Chapter 4: Atmosphere & Global Radiation

Atmosphere

It is the medium through which radiation flows on its way to Earth's surface. Unique in our solar system because it is characteristically able to support life, providing oxygen and carbon dioxide for animal and plant respiration. In addition, the atmosphere serves as a buffer that shields earth from the negative effects of solar radiation, allowing mostly visible and infrared wavelengths to reach earth.

Counter-radiation

Longwave radiation that is emitted towards the earth's surface from the atmosphere. The balance that currently is just right for the planet to be neither too hot nor too cold.

Global radiation budget

Refers to the ratio between incoming radiation (shortwave radiant energy, insolation) and outgoing radiation (re-radiated and reflected longwave) The difference between the incoming and outgoing values equal the net radiation. Net radiation averaged annually the entire planet is zero, but varies for different locations at different time

Stratosphere --> Stratopause

The upper limit where temperatures are at their highest, below the ozone layer, temperatures remain fairly constant

Direct radiation

Travels from the sun directly to the surface of the earth where it is absorbed. Approx. 25% of all radiation.

Urban landscapes

*Absorb more radiation due to their darker color (Roofs, concrete, and asphalt) *Conduct more energy due to building material *Have less shade due to fewer trees *Reduce wind speed and airflow due to the shape and density of buildings *Also generate more waste heat from things like heating and cooling systems and car engines

Troposphere --> Tropopause

*The elevation of the upper limit of the troposphere, called the tropopause depends upon surface temperatures and pressures and therefore varies with season and latitude. *At the tropopause the temperature stops decreasing and begins to increase *Temperature decreases as altitude increases in the troposphere, because the distance from the air's source of heat is increasing

Key concepts about the composition of the Atmosphere

1. Although the atmosphere is technically about 10,000 km (6000 mi) thick, the vast majority of the air is found in the lowermost 30 km (10 mi). 2. The atmosphere contains constant gases (primarily nitrogen and oxygen), variable gases (mainly carbon dioxide and water vapor), and particulates. 3. The atmosphere consists largely of nitrogen (78%) and, to a lesser extent, oxygen (21%). 4. Although variable gases and particulates compose less than 1% of the atmosphere, they nevertheless affect atmospheric processes and climate in important ways. A good example of the impact of these gases is the greenhouse effect and the way it moderates temperature on Earth.

Key concepts: How solar radiation flows on earth

1. Once solar radiation reaches the atmosphere, it begins to flow along several different pathways. Some of it flows directly to the surface, whereas other parts are reflected off clouds or scattered by particulates. 2. Insolation that reaches the surface is either absorbed or reflected (a function of albedo). 3. Radiation that is absorbed is re‐radiated as longwave radiation. 4. The amount of energy reflected or absorbed depends in large part on the angle of incidence, which, in turn, varies by latitude and season.

Sensible heat loss

1. Sensible heat can be transferred to the atmosphere as warm air rises upward through the process of convection 2. Sensible heat can be transformed to latent heat through evaporation. Latent heat (heat that is absorbed and held in a gas/liquid during the process of evaporation/melting) is conducted upward in water vapor that has evaporated from land and ocean surfaces

Key concepts about the Electromagnetic spectrum and solar energy

1. The Sun produces energy that radiates to Earth as various sizes of electromagnetic waves. 2. The electromagnetic spectrum is the total wavelength range of electromagnetic energy. 3. An inverse relationship exists between temperature and radiation wavelength. 4. A direct relationship exists between the temperature of an object and the amount of electromagnetic radiation it produces. 5. The Sun produces electromagnetic energy at a generally constant rate over time. The amount of energy that reaches the top of Earth's atmosphere is known as the solar constant.

Key concepts: Global radiation budget

1. The global radiation budget refers to the balance between incoming and outgoing radiation on Earth. 2. Over the long term, the global radiation budget is balanced. However, even though the long‐term radiation budget is balanced, a great deal of variability occurs across Earth as a whole. 3. In general, low latitudes have a net surplus of radiation, whereas high latitudes have a net deficit. This imbalance is important because it drives atmospheric circulatory processes. 4. Net radiation depends on a complex interaction of several variables, including angle of incidence, latitude, season, day length, and albedo. 5. In an effort to supplement current energy supplies, efforts are under way to increase the production of renewable solar energy. The major limitations are that production of solar energy with current technology is inefficient, and the Sun does not shine consistently in many places.

Reflected radiation amounts/how

28% is reflected or scattered back to space, 21% by clouds, 7% by dust particles

Percentages of the Path of solar radiation to earth

48% of all solar radiation that makes its way to Earth comes in contact with the surface, as primarily direct- (25%) or indirect radiation (20%). 52% of all solar radiation that makes its way to Earth NEVER reaches the surface; 28% is reflected back into space and 24% is absorbed by the atmosphere.

Stratosphere and climate change

A key focus of the mission is water vapor and its effect on Earth's energy budget, ozone layer and climate. Studies have shown that even small changes in stratospheric humidity may have significant climate impacts. Climate researchers believe that greenhouse gases cool the stratosphere, which allows a greater number of clouds to form. Water destroys ozone. Since clouds are controlled by moisture, their accumulation in certain parts of the lower stratosphere can greatly impact the presence of ozone

Positive lapse rate - Troposphere

A lapse rate where there is a decrease in temperature with increasing height. Temperature decreases 3.5 degrees per 1000 feet

Reflected radiation

About 3% of all incoming radiation is reflected in such a way that it does not provide heat. In any case, the proportion of incoming radiation reflected by a surface is dependent upon the albedo of that particular surface.

Maritime vs. continental effect

Although radiation budget largely influences temperature, other factors, such as time of day and cloud cover can play an important role. *Maritime places are those located near a significantly large body of water, ex: San Francisco, California *Continental localities include those that are surrounded by large land masses, ex: Topeka, Kansas (Both are at the same latitude)

Insolation

Amount of solar radiation that strikes a surface perpendicular to the Sun's incoming rays

Regional temp influence - time of day

As the day progresses from the morning sunrise, the sun appears to be climbing higher into the sky. At a certain point, the sun is at what will be its highest point for the day, at that time incoming solar radiation also reaches its peak. This point depends on several factors including latitude and season.

Net radiation - Day Length

Because of Earth's axial tilt and orbital position, day length varies at different locations on earth at different times of the year. This has a significant effect on the amount of daily insolation received, particularly outside of the tropics. (ex: on the Summer Solstice the North Pole receives 24 hours of sunlight. On this day the North Pole receives 500 watts/m2 of insolation, in contrast to the 0 watts/m2 it receives on the Winter Solstice. A similar pattern of daily insolation emerges in the midlatitudes, only it is less extreme.)

Primary urban pollutants

Comes directly from domestic, industrial, electricity-generation, and transportation (internal combustion engines) sources generally associated with, or at least more concentrated, in cities. Such sources release the following primary gaseous pollutants: Carbon dioxide -- greenhouse gas Water vapor --- greenhouse gas Hydrocarbons -- contributes to smog generation and acid rain Carbon monoxide -- poisonous to humans Nitrogen oxides -- one of the main ingredients involved in the formation of ground-level ozone; contributes to the formation of acid rain Sulfur oxides -- contributes to the formation of acid rain Many of these effluents are considered 'status-symbol' pollutants because they are typically associated with industrially developed (and consumer-driven) countries

Solar energy

Created in vast quantities by nuclear fusion within the sun. This energy works its way to the surface of the sun, where it is emitted as electromagnetic radiation. From this point this energy travels along straight lines (or rays) through space at the speed of light

Variable gas - Carbon dioxide

Currently makes up about .04% of the atmosphere. Despite this very small percentage, CO2 is a critical part of the atmosphere (1) plants absorb CO2 and release oxygen as a by-product (2) atmospheric CO2 contributes significantly to the greenhouse effect. The concem now is that CO2 levels are rapidly rising beyond recent historical norms due to human industrial activity, specifically the consumption of fossil fuels. As a result, Earth is in the midst of a rapid warming trend that may have major environmental consequences in the future.

The amount of water vapor

Depends on many variables such as the proximity to a large body of water or the air temperature. Perhaps the most important is temperature: warm air can hold more water than cold air (warm air has a large capacity, cold air has a low capacity). This vapor/temperature relationship is an important principle in physical geography because it directly influences the process of precipitation

Variable gases

Differ in their proportion of the atmosphere over time and space, depending on environmental conditions. The most important variable gases are carbon dioxide, water vapor, and ozone

The process of Greenhouse effect

Earth receives shortwave radiation from the Sun, which passes through the atmosphere and is absorbed by the surface. Subsequently, the Earth releases energy as longwave radiation. Some of this radiation flows directly back into space, but most is absorbed by the atmosphere, where it is held in large part by CO2 (water vapor is another greenhouse gas). The atmosphere then redirects some longwave energy back to the surface as counterradiation. Some atmospheric longwave energy escapes to space.

Blue halo

Earth's visible edges appears as a blue halo, this is the result from atmospheric gases scattering blue wavelengths of visible light more than other wavelengths. At high altitudes the atmosphere becomes increasingly thinner, so much so that it essentially ceases to exist. Gradually, the atmospheric halo fades into he blackness of space.

Energy balance - latent heat flow

Heat that causes evaporating liquids to change to gases.

Net radiation - Angle of incidence

If the sun is high in the sky, the radiation received is more direct, and therefore, more intense. *Remember the rays hitting the surface of the earth differ in the area they cover depending upon latitude. Basically, the same amount of energy is directed at a smaller or larger area on the surface of the earth, and therefore will heart the earth surface accordingly. When the sun is lower in the sky, as it is in higher latitudes, the result is less energy per unit area. *In the tropics (lower latitudes) the sun angle is always high and more radiation is received. Also recall that sun angle influences how much radiation will be reflected or absorbed when it strikes the earth. At a lower angle, more radiation is reflected.

Ozone formation

In the initial stage of this reaction, O2 absorbs UV energy, which causes the oxygen molecule to split into two oxygen atoms (O + O). Subsequently, one of the O atoms combines with an O2 molecule to form ozone. Ozone is naturally destroyed when it absorbs UV radiation and splits from O3 into O2 + O. The single oxygen atom can then recombine with another O2 molecule to form ozone. Ultimately, O3, O2, and oxygen atoms (O) are repeatedly formed, destroyed, and re‐formed in the ozone layer in a way that absorbs UV radiation each time a transformation takes place.

Ozone depletion

In the last 20th century, due in part to the release of chlorofluorocarbons (CFCs) associated with air conditioners and other cooling systems. CFC molecules are very stable in the atmosphere and gradually diffuse upward from the surface to the ozone layer. Once they reach this altitude, CFCs absorb UV radiation and break down into chlorine oxide (ClO) molecules that, in turn, attack ozone molecules and convert them into oxygen atoms. The net effect of this process is that the ozone layer is depleted and more UV radiation reaches the ground because less is absorbed in the atmosphere. (Discovered through satellite remote sensing)

Albedo - reflected radiation

Is the reflectivity of various features on the earth and in the atmosphere. Although you may not be directly aware of albedo, you are probably indirectly aware of its effects. *Dark objects: reflect less radiation and have a low albedo (ex: dark forest 10% albedo, most radiation is absorbed) *Bright objects: reflect more radiation and have a high albedo (ex: snow glacier 80% albedo, most radiation is reflected)

Why does this occur? (maritime vs. continental effect)

Large bodies of water, such as the pacific ocean (and even Lake Michigan) store tremendous amounts of heat energy. Radiation can penetrate to great depths in the ocean and currents constantly mix the water. As a result, the ocean maintains a constant temperature more or less for most of the year. As water is evaporated from the ocean, heat energy is transferred to the atmosphere in the form of latent heat, that in turn, moderates the air temperature of places such as San Francisco. Surrounding land masses do not store nearly as much heat as oceans do. Radiation does not penetrate to great depths in land masses and mixing does not occur. As a result continental localities exhibit dramatic annual temperature variations where annual radiation fluctuates greatly, like places such as Topeka.

Particulates

Less than 1% of earth's atmosphere. Microscopic bodies carried in the air, existing in both liquid and solid form. Liquid variety comes in the form of clouds and rain, which develop when water vapor changes from its physical state due to temperature changes in the atmosphere. Solid variety comes from an assortment of forms snow, hail, pollutants, wind-blown soil (dust), smoke, volcanic ash, pollen grains from plants, and salt spray from breaking waves. Densest near their place of origin.

Difference in amount of energy received at different latitudes

Lower latitudes to receive more energy than is released to the atmosphere causing an energy surplus higher latitudes receive less energy than is released to the atmosphere causing an energy deficit. That said, some places on the planet have a net surplus (as in the Tropics) while others have a net deficit (as in the Poles). Note that it is possible to have a deficit during certain times of the year, but a surplus during other times. This equator-versus-pole energy imbalance is the fundamental driver of atmospheric and oceanic circulation

Constant gases

Maintain more or less the same proportion in the atmosphere. Nitrogen and oxygen are the primary constant gases and together make up 99% of the atmosphere. Argon is the other constant gas, composing approx. 1% of the atmosphere. It is inert (chemically inactive) and a little importance in natural processes.

Role of particulates

Nevertheless play an important role in weather and climate. Precipitation would not occur if dust particles were not present in the atmosphere because they provide a nucleus around which water condenses in the first step of cloud formation. Other particulates, such as smoke and volcanic ash are important because they either absorb or reflect solar energy. These combined processes influence local weather and regional climate by moderating the temperature of the atmosphere. Although most are positive, some can cause negative environmental and health effects (toxic air pollutants)

Constant gase - Nitrogen

Nitrogen occurs in molecular form as two nitrogen atoms bond together. This gas makes up 78% of the atmosphere and is derived from the decay and burning of organic material, volcanic eruptions, and the chemical breakdown of specific kinds of rocks. Although nitrogen is largely inert in the atmosphere, it is critical to plant life because it can be transformed, or fixed, into chemical compounds (ammonia or nitrates) in the soil. These compounds are absorbed by plants and incorporated in their tissues as proteins. Nitrogen maintains a constant proportion of the total atmosphere because what is added is balanced by what is removed through precipitation and various biological processes.

Constant gas - Oxygen

Oxygen makes up 21% of the atmosphere and is a by-product of photosynthesis. In contrast to the inert nature of nitrogen, oxygen gas is very active and can combine with a variety of other elements through the process of oxidation. Oxygen is essential to animal respiration because it is required to convert foods into energy. Oxygen is a constant gas because the amount produced by plants balances the amount absorbed by various organisms through respiration.

Variable gas - Ozone

Ozone is a form of oxygen that has 3 oxygen atoms, rather than the 2 found in normal oxygen. Atmospheric ozone forms when gaseous chemicals react in the upper atmosphere with light energy. Ozone primarily occurs in two layers in the atmosphere: ground level and within the stratosphere. Ground level is a form of pollution (smog) created when nitrogen oxides and organic gases emitted by automobiles and industrial sources react. This form can be linked to cardiorespiratory illness and may also damage crops.

Indirect radiation

Reaches earth after it has been scattered or reflected. Approx. 20% of all radiation (some 3% of radiation reaches earth's surface directly but it is reflected by the surface, back to space and does not provide heat)

Net radiation - Seasonality

Seasonality refers to annual changes in the amount of insolation over the course of a year as explained by Earth-Sun relationships, Earth's tilt and its path around the sun on the plane of ecliptic. In other words, the cyclical variation in the hours of sunlight (day length) as well as daily insolation received at a location, as Earth travels around the sun. Incoming sunlight increases in the hemisphere experiencing summer, which makes the energy imbalance strongly positive (more watts of energy coming in than going out). As the September equinox approaches, a zone of positive net radiation is nearly centered over the equator, and energy deficits lie over the poles. As the season changes into winter, the net radiation becomes negative across much of the Northern Hemisphere and positive in the Southern Hemisphere. The pattern reverses on the March equinox

Fluctuations in the atmosphere

Shape the course of environmental conditions at every moment on earth's surface. How solar radiation flows in the atmosphere is key to understanding earth's temperature, atmospheric circulation, and precipitation patterns. *Short term fluctuations of the atmosphere are referred to as weather *Long term fluctuations of the atmosphere are referred to as climate (Climate is what you expect, weather is what you get)

The flow of solar radiation on earth

Solar radiation entering earth's atmosphere can take various paths. Only 48% reaches the surface of the earth (insolation)

Solar constant

Sun produces energy at a nearly constant rate, the output of solar radiation is also nearly constant. As a result generally constant production and emission, the amount of solar radiation received in an area of fixed size in space and at right angles the Sun is also constant. This amount of received energy, which is referred to as the solar constant, has a value of about 1370 watts per square meter (W/m2) at the top of the atmosphere. Reaches earth in about 8 minutes

Negative lapse rate -Stratosphere

Temperatures increase as you gain altitude in this layer. This is due to the presence of the ozone layer where ultraviolet radiation is filtered and re-radiated as infrared energy that is safer for life on earth.

Thermosphere

Temperatures increase dramatically in this upper layer of the atmosphere, which occurs between 80 and 480 km (50 to 300 miles) in elevation. Oxygen molecules are widely scattered in this portion of the atmosphere, which is probably the best known as ionization within this layer often results in the colored glowing lights, known as Aurora Borealis (Northern lights) or Aurora Australis (Southern lights)

Why is the sky blue?

The apparent color of the sky is determined by the interaction of solar radiation and the atmosphere. Particulates in the air absorb and reflect radiation in blue wavelengths

Composition of the atmosphere

The atmosphere consists of air, an invisible medium that surrounds and protects earth. The fundamental components of the atmosphere can be divided into three categories: (1) constant gases (2) variable gases (3) particulates. Each of these perform a unique roles essential to life on earth

Layers of the atmosphere

The atmosphere extends from the surface of the earth (land or water) to a height of about 480 km (300 miles) Each layer is distinguished by its temperature as well as the elements it contains. (Extending up from Earth) 1. Troposphere 2. Stratosphere 3. Mesosphere 4. Thermosphere

Ozone hole

The decrease in stratospheric ozone observed on a seasonal basis over Antartica and to a lesser extent over the Arctic

Net radiation

The difference between incoming and outgoing flows of radiation. Many factors can influence net radiation including the varying output of the sun due to sunspot and solar flares, the elliptical nature of the Earth's orbit and the changes in the thickness and properties of the atmosphere.

Principles about electromagnetic radiation

The first principle is that an inverse relationship exists between the temperature of an object and the wavelength of the electromagnetic radiation it emits. In other words, hotter objects emit radiation with shorter wavelengths than cooler objects. For example, the Sun has a surface temperature of about 6000°C (11,000°F) and emits energy as shortwave radiation, which includes gamma rays, X‐rays, ultraviolet (UV) radiation, visible light, and near‐infrared radiation. The Earth, in contrast, is a much cooler object (~16°C, 61°F) and thus emits longwave radiation in the thermal infrared part of the spectrum (Figure 4.3). Keep in mind, though, that the vast majority of energy released by Earth initially originated at the Sun. The second principle of electromagnetic radiation is that a direct relationship exists between the absolute temperature of the object and the amount of radiation it emits. This relationship is described by the Stefan-Boltzmann law and means that hotter objects emit more radiation than cooler ones. As a result, Earth emits much less radiation than the Sun. This temperature/emitted radiation relationship is exponential, meaning that a small temperature increase in an object results in very large increases in emitted radiation.

Stratosphere

The layer of calm, clear air, between 12 km and 50 km (7.5 to 31 miles) in elevation, that contains very little water vapor. (Jets fly in the lower part).

Ozone layer

The layer of the atmosphere that contains high concentrations of ozone, which protects the Earth from ultraviolet (UV) radiation. Absorbs UV radiation from the sun.

Short wave radiation

The portion of the electromagnetic spectrum that includes gamma rays, X‐rays, ultraviolet radiation, visible light, and near‐infrared radiation. (from the sun)

Long wave radiation

The portion of the electromagnetic spectrum that includes thermal infrared radiation. (from the earth)

Urban vs. rural effect

The presence of a city can have an influence on the absorption and release of solar radiation, due to the presence of paved surfaces. Cities generally experience warmer temperatures than their rural counterparts, which may only be miles away.

Greenhouse effect

The process through which the lower part of the atmosphere is warmed because long wave radiation from earth is trapped by carbon dioxide and other greenhouse gases. This process warms the atmosphere, which, in turn, warms Earth. Another significant greenhouse gas is methane, which is derived from natural gas and decaying organic matter. Methane currently makes up about 0.00017% of the atmosphere. You may associate the greenhouse effect most closely with the concept of global warming, an environmental issue that greatly concerns many scientists today.

The electromagnetic spectrum

The radiant energy produced by the Sun that is measured in progressive wavelengths. Humans can see radiation directly only in the visible light part of the spectrum, which ranges from violet with the shortest wavelength of 375 nm to red with the longest wavelength 740 nm

Reasons for other colors in the sky

The sky becomes more colorful when the sun is low in the sky, either at dawn or dusk. This occurs because solar radiation not only has the vertical dimension of the atmosphere to pass through, but a significant horizontal dimension as well. Radiation must pass through more of the atmosphere to reach your line of sight and the longer wavelengths (yellows, oranges, and reds) are subsequently scattered and can then be seen When the air is clear, the sky at sunset will be more yellow When dust or salt particles are in the air, the sunset will appear more red because the blue wavelength is completely scattered before it reaches your eye.

Net radiation - Latitude

The sun can be directly overhead only between 23.5°N and S latitudes (between Tropics of Cancer and Capricorn), and the sun's rays hit these locations more directly. This Earth-Sun relationship (Earth's tilt) influences net radiation, which influences global circulation patterns. As we have already discussed, the mid- and high latitudes, on average, receive less insolation throughout the year due to the sun angle.

Temporal lag

The sun then appears to be moving lower in the sky until it sets behind the horizon. The warmest part of the day occurs a few hours after the sun has been at its highest point in the sky. This is called a temporal lag and occurs in part because incoming radiation still exceeds outgoing radiation for several hours after solar noon. It is also the result of a delay in the release of stored radiation as heat from the earth to the atmosphere. Remember, the earth's atmosphere is warmed from the surface, up.

Troposphere

The zone of the biosphere and active weather, extending from the surface to about 12 km (7.5) miles on average. It is generally warmed by the long wave radiation emitted from earth. It is always thicker at the equator than at the poles, ranging from a height of about 18 km to a height of around 8 km. The equatorial regions receive more intense radiation from the sun and, therefore, the air over the equator is warmer than the air around the poles. As air warms it expands and thus takes up more space, making it seem thicker. The height also varies with seasons; highest in the summer and lowest in the winter

Mesosphere

This is a layer of decreasing temperature that occurs between about 50 and 80 km (30 to 50 miles) in elevation. The decrease in temperature that is observed in this layer increases with vertical distance from the ozone layer below. Sunlight reduces molecules in the mesosphere to individual electrically charged particles called ions through a process known as ionization. This can disrupt communications between astronauts and ground control.

Fluctuations of Carbon dioxide in the atmosphere

Thought to be a primary component of major climate change. *Low CO2 = more heat escapes into space and earth cools *High CO2 = more heat is trapped and the earth warms (valuable and invaluable part of our atmosphere

Variable gas - Water vapor

Water is found in three physical states: liquid, solid (ice), and gas (water vapor) The amount of water vapor in the atmosphere near earth's surface is about 2% in most parts of the planet, but can range from just less than 1% over deserts and polar regions to about 4% in the tropical zones. It is essential because it absorbs and stores heat energy from the sun and is thus an important component, along with CO2 of the greenhouse effect. As airflow within the atmosphere moves vapor around, the effect is to moderate temperature and transport energy around Earth.

Absorbed radiation

more than 95% of the radiation that makes it to Earth's surface is absorbed by the various land and water bodies and heats of earth. This radiation can be re-radiated back into space as longwave radiation or it can be stored as sensible heat (heat that can be measured by a thermometer)

4 key factors of net radiation

1. Angle of incidence 2. Latitude 3. Seasonality 4. Day length

Regional influences on temperature

1. Latitude 2. Seasons/length of day 3. Time of day

Local influences on temperature

1. Maritime vs. continental effect 2. Urban vs. rural effect

Energy balance in the atmosphere (3 types of flows)

1. insolation 2. sensible heat 3. latent heat * The temperature depends upon how much heat is involved in these three flows at any given time or place. -Sensible heat values are highest in the subtropics (desert regions). -Moist, vegetated surfaces have high latent heat values and low sensible heat values -On land the highest annual values for latent heat occur in the tropics (at the equator), due to high amounts of water vapor in the atmosphere, and decrease towards the poles.

Absorbed radiation amounts/how

24% is absorbed, 3% by clouds, 18% by dust and other components, 3% by ozone

Energy balance - sensible heat flow

Heat that we can sense on our skin.

Energy balance - Insolation flow

Radiant heat from the sun that reaches earth's surface.

Regional temp influence - seasons/length of day

The amount of insolation received at a location and length of day varies over the course of a year due to Earth-Sun geometry, that is, Earth's axial tilt. The degree to which both will vary is determined by latitude. More dramatic changes occur in both net radiation received and day length with increasing distance from the equator.

Sun's Angle of Incidence

The amount of radiation reflected depends not only upon albedo, but also on the sun angle, or angle of incidence. When the sun angle is high, more radiation is absorbed because it flows directly When the sun angle is lower, more radiation is reflected (ex: water has an albedo value around 5% when the sun is directly overhead, but when the sun is near the horizon, the albedo value is around 65%)

Radiation and temperature

The local temperature at any one time on the Earth is measured by a thermometer and reported as the air temperature, the degree of warming that occurs just above the surface. It depends upon the amounts of energy involved in incoming and outgoing radiation and the energy balance. What we feel when we walk outside may not be accurately reflected in the air temperature. It can be influenced by other factors like wind and humidity.