1. Transmission refers to the passage of
shortwave and long wave energy through either the atmosphere or water.
2. Refraction: The speed of insolation
entering the atmosphere changes as it passes from one medium to another; the
change of speed causes a bending action called refraction.
3. Reflection: A portion of arriving
energy bounces directly back into space without being converted into heat
4. Albedo is the reflective quality of
a surface. It is the percentage of insolation that is reflected back to space.
Earth and
its atmosphere reflect 31% of all insolation in a year. An increase in albedo
and reflection of shortwave radiation caused by clouds is termed cloud-albedo
forcing. Clouds reflect radiation and thus cools earth’s surface. An
increase in greenhouse warming caused by clouds is described by the term cloud-greenhouse
forcing.
5. Scattering represents 7% of Earth’s
reflectivity, or albedo. Scattering of insolation by clouds and atmosphere
creates diffuse radiation that is transmitted to Earth
6. Absorption is the assimilation of
radiation by molecules of a substance and its conversion from one form to
another—for example, visible light to infrared radiation (heat).
a)
Conduction is
the molecule-to-molecule transfer of energy as it diffuses through solid
objects.
b)
Convection is the transfer of energy by gases and liquids in vertical motions.
c)
Advection
is the transfer of energy by gases through a mixing of the gases in a
horizontal motion.
Radiant
energy from the Sun comprises:
a) Shortwave
radiation inputs and ...
b) Long
wave radiation outputs
Some
longwave radiation is absorbed by carbon dioxide, water vapor, methane, CFCs
(chlorofluorcarbons), and other gases in the lower atmosphere and is then
reradiated to Earth, thereby delaying energy loss to space. This process is
termed greenhouse effect. Infrared radiation (heat) is not actually
trapped, as it would be in a greenhouse, but its passage to space is delayed
(detained) as it is absorbed and reradiated.
Earth-Atmosphere
Radiation Balance
In the Tropics,
high insolation angle and consistent day length cause more energy to be gained
than lost (energy surpluses). In the Polar regions, extremely low
insolation angle, highly reflective surfaces, and up to 6 months of no
insolation annually cause energy to be lost (energy deficits). The greatest
insolation input occurs at the time of the Summer Solstice in each hemisphere.
Adding and subtracting the energy flow at the earth’s produces net radiation
(NET R), or the balance of all radiation at Earth’s surface—shortwave (SW)
and long wave (LW). +SW–SW+LW–LW
= NET R
ANNUAL
TEMPERATURE PATTERNS:
In the
northern hemisphere January is the coldest month (after winter
solstice) and the warmest months are July and August (occurring after
summer solstice).
Temperature is a measure of the average
kinetic energy (motion) of individual molecules in matter. Temperature is
caused by the absorption or emission (gain or loss) of heat energy. Sensible
Heat is the temperature we feel in our bodies resulting from heat transfer
from warmer objects.
TEMPERATURE
SCALES
Absolute
zero temperature refers to the temperature at which all atomic and molecular motion in
matter stops (-273oC, -459oF and… 0 Kelvin
a) Fahrenheit
scale: Developed by a German
physicist, Daniel G. Fahrenheit. Melting point of water = 32o
and the boiling point = 212o
b) Celsius
scale: Developed by a Swedish astronomer Anders Celsius. Melting point of
water = 0o
and boiling point = 100o.
c) Kelvin
scale:
Proposed by British Physicist, Lord Kelvin (born William Thompson). This scale
is used mainly in science because temperature readings start at Absolute zero.
Melting point of ice is 273K and the boiling point of water is 373K.
PRINCIPAL
TEMPERATURE CONTROLS:
1. Latitude
(the distance north or south of the equator
2. Altitude
(location above sea level), lapse rate (6.4oC/1000m, or 3.5oF/1000
feet)
3. Cloud
cover (reflect, absorb, and re-radiates energy),
LAND
& WATER HEATING DIFFERENCES
a) Evaporation
– during evaporation, heat energy is absorbed and stored in the water vapor
(Latent heat). About 84% of evaporation is from oceans.
b) Transparency
– light penetrates a body of water to and average depth of 200 ft. (60m) in the
ocean distributing heat over greater dept and volume.
c) Specific
heat – water has greater specific heat than soil/land because water
requires more heat to raise its temperature.
d) Movement
– Land is a rigid, solid material. Water is fluid and capable of movement
hence mixes heat over a larger volume than rigid land
e) Ocean
currents: Warm ocean currents (Gulf Stream) supply high temperatures
to adjacent lands while Cool currents create cool and dry conditions on
adjacent lands.
Land/Water
Contrasts
Land
heats and cool faster than water. Moderate temperature patterns are associated
with water bodies, and extreme temperatures occur inland.
Maritime
effect, or
marine, describes locations that exhibit the moderating influences of the
ocean, usually along coastlines or on islands.
Continental
effect (Continentality) refers to the condition of areas that are less affected by the sea and
therefore have a greater range between maximum and minimum temperatures
diurnally and yearly.
On a
Temperature map an ISOTHERM connects points of equal temperature. Isotherms generally are
zonal,
trending east-west, parallel to the equator. The thermal equator (isoline connecting
all points of highest mean temperature) trends southward in January and shifts
northward with the high summer Sun in July.
URBAN
HEAT ISLAND
On the
average, both minimum and maximum temperatures are higher in URBAN areas than
nearby rural settings. Cities experience unique set of altered microclimatic
effects: increased conduction, lower albedos, higher NET R values, increased
water runoff, complex radiation and reflection patterns, anthropogenic heating,
and the gases, dusts, and aerosols of urban pollution. Urban surfaces of metal,
glass, asphalt, concrete, and stone conduct up to three times more energy than
wet sandy soil and thus are warmer. Air pollution, including gases and
aerosols, is greater in urban areas than in rural ones. Every major city
produces its own urban heat island.