Section 2

Atmosphere contents

nitrogen, oxygen, argon, carbon dioxide

conduction

transfer of energy between two objects in contact with each other is called conduction -heat flows from watmer objects or substances to the cooler ones they are in contact with -chainlike fashion, heat transfered one molecule to another -occurs at the interface between the atmosphere and the earths surface

Tropic of cancer

-23.5 degrees north latitude -This imaginary line around Earth marks the northernmost latitudinal position where the sun's rays can ever be directly overhead at noon

Summer solstice

-About June 21, Earth is in a position in its orbit so that the northern tip of its axis is inclined toward the sun at an angle of 23.5 degrees (plane of the ecliptic is (the 90 degree sun angle) is directly on 23.5 degrees N latitude -On June 21st, in the Northern Hemisphere, it is the longest day with the highest sun angles of the year -Dec. 21, Southern Hemisphere

Winter Solstice

-June 21st is the winter solstice in the southern Hemisphere -therefore in the southern hemisphere, june 21 is the shortest day with the lowest sun angles of the year -December 21 Northern Hemisphere

Equinox 2

-March 21 -the vernal equinox in the Northern Hemisphere -days and nights will be equal all over Earth, 12 hours of darkness, 12 hours of daylight

subtropical highs

-North and south of the equatorial low centered at 30 degrees N and 30 degrees south, cells of relatively high pressure dominate. -result from dynamic air motion related to the sinking of convectional cels initiated at the equatorial low

Equinox

-September 22 -the autumnal equinox in the Northern Hemisphere -day and night will be of equal length at all locations on Earth -daylight hours are identical for both hemispheres and at all latitudes -Earth's axis points neither towards or away from the sun, the circle of illumination passes through the poles and it cuts Earth in half along its axis

Tropic of capricorn

-Six months later, at the time of the December solstice, the sun's rays are vertical and the noon sun is directly overhead 23.5 degrees south of the equator. -imaginary line marking this southern limit of the 90 degree solar rays at noon

memosphere

-above the stratosphere -temp tends to drop with increased altitude

Parallelism of the axis

-as earth revolves around the sun, the planetary axis remains parallel to all of its former positions-that is, at every position in Earth's orbit, the axis points toward the same spot in the sky. -for the North Pole, that spot is close to the North Star called Polaris -Earth's axis always points in the same direction in respect to stars outside our solar system, but its orientation in respect to the sun does change during its annual orbit: possible explanation for climate changes and the ice ages (Milankovitch cycles)

radiation

-electromagnetic energy is transferred from the sun through space to EArth -all objects with a temp above absolute zero emit electromagentic radiation

Troposphere

-layer lying closest to the Earth, thickness is least at the poles and greatest at the equator -where weather takes place -water vapor and particulates are concentrated in this layer -temp. decreases with increased altitude (normal lapse rate) -3.6 degrees F/1000ft

Analemma

-often drawn on globes as big bottomed figure 8 shows the declination the sun throughout the year. -charts the passage of the 90 degree rays of the sun north and south over the 47 degree of latitude that they cover during a year -solar declination: the latitude where the noon sun is directly overhead on a given day

equatorial low

-region on Earth of greatest annual heating, the low pressure of this area, is determined primarily by thermal factors which cause the air to rise

Revolution

-revolves around the sun in a slightly elliptical orbit with an average distance from the sun of about 150 million kilometers (93 million mi) -no relationship to seasons -perihelionm, aphelion -North and southern hemispheres are reversed -period of time that Earth takes to make one revolution around the sun determines the length of 1 year -365 rotations on its axis during the time it takes to complete one revolution of the sun; therefore year has 365.25 -because of the difficulty of dealing with a fraction we have leap year (every fourth year) and extra day added as Feb. 29th -earths orbit around the sun changes from being more circular to more eliptical through a cycle of 1000 years

Insolation

-solar radiation received by the Earth system -short for incoming solar radiation -main source of energy -responsible for seasonal variations -duration of daylight and the angle of the sun's rays -intensity of insolation received at any given latitude can be found using Lambert's law -can be calculated using the sun's zenith angle

thermosphere

-temp increase until they approach 1100 degrees C at noon -air is thin particurally a vacuum and little heat can be transfered

stratosphere

-the layer of the atmosphere directly above the troposphere -ozone layer -protect from excessive UV radiation -absorbed radiation results in the release of heat, thus temp. increases in the upper parts of the stratosphere

Angle of inclination

-the tilt of Earth's axis away from being perpendicular to the orbital plane -23.5 -wobbles through time and will not always remain at at 23.5 -

Rotation

-turning of the Earth on its axis, an imaginary line extending from the North Pole to the South Pole -making one complete turn with respect to the sun in 24 hours -eastward direction -rotation is in a direction that opposite to the apparent movement of the sun, moon, and stars across the sky -looking down on the globe from the North Pole, the rotation direction is counterclockwise -this eastward direction of rotation moves the zones of daylight and darkness across Earth's surface and also affects the circulatory movements of the atmosphere and oceans -As the Earth rotates, new longitudes are continually moving into the illuminated half of the planet while others are moving into the darkened hemisphere: "circle of illumination"

Speed of rotation

-unaware because the angular velocity is constant for each place on Earth's surface; the atmosphere rotates with the Earth; and there are no nearby objects to which we can compare Earth's movement

Rotational velocity

-varies with the distance of a place from the equator -angular velocity is 360 degrees per 24 hours or 15 degrees per hour -linear velocity at the poles is zero -equator has the greatest linear velocity, distance traveled by a point in 24 hours is longest on Earth

convection

-vertical transfer of heat through the atmosphere -parcels of air near the surface are heated, they expand in volume, becoming less dense than the surrounding air, and therefore rises