GEOL 314 LECTURE 3 - Atmospheric Convection and Circulation

Insolation distribution

Insolation is not uniformly distributed throughout Earth, equator receives more and poles less due to angle as radiation is spread out over a greater area near the poles (lower energy per unit value)

Heat difference variables

Temperature difference from pole to equator, seasonal temp differences, heat moves from equator to poles

Lapse rate

Atmosphere broken up into layers due to this; refers to how temp changes as altitude increases, as pressure increases temperature does and vice versa

Pressure and temperature in the atmosphere

Ideal gas law shows that T ∝ P, as elevation increases pressure decreases therefore temperature decreases

Atmospheric convection

1. Insolation is absorbed by Earth’s surface

2. Heat from the surface is transferred to air by conduction

3. Heated air rises, it is less dense as air molecules have expanded, and cooling air takes its place

4. The rising air begins to cool until eventually it is equivalent to the rest of the gas particles in temperature and stops rising

5. Begins to sink

Air column

Air expands over a hot surface and rises as a column, the top is high pressure as there are more air molecules at the top, air cools and sinks to replace air at the bottom of column so is low pressure as there are less air molecules

Marine layer

Layer of cold, dense air just above the ocean, as it is cold the layer sits at the bottom and as there is a lot of it, is dense; atmospheric pressure differences move it onto land

Marine layer movement

Hot air rises in a different area, so marine layer must replace it so moves onto land

Atmospheric inversion

An increase in elevation results in higher temperature as opposed to it causing lower temperatures, can trap pollutants and significantly impact air quality

Atmospheric inversions and seasons

More AIs in the summer as there are more hot conditions that bring marine layers onto land; more sunlight also oxidates car emissions to become smog which become trapped

Water properties

High specific heat capacity, hydrogen bonds

Sensible heat

Measurable heat such as air temperature from thermometer

Latent heat

Energy absorbed or released during phase change

Precipitation

Air mass containing water vapor rises and water condenses as it cools, eventually limit to water vapor that can be held is reached and released as precipitation

Cloud

Visible aggregate of water droplets and/or ice crystals suspended in atmosphere

Relative humidity

Comparison of actual amount of water vapor in air vs amount that COULD be present if same air were 100% saturated

Undersaturation of water vapor

If RH is undersaturated then evaporation can occur

Oversaturation of water vapor

Oversaturation in RH causes clouds to form and precipitation to occur

Storm formation

Water evaporates more easily in warmer temperatures, evaporated water in warm air rises to form clouds which precipitate as they cool and air from ocean moves to replace rising air as wind

Mid-latitude storms

Cold air collides with warm air and pushes the latter up to form clouds and precipitation

Global warming and storms

The warmer the air, the more moisture it can hold for rainfall; warmer oceans give more energy for hurricanes → heavier, more intense, prolonged storms; increases impact of storm surges

Orographic barriers

Physical formations that impede wind and precipitation paths eg. mountains, valleys

Storm surge

Temporary increases in sea level due to atmospheric changes in pressure and wind

High pressure system

Falling air causes this pressure system

Low pressure system

Rising air causes this pressure system