S-Cool Revision Summary

S-Cool Revision Summary

Weather and climate

When referring to weather and climate it is important to distinguish the difference between the two:

Weather

This relates to hourly, daily atmospheric conditions such as precipitation, hours of sunshine, cloud cover, temperature and humidity. The most important fact is that it is short-term.

Climate

The climate of a place is based on the average weather conditions for a particular place taken over a minimum of a 30-year period. It is a general picture and the weather received for a place can be vastly different from its usual climate.

Recording data

Weather and climate is recorded in a variety of ways, but for an exam the most important points to know are:

  1. How to interpret a climate graph.

  2. How to interpret a synoptic weather chart.

Synoptic charts

synoptic chart shows certain meteological characteristics for specific weather stations, (usually pressure, temperature, cloud cover, present weather, wind strength and direction).

In addition to this, satellite photographs are also used. Isobars are present on the map and are similar to contour lines - the closer together they are, the stronger the wind is.

The diagrams below show the weather symbols for pressure and temperature, wind, weather and cloud:

Heating of the Atmosphere

There are four vertical layers within the atmosphere, each with its own particular characteristics. The outer limit of the atmosphere is set at 1000km, but the vast majority of our weather and climate is found within the lower 12km.

Beginning at the earth's surface, the four layers of the atmosphere are listed below:

  1. Troposphere

  2. tratosphere

  3. Mesosphere

  4. Thermosphere

Radiation

Short wave

Energy that comes from the sun and passes through the atmosphere to earth is in the form of short wave radiation or insolation. It is responsible for the Earth's weather and climate and is converted via photosynthesis to support all forms of life.

Long wave

Once insolation has reached the surface of the Earth, it is converted into heat energy. The ground begins to warm and slowly heats the atmosphere above it, meaning that the atmosphere is warmed from ground level upwards. The amount of heating of the atmosphere that occurs depends on the surface (for example, water, ice, grass, sand) that is being heated.

Solar energy distribution

As energy passes through the atmosphere on its way to Earth, much of it is lost resulting in under 50 % actually reaching the Earth's surface. Energy is lost via the processes of absorption, by ozone, dust, clouds and carbon dioxide.

Scattering: This happens if gas molecules divert incoming radiation.

Reflection: Clouds reflect energy back into space (acts as a barrier).

Energy Transfers and Insolation

Energy transfers occur within the atmosphere in order to maintain a balance between the amount of energy received at the poles and the equator.

Negative heat balance: Exists at the poles - a loss of energy to the atmosphere.

Positive heat balance: Exists within the tropics, a surplus of energy.

Heat transfers

Horizontal heat transfers

The transfer of heat from the equator to the poles occurs via winds - 80% (large scale to small scale) and ocean currents (20%).

Vertical heat transfers

Exist to stop the atmosphere from cooling and the Earth's surface from overheating. They occur via conduction, convection, latent heat transfers and radiation.

Insolation

Long-term factors

These are factors which influence the amount of radiation reaching the Earth that remain relatively constant over time.

Height of the Sun:

Lower latitudes (equatorial regions) have higher temperatures than higher latitudes (Poles) this is as a result of the amount of heating that each area receives.

Height above sea level:

It is important to remember that the atmosphere is heated from ground level upwards via long-wave radiation.

Distance from land and sea:

Land and sea have vastly different specific heat capacities (the amount of energy needed to raise 1kg of a substance by 1 degree).

Prevailing winds:

The temperature of a wind and the subsequent effect it has on an area is dependent on:

  1. Where it originated.

  2. The surfaces it has blown over.

Atmospheric Circulation and Motion

The tri-cellular model

This shows how energy is redistributed across the globe and ensures there is not a surplus at the equator and deficit at the Poles. There are three major cells present: Hadley, Ferrel and Polar.

Atmospheric motion

There are two ways air can move in the atmosphere - vertically and horizontally (winds). Winds occur due to differences in pressure, shown by isobars on a synoptic chart.

The Coriolis force

This relates to the apparent deflection of winds to the right in the northern hemisphere and the left in the southern hemisphere due to the spinning of the Earth.

Pressure gradient

The movement of air between areas of high and low pressure. Isobars show this phenomenon and the closer the isobars, the stronger the winds. Winds act to balance out differences in pressure, humidity and temperature.