Wind_ Small-Scale __and Local Systems

Page 1

Introduction to the Incident

  • Date and Flight Information: United Airlines Boeing 747 on December 28, 1997, with 374 passengers.

  • Flight Path: En route to Hawaii from Japan, cruising altitude at 31,000 feet.

  • Incident: Suddenly encountered severe air turbulence east of Tokyo after 2 hours of uneventful flight.

  • Injuries: 160 passengers injured; one passenger fatality due to severe head injuries after being thrown against the ceiling.

Turbulence and Atmospheric Phenomena

  • Atmospheric Phenomenon: Investigation of the causes of turbulence and atmospheric conditions leading to such incidents.

  • Key Focus: Wind patterns, small-scale and local systems affecting turbulence.

Page 2

Scales of Atmospheric Motion

1. Microscale Motion

  • Definition: The smallest scale of atmospheric motion; eddies with diameters of a few meters or less.

  • Effects: Disperses smoke, sways branches, and lifts dust.

  • Formation: Caused by convection or wind interacting with obstructions, typically very short-lived.

2. Mesoscale Motion

  • Definition: Intermediate scale of atmospheric motion; lasts longer than microscale.

  • Examples: Local winds, thunderstorms, tornadoes, small tropical cyclones.

  • Size Range: Eddies can measure a few kilometers to about 100 km in diameter.

3. Synoptic Scale Motion

  • Definition: Larger weather systems, typically ranges hundreds to thousands of square kilometers.

  • Examples: Mid-latitude storm systems, hurricanes, typhoons.

  • Weather Impact: Longer lifespan, often lasting days to weeks.

4. Global Scale Motion

  • Definition: The largest wind patterns influencing the entire Earth's atmosphere.

  • Examples: Jet streams and large cyclone circulations.

Page 3

Wind Dynamics

Laminar and Turbulent Flow

  • Laminar Flow: Smooth, horizontal moving air over stationary air; involves minimal friction.

  • Eddy Viscosity: Turbulent flow generates internal friction impacting wind speed.

  • Mechanical Turbulence: Created by obstructions causing irregular air motion.

Effects of Turbulence

  • Surface Winds: Typically stronger in the afternoon due to increased vertical mixing.

  • Boundary Layer: The frictional influence affecting wind near the surface.

Page 4

Eddies and Atmospheric Stability

  • Eddies: Spinning air globs that arise from turbulence, more likely in unstable air.

  • Wind Shadows: Formation of eddies behind objects leads to varying wind speeds and directions.

  • Stable vs Unstable Air: Vertical mixing impacts the strength of surface winds.

Page 5

Large-Scale Wind Influences

Atmospheric Barriers

  • Obstructions Impact: Eddies form on the leeward side impacting wind behavior.

  • Hurricane Speeds: The vast majority of atmospheric structures can affect localized weather events.

Force of Wind

  • Proportionality: Wind force is proportional to wind speed squared.

  • Examples of Wind Force: Instances of wind affecting structures, moving objects unexpectedly.

Page 6

Eddies and Air Pockets

  • Production of Eddies: Eddies imply abrupt change in wind speed and direction; forms turbulence.

  • Clear Air Turbulence: Often unnoticed, leading to severe flight conditions.

  • Air Pockets: Unexpected drops in aircraft may occur due to sudden entry into eddy zones.

Page 7

Understanding Clear Air Turbulence (CAT)

  • Formation: Occurs aloft near jet streams; sudden air shifts can cause severe turbulence.

  • Aircraft Safety: Importance of wearing seatbelts due to the potential for sudden drops.

Page 8

Influence of Wind on Earth’s Surface

  • Wind Erosion: Illustration of wind’s impact on landscapes, including sand dunes and ripples.

  • Wind and Water: Effects of wind on lake and ocean wave formations.

Page 9

Wind Dynamics in Desert Conditions

  • Dust Storms and Winds: Winds can lift fine particles, leading to dust storms known as haboobs.

  • Dust Devils: Smaller, rotating updrafts that form in hot conditions, impacting soil and visibility.

Page 10

Patterns of Urban Wind Influence

  • Snow and Landscape: Wind's role in reshaping mountains and snow patterns.

  • Vegetation Influence: How wind impacts plant growth, especially in dry regions.

Page 11

Coastal Wind Patterns

  • Winds Creating Waves: Wind-induced waves and their characteristics.

  • Seiches: Occasional oscillation of water levels due to wind effects on large water bodies.

Page 12

Wind Properties and Measurement

  • Wind Measurements: Describe various measurements including wind speed, direction, and their applications.

  • Instruments: Overview of wind measurement tools, such as anemometers, wind vanes, and pilot balloons.

Page 13

Applications of Wind Data

  • Impacts on Agriculture: Influence of prevailing winds on crop productivity.

  • Urban Planning: How wind data is used in city planning and environmental assessment.

Page 14

Key Takeaways

  • Summary of Key Concepts: Recap of the historical context of winds, their effects on landscapes, and societal implications.

  • Wind's Role in Weather Systems: Importance of understanding wind patterns for predicting weather outcomes.

Page 15

Future Directions

  • Advancements in Wind Energy: Increasing reliance on wind energy development across various regions.

  • Research and Innovations: Ongoing efforts towards enhancing wind energy efficiency and reducing ecological impact.