Atmospheric Disturbances

Atmospheric Disturbances Overview

Defining Atmospheric Disturbances: Includes high and low-pressure systems which affect weather.
- Anticyclones:
  - High-pressure systems characterized by subsiding and diverging air.
  - Associated with fair weather as the warming of air occurs adiabatically.
  - Canadian anticyclones can lead to polar air outbreaks during winter.
  - Anticyclones from continental (CT) air masses bring hot, clear weather.
Cyclones:
- Low-pressure systems characterized by converging and rising air.
- Cyclonic uplift leads to cloud formation and precipitation, demonstrating more variability in the weather produced.
- Midlatitude and extratropical cyclones develop where cold, dry polar air meets warm, humid tropical air.
- These typically bring highly variable weather, especially in fall and spring, along polar fronts.

Path of Disturbances: Typically, atmospheric disturbances in North America travel from west to east, in line with the prevailing westerly winds.
Midlatitude Cyclones:
- Defined as well-organized low-pressure systems found in mid latitudes (30s to 50s degrees latitude).
- Interaction between migrating warm and cold fronts, particularly highlighted during winter with strong temperature contrasts.
- Canadian cold air masses and warm air from the Gulf of Mexico collide, creating severe weather.

Interaction of Air Masses:
- The mixing of cold Arctic air and warm tropical air leads to weather changes.
- Rossby waves influence the movement of the jet stream, allowing colder air to move southward.
ITCZ's Role:
- The Intertropical Convergence Zone (ITCZ) moves south, enabling polar fronts to also shift southward, increasing disturbances that lead to cyclones.
- Increased interactions between cold and warm fronts create potential for severe weather events.

Cyclones:
- Characterized by counterclockwise motion in the Northern Hemisphere and the potential for violent precipitation and storm systems.
- Warm and cold fronts meet, creating areas of rising air and dynamic weather changes.
Anticyclones:
- High pressure systems promote clear skies, often bringing fair weather and might produce cumulus or cirrus clouds.
- Characterized by clockwise rotation, with air diverging away from the center.

Cyclogenesis Process:
- Involves complex interactions between high and low-pressure air systems.
- Upper-level divergence allows air to rise, thereby forming low pressure (cyclonic motion).
- Cold fronts push against low-pressure centers, leading to precipitation and atmospheric disturbances.

Polar Jet Stream Influence:
- Contributes significantly by pulling Arctic air southward and affecting surface weather patterns.
- The interaction creates temperature distribution and varies precipitation rates due to temperature contrasts.
Waveforms:
- Rossby waves modulate air movement at high altitudes and cause fluctuations in surface weather.

Types of Fronts:
- Cold Fronts: Movement pushes cold air into warm air causing significant precipitation and wind changes.
- Warm Fronts: Warm air rises over cooler air resulting in gradual precipitation.
- Located near Low Pressure: Interaction of these fronts lead to dynamic storm systems with both frontal lifting and surface convergence.

Stages of Development:
- Cold fronts push in from the north, while warm fronts advance from the south, initiating cyclonic circulation.
- Heavy rain occurs just behind cold fronts, while warm fronts may bring gentle rain leading to differing weather patterns as the system develops.
- Eventually can lead to occlusion where air masses mix, indicating major weather systems involving both precipitation and temperature shifts.