403 Clouds, Precipitation and cloud

What are the three main factors that determine cloud characteristics

• Temperature of air

• Stability of air

• Moisture content

What are the formation factors for orographic lift

• Slope steepness

• Height of terrain

• Wind direction

• Wind speed

• Humidity

• Stability

What are the dissipation requirements for orographic lift

• Change of air mass

• Change of wind direction

• Change of wind speed

What are the formation factors for mechanical turbulence

• Rough ground

• Strength of wind

• Humidity

• Stability

What are the dissipation requirements of mechanical turbulence

• Change of air mass

• Decrease in wind speed

What are the formation factors of convergence

• Horizontal and vertical extent of the convergence

• Decrease in wind speed

What are the dissipation requirements for convergence

• Change of air mass

• Filling of the low

What are the formation factors of convection

• Uneven heating of the ground

• Advection of cold air over warmer surface

What are the dissipation requirements of convection

• Heating stops

• Loss of advection or warmer surface

What are the ideal conditions for fog

• High relative humidity

• Presence of condensation nuclei

• Cooling of the air or addition of water vapour

What types of fog are formed by cooling of the air

• Radiation

• Advection

• Upslope

What types of fog are formed by adding water vapour

• Frontal

• Steam

• Ice

How is radiation fog formed

Cooling of the air at night in calm conditions with a clear sky creating an inversion

What are the conditions for formation of radiation fog

• Clear night

• Light winds

What are the conditions for dissipation of radiation fog

Daytime heating

Increasing wind

How is advection fog formed

Warm moist stable air id blown across a cooler surface. Air temperature falls until dew point is reached

What are the conditions for the formation of advection fog

• Moderate wind

• Advection of warm air over a colder surface

What are the conditions for dissipation of advection fog

• Change of wind

• Increase of wind

• Daytime heating

What are the characteristics of advection fog

• Can cover a large area

• Can persist for a long time

• Forms in the warm sector of frontal waves

• Can be blocked by higher terrain

• Thins with daytime heating

• If over water daytime heating has little effect

How is upslope fog formed

Air is pushed up a slope causing it to cool to the dew point

What are the requirements for the formation of upslope fog

• Sloping terrain

• Moderate winds

What are the requirements for the dissipation of upslope fog

• Daytime heating

• Increasing wind

• Change in wind direction

What are the characteristics of upslope fog

• Persists until a change in air mass or wind direction

• Dissipates on the leeward side of the upslope

How is frontal fog formed

Precipitation falls into dryer air below and evaporates until the dew point is raised