Wednesday February 26, 2025
Lecture 6- air-sea interactions
The atmosphere and the eocen are linked
- Solar energy heats earth, generates winds
- Affected by seasons
- wind drive ocean currents
- extreme weather events are often driven by the ocean
- oceans modulate atmospheric temperature
o Global warming affects oceans
What causes earth’s seasons
-Earths orbit it slightly elliptical= Not the cause for seasons
What causes earths season- axial tilt?
-Earth’s axis of rotation is tilted 23.5 degrees with respect to the plane of the ecliptic
- plane of the ecliptic-plane traced by Earth’s orbit around the sun
What causes most places on Earth to have seasons?
a. Earth is closer to the sun in the Northern hemisphere summer and farther away in the
Northern Hemisphere winter
b. The spin axis is tilted 23.5 degrees to the plane of earth’s orbit, causing solar radiation
to vary in angle as earth revolves around the sun
c. The spin axis changes with tilt, causing winter when the tilt is great and summer when
the tilt is small
d. Days are longer during summer than winter, so the extra sunshine causes it to be
warmer in summer and less sunshine causes it to be colder in winter
e. There is more ice in winter, so it is colder, and less in summer, when it is warmer
Explanation: A and C are common misconceptions. D sounds right but it is the tilt that causes
seasons, not the varying length of daylight. E is nonsense
Earth’s seasons; Solar declination
- Sun’s declination varies between 23.5 degrees north and 23.5 degrees south latitudes
- Declination- angular distance of sun from equatorial plane
- Region between these latitudes called the tropics
o 23.5 degrees North: Tropic of Cancer
o 23.5 degrees South: Tropic of Capricorn
Earths seasons: The solstices
- Summer solstice
o About June 21
o Sun directly overhead at Tropic of Cancer: 23.5 degrees north latitude
- Winter solstice
o About December 21
, o Sun directly overhead at Tropic of Capricorn-:23.5 degrees south latitude
Earth’s seasons: The equinoxes
- Vernal spring equinox
o About March 21
- Autumnal equinox
o About September 23
- Sun directly overhead at the equator on equinoxes
Earth’s seasons: Lands of midnight sun
- Arctic Circle
o North of 66.5 degrees north latitude
o No direct solar radiation during Northern Hemisphere winter
o Sun does not set during the summer
- Antarctic Circle
o South of 66.5 degrees south latitude
o No direct solar radiation during Southern Hemisphere winter
o Sun does not set during the summer
The summer solstice in the Northern Hemisphere is on or about June 21. Where is the sun
relative to the earth on this date?
a. The sun is directly overhead along the equator
b. The sun is directly overhead along the Tropic of Capricorn
c. The sun reaches its most northerly point in the sky directly over the Tropic of Cancer
d. The sun reaches its most southerly point in the sky directly over the Tropic of Capricorn
e. The sun is directly overhead at the Arctic Circle
Explanation: This answer is the definition for the start of summer or the summer solstice in the
Northern Hemisphere. This is the date when the Northern Hemisphere receives the most direct
sunlight
Distribution of solar energy with latitude
- Concentrated solar radiation at low latitudes
o High angle of incidence
- Solar radiation more diffuse at high latitudes
o Low angle of incidence
, Solar absorption depends on sun elevation
- More radiation is absorbed when the sun is high in the sky
- Less radiation is absorbed when the sun is at a low angle
Elevation of 90° 60° 30° 15° 5°
the sun
above the
horizon
Reflected 2 3 6 20 40
radiation (%)
Absorbed 98 97 94 80 60
radiation (%)
Memorize the trend not table solar absorption depends on sun elevation
-more radiation is absorbed when the sun is high in the sky
Distribution of solar energy: Absorption and reflection
- Atmosphere, land, and ocean absorb and reflect sunlight
o Albedo- 0-100%
Relatively of a surface
Higher albedo=more heat reflected back to space
Average for earth is 30%
- Angle of sun and albedo determine absorption/reflection of incoming sunlight
Ocean heat is gained and lost at different latitudes
- High latitudes-more heat lost than gained
o Ice and clouds have high albedo
o Low solar ray incidence
- Low latitudes-more heat gained than lost
o High solar ray incidence
o Land and sea have low albedo
Lecture 6- air-sea interactions
The atmosphere and the eocen are linked
- Solar energy heats earth, generates winds
- Affected by seasons
- wind drive ocean currents
- extreme weather events are often driven by the ocean
- oceans modulate atmospheric temperature
o Global warming affects oceans
What causes earth’s seasons
-Earths orbit it slightly elliptical= Not the cause for seasons
What causes earths season- axial tilt?
-Earth’s axis of rotation is tilted 23.5 degrees with respect to the plane of the ecliptic
- plane of the ecliptic-plane traced by Earth’s orbit around the sun
What causes most places on Earth to have seasons?
a. Earth is closer to the sun in the Northern hemisphere summer and farther away in the
Northern Hemisphere winter
b. The spin axis is tilted 23.5 degrees to the plane of earth’s orbit, causing solar radiation
to vary in angle as earth revolves around the sun
c. The spin axis changes with tilt, causing winter when the tilt is great and summer when
the tilt is small
d. Days are longer during summer than winter, so the extra sunshine causes it to be
warmer in summer and less sunshine causes it to be colder in winter
e. There is more ice in winter, so it is colder, and less in summer, when it is warmer
Explanation: A and C are common misconceptions. D sounds right but it is the tilt that causes
seasons, not the varying length of daylight. E is nonsense
Earth’s seasons; Solar declination
- Sun’s declination varies between 23.5 degrees north and 23.5 degrees south latitudes
- Declination- angular distance of sun from equatorial plane
- Region between these latitudes called the tropics
o 23.5 degrees North: Tropic of Cancer
o 23.5 degrees South: Tropic of Capricorn
Earths seasons: The solstices
- Summer solstice
o About June 21
o Sun directly overhead at Tropic of Cancer: 23.5 degrees north latitude
- Winter solstice
o About December 21
, o Sun directly overhead at Tropic of Capricorn-:23.5 degrees south latitude
Earth’s seasons: The equinoxes
- Vernal spring equinox
o About March 21
- Autumnal equinox
o About September 23
- Sun directly overhead at the equator on equinoxes
Earth’s seasons: Lands of midnight sun
- Arctic Circle
o North of 66.5 degrees north latitude
o No direct solar radiation during Northern Hemisphere winter
o Sun does not set during the summer
- Antarctic Circle
o South of 66.5 degrees south latitude
o No direct solar radiation during Southern Hemisphere winter
o Sun does not set during the summer
The summer solstice in the Northern Hemisphere is on or about June 21. Where is the sun
relative to the earth on this date?
a. The sun is directly overhead along the equator
b. The sun is directly overhead along the Tropic of Capricorn
c. The sun reaches its most northerly point in the sky directly over the Tropic of Cancer
d. The sun reaches its most southerly point in the sky directly over the Tropic of Capricorn
e. The sun is directly overhead at the Arctic Circle
Explanation: This answer is the definition for the start of summer or the summer solstice in the
Northern Hemisphere. This is the date when the Northern Hemisphere receives the most direct
sunlight
Distribution of solar energy with latitude
- Concentrated solar radiation at low latitudes
o High angle of incidence
- Solar radiation more diffuse at high latitudes
o Low angle of incidence
, Solar absorption depends on sun elevation
- More radiation is absorbed when the sun is high in the sky
- Less radiation is absorbed when the sun is at a low angle
Elevation of 90° 60° 30° 15° 5°
the sun
above the
horizon
Reflected 2 3 6 20 40
radiation (%)
Absorbed 98 97 94 80 60
radiation (%)
Memorize the trend not table solar absorption depends on sun elevation
-more radiation is absorbed when the sun is high in the sky
Distribution of solar energy: Absorption and reflection
- Atmosphere, land, and ocean absorb and reflect sunlight
o Albedo- 0-100%
Relatively of a surface
Higher albedo=more heat reflected back to space
Average for earth is 30%
- Angle of sun and albedo determine absorption/reflection of incoming sunlight
Ocean heat is gained and lost at different latitudes
- High latitudes-more heat lost than gained
o Ice and clouds have high albedo
o Low solar ray incidence
- Low latitudes-more heat gained than lost
o High solar ray incidence
o Land and sea have low albedo
