A Powerful Tool for Inquiry, Integration and Understanding in Social Studies
There is a place on earth that averages almost five hundred inches of rain a year while another location less than twenty miles away averages only ten inches of rain per year. How is this possible you ask? It is caused primarily by of one of nine climatic controls and in this case the main climatic control is mountains or mountain barriers. Mountain barriers as a climatic control can cause extremely wet and dry conditions. The above situation happens to be on the island of Kauai in the Hawaiian Islands. Most of the islands of Hawaii have a similar wet and dry side if the volcanic mountain that formed it is high enough to trigger the precipitation. Some of the lower elevation islands of Hawaii are deserts. If students learn the climatic control of “mountains” and just eight more things that control the climate on our planet, they can problem solve about what the climate is like for any place on planet Earth. In addition to mountain barriers, the remaining eight controls are: latitude, altitude, land-water distribution, ocean currents, wind and pressure belts, air masses and fronts, storms or low-pressure cells, and the jet stream. We will examine these nine climatic controls in detail and also use them to begin to understand some extreme conditions on Earth later in this article. To begin, however, let’s examine what climate is and why it is important, how and where climatic data is reported, and some ways to analyze climatic data.
What is climate? Some confuse weather and climate as I recently saw in a teacher-made handout for fifth graders that said they were basically the same thing--wrong. They are similar in that weather and climate both have the same two elements or variables--temperature and precipitation. Weather is simply the day to day changes in temperature and precipitation while climate is the average of those changes over a period of time--usually months or years. If you heard that it rained somewhere last night, it wouldn’t tell you much about a place. However if you heard that a place averages over 400 inches of rain a year, one would know much more about that place.
Once you know something about the climate of a place, many more inferences can be made about that place. For instance climate helps determine native vegetation or what grows naturally in a place. Areas that average less than 10 inches of rain per year would usually have desert vegetation while areas that average more than 40 inches would probably be forested. Areas in between ten and forty inches would probably be grasslands. Native vegetation in turn largely determines the native animals--herbivores in grassland areas and tree dwelling animals in forested areas. Climate also largely determines the activities of humans that live in an area--crops that can be grown, how people dress, how they build houses, and even to a large extent how they make money.
As shown in Figure 1, climatic data is usually reported in the form of monthly and yearly averages (Kendall et. al.1974).
J F M A M J J A S O N D YEAR
TEMP 32 37 45 56 65 75 81 80 72 60 45 36 57
PREC 1.1 1.6 2.6 4.5 4.1 3.1 3.2 3.3 2.5 2.0 1.7 .9 30.6
TEMP 29 33 43 54 64 74 79 78 69 58 43 32 55
PREC 1.0 1.3 2.0 3.0 4.4 4.0 3.6 4.1 4.1 2.5 1.8 1.0 32.8
TEMP 30 32 35 40 46 51 55 55 51 44 37 33 42
PREC 7.1 6.8 5.6 5.4 4.3 3.5 4.0 7.1 9.7 11.7 8.8 7.4 81.4
TEMP 10 13 24 38 48 58 66 65 57 45 29 17 39
PREC 1.0 1.0 1.5 2.1 3.4 4.4 3.9 3.5 3.7 2.7 1.5 1.2 29.9
SAN ANTONIO, TEXAS
TEMP 53 55 63 69 75 81 83 83 79 70 61 54 69
PREC 1.4 1.6 1.8 2.7 3.3 2.7 2.5 2.6 3.5 2.0 2.2 1.8 28.0
Various types of climates can be identified and classified by analyzing this climatic data. Identifying climates from raw climatic data may be above the skill level of your students, but they can be shown the various climate types derived from climatic data on a climate map in many atlases. Students can learn to analyze raw climatic data by comparing data from various locations for the coldest, warmest, wettest or driest months or years. Climatic data can be easily obtained from the Weather Channel web site at: www.weather.com. Simply type in a zip code for a location, click on the “averages and records” link. Monthly averages in precipitation and temperature are reported in the mean average. Yearly totals and averages are not reported on the Weather Channel site but with simple mathematics those can be figured. Imagine that, students doing math in social studies or math students doing a real-world geography problem in math class. Climatic data can also be obtained from National Weather Service web site.
In a climograph, a bar graph plots the monthly precipitation while temperature is plotted with a line graph. Locations that have major swings in temperature have a distinctive “V” if they are in the Southern Hemisphere (Figure 2) and a bell shape if they are in the Northern Hemisphere (Figure 3). The climatic control land-water distribution plays a major role in this temperature swing. Major swings in temperature would indicate that the location is probably not near an ocean and may be in the middle of a continent or a large landmass. Extreme wet or dry seasons or climates can also easily be seen with a climograph.
Having students construct their own climographs from raw climatic data is an excellent way for students to improve their graphing skills and at the same time really examine the climate of a particular location (Ludwig; et al 1991). I use an 8.5 x 11 inch template like the one shown in Figure 4. Students can look up additional information about the site like elevation, the longitude and latitude and maybe even the type of climate. Have students graph locations from a wide range of climatic zones and then let the students display their distinctively different climographs. Students could also point out the locations of their reporting stations on a world map.
Two of the nine climatic controls have been examined thus far--mountain barriers and land-water distribution. More problem solving work can be done when students are familiar with the other seven. One of most obvious controls and one the ancient Greeks were well aware of is latitude or distance from the equator. The general rule of latitude is that the farther from the equator you go, the cooler the temperature. The Greeks thought that this was the main climatic control and about 2000 years ago, a man named Strabo divided the world into three climatic zones—“Torrid, Frigid, and Temperate” (James 1972). While we don’t use Strabo’s labels, we still recognize the low, high, and middle latitude zones. However, latitude alone doesn’t tell the whole story because within Strabo’s “torrid” zone near the equator there are many areas with snow and ice.
The climatic control responsible for snow and ice near the equator is altitude. Examples could be found high in the Andes in South America or on Mt. Kilimanjaro on the continent of Africa. The general rule is the higher the altitude, the cooler the climate will be. More specifically, according to the Normal Lapse Rate, for every 1,000 ft. of altitude the temperature will drop an average of 3.5 degrees (Strahler and Strahler 2000). As an example, let’s say the temperature is 60° in Colorado Springs at approximately 5,000 ft of altitude. What is the temperature on top of Pikes Peak at 14,000 plus ft. just a few miles away? With a change of about 9,000 feet, and cooling at 3.5° per 1,000, it could be a cold 29°.
While altitude and the mountain barriers mentioned earlier are two
different controls, they are related.
As air goes up one side of a mountain it cools causing the moisture in
the air to condense and form clouds.
If these clouds continue to rise up the side of the mountain, molecules
of water in the clouds will get so cold and heavy they will begin to fall in
the form of precipitation—either snow or rain. All of the moisture can be wrung out of the air if the
mountain barrier is tall enough, so that any air going over the top of a
mountain is dry. This dry air can
create a “rain shadow” like the dry side of Kauai or the semi-arid plains of
eastern Colorado and western Kansas in the shadow of the Colorado Rockies.
Mountain barriers can also cause sudden temperature changes. A rising wind going up a mountain cools
even faster than the Normal Lapse Rate.
Due to changes in pressure, a rising wind can cool at 5.5° per thousand
feet in what is known as the Adiabatic Rate (Strahler and Strahler 2000). In addition, according to this same
rate, a descending wind will warm at 5.5° per thousand feet. This descending wind is sometimes
referred to as a “Chinook” wind.
One translation of this Eskimo word Chinook is “snow eater.”(Geer 1996)
The land-water distribution control mentioned in the section on climographs needs further explanation. Land-Water distribution has two parts: marine-modification and continentality. Marine-modification can be explained with an analogy. A big pot of water takes a long time to heat up on the stove. However, once that pot is heated, it will continue to stay warm for a long time even with the fire turned off underneath. Making up over two/thirds of the surface of earth, the oceans on our planet are like that big pot of water. While the temperature of the oceans may vary from one place to another, they tend to remain a fairly constant temperature in a place throughout the year. Places located near those oceans have a much smaller temperature swing than those in the middle of a continent. Take Seattle on Puget Sound of the Pacific Ocean where a cold day in the winter might be 23° and a hot summer day in Seattle might be 87°. Continentality, described briefly in the climograph section, is characterized by extreme sudden swings in temperature and can be extremely cold in the winter and extremely hot in the summer. For example, on that cold day winter day when Seattle was at 23°, a place with the same latitude as Seattle, Bismarck in North Dakota might be experiencing a fairly normal 30 degrees below zero. Conversely when it was a hot 87° in Seattle, it could be 115° in Bismarck. Other places in the middle of continents like Kansas can be extreme. Emporia, Kansas recorded a record low -25° in December of 1989 and had a record high temperature of 112° in July of 1980 (www. weather.com). Students are intrigued to learn that places in Alaska near the coasts can have milder winters than places like Kansas.
Another factor that helps keep the coast of Alaska warm is the climatic control of ocean currents. The warm Japanese current flows north and east across the Pacific into the Gulf of Alaska. Ocean currents that flow away from the equator are considered warm while those flowing towards the equator are considered cold. You may have noticed the difference if you have ever swum in the warm Gulf Stream Current along the coast of Florida, as opposed to swimming in the cold California Current along the West Coast of the United States. The direction that currents move is caused in part by the Coriolis effect which states that any free moving object like air or water tends to turn in a clockwise manner in the Northern Hemisphere and counter clockwise in the Southern Hemisphere (Kendall et al 1974). When you pull the plug on your bathtub, you notice the Coriolis effect by the direction the water swirls into the drain. The general rule regarding the effect that ocean currents have on climate is that warm currents can keep areas in high latitudes warmer than they should be and cold ocean currents can keep areas in low latitudes near the equator cooler than they should be. The warm Gulf Stream keeps the fiords of the Scandinavian Peninsula free of ice and also allows for palm trees on the southern coasts of Ireland and Britain. The cold California Current and the cold Peru Current meet near the Equator and keep the Galapagos Islands much cooler than their tropical, low latitude location would suggest.
The remaining four controls of wind belts, storms, air masses. and the jet stream are considered less permanent because they tend to vary with the seasons. Near and on either side of the equator are the wind belts known as the prevailing Easterly Wind Belt. These easterly winds have also been called the “Trade Winds.” These Easterly Wind Belts near the Equator are also known for their low pressure resulting from lots of evaporation and resulting thunderstorms. It is also in this topical zone that the Earth’s cyclones and hurricanes are formed. These storms are also a climatic control and will be examined shortly. Moving towards the poles in both hemispheres, are the Prevailing Westerly Wind Belts. The air in these belts is generally drier and with higher air pressure than the wet low-pressure zones near the equator. Most of the worlds deserts are in this dry high pressure zone. Most of the continental United States is in the Prevailing Westerly Wind Belt for most of the year. The wind belts do move with the seasons and for a very short time, the extreme southern part of the United States is in the Easterly Wind Belt. The fact that we lie in the westerly wind belt is the reason most of our weather tends to move from west to east across our country. Combining the controls of wind belts and mountain barriers helps explain why much of the western United States has such a dry climate. Moisture laden wind coming off the Pacific Ocean has to cross several mountain ranges which creates large rain shadows as little moisture is able to make it across the many mountain ranges of the West. Early Europeans knew about the wind belts and those coming to the New World sailed south until they caught the trade winds, and then to go back to Europe had to sail north to catch the westerly belt to sail home.
Storms as a climatic control refers to moving low pressure cells that in the Western Hemisphere are referred to as hurricanes. They are called typhoons in Asia and “willy willies” down under in Australia. They can be considered climate because with regularity they strike in certain areas and greatly contribute to the annual rainfall. The Caribbean Islands can expect several hurricanes a year but mainly during the months from May to November (Strahler and Strahler 2000).
Air masses are simply big blobs of air that take on characteristics of where they are formed but then tend to move somewhere else. The last of the nine climatic controls is the jet stream, and it is often responsible for the movement or sometimes lack of movement of air masses. The Jet Stream is a high altitude and high velocity wind that moves from west to east and in a serpentine fashion across planet earth. There are in fact several jet streams and the United States often has at least two jet streams affecting our weather and climate. Quite often during the winter months, a jet stream will pick up a cold air mass out of the arctic and blast the Midwest or Great Lakes region with cold air. Sometimes the jet stream will block air masses from reaching the Midwest and a mild spell occurs.
With a list of all nine controls (figure 6) and an atlas for reference, students are asked to analyze all data and try to identify which control or combination of controls could cause such extreme conditions.
This could be done through whole class discussion or in small groups. In the first section subtitled “Bring on the lemonade,” Al’Aziziya in Libya is in the dry high pressure Westerly Wind Belt with lots of sunshine. It is also in a rain shadow of the Atlas Mountains, and on the eastern side of the Sahara Desert with westerly winds blowing hot air in from the desert. The major climatic controls for Dallol in Ethiopia are low latitude and low altitude. In the second section subtitled “Brrrr,” the major climatic controls causing these extremely cold temperatures in Antarctica are very high latitude, land-water distribution in the form of continentality, and also high altitude as there are mountains on the continent of Antarctica. It might be interesting to have students figure the range of temperature on planet earth by figuring the difference between a record high of 136° in Libya and a record low of -126°in Antarctica. We tend to think of other planets as having weird temperatures, but even on planet earth the temperature varies by more than 250°.
In the section on temperature change several different controls are responsible for the different sites. Olekminsk in Russia’s Siberia is situated in the middle of the largest landmass on earth and is subject to extreme continentality of the land-water distribution control. Browning, Montana is also subject to continentality but the one-day change was brought about by a cold air mass on the jet stream. The two-minute jump in Spearfish, South Dakota, is a result of a Chinook wind that came down out of the Black Hills.
The record rainfall in Cherrapunji is the result of a monsoon rain that rolls onto the Indian Peninsula at about the same time each year. The warm, wet air mass building over the Indian Ocean moves with the change of seasons and the deluge begins-- sometimes terrible flooding in India and Bangladesh. The one-day record at La Reunion in the Indian Ocean was the result of a typhoon. The yearly average rainfall at Kauai is caused by mountain barriers and was explained earlier. The tropical moist air around Java with its low latitude results in a thunderstorm almost every day of the year. The record snowfall in Washington State is a result of the moisture- laden air of the Pacific, driven by the prevailing westerly winds, rising up into the Cascade Mountain Range creating very wet conditions on the western slope of this mountain barrier.
Probably one of the strangest places on Earth regarding climate is the “dust bowl” of Colima in Chile. The prevailing easterly winds blow off the Atlantic and rise up to the Andes Mountains on the South American continent. The Andes act as a mountain barrier that wrings all of the moisture out of the air and creates the Amazon River. However, no moisture makes it over the Andes to Colima and this narrow strip of desert along the West Coast of South America is a great example of a rain shadow.
Another problem solving and climate activity that my students have enjoyed is The Gang of Fourteen: A Game for Learning about World Climates (Montgomery et al1988). This activity has students analyze climatic data to find the whereabouts of members of a terrorist gang and ultimately where a bomb is hidden. “The Gang” makes an excellent culminating activity to a unit on climate.
The Earth is a fascinating place with diverse conditions. Through the study of climate, many causes of that diversity can be better understood. Inquiry methods and problem solving seem to be an important focus in schools these days. Climate is an excellent field of study for inquiry as climatic data is easily acquired and can be analyzed or manipulated into climographs. Climate also facilitates integration of disciplines as geography can provide for real world math problems as well as connections to the other hard sciences. As educators, we can give students a powerful and important tool to use for a lifetime by teaching them about climate.