Lithosphere - describes the solid inorganic portion of the Earth (composed of rocks, minerals and elements). It can be regarded as the outer surface and interior of the solid Earth. On the surface of the Earth, the lithosphere is composed of three main types of rocks: Igneous - rocks formed by solidification of molten magma. Sedimentary - rocks formed by the alteration and compression of old rock debris or organic sediments. Metamorphic - rocks formed by alteration of existing rocks by intense heat or pressure. Atmosphere - is the vast gaseous envelope of air that surrounds the Earth. Its boundaries are not easily defined. The atmosphere contains a complex system of gases and suspended particles that behave in many ways like fluids. Many of its constituents are derived from the Earth by way of chemical and biochemical reactions. Hydrosphere - describes the waters of the Earth (see the hydrologic cycle). Water exists on the Earth in various stores, including the atmosphere, oceans, lakes, rivers, soils, glaciers, and groundwater. Water moves from one store to another by way of: evaporation, condensation, runoff, precipitation, infiltration and groundwater flow. Biosphere - consists of all living things, plant and animal. This zone is characterized by life in profusion, diversity, and ingenious complexity. Cycling of matter in this sphere involves not only metabolic reactions in organisms, but also many abiotic chemical reactions.

At one point in its orbit, the northern part of the earth has its maximum inclination toward the sun. Since the earth's axis is tilted 23 ½ degrees, then on this particular day, the sun's rays are striking the earth directly at a latitude approximately 23 ½ degrees north of the equator (that is, the sun's rays are coming in at an angle of 90 degrees here; this is the subsolar point).  This occurs on about June 21 or 22 each year, and the day is known as the Summer Solstice (summer for those who live in the Northern Hemisphere, that is.  It might be safer and more generally applicable to call it the June Solstice). If you were at 23 1/2 degrees north latitude on that day, and you looked up at noon, the sun would be directly overhead. This latitude is the farthest north on the Earth that the sun's rays will be directly overhead. Farther north, at noon, the sun will never be directly overhead, but always at least a little bit to the south. The latitude of 23 ½ degrees north is known as the Tropic of Cancer, and it is the northern boundary of the tropics.

Let's take a look at the opposite end of the year, six months later, on December 21 or 22. On this day, the earth has gone halfway around its orbit, and is opposite the point where it was on the summer solstice. The situation is exactly reversed. The southern hemisphere of the earth is tilted toward the sun, and the sun's rays are perpendicular to the earth's surface at 23 ½ degrees south. This is the subsolar point: the sun is directly overhead at noon at this latitude.  The farthest south that the sun's rays shine directly is latitude 23 ½ degrees south, the Tropic of Capricorn. This is the southern boundary of the tropics. On this day, the area north of the Arctic Circle gets no sunlight, and the area south of the Antarctic Circle gets 24 hours of light. This is called the Winter Solstice (or the December Solstice). It is summer for the Southern Hemisphere (and the longest day of the year for the Southern Hemisphere), and winter for the Northern Hemisphere (and the shortest day of the year for the Northern Hemisphere).

Now for the intermediate situation. The subsolar point is at the Tropic of Cancer in June, and at the Tropic of Capricorn in December.  Midway between the solstices are two dates when the sun shines directly on the equator, and we have a situation like our hypothetical one, where the earth's axis is perpendicular to the ecliptic. (The axis is still tilted, still pointing at the North Star, but it is tilted sideways with respect to the sun, rather than towards or away from the sun). The circle of illumination passes through the poles, the sun's rays strike the equator at an angle of 90 degrees, and every part of the earth has 12 hours of daylight and twelve hours of night. This happens twice in the year. These two days are called the equinoxes. (equinox means equal night, since days and night are equal at twelve hours).  March 20 or 21 is the vernal equinox or spring equinox (for the Northern Hemisphere), and the subsolar point is heading north, on its way to the Tropic of Cancer. September 22 or 23 is the autumnal equinox, or fall equinox (for the Northern Hemisphere); the subsolar point is on the way south.

Watch the animation several times to observe the seasonal changes in sunlight in both hemispheres. Move through the animation and identify frames of the movie that represent solstices and equinoxes.

Numerous factors contribute to the large -scale atmospheric circulations that affect our climate. These include: the near-spherical shape of earth and the north/south movements of the sun relative to the earth as the seasons progress marked differences in heating of land and sea surfaces the rotation of the earth which causes winds to be deflected to the right in the northern hemisphere and to the left in the southern hemisphere. This is known as the Coriolis effect and results in the formation of giant eddies (cyclones and anticyclones).

As the picture illustrates, the ocean has a huge influence on the climate. Climates can be classified as "marine" or "continental" depending on distance to the ocean. Both the highest and the lowest temperatures appear in the interior, far from the moderating influence of the ocean. Note how the lines of climate zones tend to run parallel to the coast, especially in western North and South America, or from interior to exterior of the continent, as in Australia. Precipitation is highest where warm marine air has access to coastal mountain ranges, as for example in the coastal regions of Oregon and Washington.  

Earth Systems: The Climate "Climate is what you expect; weather is what you get!"

Introduction Warm near the equator and cold at the poles, our planet is able to support a variety of living things because of its diverse regional climates. The average of all these regions makes up Earth's global climate.

Introduction, continued Weather and climate are the result of a complex series of interactions between all elements of the earth system (hydrosphere, atmosphere, biosphere, lithosphere) but are largely controlled by the interaction between the Earth and Sun. The distribution of solar radiation on Earth's surface regulates the order of the seasons and divides day and night.

The Big Picture The big factors that influence weather and climate worldwide are the Sun, the water cycle, and the atmosphere. The largest influence on our planet’s weather and climate is the Sun because the amount of sunlight a location receives will determine its climate. Additionally, changes in the Sun’s energy output through time, as well as changes in the amount of sunlight let into the Earth system can drastically affect our world The amount of solar energy received at any location on Earth will affect the amount of precipitation and evaporation. This endless process of water transport, from clouds to ground and back again, is called the water cycle. Our atmosphere protects Earth from extreme temperatures and provides the stage for dramatic weather events.

The Sun: it’s a scorcher! The Sun has a powerful influence on our planet: it is the source of light and heat essential for life on Earth. This solar radiation drives the atmospheric circulation systems that determine climate and weather. For instance, wind occurs when sunlight heats the ground, which heats the air above it, which rises, so that cool air whisks in to take its place. The Sun is an integral part of the water cycle as well. Water evaporates from oceans as sunlight warms the water surface and forms clouds that may eventually cause a downpour. The Sun also affects our world over longer time scales. Over a year, our seasons change as different hemispheres of the Earth are situated closer or farther from the Sun through the year as the Earth, tilted on its axis, revolves around the Sun. Over much longer time scales, changes in the Sun may have contributed to the climate changes that caused the ice ages in the past few million years.

Reason for the Seasons There are three ways that Earth's orbit changes over time: Revolution: Eccentricity is the shape of the Earth's orbit around the Sun. The eccentricity varies over about 100,000 years between slightly more or less elliptical. Inclination or tilt: the angle of the Earth's axis relative to the plane of its orbit varies between 21.5 and 24.5 degrees over a period of 41,000 years Parallelism: means that the earth's axis remains parallel to its former position as it revolves around the sun. Axis "always" points in the same direction. Precession: Earth wobbles on it axis as it spins completing a full wobble every 23,000 years.

Insolation Incoming Solar Radiation: Solar Radiation intercepted at the surface of the earth. Amount and intensity are determined by the sun angle, day length, path length, ground slope, and state of the atmosphere. Sun Angle Angle a beam of light makes with the  surface of the earth. Determines the area of illuminated and intensity of heating. Perpendicular rays (A) concentrate energy over the smallest area. As the sun angle decreases (B) the area illuminated increases (indicated by dashed line).

June Solstice

December Solstice

Vernal and Autumnal Equinox

Day Length affects Climate and Weather

Latitude affects Climate and Weather

Observe seasonal changes in the amount of sunlight reaching locations on Earth The geostationary satellite that took these images remains directly over the same location in the western Pacific Ocean at all times. Each day, from January through December, just as the point below the satellite turned from day to night, an image was captured. Only the daily weather and the angle at which sunlight hits Earth change from frame to frame in the animation. The tilt of Earth's axis results in 24-hour daylight at the North Pole and almost complete daylight north of the Arctic Circle during summer in the Northern Hemisphere and perpetual darkness during winter. The situation is reversed south of the Antarctic Circle.

What is the difference between weather and climate? Weather is the mix of events that happen each day in our atmosphere including temperature, rainfall and humidity. Weather is not the same everywhere. Perhaps it is hot, dry and sunny today where you live, but in other parts of the world it is cloudy, raining or even snowing. Weather events are recorded and predicted daily by meteorologists worldwide.

What is the difference between weather and climate? . . . continued Climate is the average weather pattern in a place over many years, including the variations of the seasons. The climate of a region depends on many factors including the amount of sunlight it receives, its altitude, topography, and how close it is to oceans. Climate varies with latitude

Factors that control climate

Wind

Wind, continued Global wind patterns are caused by unequal heating of the Earth's surface and by the rotation of the Earth. Warm air rises, cold air sinks (convection) along with the Coriolis effect causes the winds to curve.

The Coriolis Effect Air flows from areas of higher pressure to areas of lower pressure. Based on this fact, the predicted wind direction for the area on the left side of this satellite image would be from the southeast. The Coriolis effect influences wind by deflecting its path to the right in the Northern Hemisphere. The sequence of weather satellite images shows that the actual wind direction is from the southwest. The satellite images show atmospheric motion over the northern Pacific Ocean for a 36-hour period.

Climate and Regional Pattern Maps Climate is typically described by the regional patterns of seasonal temperature and precipitation over 30 years. Average annual temperature, average rainfall, average cloud cover, and average depth of frost penetration are all typical climate-related statistics. The main expression of climate on land is in the vegetation and the soil type produced in each climatic region. The idea to classify climate by temperature, rainfall and vegetation was introduced by Wladimir Köppen in 1900. This classification of climates was later modified by Rudolph Geiger Climograph for Cleveland, Ohio

Koppen-Geiger Climate Classification Humid Tropics (A): Known for their high temperatures year-round and for their large amounts of perennial precipitation. These regions are found near the equator. Arid Climates (B): Characterized by little precipitation and huge daily temperature range. Humid Middle Latitudes Climates (C): Dominated by land/water differences. The eastern seaboard of the U.S. would be an example of this class, with cool winters and mild summers. Continental Climate (D): Found in the interior regions of land masses of exceptional size (i.e. Omaha, in the middle of the U.S.A.). Total precipitation is not very high in amount, and seasonal temperatures vary greatly. Cold Polar Climates (E): Areas covered by permanent ice and tundra. Here, average temperatures reach above freezing only about one third of the year.

A World Map of Koppen Climate types Smaller case letters refer to subclassifications that are not discussed here. The Ocean has a HUGE influence on climate. Both the highest and lowest temperatures appear in the interior, far from the moderating influence of the ocean.

Local Climate

*The highlighted areas represent topics covered thus far.

The End