Transcript Energy, albedo, and latent heat (changing states of water)

Energy, albedo, and latent heat (changing
states of water)
Unit Objectives
• To define, describe and illustrate some of the forms of
energy that influence weather and climate on the
surface of the earth, in the oceans, and in the
atmosphere.
• To describe the process of latent heat exchange through
the process of the changing states of water.
• To define and illustrate the concept of albedo and to
explain how it influences the differential heating of the
earth.
• To describe and illustrate the differential heating and
cooling of the continental land masses as opposed to
the oceans.
Energy, Potential and kinetic
• Energy is the ability or capacity to do work. Work is done on
matter when matter is either pushed, pulled, or lifted over some
distance.
• The total amount of energy stored in any object determines how
much work that object is capable of doing. For example water
behind a dam – this would be called gravitational potential
energy.
• The formula would be PE = mgh where PE equals potential
energy, m equals the mass of the object, g is the acceleration of
gravity and h is the height of the object above the ground.
• A substance can also possess potential energy if it can do work
when a chemical reaction takes place. Thus coal, petrol and food
all contain potential chemical energy.
Kinetic Energy
• Any moving substance possesses energy of motion
called kinetic energy. The kinetic energy (KE) of
an object is equal to half its mass multiplied by its
velocity squared; thus
KE = ½ mass x velocity(squared).
Hence the faster an object moves the greater its
kinetic energy, so a strong wind possesses more
energy than a gentle breeze.
• The most important energy in terms of weather and
climate is radiant energy.
• The total amount of energy in the universe remains
constant, energy merely changes forms. This is the
law of the conservation of energy also known as
the first law of thermodynamics.
Fahrenheit, Celsius and Kelvin Scales
Temperature of the air or
any other substance is a
measure of its average
kinetic energy. Hence
temperature, is a measure
of the average speed of
the atoms and molecules.
Specific Heat
The heat capacity of a substance is the ratio of the amount of heat
energy absorbed by that substance to its corresponding temperature
rise. The heat capacity of a substance per unit mass is called specific
heat. Hence specific heat is the amount of heat needed to raise the
temperature of one gram of a substance one degree Celsius. (Ahrens,
pg 30)
Changing states of water and latent heat
The heat energy required to change a substance, such as
water, from one state to another is called latent heat
How the process works and why it’s
significant
• Ice melts and 80 calories of energy passes to the
liquid water. Liquid water evaporates and the water
vapour absorbs 600 calories of energy. There is now
680 calories of energy in the water vapour. The water
vapour condenses into water and releases 600 calories
of energy into the air. The liquid water freezes and
releases 80 calories of energy into the air. Air is a
poor conductor of heat, it’s the changing states of
water that transfers energy from the earth’s surface
upward into the atmosphere where circulation
patterns transfer surplus energy poleward.
Convection
• The transfer of heat by the mass movement of a fluid,
such as water or air, is called convection. Commonly
occurs in liquids and gases because they can move freely
and currents often occur within them. Convection occurs
naturally in the atmosphere and within the oceans.
Energy transformations
Albedo
• The percent of radiation returning from a surface
compared to that which strikes it.
Global Warming and Albedo
• Changing patterns of global albedo may have a
significant impact on global warming.
• Melting glaciers and ice caps, by increasing
absorption of radiation could accelerate global
warming.
• Changing land use patterns, such as the devastation
of the rainforests in the Amazon basin, could
influence circulation patterns within the intertropical
convergence zone by limiting the total amount of
evapotranspiration (the amount of water vapour)
transported into the atmosphere.
Deforestation in the Amazon
Melting glacier in Greenland
Water and Land Differences
• The different reactions of land and water to
solar radiation greatly influences the resultant
temperatures, pressure cells, and circulation
patterns on the surface of the earth.
Differential heating on land and water
Continents heat up quickly during the day and give up heat rapidly
at night. Oceans take a long time to heat up but retain the heat
longer.
Mean Surface Temperatures - July
The climate system involves the interaction of
many aspects of the environment
Summary
• The distribution of solar radiation causes
several transformations of energy to occur.
Processes are initiated that function to
redistribute the energy from the surplus areas
to the energy deficient areas. Due to
differences in albedo and the varied landscape
of the globe particular patterns are evident that
influence the temperature and other aspects of
weather on the surface of the earth.