GEOG 111 1st Edition Lecture 4 Outline of Last Lecture I Solar and Terrestrial Radiation II Radiation Laws a Stefan Boltzmann Law b Weins Law III Sunspots IV Earth atmosphere influences on radiation a Absorption b Reflection c Scattering Outline of Current Lecture I Two components of solar radiation a Direct beam b Diffuse light II Factors of Atmospheric Transmissivity III Earth Sun Geometry Current Lecture I Solar radiation can be partitioned into two components a Direct beam divided into light and dark directly from the sun when clouds block direct beam they create shadows b Diffuse light sky light from diffused radiation i As wavelengths from the sun are scattered c Inverse relationship between direct beam and diffuse i Less scattering high direct beam low diffused light dark blue sky ii More scattering low direct beam high diffused light lighter blue sky II Three controlling factors of atmospheric transmissivity the ease with which radiation is transmitted through the atmosphere can be visible light or infrared radiation from the Earth 1 Clouds no direct beam all diffuse 2 Haze microscopic particles aerosols in the sky direct beam decreases diffused light increases These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute 3 Elevation atmosphere is thinner at higher altitudes so less light gets scattered and the sky is a darker blue direct beam increases diffused light decreases ii What color is the sky during a typical day on the moon 1 Black because there is no scattering taking place II Earth Sun Geometry a Seasonal changes in earth sun geometry controls the intensity of solar radiation and the length of the day b Two independent motions affect earth sun geometry i Rotation counterclockwise West to East goes 360 degrees in 24 hours 1 This is why we have time zones 2 We go later in time to the east Europe is ahead of us and earlier in time to the west The sun rises and sets later on the western edge of a time zone region and earlier on the eastern edge of a time zone region ii Revolution the earth revolving around the sun on the plane of the ecliptic 1 Takes 365 25 days 2 Due to the earth s elliptical path not a perfect circle the distance between the earth and sun varies during the year 3 Perihelion around January 3 a Earth is closest to the sun b 147 500 000 km 4 Aphelion around July 4 a Earth is farthest away from sun b 152 500 000 km
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