Solar Radiation, Seasons, & Winter

Flashcards covering key concepts related to solar radiation, Earth's orbit, and the mechanisms behind Earth's seasons, based on Professor Noah Molotch's lecture.

Perihelion

The point in Earth's elliptical orbit when it is closest to the Sun, occurring around January 3rd.

Aphelion

The point in Earth's elliptical orbit when it is farthest from the Sun, occurring around July 4th.

Plane of the Ecliptic

The plane of Earth's orbit around the Sun.

Top-of-Atmosphere Solar Radiation (Etoa)

The amount of solar energy incident at the top of Earth's atmosphere, calculated as Etoa = Energysun / (4πR^2), with R being the Earth-Sun distance.

Watts per meter squared (W m^-2)

The units used to measure incident radiation or energy per unit area.

Uneven Distribution of Solar Energy

A phenomenon caused by Earth's curvature, resulting in tropics receiving more concentrated insolation (approximately 2.5 times more) than the poles.

Lambert's Cosine Law

A principle stating that the energy (E) incident on a surface is proportional to the cosine of the angle (θ) between the incoming rays and the surface normal (E = Eo X cosθ), explaining how energy changes with angle.

Revolution

Earth's orbit around the Sun, which takes approximately one year (365 days) and is one of the reasons for the seasons.

Rotation

Earth's spin on its axis, occurring once every 24 hours, contributing to day and night cycle and is one of the reasons for the seasons.

Tilt of Earth's Axis

The 23.5° inclination of Earth's rotational axis relative to the plane of the ecliptic, a primary cause of seasonal changes.

Axial Parallelism

The condition where Earth's axis maintains its alignment in space (pointing towards Polaris) as it revolves around the Sun, ensuring consistent seasonal patterns.

Sun's Altitude

The angle of the Sun above the horizon, which is lower during winter months.

Declination

The latitude of the subsolar point (where the Sun's rays are directly overhead), which is in the southern hemisphere during the Northern Hemisphere's winter.

Winter Solstice

Occurs around December 21 or 22 when the subsolar point is at the Tropic of Capricorn (23.5° S latitude).

Spring Equinox

Occurs around March 20 or 21 when the subsolar point is at the Equator.

Summer Solstice

Occurs around June 20 or 21 when the subsolar point is at the Tropic of Cancer (23.5° N latitude).

Fall Equinox

Occurs around September 22 or 23 when the subsolar point is at the Equator.

Subsolar Point

The single point on Earth's surface where the Sun's rays are perpendicular to the surface and thus directly overhead at solar noon.