1. Chapter 25.1 “Factors that Affect Climate”
Modified from many sources & Holt CA Earth Science
by L. Smith

2. Factors That Affect Climate
CLIMATE = The AVERAGE weather conditions over a LONG period of time
CLIMATE = WEATHER

3. Factors That Affect Climate
CLIMATE = most often described by:
AVERAGE TEMPERATURE
and
ANNUAL PRECIPITATION

4. Factors That Affect Climate
I. Latitude
II. Heat Absorption & Release
III. Topography

5. Factors That Affect Climate
I. Latitude
• The sun’s rays strike the equatorial region at a much more direct angle than the poles, making the average temperature at the poles much colder and the average temperature at the equator much warmer.

6. http://www. geogrify. net/GEO1/Lectures/EnergyAtmosphere/SolarEnergy
Latitude
Makes no sense without caption in book
Solar energy striking the Earth’s surface near the poles is less intense than radiation striking the Earth near the equator.

7. Latitude
Makes no sense without caption in book

8. Latitude Global Wind Patterns
Differing amounts of solar energy, and the spinning of the Earth, create different wind patterns at different latitudes .
Makes no sense without caption in book

9. Latitude Global Wind Patterns
Wind patterns at different latitudes then influence precipitation patterns.
Makes no sense without caption in book

10. Factors That Affect Climate
II. Heat Absorption & Release
• Different surfaces heat and cool at different rates creating wind patterns and ocean currents.

11. Heat Absorption & Release
Land vs. Water
The differential heating and cooling of land and water creates winds.
Land heats AND cools faster than water.
Makes no sense without caption in book

12. Heat Absorption & Release
Specific Heat & Evaporation
Specific heat is the amount of energy required to raise the temperature of a substance 1 degree C.
Makes no sense without caption in book

13. Heat Absorption & Release
Specific Heat & Evaporation
Water requires a larger amount of energy to increase temperature than most substances.
Evaporation of water absorbs a lot of energy too (think sweat!).
Makes no sense without caption in book

14. Heat Absorption & Release
Ocean Currents
Ocean currents can have a large influence on air masses over the land
they contact.
Makes no sense without caption in book

15. Heat Absorption & Release
El Niño Southern Oscillation
• El Niño - the name given to the periodic warming of the ocean that occurs in the central and eastern Pacific.
• At irregular intervals of 3-7 years, these warm countercurrents become unusually strong and replace normally cold offshore waters with warm equatorial waters.
Makes no sense without caption in book

16. Heat Absorption & Release
El Niño Southern Oscillation
• A major El Niño episode can cause extreme weather in many parts of the world.
Increase precipitation and landslide activity in southern California and the Southwest
Drought to the northern Rocky
Mountains
Makes no sense without caption in book

17. Heat Absorption & Release
Normal Conditions
Makes no sense without caption in book

18. Heat Absorption & Release
Normal Conditions
Normally, strong trade winds blow from the east along the equator, pushing warm water into the Pacific Ocean.
Makes no sense without caption in book

19. Heat Absorption & Release
El Niño Conditions
Makes no sense without caption in book

20. Heat Absorption & Release
El Niño Conditions
An El Niño condition results from weakened trade winds in the western Pacific Ocean near Indonesia, allowing piled-up warm water to flow toward South America.
Makes no sense without caption in book

21. Heat Absorption & Release
La Niña
• Researchers have come to recognize that when surface temperatures in the eastern Pacific are colder than average, a La Niña event is triggered that has a distinctive set of weather patterns.
Droughts in parts of the South and Southwest from Arizona to Arkansas and Louisiana
Above normal precipitation in the Northwest and the Tennessee Valley area
Makes no sense without caption in book

22. Heat Absorption & Release
Seasonal Winds
Monsoons are the seasonal reversal of wind direction associated with large continents, especially Asia (which affects the Indian sub-continent).
Makes no sense without caption in book

23. Heat Absorption & Release
Monsoons
In summer, the wind blows from sea to land.(wet)
In winter, the wind blows from land to sea.(dry)
Makes no sense without caption in book

24. Monsoon Photos More about monsoons--click here
Across the often-parched Desert Southwest and the adjacent arid lands of northwest Mexico, the intense heat of early summer is typically broken by a welcome and beneficial visitor: rain. Each year, mid- and late-summer downpours play a vital role in dryland farming, ranching, and wildfire control.
These rains aren't ordinary summer showers—they're part of a much broader phenomenon called the North American Monsoon. Lower pictures probably Pakistan?

25. Factors That Affect Climate
III. Topography
• Topographic features such as mountains play an important role in the amount of precipitation that falls over an area.

26. Topography Elevation Elevation is height above sea level
Temperature generally decreases as elevation increases.
Makes no sense without caption in book

27. The Rain Shadow Effect
As humid air on the windward side of the mountain moves up the slopes it cools, condenses, and forms clouds and rain.
By the time the air reaches the leeward side of the mountain, most of the moisture is lost.

28. The Rain Shadow Effect
The dry area on the leeward side of the mountain is called a rain shadow.
RAIN
SHADOW

29. The Rain Shadow Effect Average Annual Precipitation
The Sierra Nevada, like much of California, has a Mediterranean climate of warm, dry summers (driven by high pressure systems off the coast) and cool wet winters (governed primarily by the onshore movement of winter storm fronts down the Pacific Coast). Most precipitation falls between October and April, though the Sierra crest is subject to summer thunderstorms.
Precipitation ranges from less than 10 inches per year on the South Fork of the Kern River to over 80 inches per year in the mountains surrounding the North Fork of the Feather River. As is true for the Pacific Coast in general, precipitation is higher in the northern Sierra than in the southern end of the range. Even though the Sierra crest is over twice as high in the south, maximum precipitation is only half of that at the northern end of the range.
In the higher elevations (above about 5000 ft.), most precipitation occurs as snow (see Average Winter Snow Depth). In the lower elevations, most precipitation occurs as rain. In the lowest part of the foothills adjacent to the Central Valley, snow is extremely rare, and may not occur for decades.
The Sierra Nevada range acts as a giant water trap, wringing all the moisture from the Pacific storms as they move east. This is a boon to California agriculture, since the water from the Sierra flows into the Central Valley, but it also creates a vast rain shadow desert that stretches for five hundred miles to the east.
...

30. The Rain Shadow Effect
The dry area on the leeward side of the mountain is called a rain shadow.
Average Annual Precipitation
The Sierra Nevada, like much of California, has a Mediterranean climate of warm, dry summers (driven by high pressure systems off the coast) and cool wet winters (governed primarily by the onshore movement of winter storm fronts down the Pacific Coast). Most precipitation falls between October and April, though the Sierra crest is subject to summer thunderstorms.
Precipitation ranges from less than 10 inches per year on the South Fork of the Kern River to over 80 inches per year in the mountains surrounding the North Fork of the Feather River. As is true for the Pacific Coast in general, precipitation is higher in the northern Sierra than in the southern end of the range. Even though the Sierra crest is over twice as high in the south, maximum precipitation is only half of that at the northern end of the range.
In the higher elevations (above about 5000 ft.), most precipitation occurs as snow (see Average Winter Snow Depth). In the lower elevations, most precipitation occurs as rain. In the lowest part of the foothills adjacent to the Central Valley, snow is extremely rare, and may not occur for decades.
The Sierra Nevada range acts as a giant water trap, wringing all the moisture from the Pacific storms as they move east. This is a boon to California agriculture, since the water from the Sierra flows into the Central Valley, but it also creates a vast rain shadow desert that stretches for five hundred miles to the east.

31. Climate Data for Two Cities
This climate graph shows data for two cities, both located in Arizona. Phoenix has an elevation of 338 m and Flagstaff has an elevation of 2134 m.
How does the elevation affect the annual temperature and precipitation?
What causes this difference to occur?

32. Other Factors That Affect Climate
IV. Bodies of Water
• Large bodies of water, such as lakes and oceans, alter the climate of an area.
Places downwind of a large body of water generally have cooler summers and milder winters than places of the same latitude that are further inland.

33. Other Factors That Affect Climate
IV. Bodies of Water
• Coastal areas (or areas near large lakes like the Great Lakes) generally have more precipitation than inland areas.

34. Other Factors That Affect Climate
V. Atmospheric Circulation
• Global winds are another factor that influences climate because they distribute heat and moisture around Earth.

35. Other Factors That Affect Climate
V. Atmospheric Circulation
• Low-pressure zones at the equator and in the sub-polar regions form clouds that drop much more annual precipitation in the form or rain or snow depending on the average temperatures of the area.

36. Other Factors That Affect Climate
V. Atmospheric Circulation
Notice the cloud cover over the equator (equatorial low) and clear skies over the tropics (subtropical highs.)

37. Other Factors That Affect Climate
VI. Vegetation
• Vegetation can affect both temperature and precipitation patterns in an area by influencing how much of the Sun’s energy is absorbed and how quickly this energy is released.

38. Other Factors That Affect Climate
VI. Vegetation
Plants release water vapor through their leaves into the air via transpiration.
Vegetation also releases particles that act as cloud seeds and increase precipitation.