FRONTS AND AIR MASSES

FRONTS
Fronts are boundaries between air masses of different temperatures and humidity.
They are three-dimensional transition zones where two contrasting air masses meet.
They are typical features of mid-latitude (temperate) regions and are rare in tropics and polar regions.

The concept of fronts was developed by Norwegian meteorologists during World War I.

FRONTOGENESIS AND FRONTOLYSIS
Frontogenesis: Formation of a front due to convergence of two air masses.
Frontolysis: Dissipation of a front when one air mass completely dominates the other.
Mid-latitude cyclones form due to frontogenesis.

CHARACTERISTICS OF FRONTS
• Sudden change in temperature and pressure.
• Wind shift occurs across the front.
• Cloud formation and precipitation due to ascent of warm air.
• Intensity of rainfall depends on slope of ascent and moisture content.

TYPES OF FRONTS

1. STATIONARY FRONT
• When neither air mass advances.
• Winds blow parallel to the front.
• Causes prolonged rainfall.
• Can cause floods if cyclones move along it.

2. COLD FRONT
• Cold air advances and replaces warm air.
• Steep slope, fast moving.
• Causes violent weather: thunderstorms, heavy rain.
• Sharp fall in temperature after passage.

3. WARM FRONT
• Warm air advances over cold air.
• Gentle slope.
• Causes widespread gentle rainfall over long duration.
• Cloud sequence: Cirrus → Stratus → Nimbostratus.

4. OCCLUDED FRONT
• Cold front overtakes warm front.
• Warm air is lifted completely off the ground.
• Weather is mixed type of cold and warm front.
• Common in mature mid-latitude cyclones.

AIR MASSES

DEFINITION
An air mass is a large body of air with uniform temperature and humidity over a large area.

SOURCE REGION
Large homogeneous areas where air mass forms:
• Subtropical high pressure belts
• Polar regions
• Deserts and oceans

CONDITIONS FOR FORMATION
• Uniform surface
• High pressure
• Stable atmosphere
• Weak winds
• No turbulence

TYPES OF AIR MASSES

1. Continental Polar (cP)
• Source: Arctic and high latitude continents
• Cold, dry, stable
• Causes cold waves in winter

2. Maritime Polar (mP)
• Source: Cold oceans
• Cool, moist, unstable
• Causes rainfall and fog

3. Continental Tropical (cT)
• Source: Hot deserts
• Hot, dry, stable
• Causes heat waves

4. Maritime Tropical (mT)
• Source: Tropical oceans
• Warm, humid, unstable
• Causes heavy rainfall

5. Continental Arctic (cA)
• Extremely cold and dry
• Source: Arctic and Antarctica

IMPORTANCE
• Interaction of air masses produces cyclones, storms, fronts and rainfall.
• Controls weather patterns of temperate regions.

---

PDF File:

No PDF attached

---

Subject: Geography

← Back