Climates

What is Climate Climateaverage over a long- term Climate is an average of weather conditions in a region over a long- term period of time. Weathershort-termcondition Weather is the short-term condition of the atmosphere over a region.

Global Climate interactionsolar energy Earth’s surfaceatmosphere Global climate is determined by the interaction of solar energy with the Earth’s surface and atmosphere: - by conditions of temperature and humidity. Climate is important is determining: habitability land use Effect of climate is the availability of water at the surface and within the ground.

The Water Cycle and Climate The water cycle involves the transfer of moisture between the land and sea, and between different latitudes. andSince climate is determined by the amount of moisture and the potential for evapotranspiration, climate is tied to the water cycle.

The Earth’s Water Cycle Is a Closed System

Latitude Affects Moisture Exchange Some latitudes have a surplus of precipitation over evaporation, other latitudes have a precipitation deficit. –3–3 main belts of surplus are: the equatorial zone 0 o to 10 o North and South mid-latitude zones 40 o to 70 o in each hemisphere –2–2 main belts of deficit are: ~10 o to 40 o in each hemisphere

Insolation INSOLATION INcoming SOLar radiATION Insolation Insolation is the term that refers to the amount of radiation from the Sun that is received by the Earth. Intensity of insolationrate Intensity of insolation is the rate at which solar energy is received by a given area of the Earth’s surface per unit of time.

Intensity and Area Intensity of insolationinverselyrelated area Intensity of insolation is inversely related to the area of the Earth’s surface receiving it. As area gets bigger, intensity gets lower.

Intensity vs Area

Factors Affecting Insolation Some of the many factors that affect insolation are: –A–Angle of insolation –T–Type of surface –L–Length of time insolation is received –A–Atmospheric conditions

Angle of Insolation angle of insolation The angle which the Sun’s rays strike the surface is called the angle of insolation. The angle can be from 0 o to 90 o. 90 o direct verticalrays Rays at a 90 o angle are called direct, or vertical, rays. more direct rays higher temperatures Areas receiving more direct rays will have higher temperatures.

Angle of Insolation

Time and Intensity Angle of the Sun varies with time, so time will affect intensity. –At sunrise and sunset the angle of the Sun’s rays is the least and so the intensity is least. –At noon the Sun’s rays are at their greatest angle (most direct) and so the intensity of insolation is also the greatest.

Time and Angle

Earth’s Shape Affects Intensity of Insolation Since the Earth is an oblate sphere, there is only one location that receives vertical rays from the sun. The more you move away from the direct rays, the lower the angle of the rays and the lower the intensity.

Intensity of Insolation Diagram

Vertical Rays at Summer in Northern Hemisphere

Seasons and Intensity of Insolation Intensity of isolation varies with the seasons of the year. Seasonsare causedtilt of the Earth’s axisrevolutionSeasons are caused by the tilt of the Earth’s axis and the revolution around the Sun.

Seasons of the Earth

Latitude and Intensity of Insolation At noon on the date of the equinoxes, the sun is directly over the equator. At this time the angle of the sun is the same as the observers latitude.

Seasonal Angles of the Sun

Duration of Insolation The duration of insolation is the number of daylight hours at a given location. Daylight hours vary with latitude and time of year. There is a direct correlation between angle and intensity of insolation and duration of insolation. –Ex. Jun. 21 in Northern Hemisphere when angle and intensity are greatest, duration is longest.

Length of Day / Duration

Radiative Balance Radiative balanceRadiative balance exists when a substance gains the same amount of radiation as it gives off. Earth radiates infrared energyThe Earth continuously receives insolation and radiates infrared energy from its surface.

Maximum and Minimum Temperatures Maximum radiative energy reaches the Earth when the angle and intensity of insolation are the greatest. solar noon –On a daily basis this is at solar noon (when the Sun’s rays are most direct). afterHighest temperatures are after this time. –Earth begins to receive more energy than it gives off (reradiates). –Highest temperatures occur mid-afternoon. –Lowest temperatures occur just after sunrise.

Time of Year afterJune 21In the Northern Hemisphere the hottest time of year is after June 21 (greatest angle and duration of insolation). HottestAugust radiative balanceHottest time of year is in August when the amounts of incoming and outgoing energy are in radiative balance. ColdestafterDec 21 FebruaryColdest time of year is after Dec 21 (least angle and duration) occuring in February.

Duration and Temperature Temperature at the surface is d dd directly related to duration of insolation. The longer the duration the higher the temperature Note: the shortest days also have the lowest angle.