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South Carolina Seasonality

Seasonality is caused by the tilt of the Earth relative to its orbital plane around the Sun. This causes both: The strength of sunlight reaching the surface, and The length of the day to vary on a regular, yearly cycle. Observations we expect to make: Temperature is positively correlated with the strength of sunlight reaching the surface. Temperature is positively correlated with day length

NOT TO SCALE! Sun Radiation illuminated sideday dark sidenight

S NOT TO SCALE! Sun Radiation axis of rotation equator N

NOT TO SCALE! Sun Radiation Solar radiation shining more directly on Southern Hemisphere South - Summer North - Winter

NOT TO SCALE! Radiation Solar radiation shining more directly on Northern Hemisphere North - Summer South - Winter

South: summer North: winter South: fall North: spring South: winter North: summer South: spring North: fall

Equinox – Two specific points in the Earth’s orbit when each hemisphere gets 12 hours of sunlight. Spring equinox in the Northern Hemisphere is Fall Equinox in the Southern Hemisphere. Solstice – Two specific points in the Earth’s orbit when the amount of day length in one hemisphere has reached a maximum, and in the other has reached a minimum. Winter solstice in the Northern Hemisphere is Summer solstice in the Southern Hemisphere. Equinox dates – September 22, March 22 Solstice dates – December 22, June 21

Equinox – Two specific points in the Earth’s orbit when each hemisphere gets 12 hours of sunlight. North Pole on March 22South Pole on March 22 Twice a year (September 22 nd, March 22 nd ) every latitude on Earth gets exactly 12 hours of sunlight.

Solstice Solstice – Two specific points in the Earth’s orbit when the day length in one hemisphere has reached a maximum and in the other has reached a minimum. North Pole June 21South Pole on June 21 On the longest day of the year in the Northern Hemisphere (June 21 st ), the Sun never sets on any latitude above the Arctic circle (blue) and latitudes below the Antarctic circle (red) get no sunlight at all.

Subsolar latitude Subsolar latitude – the latitude at which the Sun appears directly overhead at noon on that day. June 21 st

Polaris appears above your horizon Rock Hill Latitude= 35 o N Polaris appears 35 above horizon to observers in Rock Hill Polaris appears 35 o above horizon to observers in Rock Hill Rock Hill Latitude= 35 o N September 22 nd 35 o 90o - 35o = 55o 35 o At midday, the Sun appears 35 o down from vertical to an observer in Rock Hill, or: 55 o above the horizon. 55 o Sun directly overhead at the equator

June 21 st 90 o o = 78.5 o At midday, the Sun appears: 78.5 o above the horizon. Polaris appears above your horizon Rock Hill Latitude= 35 o N Polaris appears 35 above horizon to observers in Rock Hill Polaris appears 35 o above horizon to observers in Rock Hill Rock Hill Latitude= 35 o N 35 o 23.5 o 180 o -145 o o = 11.5 o down from vertical to an observer in Rock Hill, or: 145 o 11.5 o 78.5 o Sun directly overhead at 23.5 o N 11.5 o

December 22 st 90 o o = 31.5 o At midday, the Sun appears: 31.5 o above the horizon. Polaris appears above your horizon Rock Hill Latitude= 35 o N Polaris appears 35 above horizon to observers in Rock Hill Polaris appears 35 o above horizon to observers in Rock Hill Rock Hill Latitude= 35 o N 35 o o = 58.5 o down from vertical to an observer in Rock Hill, or: Sun directly overhead at 23.5 o S 31.5 o 23.5 o 35 o 58.5 o

June 21 st September 22 nd December 22 nd Midday Sun Angle 0o0o 50 o 40 o 30 o 20 o 10 o 60 o 80 o 90 o 70 o 31.5o55.0o 78.5 o