Unit 2 World Climate Patterns

Transcription

1 Unit 2 World Climate Patterns Weather the day to day or short term conditions of the atmosphere. Weather includes variables such as temperature, precipitation, humidity, cloud cover, wind, and air pressure. Climate Also includes key weather variables of temperature, moisture and air movement but only in terms of their general patterns in a region over the course of many decades. The main factors that affect both weather and climate are: 1. Temperature 2. Moisture 3. Air Movement The Earth sun relationship - Sun provides light and heat for all the earth and for all other bodies in our solar system. - Sun characteristics - Distance from the earth: km - Size: 109 time the Earth s diameter - Temperature: degrees at core Outcome 2.1: Distinguish between the terms rotation and revolution. Rotation the earth rotate on its axis once every 24 hours. (spinning affect) Revolution- The earth revolves around the sun on it orbit once every 365 days. ( travelling around) Outcome 2.2 Explain how cloud cover influences the range of temperature from day to night. Only about one half of the suns solar radiation reaches the earth s surface. Cloud cover influences the range of temperature from day to night. Because on clear, cloudless days, radiation both from the sun to the earth and from the earth surface back to space is at its highest.

2 As a result, heating from the sun is strongest during the day, and heat is lost from the earth surface more rapidly at night. This is why temperature ranges between day and night tend to be the greatest on a clear and cloudless day. Example deserts On the other hand, on cloudy days, clouds block out the sunlight, limiting the heating of air. Cloud cover at night holds in heat, blocking radiation from escaping the earth s atmosphere and limiting the cooling of air. Temperature range is more limited between night and day. Outcome 2.3 Define the terms equinox and solstice. Equinox- having day and night of equal length. The sun is directly overhead at 12 noon on the equator. Happens on (September 21 autumnal equinox) and (March 21 vernal equinox) Solstice- the time (June 21 or December 22) at which the overhead sun is furthest from the equator and appears to stand still before returning towards the equator. The longest day occurs at the summer solstice, the shortest day at the winter solstice. Outcome 2.4 Explain how changes in the seasons, in the northern and southern hemisphere, relate to the earth s revolution around the sun. As the earth revolves around the sun, different parts of the earth are inclined towards or away from the sun. Thus, in the winter season, in the northern hemisphere our days are short because we are titled away from the sun. The opposite is true during the northern hemisphere summers as our days are long because we are titled towards the sun. Outcome 2.5 -Describe the factors that account for difference in length of day as seasons change. Seasons are directly related to the Earth s revolution around the sun because of the tilt of the axis, different places on the Earth s surface experience different lengths of day and night on any one day. Also, the intensity of the sun s rays varies depending on the amount of atmosphere the rays pass through- when the sun is overhead, the sun s rays are most intense. Because earth revolves around the sun the length of day and night and the intensity of the sun s rays change gradually because there is a gradual change in the way each hemisphere leans towards or away from the sun. As earth revolves around the sun, the seasons are characterized by gradual transitions from on to another as each hemisphere receives more or less sunlight.

3 -Summer days are longer then winter nights because we are titled towards the sun for direct rays, and longer period of time. (northern hemisphere) Outcome 2.6- Describe the factors that account for difference in temperature as seasons change. Two factors account for the difference in daylight hours and the amount of heat received during each season: - Tilt of the earth on its axis influencing where the direct rays of the sun are shining during that season. (shorter the distance, the higher the temperature). - Curvature or shape of the earth influencing the angle of the rays. (angled rays have less intense heat than direct rays). Outcome 2.7- Explain how greenhouse effect moderates climate. Often mistaken and misunderstood for global warming. Greenhouse is a good thing, it moderates our temperature. Plants without atmospheres have an extreme variation in temperature between day and night. Without an atmosphere plants have nothing to hold heat in. On earth the atmosphere reflects almost 50% of radiant energy. Here on earth the atmosphere acts like glass on a greenhouse keeping in much of the heat. Greenhouse gases include: - Carbon dioxide - nitrous oxide - methane - CFC s (chlorofluorocarbons) These gases occur in the atmosphere in minute (very small) amounts, and influence the heat balance of the atmosphere and the earth s surface. As these gases increase, they cause a warming effect (global warming) of the earth similar to that of the glass in a greenhouse. The ozone layer is a naturally produced life protecting shield 15 miles above the earth surface. In the stratosphere, it acts as an umbrella filtering the suns most dangerous ultraviolet rays from the earth, protecting humanity and nature from potentially disastrous environmental problems.

4 Outcome 2.8 and 2.9 Generalize that temperatures tend to decrease from low to high latitudes. Be careful about how you talk about this. If we say the further south one goes the warmer it gets we would be wrong. Once we went far enough south to go past the equator the temperatures would start getting colder again. The best way to word is as Latitude increases temperature decreases Why the poles are colder than the tropics - The poles of the earth are colder that the equatorial regions of the earth because of the earth s spherical shape. - Light rays reaching earth from the sun are almost exactly parallel. Because of the spherical shape of the earth the equator would receive the most intense direct solar radiation and the poles which are further away world receive less solar radiation spread over a larger surface area. The sun s rays would strike the earth away from the equator more on an angle. Outcome 2.11 Define prevailing winds. Prevailing winds- winds that are the most frequent in a region. Convention current patterns are complicated by 2 factors: 1. Earth s rotation 2. The uneven distribution of land and water over the earth s surface. Thus, the movement of air from the equator to the polar regions is divided into 3 different convection cell for each hemisphere. These cells develop between: a. 0 degrees (equator) and 23.5 degrees latitude called trade winds b degrees and 66.5 degrees latitude called westerlies c degrees latitude to the poles called polar easterlies. The convection cells create high and low pressure belts around the earth and wind blows between them. Since convection cells are constant, the patterns of wind blowing from high to low pressure areas are also constant and predictable. These patterns are called prevailing winds.

5 Two factors that can change prevailing winds are: 1. Variations in the earth s surface remain constant throughout the year. 2. The earth s position relative to the sun varies depending on the season. Outcome Describe conditions that result in land breezes and sea breezes. Sea breeze Occurs during the day when the land is heated by the sun. Air above the land heats up and becomes less dense. This warm air raises and moves over the ocean where it cools down and becomes denser forcing the air below to move inland. Thus creating a sea breeze. Land Breeze- Is the opposite of a sea breeze. Land breezes occur at night. During the night the land cools much quicker than the ocean. Air above the ocean is heated and rises. This warm air moves on shore over land where it cools, forcing the air below to move out to the water. Thus, creating a land breeze. Outcome State the impact of the coriolis effect on wind direction. Moving air on or above the earth s surface will drift sideways due to the earth s rotation. -Northern Hemisphere objects or fluids moving horizontally tend to deflect to the right. - Southern Hemisphere objects or fluids moving horizontally tend to deflect to the left Infer how wind systems relate to major pressure belts Refer to handout Explain how wind systems and temperature are related. a) What time of year it is b) type of wind c) Land and water

6 What time of year depends on how much sunlight a particular latitude receives At spring and fall equinoxes, the sun shines directly over the equator. At other times of the year because of the earth s tilt and revolution it shines over a latitude between the topic of cancer and tropic of Capricorn Wind system shift as the location that receives direct overhead sunlight. The pattern of wind systems during January and July are different Define windward, Leeward, and rain shadow. Windward- the side of a mountain facing the wind. Leeward The side of a mountain sheltered from the wind. Rain shadow An area of relatively low precipitation to the leeward side of uplands Explain how the types of rainfall (ie. Orgoraphic/relief, frontal/cyclonic, and convectional) is related to the nature of location. Relief Rainfall Moisture laden air blows off the sea; it is forced up by mountains (high relief); air cools at higher altitudes; cool air holds less moisture; clouds condense and rain falls; most rain falls on the windward side of the relief; leeward side is often in a dry rain shadow because the moisture has all been lost. Frontal Rainfall Warm Moisture laden air meets cold air; warm air is less dense & is forced up over the cooler, more dense air; warm Moisture laden air cools at higher altitude; cool air holds less moisture; clouds condense and rain falls.

7 Convectional Rainfall Usually occurs in hot areas like tropics or continental summer; sun heats the earth causing large amounts of water to evaporate; hot air rises forming convection currents (hence the name); warm moisture-laden air cools at higher altitude; cool air holds less moisture; consequently clouds condense and rain falls Explain how wind systems and precipitation are related. - Wind has to be moist or it will never result in condensation or precipitation. - Warm moist air rises and will cool resulting in condensation and precipitation. Example: Summer in St. George s, the wind over the water is cool. So when it reaches land it will hold more moisture resulting in dryer conditions. Winter- the water is warmer than the land so the wind holds more moisture and when it reaches the land it cools and can no longer hold as much moisture causing snowfall. Outcome 2.19 Define the term ocean current. Ocean current- a permanent or semi-permanent horizontal movement of unusually cold or warm surface water of oceans, to a depth of about 100 m. Outcome Analyze how ocean currents can create different climatic conditions for two locations on the same latitude. Equatorial currents warmer and originate at or near the equator. There are north equatorial currents and south equatorial currents which are north and south of the equator. Polar currents that originate from the north and south poles which are cold currents. Depending on the type of current flowing nearby, two cities on the same latitude can experience variations in temperatures. Chile and Brazil are both in South America near the 23 degree latitude marker, however, temperatures are different. Chile s temperature is regulated by the Humboldt (Peru) current which is cold water current. Brazil s temperature is regulated by Brazil current which is warm water current.

8 Outcome 2.21 Define temperature range Temperature range- the range between the highest and lowest average annual temperature of a region. Example: -5 to + 22 temperature range would equal to + 33 Temperature range would equal 28 Outcome 2.22 Analyze the relationship between range in temperature and distance from the ocean. Continental vs. Maritime Climates As distance form the ocean increases, annual temperature range increases. Continental climates experience greater extremes of temperature than coastal climates at the same latitude. The plains region of Saskatchewan, for example, experience a continental climate. The winter temperatures are very cold. The summer temperatures are fairly hot. It is interesting to note that summer temperatures in Central Labrador are often higher than summer temperatures in the island portion of the province. Coastal Newfoundland would experience a Maritime climate. The winter temperatures would be very mild. The summer temperatures would be warm but not hot. Outcome 2.23 Define monsoon Monsoon From Arabic for 'seasonal wind'; a sudden wet season in the tropics. Outcome 2.24 Explain why winter and summer monsoons occur. India s Winter Monsoon Continental Asia cools & high atmospheric pressure results; wind blows southward towards the low over Indian ocean; very little rain or dry season results because the wind is blowing over dry land and does not pick up water. India s Summer monsoon Continental Asia heats up & low atmospheric pressure results; wind blows northward towards the low over India; tremendous rains result because the wind is blowing over the warm Indian Ocean

9 Outcome 2.25 Describe the relationship between seasonal level of precipitation and distance from the ocean. The range will be smaller (less precipitation) the further you move inland. Outcome 2.26 Define elevation. Elevation the distance above sea level. Outcome 2.27 Describe the relationship between the elevation of a point and its temperature and precipitation. As you go up in elevation eth temperature decreases. Typically, for every 300m increase in elevation the temperature decreases by 2 degrees. For 100 m of dry air, decreases 1 degrees For 100m of moist air, decreases 0.6 degrees Remember- the windward vs. leeward side of the mountain. When it comes to precipitation: elevation increases, precipitation increases on the windward side. Outcome 2.28 Analyze the relationship between temperature and precipitation of a point and its location relative to a mountain system. Refer back to outcome 2.16

10 Outcome 2.30 Tropical Climates All Tropical Climates have average temperatures over 18oC every day due to low latitude & warm ocean currents & prevailing winds. You will notice on the climate graphs below that the line indicating temperature is fairly flat right around 20oC. Viewing figure 5.1 on page 75 of your text you can see that almost all of the tropical wet and the tropical wet&dry climates are located between the tropic of cancer and the tropic of capricorn. o Tropical Wet sub region ; heavy rain all year due to hot temp & resulting convectional rain. o Tropical wet& dry sub region; very heavy summer rain & very dry winter due to seasonal shift in prevailing winds. (monsoon regions) Dry Climates All Dry climates receive less than 500mm precipitation annually. o The region has more evaporation than precipitation leaving it in a water deficit. o There is little vegetation & it is often windy o Climate graphs of arid and semi-arid regions are difficult to distinguish from each other but easy to distinguish from all other climates because of the low precipitation bars. Arid or desert dry climates occur mostly between 10-30oN & 10-30oS and receive mm rain annually. Semi-arid steppe dry climates are really transition Zones between desert & Forest. They receive mm rain annually which is often enough to support grasses but not forests. Activity Assigned Readings "Using Climate Data" Pages "Tropical climates" on pages Assigned Activities Complete question #1 on page 74 of your text. Temperate Climates A review of figure 5.1 on page 75 of your text reveals that temperate mild climates occur in both hemispheres while the temperate cold climates only occur in the northern Hemisphere. The distinguishing feature on a climograph is the curved temperature line. Temperate Mild Winter o Temperature varies with seasons o Mid Latitudes o Mild winter o Summer temperatures vary but winters are warmer than 3ºC

11 Temperate cold Winter o Temperature varies with seasons o Mid-high Latitudes o cold winters Summer temperatures vary but winters are colder than 3ºC Polar Climates Polar climates are distinguished by their extremely low winter temperatures and low summer temperatures. o Tundra: summer temperature never above 10oC o Ice Caps: summer's average monthly temperature is never above 0oC Highland Climates These climates are only characterized by their elevation and decreased temperature because of that. However the climates vary with latitude of the mountain, closeness to the ocean etc. Some alpine regions can be like the tundra and the ice cap of a mountain is like the polar ice caps. Climatic Conditions & Human Activity Positive Influences of Climate Good tourist industry in subtropics like Florida; sports are affected: golf summer, hockey winter; religious tradition of Christmas strongly associated with winter conditions; clothes fashion changes with the season; school closed during summer season in temperate zone. Negative Influences of Climate Transportation is affected; winter tires in temperate zone; snow clearing budgets can be high; school closed during winter storms in temperate zone. Case Studies To get an idea of the variety of ways that weather and climate can negatively and positively influence human activity you can peruse the following cases. o Hurricanes tornados and tropical storms occur in specific regions on a regular basis protection of property, evacuation plans, family safety plans, cleanup budgets and insurance are all impacts of hurricanes; o hurricane Damage Protection in Florida p.89; o tornado Kills 400 in Bangladesh p. 87; o seasonal Activity is affected by climate. Farming, fishing and tourism are scheduled around the seasons; o growing coffee in Brazil.

12 Global Warming Global warming is the gradual increase of the earth's average temperature since the industrial revolution. It is a fact that the earth's average temperature is increasing. The negative effects associated with global warming are also factual. However, it is important to note that some scientists dispute the fact that it is due to human activity. Some scientists believe the recent increase in temperature is a part of the normal rhythm s of change in the earth's atmosphere. Global warming vs. Greenhouse effect It is also important to draw a distinction between global warming and the greenhouse effect. The greenhouse effect is a good thing and moderates our temperatures here on earth. It operates by specific gasses like carbon dioxide and methane. Global warming is due to the human activity that has increased the level of these greenhouse gasses and consequently increased the the earth's temperature. Human Impact on Greenhouse Gasses It is believed that humans have changed the balance of greenhouse gasses in the atmosphere in two ways: 1. Increased carbon dioxide emissions due to the combustion of fossil fuels. Coal, Gasoline, Furnace oil, Propane, diesel, and jet fuel are all examples of fossil fuels we burn and result in carbon dioxide emissions. 2. Cutting forests which results in fewer trees. Trees and all plants recycle carbon dioxide into carbohydrates consequently reducing atmospheric carbon dioxide. When these trees are removed the level of carbon dioxide in the atmosphere increases. Global warming & Climate change Obviously global warming results in temperature changes. However that temperature change affects precipitation as well. In some areas it increases precipitation and in other areas it reduces precipitation.