1. Chapter 16: Weather & Chapter 17: Climate

2. 16.1 What is Weather? The weather affects several aspects of one’s life… Clothing Transportation Activities Weather refers to the present state of the atmosphere and describes current conditions. Factors that determine the weather are: Air Pressure Wind Temperature Amount of Moisture in Air (Humidity)

3. 16.1 What is Weather? The water cycle forms the basis of our weather! Interaction of air, water, and sun causes our weather! Humidity… Water molecules fit into spaces between molecules of air in the atmosphere. The amount of water vapor held in the air is called humidity! Varies from day-to-day due to the temperature and air changing. Cold winter days = low humidity, feels crisp and dry Hot summer days = high humidity, feels warm and sticky

4. 16.1 What is Weather? Relative Humidity = measure of the amount of water vapor that air is holding compared to the amount it can hold at a specific temperature. When air holds as much moisture as it can at a certain temperature, it is said to be saturated. Measure it with a psychrometer (difference in wet and dry bulbs) Ex.) Figure 16-3 (pg. 484) The temperature at which air is saturated and condensation takes place is the dew point. Changes with the amount of water found in the air. Ex.) Dew

5. Let’s due the math up here: What is the amount of water vapor in air, when the air is only 80% saturated? We will do the math together Pg. 483 (Do the math practice)

6. 16.1 What is Weather? Cloud Formation/Classification… Clouds form as warm air is forced upward, expands, and cools Relative humidity reaches 100% & the air is saturated. Water vapor begins to condense in tiny drops around nuclei, small particles of dust, salt, and smoke in the atmosphere. Drops are so small that they become suspended in the air and form clouds!

7. All clouds are classified on height and shape 1.) Stratus – Form layers (or smooth) even sheets in the sky. Form when layers of air cool below their dew point temperatures, these clouds appear. Form at low altitudes, associated with fair weather/precipitation

8. Continued: 2.) Cumulus – Masses of puffy, white clouds, often with flat bases. Ex.) “Cauliflower Clouds”. Form when air currents rise, can tower to great heights Associated with fair weather and thunderstorms

9. Continued: 3.) Cirrus – Fibrous (or curly), high, thin, white, and feathery clouds containing ice crystals. Associated with fair weather, but may indicate approaching storms.

10. 16.1 What is Weather? Height… 1.) Cirro -… Describes high clouds; base starting above 6000m 2.) Alto -… Describes middle elevation clouds; base is between 2000 – 6000 m

11. Strato -… Describes low elevation clouds Some clouds combine the altitude prefix with the term stratus or cumulus Ex.) Cirrostratus = High clouds, look like fine veils, made of ice crystals, create “halos” around the moon/sun

12. 16.1 What is Weather? Rain Capacity: Nimbus clouds Dark clouds associated with precipitation Cumulonimbus cloud: ( nimbus cloud towers a cumulus) Sudden, gigantic thunderstorms can be unleashed from them! Nimbostratus clouds bring long, steady rain. They often have streaks that extend to the ground

13. 16.1 What is Weather? Precipitation… Water falling from clouds is called precipitation. 4 types: Rain = Drops of water falling in temperatures above freezing Snow = Forms when air temperature is so cold that water vapor changes directly to a solid Sleet = Forms when snow passes through a layer of warm air, melts, and then refreezes near the ground. Hail = Forms in cumulonimbus clouds of a thunderstorm when drops of water freeze in layers around a small nucleus of ice. Grow larger as they’re tossed up and down by rising and falling convection currents

14. 16.2 Weather Patterns Weather is constantly changing due to the constant movement of air and moisture in the atmosphere. Air Masses… An air mass is a large body of water that has the same properties as the surface over which it develops. Develops over Land = Dry Air Mass Develops over Water = Wet Air Mass Develops in Tropics = Warmer Air Mass Develops in Arctic = Cold Air Mass

15. 16.2 Weather Patterns Pressure Systems… Variation in atmospheric pressure affects the weather. High Pressure = Descending Air, Difficult for Clouds to Form, Brings Good Weather Low Pressure = Rising Air, Easy for Clouds to Form, Brings Bad Weather Fronts… Low pressure systems form along boundaries of air masses; this boundary is called a front. Storms/Precipitation occur at these fronts. At a front, air at the surface moves from area of high pressure to area of low pressure.

16. Fronts: Fig. 4 (Pg. 492) Most changes in weather occur at four types of fronts: 1.) warm: warm air advances over cold air 2.) cold: cold air moves towards warm 3.) occluded: 3 air masses, forces warm air from surface 4.) stationary: neither cold air or warm air advances Fronts typically bring a change in temperature and a change in the wind direction.

17. 16.3 Weather Patterns Severe Weather… Includes: Blizzards, Thunderstorms, Tornadoes, and Hurricanes Thunderstorms… Occur when warm, moist air moves upward rapidly, cools, condenses, and forms cumulonimbus clouds that can reach heights of 18,000 km Falling droplets collide with other droplets and grow larger As they fall, they create downdrafts of air that cause strong winds.

18. 16.3 Weather Patterns Thunderstorms Continued… Lightning occurs when a rapid uplift of air builds up electric charges in the clouds Opposites attract ( +  - ) Thunder Occurs from lightning ~30,000 degrees C (5 times the temperature of the sun). Heats quick and cools quick causing molecules to contract back and forth forming sound heard as thunder. Can be extremely detrimental! Large hail stones, high winds, flooding, lightning strikes, etc.

20. 16.3 Weather Patterns Tornadoes… A tornado: violent, whirling wind that moves in a narrow path over land Usually in a direction from southwest to northeast. Most form along a front! In severe thunderstorms, wind occurs at different speeds/heights ( wind shears). Strong updrafts tilt the wind shears to produce a rotation inside the thunderstorm (funnel clouds) Destructive winds can reach up to 500 km/hr, last a few minutes, extremely destructive.

22. 16.3 Weather Patterns Hurricanes… A hurricane is a large, swirling, low pressure system that forms over tropical oceans Similar to a machine that turns heat energy from the ocean into wind. Winds must be at least 120 km/hr to be called a hurricane! Loses power once it reaches land Most hit in the Gulf of Mexico or along the Atlantic Coast.

23. 16.4 Forecasting Weather Weather Observations… A meteorologist studies the weather. Take measurements of temp, air pressure, winds, humidity, and prec. Doppler radar, computers, and instruments attached to balloons are used to gather data. Weather Forecasts… Meteorologists at the National Weather Service (NWS) will issue weather advisories, watches, and/or warnings. Once issued, one should take necessary actions to best prepare for the severe weather (floods, thunderstorms, hurricanes, blizzards, wind chills, etc.) ahead.

24. 16.3 Forecasting Weather Weather Information… NWS obtains its information from meteorologists from around the world They utilize this information to create a map that contains symbols, which is called a station model. Pg. 479 Figure 18 represents a typical station model. In addition to station models, weather maps have lines that indicate atmospheric pressures and temperature. A line that connects points of equal temperature is called an isotherm. (Iso = Same, Therm = Temperature) An isobar is a line drawn to connect points of equal atmospheric pressure.

26. 17.1 What is Climate? Climate is the characteristic weather of a region. Temperatures on Earth range from -89.2 o C to 57.8 o C Climate is determined by averaging the weather over a long period of time (30 yrs.) Temperature Precipitation Air Pressure Humidity Days of Sunshine

27. 17.1 What is Climate? Factors that affect the climate are: Latitude Topography Location of Lakes/Oceans Availability of Moisture Global Wind Patterns Ocean Currents Location of Air Masses

28. 17.1 What is Climate? Latitude & Climate… Amount of solar energy received by certain locations depends on Earth’s tilt Latitudes close to the equator receive the most radiation Tropics = Region between latitudes 23.5 degrees north/south; receive most solar radiation; always hot temperatures Polar Zones = extend from the poles at 66.5 degrees north/south latitudes Temperate Zones = Located between the tropics and polar zones; moderate temperature; where US is located

29. 17.1 What is Climate? Large bodies of water… Warm winters/ cool summers Ex.) Duluth Ocean currents also affect coastal climate Winds blowing from the sea contain more moisture than those blowing from the land. Coasts tend to be wetter, interior tends to be drier

30. 17.1 What is Climate? Mountains… Colder in the mountains than at sea level Side of mountains facing the wind, air rises, cools, and drops its moisture as precipitation. On the other side, the air descends, heats up, and dries out the land. Deserts form in this way. Large Cities… Radiation that strikes cities is absorbed by buildings, streets, and cars Causes a “heat island” effect. Cities can be 10 degrees warmer in the summer than surrounding rural areas!

32. 17.2 Climate Types Climatologists (those who study climates) classify climates based on a system Developed by meteorologist/climatologist Wladimir Köppen. Köppen Climate Types… He divided them into six groups: tropical, mild, dry, continental, polar, and high elevation.

33. 17.2 Climate Types Organism Adaptations… Type of climate determines the type of vegetation present and animals present An adaptation is any structure or behavioral feature that helps an organism survive in its environment Climatic Factors that may limit where an organism can live are: temperature, moisture, and amount of daylight

34. 17.2 Climate Types Structural Adaptations… Some organisms have body structures that enable them to survive in particular climates Fur of mammals insulates them from cold temperatures Cacti’s thick, fleshy stem keeps water inside the plant from evaporating.

35. 17.2 Climate Types (Do Not Write) Behavioral Adaptations… Some organisms display behavioral adaptations that help them survive in certain climates. Rodents and certain other mammals undergo a period of inactivity in winter called hibernation. Bees cluster together during cold temperatures to keep from freezing During hot, sunny days, snakes hide under rocks in the desert to keep cool and search for food at night. Lungfish survive periods of intense heat by going through an inactive state called estivation (burrow into mud and secrete capsules around themselves)

36. 17.3 Climatic Changes Seasons… Weather tends to change with the seasons in temperate zones! Seasons are short-term periods of climate change caused by regular variation in daylight, temperature, and weather patterns. Variations are due to changes in the amount of solar radiation an area receives.

37. 17.3 Climatic Changes Effects of Latitude… Latitudes near equator (tropics), receive constant amount of solar radiation/ only experience dry / rainy seasons. High altitudes (polar zones) experience great differences in temperature and in number of daylight hours.

38. 17.3 Climatic Changes El Niño… This is a climatic event that starts in the tropical Pacific Ocean and sets off changes in the atmosphere. Used to occur every 3-7 years but now occurs more frequently. Pacific Ocean warms along the equator. Ex.) Ocean temperatures increase by 1 to 7 degrees C off the coast of Peru. Sea level rises!

39. 17.3 Climatic Changes Does not directly cause unusual weather Warmer water brings more evaporation Scientists believe it is caused by global warming

40. 17.3 Climatic Changes Climatic Change… Earth’s climate remains fairly constant However Earth’s climate does change

41. 17.3 Climatic Changes In the past 2 million years, glaciers have covered large parts of Earth’s surface. These periods of extensive are called “ice ages”. For last 3 million years, we have alternated with warm periods called interglacial intervals. Most interglacial periods last about 12,000 years.

42. 17.3 Climatic Changes Theories Explaining Major Climatic Changes… Some possible explanations include: Catastrophic Events (meteor impact, volcanic eruptions) Increase in Clouds (Increase in Greenhouse Gases) Movement of Plates in Earth’s Crust Earth’s Movement in Space (it’s tilt in regards to solar radiation) Change in the shape of Earth’s orbit around the Sun (Changes over a 100,000 year cycle)

43. 17.3 Climatic Changes Climatic Changes Today… Greenhouse Effect = Natural heating caused by gases in our atmosphere trapping heat; illustrated in Main Gas involved is Carbon Dioxide (CO 2 ) Not always a bad thing; without it we could not survive (too cold) Global Warming = global temperatures are rising Believed to be caused by increasing greenhouse gases Ice caps will continue to melt Low-lying areas could experience flooding

44. 17-4 How can Global Warming be Slowed? Human Activities / Carbon Dioxide… 1.) Burning of Fossil Fuels Natural Gas, Petroleum, Coal are burned for energy 2.) Removal of Vegetation / Deforestation Deforestation = Mass Removal of Trees Forests being cleared for mining, roads, buildings, grazing cattle, and drilling for oil

45. 17-4 How can Global Warming be Slowed? Ways to Reduce Carbon Dioxide… Conserve Electricity Plant Vegetation Futuristic Ideas to Cool Our Planet… Reforestation = Planting of Trees Wind Farms Solar Energy Small Water Turbine Engines