Met 2 - the motion of the atmosphere

What drives air movement in the atmosphere?

The sun's energy (indirectly)

Does the atmosphere absorb heat directly from the sun?

No, it is heated from below by the Earth’s surface

What causes non-uniform heating of the Earth's surface?

Spherical shape and atmospheric obliquity

Why is the equator warmer than the poles?

Receives more concentrated solar radiation

How is heat transferred from Earth's surface to the atmosphere?

Conduction, terrestrial radiation, and convection

What creates seasons?

Tilt of the Earth and its orbit around the Sun

Where is surface pressure low and high due to heating?

Low at tropics, high at poles

What causes surface wind?

Air moving from high to low pressure

Why does land heat and cool faster than water?

Land has lower heat capacity and changes temperature quickly

What retains heat after summer?

Oceans

What does uneven heating cause?

High and low pressure areas, and wind

Why is pressure measurement important in meteorology?

To assess and forecast weather

What complicates pressure measurement?

Differences in elevation

How much elevation difference equals 1 mb pressure difference?

Approximately 27 ft

What is QFF?

Sea-level pressure value adjusted from station pressure

What are isobars?

Lines connecting points of equal sea-level pressure

What do closely spaced isobars indicate?

Strong pressure gradient and stronger winds

What do widely spaced isobars indicate?

Weak pressure gradient and lighter winds

How does air flow in relation to pressure gradient?

From high to low pressure

What is convergence?

Air flowing into a low-pressure system and rising

What is divergence?

Air spreading out from a high-pressure system and sinking

Where is surface low pressure associated with an upper high?

In a low-pressure system due to rising air

Where is surface high pressure associated with an upper low?

In a high-pressure system due to sinking air

Why doesn’t air flow directly from high to low pressure?

Because of the Coriolis force

What causes the Coriolis force?

Earth’s rotation

Which way does Coriolis deflect moving air in the northern hemisphere?

To the right

Where is the Coriolis force strongest?

At the poles

Where is Coriolis force zero?

At the equator

What is geostrophic wind?

Wind that flows parallel to straight isobars when pressure gradient and Coriolis forces balance

What is gradient wind?

Wind that flows around curved isobars near highs and lows

How does wind speed compare around high and low pressure areas?

Slower around lows, faster around highs (with same isobar spacing)

What two elements define wind velocity?

Direction and speed

How is wind direction reported in weather forecasts?

In degrees true

How is wind direction reported by ATSUs?

In degrees magnetic

What units are used to report wind speed?

Knots (KT), metres per second (MPS), or kilometres per hour (KMH)

What unit is standard in aviation for wind speed?

Knots (KT)

What is a rule of thumb to convert MPS to knots?

Double the MPS value (e.g., 10 MPS ≈ 20 KT)

How does surface friction affect wind?

It changes both wind speed and direction