PHSC 3033: Meteorology Seasons

PHSC 3033: Meteorology Seasons

Changing Aspect Angle Direct Sunlight is more intense and concentrated. Solar Incidence Angle is Latitude and Time/Date Dependent Daily and Seasonal Variation

Zenith There is much less atmosphere to travel through directly overhead than on the horizon. The sun is more direct and intense.

Daily Solar Intensity By the time the sun gets on the horizon, it is at a grazing angle and heavily scattered, refracted and absorbed.

Diurnal Temperature

Earth s Tilt (Seasonal) Seasons Reasons Tilt of rotational axis with respect to its orbit around sun Solar Radiation (Earth s daily rotation) More Direct Sun Light Longer Duration of Day Light Hours Orbit Variations (Very Long-Term, Small Effects) tilt eccentricity precession

Tilt Earth s rotational axis remains fixed with respect to the stars.

Earth s Circle of Illumination 50 % of the earth s surface is illuminated by the sun, every hour of every day.

Incident Angle

Winter Solstice Sunlight is most direct at the Tropic of Capricorn (23.5 S) on ~ January 21-22.

. Earth From Space - January

. Earth From Space - July

December Solar Insolation

Day Light Hours (June Solstice)

June Solar Insolation

Day Light Hours (Equinox)

Day Light Hours

Combined Annual Average Solar Insolation

Solar Altitude Angle Calculation of the Solar Altitude at Local Noon What is your Latitude? What is the Date? For the date and latitude, what is apparent latitude (declination) of the Sun? Calculate the distance in degrees between your latitude and the declination of the sun. 90 degrees minus the latitude declination difference will be the solar altitude at local noon for your location on that date. Solar Altitude = 90 - solar latitude - observer latitude

Solar Altitude Angle (Solstice)

Seasonal Solar Latitude

Solar Altitude Angle Solar Altitude at Local Noon, Russellville, AR What is your Latitude? What is the Date? For the date and location, what is apparent latitude (declination) of the Sun? Calculate the distance in degrees between your latitude and the declination of the sun. 90 degrees minus the latitude declination difference will be the solar altitude at local noon for your location on that date. Solar Altitude at NOON = 90 [Difference in Latitude on Earth between you and direct sun]

Solar Altitude Angle Solar Altitude at Local Noon, Russellville, AR What is your Latitude? 35 degrees What is the Date? 2011 Jan 19

Solar Altitude Angle Solar Altitude at Local Noon, Russellville, AR What is your Latitude? 35 degrees What is the Date? 2011 Jan 19 For the Date, What is the apparent latitude (declination) of the Sun? 21 o

Solar Altitude Angle Solar Altitude at Local Noon, Russellville, AR What is your Latitude? 35 degrees What is the Date? 2011 Jan 19 For the Date, What is the apparent latitude (declination) of the Sun? 21 o Calculate the distance in degrees between your latitude and the declination of the sun. 35 N + 21 S = 56 degrees

Solar Altitude Angle Solar Altitude at Local Noon, Russellville, AR What is your Latitude? 35 degrees What is the Date? 2011 Jan 19 For the Date, What is the apparent latitude (declination) of the Sun? Calculate the distance in degrees between your latitude and the declination of the sun. 35 N + 21 S = 56 degrees 90 degrees minus the latitude declination difference will be the solar altitude at local noon for your location on that date. 90-56 = 34

Altitude-Azimuth Russellville 2011 Jan 19 Zenith Ecliptic (Path of the Sun) NCP 34 degrees N S W

Solar Altitude Angle http://aa.usno.navy.mil/aa/data/ Astronomical Applications Dept. U.S. Naval Observatory Washington, DC 20392-5420 RUSSELLVILLE, ARKANSAS W 93 08, N35 17 Altitude and Azimuth of the Sun Jan 19, 2011 Central Standard Time Altitude Azimuth (E of N) h m o o 11:40 33.6 167.8 12:00 34.3 173.4 12:20 34.5 179.0 12:40 34.4 184.7 13:00 33.9 190.3

Solar Altitude and Azimuth Angles Altitude = tan -1 (h / l) Azimuth = 180 tan -1 (w / n) compass direction N-S line n Meter-Stick Height h w Length of shadow l

Thermal Inertia For Any Given Northern Latitude Maximum Daily Solar Insolation Occurs At Maximum Yearly Solar Insolation Occurs On Hottest Hour of the Day (on average) Hottest Month of the Year (on average) It takes awhile to heat up and cool down!

Solar Homes Application Location and Length of Overhangs Position Angle of Solar Panels Positioning of Foliage and Trees

Earth-Sun Geometry Summary Seasons Solar Energy Seasonal (Latitude) Changes Diurnal (Daily) Changes