Physical phenomena in atmosphere

Weather and Climate

are defined by the atmosphere

Weather: atmospheric conditions (short-run) existing at a given time and location.

• immediate

Climate: weather conditions over a long period of time (years, decades, centuries).

• long-term and general

Weather & Climate Elements

• Temperature

• Pressure

• Wind

• Moisture content

Atmospheric Pressure, Temperature & Wind

Atmospheric pressure: force exerted by air molecules on the earth’s surface (per square unit)

– at Sea level: 1 atm or 760 mm Hg = 101.325 kPa ~ 1.03 kg/cm2

– more gas molecules at Sea level than on mountain peak à

higher pressure is at Sea level (NEXT SLIDE).

Temperature & Pressure (based on Gas Laws)

• very warm air has low pressure

• rising air produces low pressure

• very cold air has high pressure

• sharply descending air produces high pressure

Wind

= horizontal air movement

Insolation → Unequal heating → Temperature gradients → Pressure gradients → WIND

• Air moves from high to low pressure area

• Wind levels off the uneven distribution of air pressure

• Main driving forces of the wind:

– Pressure gradient

– Coriolis Force

– Friction

Wind

as the result of pressure gradients

Physical phenomena in atmosphere

• Evaporation:

phase transition “liquid à vapor”

• Latent heat:

heat absorbed (or released) during phase transition Latent heat for water is high: 540 cal/g

• Condensation

phase transition “liquid à vapor”

• Convection currents –

heat (energy) transfer in liquid or gas

Дата добавления: 2015-09-01