2.1.4 Part 1: Air Uplift, Lapse Rates & Clouds

What fundamental process causes rising air to cool?

Adiabatic cooling (air expands due to lower atmospheric pressure and loses internal heat).

Define the Dew Point Temperature.

The temperature at which an air parcel becomes fully saturated, triggering condensation.

What are condensation nuclei?

Microscopic atmospheric particles (e.g., dust, salt) around which water vapor condenses to form cloud droplets.

What is the Dry Adiabatic Lapse Rate (DALR) value?

Approximately 9.8°C cooling per 1,000 meters of elevation (for unsaturated air).

What is the Saturated Adiabatic Lapse Rate (SALR) value?

Approximately 5–7°C cooling per 1,000 meters of elevation.

Why is the SALR lower than the DALR?

Latent heat released during condensation slows the rate of cooling.

What causes Orographic (Relief) uplift?

Moist air forced to rise over high topographic barriers like hills or mountains.

Give a UK example of high annual orographic rainfall.

The Lake District and Snowdonia (receiving over 3,000 mm of annual rainfall).

Contrast the windward and leeward sides of a mountain range.

Windward side: High cloudiness and heavy rain. Leeward side: Rain shadow with warm, dry descending air.

What causes Frontal uplift?

A warm, less dense air mass forced to rise over a cooler, denser air mass along a weather front.

Contrast warm front and cold front cloud types.

Warm front: Layered nimbostratus/altostratus (steady rain). Cold front: Steep cumulonimbus (heavy rain/thunderstorms).

What causes Convectional uplift?

Solar radiation heating the ground, creating rising warm thermal air currents.

What cloud types and rainfall are produced by convectional uplift?

Cumulus and cumulonimbus clouds, producing intense, short-duration showers or thunderstorms