Isolines & insolation
contour lines
on topographic maps they are isolines that show elevation
W/M2
one way to describe insolation.
north pole
received either 24 hours of darkness or daylight.
equator
receives virtually 12 hours of daylight throughout the year
midlatitudes
show variation in the length of day from winter to summer.
low angle of incidence
spreads this energy out over a greater area.
average daily insolation
the average of insolation over a 24-hour period.
insolation
the rate at which solar energy strikes surface.
length of the day
- 2nd most important factor that influences the amount of solar energy received at the surface. - long hours of daylight significantly increase the total energy received.
solar constant
- insolation at Earth's upper atmosphere. - about 1372 W/m2.
angle of incidence
- the angle at which the Sun's rays strike the surface. - the length of travel through the atmosphere is determined by it. - when the sun's rays strike perpendicular to Earth's surface the radiation has the shortest possible travel through the atmosphere, and this results in relatively little decrease in intensity. - when the sun's rays strike Earth at a lower angle of incidence, the radiation reaching the surface will be less intense because it must travel through much more atmosphere.
basic rules of isolines
1) an isoline connects points on a map where the value of some phenomenon is the same. 2) isolines are drawn at regular intervals. 3) always closed lines. 4) isolines never cross each other. 5) where isolines are close together, they show an abrupt horizontal change in the phenomenon; when they are far apart, they show a gradual horizontal change. 6) values inside a closed isoline are either higher or lower than those outside the closed isoline.
3 factors that determine insolation at surface
1) angle of incidence of the incoming radiation. 2) length of day. 3) obstruction of the atmosphere.
high angle of incidence
concentrates the solar energy in a small area.
isotherms
isolines that show temperature.
isobars
isolines to show atmospheric pressure.
isolines
line on a map that connects points of equal value
