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Basic Geoscience Unit 5 Lecture Radiant Energy • Radiant energy comes from the sun and travels through space to heat the earth • This heating of the earth is called radiation Absorption of Energy • Dark surfaces absorb more light, which converts into heat • Light colored surfaces reflect light and remain cooler than darker surfaces Energy From the Sun • 50% of the sun’s energy is absorbed by the surface of earth • 20% is absorbed by the earth’s atmosphere • 30% is reflected by the earth’s atmosphere and surface total Energy From the Sun • • • • • There are 3 ways for heat to move: 1. conduction 2. convection 3. radiation Heat always moves from hot objects to cooler objects Conduction • Near the earth’s surface, heat moves through matter • By contact with solids • This is conduction • Ex: hot air touching the warm dirt Radiation • Radiation are waves of energy that travel through a vacuum • Outer space is a vacuum • Shortwave radiation (powerful) comes from the sun • Long wave radiation is released by the earth back into the atmosphere Convection • Convection is heat being transferred through gases or liquids • Convection currents are formed because warm air expands and rises, cool air contracts and sinks Winds and Air Pressure • Air movement is determined by differences in air pressure • Horizontal air movement is called wind • This is the most common. • Vertical air movement are called updrafts and downdrafts. • • • • Highs= cold, heavy air Lows= warm, light air Air moves from high pressure to low pressure. The greater the difference in pressure, the faster the wind moves. Air Currents • Hot air expands and rises • Cool air contracts and sinks The Big Idea • Trade winds- reliable winds above and below the equator • Doldrums- area between the trade winds where there is little wind • Prevailing Westerlies- winds between the polar area and the trade winds (also called anti trade winds because they move in the opposite direction) • Horse latitudes- located between the westerlies and the trade winds • Little wind occurs here • Polar Easterlies- cold and dense, slow winds Sea and Land Breezes • A breeze coming from the sea towards land is a sea breeze. • This happens during the day. • A breeze coming from the land towards the sea is a land breeze. • This happens during the night. Mountain and Valley Breezes • A valley breeze happens when air moves from the valley up a mountain. • This happens during the day. • A mountain breeze happens when air moves down from the mountain into the valley. • This happens at night. Monsoons • Monsoons are winds that change direction with seasons. • During summer, the wind moves from the ocean towards the land and causes many rains. • During winter, the wind moves from the land towards the ocean and is associated with dry air. Air Masses • An air mass is a large body of air with certain characteristics of temperature and moisture throughout. • Masses over land are dry. • Masses over water are moist. Polar Air Masses • Polar air masses are cold air masses that form over polar regions. • cP- cold and dry • Ex: Canada • mP- cold and moist • Ex: north east and west coast of North America Tropical Air Masses • • • • cT- warm and dry Ex: Mexico mT- warm and moist Ex: Caribbean Boundaries In Air • Fronts are boundaries where two air masses meet • This brings changes in the weather Cold Fronts • This occurs when cold air pushes under warm because the cold air is more dense • Causes rainy and cloudy skies Warm Fronts • Occurs when warm air pushes over cold air • This front moves slowly • You will see cirrus clouds and precipitation Stationary Fronts • This occurs when air masses meet and do not move • There is little change in the weather when this happens. Occluded Fronts • This occurs when warm air is stuck between two cooler air masses. • The cool air pushes the warm air up • The weather during this time is cloudy, rainy, and snowing