from sun is SHORTWAVE RADIATION. Concerning pathways, if this radiation is coming in and there are clouds in the way, that heat gets absorbed by DIFFUSE RADIATION. If this radiation comes in directly, no clouds in the way, this is DIRECT RADIATION. Energy leaving to space is in the form of LONG WAVE RADIATION. INSOLATION: direct or diffused shortwave solar radiation thats received at the atmosphere or earth's surface. Albedo: reflectivity of a surface. Latitude is determining factor in which the angle deflects off the surface. Latitude is the determinent in air temperature. Atmosphere is highly reflective: 51% absorbed at surface. Ice and latitude cause higher degree of reflection. Energy coming in: Short Wave Energy leaving: Long Wave

To make meaningful observations about the various conditions at the different locations on the Planet we must understand the importance of heat storage as illustrated in figure 3.11 This figure explains the "lag time" concept of daily air temperature but can you use the curve as an analogy for the yearly temperature cycle?

Figure 3.11 shows the daily pattern of absorbed incoming shortwave energy and resulting air temperature. This graph represents idealized conditions for bare soil on a cloudless day in the middle latitudes. Incoming energy arrives during daylight, beginning at sunrise, peaking at noon, and ending at sunset. The shape and height of this insolation curve vary with season and latitude. The maximum heights for such a curve occur in summer, at the time of the June Solstice in the Northern Hemisphere and the December solstice in the Southern Hemisphere. The air-temperature plot also responds to seasons and variations in insolation input. Within a 24 hour day, air temperature generally peaks between 3-4pm and dips to its lowest point right or slightly after sunrise. Note that the insolation curve and the air-temperature curve on the graph do not align; there is a LAG between them. The warmest time of day occurs not at the moment of maximum insolation, but at the moment when a maximum of insolation has been absorbed and emitted to the atmosphere from the ground. As long as the incoming energy exceeds the outgoing energy, air temperature continues to increase, not peaking until the incoming energy begins to diminish as the afternoon Sun's altitude decreases. If you have ever gone camping in the mountains, you no doubt experienced the coldest time of day with a wake-up chill at sunrise. The annual pattern of insolation and air temperature exhibits a similar lag. For the Northern Hemisphere, January is usually the coldest month, occurring after the December solstice and the shortest days. Similarly, the warmest months of July and August occur after the June solstice and the longest days. (Figure 3.11): Daily Radiation and Temperature Curves: This sample radiation plot for a typical day shows the changes in insolation (solid line) and air temperature (dashed line). Comparing the curves reveals a lag between local noon (the insolation peak of the day) and the warmest time of the day.

Know these terms: Cloud-Albedo Forcing, Cloud Greenhouse Forcing, & Global Dimming ^are they related? Figure 3.7 is helpful. Check out the effect of low albedo by reading the Critical Thinking 3.1 on page 77.

GLOBAL DIMMING is the general term describing the pollution-related decline in isolation reaching Earth's surface. This process is difficult to incorporate into climate models, although evidence shows that it is causing an underestimation of the actual amount of warming happening in Earth's lower atmosphere. As discussed earlier, clouds sometimes cause cooling and other times cause heating of the lower atmosphere, in turn affecting Earth's climate. The effect of clouds is dependent on the percentage of cloud cover as well as cloud type, altitude, and thickness (water content and density). Low, thick stratus clouds reflect about 90% of insolation. The term CLOUD-ALBEDO FORCING refers to an increase in albedo caused by such clouds and the resulting cooling of earth's climate (here, albedo effects exceed greenhouse effects). High-altitude, ice-crystal clouds reflect only about 50% of incoming insolation. These cirrus clouds also act as insulation, trapping longwave radiation from earth and raising minimum temperatures. This is CLOUD-GREENHOUSE FORCING, which causes warming of Earth's climate (here, greenhouse effects exceed albedo effects). Ultimately one cools (cloud-albedo) and one warms (cloud-greenhouse).

Remember "The shorter the wavelength the greater the scattering, the longer the wavelength the less the scattering." What is diffuse radiation? See 3.1 again.

Insolation encounters an increasing density of atmospheric molecules as it travels towards earth's surface. These atmospheric gases, as well as dust, cloud droplets, water vapor, and pollutants, physically interact with insolation to redirect radiation, changing the direction of the light's movement without altering its wavelengths. SCATTERING is the name for this phenomenon, which accounts for a percentage of the insolation that does not reach Earth's surface, but is instead reflected back to space. Incoming energy that reaches earth's surface after scattering occurs is DIFFUSE RADIATION. This weaker, dispersed radiation is composed of waves traveling in different directions and thus casts shadowless light on the ground. In contrast, DIRECT RADIATION travels in a straight line to earth's surface without being scattered or otherwise affected by materials in the atmosphere.

YOU MUST LEARN THESE PRINCIPAL TEMPERATURE CONTROLS IN THE ORDER THE TEXT PRESENTS THEM. A fundamental understanding of these controls is imperative to further success in this class. If I had a bolder bold I would use it here. I cannot overstate the importance of the figures and narrative found on pages 87-91. In order to fully understand the concepts, pay particular attention to the definitions found in this section, make sure you understand the implications of specific heat.

Insolation is the single most important influence on temperature variations. However, several other physical controls interact with it to produce Earth's temperature patterns. These include latitude, altitude, and elevation, cloud cover, and land-water heating differences. LATITUDE The subsolar point is the latitude where the sun is directly overhead at noon, that this point migrates between the tropic of cancer at 23.5 N latitude and 23.5 S latitude. Between the tropics, insolation is more intense than at higher latitudes where sun is never directly overhead (at a 90 degree angle) during the year. The intensity of incoming solar radiation decreases away from the equator and toward the poles. Daylength also varies with latitude during the year, influencing the duration on insolation exposure. Variations in these two factors- sun angle and daylength- throughout the year drive the seasonal effect on latitude and temperature. From equator to poles, earth ranges from continually warm, to seasonally variable, to continually cold. Figure 3.14 ALTITUDE AND ELEVATION Within the troposphere, temperatures decrease with increasing altitude above earths surface (lapse rate). The density of the atmosphere also diminishes with increasing altitude. As the atmosphere thins, it contains less SENSIBLE HEAT. Thus, worldwide, mountainous areas experience lower temperatures than do regions nearer sea level, even at similar altitudes. Altitude and elevation, are commonly used to refer to heights on or above earths surface. Elevation usually refers to the height of a point on earths surface above some plane of reference, such as elevation above sea level. Therefore, the height of a flying jet is expressed as altitude, whereas the height of a mountain ski resort is expressed as elevation. In the thinner atmosphere at high elevations in mountainous regions or on high plateaus, surfaces lose energy rapidly to the atmosphere. The result is that average air temperatures are lower, nighttime cooling is greater, and the temperature range between day and night is greater than at low elevations. CLOUD COVERAGE At any given moment, approx 50% of Earth is covered by clouds. We learned that clouds affect the earth-atmosphere energy balance by reflecting and absorbing radiation and that their effects vary with cloud type, height, and density. The presence of cloud cover at night has a moderating effect on temperature; you may have experienced the relatively colder temperatures outside on a clear night versus a cloudy night, especially before dawn, the coldest time of the day. At night, clouds act as an insulating layer that reradiates longwave energy back to earth, preventing rapid energy loss to space. Thus, in general, the presence of clouds raises minimum nighttime temperatures. During the day, clouds reflect insolation, lowering daily maximum temperatures; this is the familiar shading effect you feel when clouds move in on a hot summer day. Clouds also reduce seasonal temperature differences as a result of these moderating effects. Clouds are the most variable factor influencing Earths radiation budget, and studies are ongoing as to their effects on Earths temperatures. LAND WATER HEATING DIFFERENCES An important control over temperature is the difference in the ways land and water surfaces respond to insolation. Land and water absorb and store energy differently, with the result that water bodies tend to have more moderate temperature patterns, whereas continental interiors have more temperature extremes. The physical differences between land (rock and soil) and water (oceans, seas, and lakes) are the reasons for land-water heating differences, the most basic of which is that land heats and cools faster than water. -EVAPORATION The process of evaporation dissipates significant amounts of the energy arriving at the oceans surface, much more than over land surfaces where less water is available. An estimated 84% of all evaporation on earth is from the oceans. When water evaporates, it changes from liquid to vapor, absorbing heat energy in the process and storing it as latent heat. You experience the cooling effect of evaporative heat loss by wetting the back of your hand and then blowing on the moist skin. Sensible heat energy is drawn from your skin to supply some of the energy for evaporation, and you feel the cooling as a result. As surface water evaporates, it absorbs energy from the immediate environment, resulting in a lowering of temperatures. (Remember that the water and vapor remain in the same temperature throughout the process; the vapor stores the absorbed energy as latent heat.) Land temperatures are affected less by evaporative cooling than are temperatures over water. -TRANSPARENCY Soil and water differ in their transmission of light: solid ground is opaque (not able to be seen through); water is transparent (able to be seen through). Light striking a soil surface does not pass through, but is absorbed, heating the ground surface. That energy is accumulated during times of sunlight exposure and is rapidly lost at night or when shaded. Maximum and minimum daily temperatures for soil surfaces generally occur at the ground surface level. Below the surface, even at shallow depths, temperatures remain about the same throughout the day. In contrast, when light reaches a body of water, it penetrates the surface because of the water's transparency- water is clear, and light passes through it to an average depth of 200ft in the ocean. The transparency of water results in the distribution of available heat energy over a much greater depth and volume, forming a larger reservoir of energy storage than that which occurs on land. -SPECIFIC HEAT The energy needed to increase the temperature of water is greater than for an equal volume of land. Overall, water can hold more heat than can soil or rock. The heat capacity of a substance is SPECIFIC HEAT. On average, the specific heat of water is about four times that of soil. Therefore, a given volume of water represents a more substantial energy reservoir than does the same volume of soil or rock and consequently heats and cools more slowly. For this reason, day to day temperatures near large water bodies tend to be moderated rather than having large extremes.

You should understand the mechanics of the simplified energy balance, e.g. what the symbols mean but I will not make you do any budget calculations at this point. You are responsible for understanding the concept of Net Radiation (the discussion starts on the bottom of page 83)

MICROCLIMATOLOGY is the science of physical conditions, including radiation, heat, and moisture, in the boundary layer or at Earth's surface. Microclimates are local climate conditions over a relatively small area, such as in a park, or on a particular slope, or in your backyard. Thus, our discussion now focuses on small scale (the lowest few meters of the atmosphere) rather than large scale (the troposphere) energy-budget components. The surface in any given location receives and loses shortwave and longwave energy according to the following scheme: +SW down - SW^ + LW down - LW^ = NET R (insolation) (reflection) (infared)("") (net rad.) SW for shortwave and LW for Longwave Figure 3.12 shows the components of a surface energy budget over a soil surface. The soil column continues to a depth at which energy exchange with surrounding materials or with the surface becomes negligible, usually less than a meter. Heat is transferred by conduction through the soil, predominantly downward during the during the day (or in the summer) and toward the surface at night (or in the winter). Energy moving from the atmosphere into the surface is reported as a positive value (a gain), and energy moving outward from the surface, through sensible and latent heat transfers, is reported as a negative value (a loss) in the surface account. NET RADIATION (NET R) is the sum of all radiation gains and losses at any defined location on Earth's surface. NET R varies as the components of this simple equation vary with daylength through the seasons, cloudiness, and latitude. On a daily basis, NET R values are positive during the daylight hours, peaking just after noon with the peak in insolation; at night, values become negative because the shortwave component ceases at sunset and the surface continues to lose longwave radiation to the atmosphere. The surface rarely reaches a zero NET R value- a perfect balance- at any one moment. However, over time, earth's total surface naturally balances incoming and outgoing energies. The net radiation available at earths surface is the final outcome of the entire energy balance process discussed in this chapter. As we have learned, in order for the energy budget at earths surface to balance over time, areas that have positive net radiation must somehow dissipate, or lose, heat. This happens through nonradiative processes that move energy from the ground into the boundary layer. The latent heat of evaporation (LE) is the energy that is stored in water vapor as water evaporates. Water absorbs large quantities of this latent heat as it changes state to water vapor, thereby moving this heat energy from the surface. Conversely, this heat energy releases to the environment when water vapor changes state back to a liquid. Latent Heat transfer is the dominant expenditure of Earth's entire NET R, especially over water surfaces. Sensible Heat (H) is the heat transferred back and forth between air and surface in turbulent eddies through convection and conduction within materials. About one-fifth of earths entire NET R is mechanically radiated as sensible heat from the surface, especially over land. Ground heating and cooling (G) is the flow of energy into and out of the ground surface (land or water) by conduction. Through the processes of latent, sensible, and ground heat transfer, the energy from net radiation is able to do the 'work' that ultimately produces the global climate system- work such as raising temperatures in the boundary layer, melting ice, or evaporating water from the oceans. The principles and processes of net radiation at the surface have a bearing on the design and use of solar energy technologies that concentrate shortwave energy for human use.

At the heart of the Planet's heat budget are the concepts found on pages 80-81 and figure 3.10. We've been talking about this for a while so I hope you are conversant in the Energy Balance topics.

Solar energy is the principal heat source at Earths surface; the surface environment is the final stage in the Sun-to-Earth energy system. The radiation patterns at Earth's surface- inputs of direct and diffuse radiation and outputs of evaporation, convection, and radiated longwave energy- are important in forming the environments where we live. Incoming solar energy in the form of shortwave radiation interacts with both the atmosphere and Earth's surface. The surface reflects or absorbs some of the energy, reradiating the absorbed energy as longwave radiation. Averaged over a year, Earth's surface has an energy gain, or surplus, while the atmosphere has an energy deficit, or loss. These two amounts of energy equal each other, maintaining an overall balance in Earth's energy "budget". 3.1 Shortwave Radiation Inputs and Albedo. Clouds, the atmosphere, and Earth's surface reflect 31% of the shortwave radiation inputs back to space. Atmospheric gases and dust and Earths surface absorb 69% of the shortwave energy. Absorbed energy is later emitted as longwave radiation. Reflected shortwave radiation, equivalent to Earth's albedo. Note high values of albedo (white) over cloudy and snowy regions, and low values (blue) over oceans. 3.2 Outgoing Longwave Radiation. Overtime, Earth emits, on average, 69% of oncoming energy to space. When added to the amount of energy reflected (31%), this equals the total energy input from the sun (100%). Outgoing energy transfers from the surface are both RADIATIVE (consisting of longwave radiation directly to space) and NONRADIATIVE (involving convection and the energy released by latent heat transfer). Outgoing longwave radiation emitted from earth and the atmosphere. Note high values (yellow) over deserts and low values (white and blue) over the polar regions.

Do you understand the concept of transmission? It is important that you do, so read Energy pathways and Principles on page 72.

TRANSMISSION refers to the uninterrupted passage of shortwave and longwave energy through either the atmosphere or water. Our earth-atmosphere energy budget comprises INPUTS of shortwave radiation (ultraviolet light, visible light, and near-infrared wavelengths) and OUTPUTS of shortwave and longwave radiation (reflected light and thermal infrared wavelengths) that pass through the atmosphere by transmission. Since solar energy is unevenly distributed by latitude and fluctuates seasonally, the energy budget is not the same at every location on Earth's surface, even though the overall energy system remains in steady-state equilibrium.

Atmospheric Patterns of Motion

The rotational directions of the pressures systems remember: -Low pressure systems will rotate counter-clockwise in the northern hemisphere and exactly the opposite in the southern-clockwise. (Cyclone) -High pressure systems in the northern hemisphere will rotate clockwise but of course in the southern hemisphere the highs rotate counter-clockwise. (Anticyclone) If you don't learn this simple lesson you are doomed!

Moving on to regional wind systems we encounter the Monsoonal Winds. You have already been introduced to them watching the Earth from Space and now you will become more familiar with the driving concepts behind them. Figure 4.18 is helpful.

These seasonally shifting wind systems are MONSOONS and involve an annual cycle of returning precipitation with the summer sun. ^Northern Hemisphere Winter Conditions: DRY land, High Pressure in the COLD. Cold air flows to the water (warm, low pressure)- because areas of high pressure flow to areas of low pressure. ITCZ above water. ^Northern Hemisphere Summer Conditions: WET land, Low pressure in the WARM. Warm air flows to the land (cold, high pressure)- because areas of High pressure flow to areas of Low pressure. ITCZ above land. This process is heavily influenced by the shifting migration of the ITCZ during the year, which brings moisture-loaded air northward during the Northern Hemisphere summer.

Rest of the material underneath Atmospheric Patterns of Motion that I didn't jot down in the sections above^.

To begin, we should remember the relationships among pressure, density, and temperature as they apply to the unequal heating of Earth's surface (Energy surpluses at the equator and energy deficits at the poles). The warmer, less dense air along the equator rises, creating low pressure at the surface, and the colder, more-dense air at the poles sinks, creating high pressure at the surface. EQUATORIAL LOW (marked by the intertropical convergence zone- ITCZ) and the weak POLAR HIGHS at the North and South Poles. Remember from our discussion of pressure, density, and temperature earlier, that warmer air is less dense and exerts less pressure. The warm, light air in the equatorial region is associated with low pressure, while the cold, dense air in the polar regions is associated with high pressure. The other pressure areas- the SUBTROPICAL HIGHS (marked with an H on the map) and the SUBPOLAR LOWS (marked with an L)- are formed by dynamic (mechanical factors). Remember in our discussion of pressure gradients that converging, rising air is associated with low pressure (Warm), whereas subsiding, diverging air is associated with high pressure (Cold)- these are dynamic factors because they result from the physical displacement of air.

Circulation in the upper atmosphere will drive surface conditions so it is important to have an understanding of conditions at the 500 mb level. Know what Rossby Waves figure 4.12 and the jet streams figure 4.13 are and where they occur. Figure 4.14 will help you understand how upper level circulation relates to the conditions on the surface.

Upper Air Winds The pattern of ridges and troughs in the upper-air wind flow is important in sustaining surface cyclonic (low-pressure) and anticyclonic (high-pressure) circulation. Along RIDGES (hill-like/curve up), winds slow and converge (pile up); along troughs (dips, opposite of ridge), winds accelerate and diverge (spread out). Warm air rises (Low Pressure) and Cold air falls (High Pressure) ROSSBY WAVES occur along the polar front, where colder air meets warmer air, and brings tongues of cold air southward, with warmer tropical air moving northward. Cold air falls and Warm air rises. The development of rossby waves begins with undulations that then increase in amplitude to form waves. As these disturbances mature, circulation patters form in which warmer air and colder air mix along distinct fronts. These wave-and-eddy formations and upper-air divergences support cyclonic (low pressure-warm) systems at the surface. Rossby waves develop along the flow axis of a jet stream. (Figure 4.12):Rossby Waves in the Upper Atmosphere. A) Upper air circulation and jet stream begin to gently Undulate within the westerlies. Cold air in a blob i the middle, rotating counter-clockwise, with Warm air flowing counter clockwise around the blob of cold air. B) Undulations increase in amplitude (height) in north-south direction, forming rossby waves. No longer a blob, formed into a now star-like-shaped blob, with trough and ridges caused from increased curvature. C) Strong development of waves produces cells of cold and warm air- high pressure (cold) ridges and low-pressure (warm) troughs. Little blobs break off of original blob of Cold air. The most prominent movement in the upper-level westerly geostrophic wind flows is the JET STREAMS, irregular, concentrated bands of wind occurring at several different locations that influence surface weather systems. The jet streams are normally 100-300 mi wide and 3000-7000 ft thick, with core speeds that can exceed 190 mph. Jet Streams in each hemisphere tend to weaken during the hemisphere's summer and strengthen during its winter as the streams shift closer to the equator. The pattern of high pressure ridges and low pressure troughs in the meandering jet streams causes variation in jet-stream speeds. (Figure 4.14): Temperature and pressure patterns for daytime sea breezes and nighttime land breezes. A) Daytime sea-breeze conditions. Warmer temperature on land (low pressure), colder temperature in the water (high pressure). Cooler air (high pressure) is drawn inland (low pressure). Heated air rises over warm land, warm air then cools and descend over cold water, rotation continues. B)Nighttime land-breeze conditions. Warmer temperature on water (low pressure), colder temperature on land (high pressure). Cooler air (high pressure) is drawn offshore (water-warmer-low pressure). Heated air rises over warmer water, air then cools and descends over cold land.

CHAPTER 4 Chapter 4 begins with revisiting the concept of air-pressure and how the winds of the planet move in response to variations in air pressure. You Must learn the forces that drive surface winds. I'll list them-you master the concepts: -Pressure Gradient Force gets the air moving, -Coriolis force deflects them from their path, -& Frictional force disrupts the equilibrium near the surface causing a further deflection from the true pressure gradient path.

Without gravity, there would be no atmospheric pressure- or atmosphere, for that matter. The other forces affecting winds are the pressure gradient force, coriolis force, and friction force. All of these forces operate on moving air and ocean currents at Earth's surface to produce global circulation patterns. The PRESSURE GRADIENT FORCE drives air from areas of higher barometric pressure (more-dense air) to areas of lower barometric pressure (less-dense air), thereby causing winds. A gradient is the rate of change in some property over distance. Without a pressure gradient force, there would be no wind. High and low pressure areas exist in the atmosphere principally because Earth's surface is unequally heated. For example, cold, dry, dense air at the poles exerts greater pressure than warm, humid, less-dense air along the equator. When these air masses are near each other, a pressure gradient develops that leads to horizontal air movement. In addition, vertical air movement can create pressure gradients. This happens when air descends from the upper atmosphere and diverges at the surface or when air at the surface converges from different directions and ascends into the upper atmosphere. Strongly subsiding and diverging air is associated with high pressure, and strongly converging and rising air is associated with low pressure. These horizontal and vertical pressure differences establish a pressure gradient force that is a casual factor of winds. The CORIOLIS FORCE makes wind traveling in a straight path appear to be deflected in relation to Earth's rotating surface. This force is an effect of earths rotation. On a non-rotating earth, surface winds would move in a straight line from areas of higher pressure to areas of lower pressure. But on our rotating planet, the coriolis force deflects anything that flies or flows across the earth's surface wind, an airplane, or ocean currents- form a straight path. Because earth rotates eastward, such objects appear to curve to the right in the northern hemisphere and to the left in the southern hemisphere. Because the speed of earths rotations varies with latitude, the strength of this defection varies, being weakest at the equator strongest at the poles. In the boundary layer, FRICTION FORCE creates drag as the wind moves across earths surface, but friction force decreases with height above the surface. Without friction force, surface winds would simply move in paths parallel to isobars and at high rates of speed. The effect of surface friction extends to a height of about 500m; thus, upper-air winds are not affected by the friction force. At the surface, the effect of friction varies with surface texture, wind speed, time of day and year, and atmospheric conditions. In general rougher surfaces produce more friction. Winds are a result of the combination of these physical forces. When the pressure gradient acts alone, winds flow from areas or high pressure to areas of low pressure. Note the descending, diverging air associated with high pressure and the ascending, converging air associated with low pressure. Together, the pressure gradient and coriolis force produce winds that do not flow directly from high to low, but that flow around the pressure areas, remaining parallel to the isobars. Such winds are Geostrophic Winds and are characteristic of upper tropospheric circulation (-strophic means 'to turn'). Geostrophic winds produce the characteristic pattern of the curve. Near the surface, friction prevents the equilibrium between the pressure gradient and corilois forces that results in geostrophic wind flows in the upper atmosphere. Because surface friction decreases wind speed, it reduces the effect of the coriolis force and causes winds to move across isobars at an angle. Thus, wind flows around pressure centers form enclosed areas called Pressure Systems, or Pressure Cells.