Oceans CH 6 - The Atmosphere and The Oceans

Solar Constant

If Earth had no atmosphere, the intensity of solar radiation available on a surface at right angles to the Sun's rays would be 2 calories per square centimeter per minute (cal/cm2/min); this value is called the solar constant Def: rate at which solar radiation is received on a unit surface that is perpendicular to the direction of incident radiation just outside Earth's atmosphere at Earth's mean distance from the Sun; equal to 2 cal/cm

Rank the latitudes in terms of their speed of rotation. Latitude with slowest rotation on top.

1. 85 Degrees N Lat 2. 60 Degrees S Lat 3. 25 Deg N Lat 4. 5 Deg S Lat

Rank the following variable gases in terms of their relative volume amounts in the atmosphere. Place the most common gas on top.

1. Water Vapor 2. Carbon Dioxide 3. Methane 4. Nitrous Oxide

Levels of Solar Radiation

Areas of Earth's surface that are equal in size receive different levels of solar radiation as they become more oblique to the Sun's rays. As latitude increases, the Sun's rays and Earth's surface become more nearly parallel, and the solar radiation received on equal surface areas decreases. With increasing latitude, the Sun's rays also have to travel an increasing distance through the atmosphere before reaching Earth's surface.

Sun's Rays --> Angles

Because the Sun is so far away from Earth, its rays are parallel when they reach Earth. Where the rays strike Earth at right angles, the same amount of radiant energy strikes each unit area. But as the angle the Sun's rays make with Earth decreases, the rays and the surface become nearly parallel, and the unit areas receive less energy.

Distribution of Solar Radiation

Instantaneous solar radiation per unit area of Earth surface has its greatest intensity at the equator, moderate intensity in the middle latitudes, and least intensity at the poles.

Heat Gain/Loss

Measurements made over Earth's surface show that, on the average, more heat over the annual cycle is gained than lost at the equatorial latitudes, while more heat is lost than gained at the higher latitudes (fig. 6.3). Winds and ocean currents remove the excess heat accumulated in the tropics and release it at high latitudes to maintain Earth's present surface temperature patterns.

Heating and Cooling of Earth's Surface

The initial source of the energy is solar radiation, which varies in both time and location on Earth's surface.

Solar Constant - Latitudes

The solar constant is approached only at latitudes between 23½°N (the Tropic of Cancer) and 23½°S (the Tropic of Capricorn), because only between those latitudes does sunlight strike Earth at a right angle. Because of Earth's spherical shape, at all other latitudes, Earth's surface is inclined to the Sun's rays at an angle other than 90°

Annual Cycles of Solar Radiation

The total Earth long-term heat budget and the average distribution of incoming and outgoing radiant energy with latitude do not include the annual cycle of radiant energy changes related to the seasonal north-south migration of the Sun. When these variations are included, the annual cycle of seasonal variation in average daily solar radiation is most pronounced at the middle and higher latitudes. Here, the angle at which the Sun's rays strike Earth and the length of daylight change dramatically from summer to winter.

If we assume that the incoming short-wave radiation is the only source of energy available to heat earth's surface and that there are 100 units of energy entering the atmosphere, then Earth's heat budget most closely matches which of the following choices?

Thirty Units are backscattered, 70 units are gained, and later 70 units are lost to space.

Heat Budget

To maintain a constant average temperature, Earth and its atmosphere must reradiate as much heat back to space as they receive from the Sun. These gains and losses in heat are represented by a heat budget Def: accounting for the total amount of the Sun's heat received on Earth during one year as being exactly equal to the total amount lost because of radiation and reflection.

Intensity of Solar Radiation

When the Sun stands directly above the equator at noon, during either the vernal or the autumnal equinox, the radiation value is about 1.6 cal/cm2/min. This value is less than the solar constant because Earth's atmosphere both absorbs and reflects portions of the Sun's energy. The solar radiation per unit of surface area decreases with increasing latitude in each hemisphere, because the greater the latitude, the longer the distance through the atmosphere the Sun's rays must travel. The combined effects of atmospheric path length and inclination of Earth's axis cause Earth to receive more solar heat in the tropics, less at the temperate latitudes, and the least at the poles. The intensity of solar radiation also varies as points on the turning Earth move from darkness to light and return to darkness and as the distance between the Sun and Earth changes seasonally.

The atmosphere is primarily heated ___

from below as Earth radiates heat upward

The atmosphere both absorbs and reflects incoming energy; because of this, the solar radiation measured at earth's surface must be ___ the solar constant.

less than