1. The Sun makes our Weather and Shapes our Climate!
The sun is really important to mountain weather because the heating and cooling of the Earth makes weather happen!
To learn more about the sun click here
What is our atmosphere made of? How high does our atmosphere go? Click here to learn more.
Photo from Solar Voyager:

2. Why do we have night and day?
Which side of the planet is in daylight now? (Click here to find out)
Where would the sun be in this picture? (Click here to find out)
North Pole
South Pole
Image:

3. Why do we have night and day?
The left side of the picture is lighter than the right side. The sun must be shining on the left side. Once the earth spins around, the other side of the earth will be lit. The side which is lit is in daylight. The dark side does not have sunshine lighting it up so it is night.
The sun is located on the left side of the picture.
North Pole
South Pole
Image:

4. Areas with More Direct Sunshine
Solar rays, or energy from the sun (yellow lines) eventually reaches the earth. The equator (the redline), receives more sunlight in a small area. This sunlight heats the equatorial region.
The solar rays at the top of the picture which reach North America are spread out over a larger area.
Since the earth is tilted on an axis, and the axis relative to the sun changes during the seasons, sometimes the northern part of the hemisphere gets more sunlight in a small area and sometimes it gets less.

5. Northern Hemisphere Seasons
Why do we have the seasons?
The earth revolves, or makes one trip around the sun every year. Since the earth is tilted on its axis, during different parts of the year, different sections of the earth get more direct sunlight.
Winter
Spring
Summer
Fall
Northern Hemisphere Seasons
Winter
Seasons-label
Image Modified From:

6. Sun’s Rays Reach Earth
The sun’s rays heat the ground. Once the ground is warmed, that energy is moved into the air.
Here are some ways energy is moved from the earth and through our atmosphere:
Convection:
Radiation:
Conduction:

7. What happens to warm air?
Warm air rises! In the summer, the sun’s rays can warm the ground enough that the air near the surface will be much warmer than the surrounding air.
To learn more about rising air, click here: Website of cool air and warm air moving with circulation
Make this image more clear
Whiteman (2000)

8. How do Clouds form?
This warmer air rises higher up into the atmosphere until it has cooled off to the same temperature as the surrounding air. If there is enough moisture in the air and the temperature has cooled down enough, the water vapor in the air will turn into liquid (cloud droplets) or solid ice crystals and will form a cloud.
Lis Cohen

9. US Topography
This is a map of the topography (elevations) of the United States. The highest peaks are white and the lower valleys are light green. The topography of the earth effects the weather and climate across the country.

10. Whiteman (2000), from Water and Climate Center, Portland, OR.
US Precipitation
Compare this picture which shows the average precipitation across the country with the US topography picture. Notice that the highest values of precipitation are often found in the mountain ranges.
Key
Red-lowest
Yellow-low
Green-Middle
Blue-High
Purple-Highest
Make a precipitation key that is better.
Whiteman (2000), from Water and Climate Center, Portland, OR.

11. Storm Track Determines Water Content of Snow
Most storms in Utah are born over the Pacific Ocean.
Move with the subtropical jet stream or the polar jet stream
Storms move over the Sierra Nevada Mountains and precipitate out some of the moisture in the clouds.

12. Western Mountain Ranges
This map shows the mountain ranges in the west. Storms often travel from the Pacific Ocean over many mountain ranges before the storms reach the Wasatch Range in Utah.
Whiteman (2000)

13. Why does the Wasatch get Powdery Snow? (Before storms reach Utah)
The Sierra Nevada Mountains of California and Nevada and the Cascade Range of Oregon and Washington get most of the precipitation from the Pacific storms.
Because much of the Pacific precipitation is intercepted by the Sierras, the prevailing westerly air currents are relatively dry upon reaching Utah.
Lis Cohen

14. 3-D View of the Wasatch

15. Mountain Precipitation
As air is lifted by the mountain, water vapor can condense into a cloud. There are a couple of processes that change these clouds droplets into much bigger rain droplets. Precipitation can happen if the rain droplets get too heavy. These raindrops then fall to the ground as rain!
Once the air makes it over the mountain, it sinks and warms.
Since the air on the other side has less moisture and the air is sinking, clouds are not likely to form. This leaves the back side of the mountains often dry and desert-like.
Orographic Lift classroom activity:
Find source

16. Sometimes Mountains Create Warm Winds

17. Winds and Mountain Range Shape
The direction of the winds relative to the shape of the mountain range will affect the way that winds move over the mountains. The best way to lift the air is to have the winds move perpendicular to the mountain range. From which direction do the winds travel in Salt Lake City (click here to find out)? How are our mountains shaped (click here to find out)?
Whiteman (2000)

18. Utah’s daily wind cycle (mountain and valley breezes)
This is a movie of how the winds change through the day. (Add Wasatch Winds movie saved on CD)
Click here to watch the wind barbs change direction throughout the day:

19. Mountain Range Shape and Winds in Utah
From what direction do the winds most often blow in Salt Lake City?
West/Northwest most of the time…. Therefore where would you find wettest and driest locations?
Click here to find out more about Salt Lake’s climate. Link to climate slide.
Color scheme and topography
Colors show elevation changes

20. Why the Wasatch has Powdery Snow (When Storms Reach the Salt Lake)
Before storms reach the Wasatch, they sometimes move over the Great Salt Lake. Since the salt lake is so salty, it never completely freezes. So in winter, the Great Salt Lake can add moisture to the air which creates more water droplets and ice crystals in clouds which can help create “lake effect snow.”

21. Why the Wasatch has Powdery Snow (Mountains lifting air)
Once the storms reach the mountains air is lifted!
Link here to Mountain Precipitation Slide.
The dry air of the Wasatch makes the snow have more air and less water in it, so the snow is fluffy.
In the Sierra Mountains, one inch of liquid water can make 10 inches of snow, whereas in the Wasatch Mountains, one inch of liquid water can become 20 inches of snow!

22. The high Mountains near Salt Lake City get much more snow than the Valley Floor

23. Mountain Warming and Cooling
Why is it cold on mountain tops? Do mountain tops ever get warmer than air that is lower down?
To listen to the audio portion click here.
Lis Cohen

24. During the Day…..
During the day, the sun heats the ground and the ground heats the air. This warm thin layer of air on the mountain slopes rises up the mountain side creating an “Upslope Flow.”
WARM AIR
UPSLOPE FLOW
Image: me

25. At Night…..
At night, the sun no longer shines on the mountainside and the air on the mountain slopes begins to cool down. This cool air slides down the mountain slope and is called the “down slope flow or drainage flow.”
COOL AIR
DOWN SLOPE FLOW

26. Mountain waves
How can the mountains change the way air flows over mountains?
Air can form waves in the atmosphere and small spinning circles of air, called eddies.

27. Mountain Winds can be dangerous to Airplanes
Click on COMET Mountain Waves Module

28. What is there to know about Mountain Meteorology?
There are still things to be learned about mountain waves so researchers are still engaging in projects and experiments to better understand mountain waves.
Picture: Sierra Waves project 1950s
There are still things to be learned about mountain waves so researchers are still engaging in projects and experiments to better understand mountain waves. Picture: Sierra Waves project 1950s

29. Mountain Wave Indicators
Lenticular clouds can develop when air moves quickly over the top of mountains. Standing waves, like water flowing over a rock in rapids, can develop which can be dangerous for airplanes. Click here to learn more
Definition of lenticular clouds
NCAR/UCAR/NSF

30. Mountains Channeling Winds
Sometimes mountains channel the winds so they move very quickly through a small space. This movement is similar to how water moves quickly out the spout of a hose if you put your finger over part of the spout.
Whiteman (2000)

31. Winds Shaping Snow
Winds can move snow from one side of the slope to another and can build giant cornices as shown in the figure. These cornices can be very dangerous to walk on. Figure a shows where this cornice might break. If these cornices break, you can trigger an avalanche.
Whiteman (2000)

32. Winds and Plants
Strong winds can affect the trees and plants. Look for signs of winds along the mountains and in the valley. Which way do you think the winds might be blowing?
In addition to wind, water, sunlight and plant species can affect tree growth.
Whiteman (2000)

33. Can air be warmer at the top of a mountain?
Sometimes storms with cold air move up to a mountain and the cold air does not make it all the way across. The cold air, since it is more dense, can easily remain in what is called a cold pool (click here to link to Jenny’s stuff).
Whiteman (2000)

34. Mountain Climates
To learn more about climates and biology click here (for older students)

35. Mountain Climates and Plants

36. Mountain Climates and Plants

37. Activities related to mountains and climate

38. Utah Climate Info
Name ___________________________________________________
1. What is Utah's highest temperature?
2. What is Utah's coldest temperature?
3. What is the average temperature in Salt Lake City for July?
4. What is the average temperature in your city for January?
5. What is the 5 day forecast along the Wasatch Front?
6. What is today's forecast for Salt Lake City?
7. What types of severe weather are found in Utah?
8. Write some facts about lightning or tornadoes.
9. Where is it the coldest today?
Map -
Places -
10. Where is it the hottest today?
Other climate data:

39. Finding out about Utah’s Weather
Wild Weather
Five Day Forecast

40. Glossary
Precipitation- rain, hail, sleet or snow.
Topography- characteristics of land in terms of elevation, slope, and orientation
Orographic- average height of the land
Orographic lift- air lifted as it travels over mountains
Perpendicular- at a 90 degree angle (see diagram)
Axis- an imaginary line that an object rotates (or spins) around
mountain ranges- a group of mountains
Water vapor- water as a gas (this gas is invisible)
Condenses- the phase change of a gas turning into a liquid
Subtropical jet stream-subtropical jet stream—A band of relatively strong winds concentrated between 20° and 40° latitude in the middle and upper troposphere. It can be present at any longitude but is generally strongest off the Asian coast. See jet stream. (AMS Glossary 2000)
jet stream—Relatively strong winds concentrated within a narrow stream in the atmosphere.

41. References
Whiteman, C. D., 2000: Mountain Meteorology: Fundamentals and Applications. Oxford University Press, New York, 355pp.