The Atmosphere B3: Weather Factors Part 1 – Energy in the Atmosphere

Weather Factors – Part 1 Heat – Heat is a major factor in weather – The movement of heat in the atmosphere causes temperatures to change, winds to blow, and rain to fall – Heat is a form of energy, and nearly all energy in the atmosphere comes from the sun

Energy from the Sun Energy from the Sun – Energy from the sun travels in the form of electromagnetic waves – Classified according to wavelength – Radiation – transfer of energy by electromagnetic waves – Most of the energy from the sun travels to Earth in the form of visible light and infrared radiation – A small amount arrives as ultra-violet radiation

Energy in the Atmosphere Before reaching the Earth’s surface, energy must pass through the atmosphere – Mesosphere – Blocks much of the UV radiation – Troposphere – Some energy is reflected or absorbed by the atmosphere, the rest passes through to the surface – Reflected - About 30% of sunlight is reflected back into space – About 25% is reflected by clouds, dust, and gases in the atmosphere – Scattering – the process in which sunlight is reflected in all directions by the air – About 5% is reflected the surface

Energy in the Atmosphere – Absorbed - About 80% of sunlight is absorbed – About 20% is absorbed by gases and particles in the air – About 50% is absorbed by the Earth’s surface – This energy heats the land and water

Energy at the Earth’s Surface When Earth’s surface is heated, it radiates most of the energy back into the atmosphere as infrared radiation – Most of this radiation cannot travel all the way back into space – Instead, it is absorbed by water vapor and other gases in the air – These gases form a ‘blanket’ that holds heat in – Greenhouse Effect – process by which gases hold heat in the air

Energy at the Earth’s Surface – Natural and necessary process that keeps Earth’s atmosphere at a temperature able to support life – Also helps to keep Earth’s average temperature fairly constant – However, increasing the amount of greenhouse gases, increases the amount of heat retained – Global Warming – the increase in Earth’s average temperature due to increasing levels of greenhouse gases

Types of Heat Energy What is the difference between temperature and thermal energy? – Temperature – a measure of how hot or cold a substance is – Thermal Energy – the total energy of motion in the particles of a substance – Example : Lit match and ice sculpture – Which has a higher temperature? Match – Which has more thermal energy? The swan because it has a lot more molecules

Measuring Temperature Temperature is one of the most important factors in weather and is commonly measured with a thermometer – Thermometer – works because liquid expands when the temperature increases – Expansion causes the liquid to rise up the tube – As the liquid cools, it contracts and gets lower in the tube – Temperature Scales – temperature is commonly measured in Celsius or Fahrenheit

Measuring Temperature – Celsius Scale – In the Celsius scale, water freezes at 0 o and boils at 100 o – Fahrenheit Scale – In the Fahrenheit scale, water freezes at 32 o and boils at 212 o – Converting – The formula to convert Fahrenheit to Celsius is: o C = 5 9 ( o F – 32) What is the formula to convert Celsius to Fahrenheit? Need to solve for F To get rid of the fraction – multiply both sides by 9 9oC9oC= X 5( o F – 32) To get rid of the 5 – divide both sides by oC9oC = 5 o F – 32 To get rid of the 32 – add to both sides 9oC9oC = oFoF

How Heat is Transferred Heat is transferred in 3 ways: radiation, conduction, and convection – Radiation – transfer of energy by electromagnetic waves through the air – Cannot see radiation, but you can feel it – Examples: – Feeling warmth when standing in sunshine – Feeling heat when you hold your hand over a lamp or a flame

How Heat is Transferred – Conduction – The direct transfer of heat from one substance to another substance that is touching it – Occurs when faster moving molecules in a hot substance bump into slower moving molecules of a cooler substance – The closer together the atoms or molecules are in a substance, the more effectively it conducts heat – The faster molecules transfer some of their energy to the slower molecules ‘heating’ them up – Example: metal conducts heat better than water

How Heat is Transferred – Convection – The transfer of heat by the movement of liquid or gases – In fluid (liquid or gas) particles can easily move from one place to another – As particles move, they take their energy with them – Example: Pouring hot water into cold water. The water molecules mixcausing the cold water to heat up and the hot water to cool down

How Heat is Transferred The three types of heat transfer – Convection Current – Movement of particles through fluid due to temperature – As particles heat up, they rise through the fluid – As particles cool down, they sink

Heating the Troposphere Radiation, conduction, and convection all work together to heat the troposphere – During the day, the sun’s radiation heats Earth’s surface – The land becomes warmer than the air – The air near the surface is warmed by both radiation and conduction – Only the air touching the surface is heated by conduction – Within the air, heat is transferred through convection currents

Heating the Troposphere Radiation Conduction Note: only the air touching the surface is heated – so it is much less air Convection Forms convection currents

In Closing – What is the difference between radiation, conduction, and convection?