Weather Theory for Canadian Aviation Groundschools

Table of Contents

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i

THE ATMOSPHERE . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

TEMPERATURE AND HEATING . . . . . . . . . . . . . . . . 2-1

Temperature Scales
Heating and Cooling Mechanisms in the Atmosphere: Conduction; Radiation; Convection; Expansion and Compression; Latent Heat; Horizontal Temperature Advection
Vertical Temperature Variations, Inversions and Isothermal Layers
Worksheet

PRESSURE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

Pressure Definition
Pressure Measurements
Pressure Units
Barometers in Aircraft
Station Pressure and Sea Level Pressure
Why do we need MSL pressures?: For forecasters; For pilots
Isobars, Pressure Systems and Their Variations: Highs; Ridges; Lows; Troughs; Secondary highs and lows; Cols
Horizontal Pressure Differences
Wind Direction
Wind Speed
Some notes on pressure systems
Worksheet

WIND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

Wind and Pressure Gradient Force
Wind in Relation to Pressure Systems
Deflection Caused By the Earth's Rotation - Coriolis Force
Aircraft Drift Caused by the Wind
Winds and Centrifugal Force
The Force and Effects of Friction: Friction; Veering and Backing of the Wind
Wind Phenomena: Large Scale Winds (thousands of miles in extent); Medium Scale Winds (hundreds of miles in extent); Small Scale Winds (tens of miles)
Worksheet

TURBULENCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

ALTIMETRY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1

Aircraft Altitude and Pressure Errors
Aircraft Altitude and Temperature Errors
Correcting Aircraft Altitude for Temperature and Pressure Errors: Pressure Correction; Temperature Correction
Correcting Aircraft Performance for Pressure and Temperature Errors: Correcting Performance for Pressure Errors using Pressure Altitude; Correcting Aircraft Performance for Non-standard Temperatures using Density Altitude
Worksheet

Moisture and Precipitation . . . . . . . . . . . . . . . . . . .7-1

STABILITY AND INSTABILITY . . . . . . . . . . . . . . . . . 8-1

What is Stability?
Some Examples of Stable and Unstable Conditions
Moisture and Instability
Modification of Stability: . . . By Changing Temperature; . . . By Changing Moisture
Characteristics of Stable and Unstable Air
Some Notes on Stability and Instability
Worksheet

CLOUDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-1

Cloud Classification System
Terminology
Layer Clouds: Low; Middle; High
Heap or Convective Clouds: Little vertical extent; Considerable vertical extent; Extreme vertical extent
Cloud Formation, Structure, Precipitation and Turbulence: Convective lift; Mechanical Lift; Orographic Lift; Convergence; Frontal Lift; Atmospheric Dynamics
Notes on Cloud Formation
Worksheet

AIRCRAFT ICING . . . . . . . . . . . . . . . . . . . . . . . . . . 10-1

Icing and Temperature: Flight in temperatures above 0 °C; Flight in very cold temperatures; Flight in temperatures from 0 °C to -20 °C
Icing and Air Frames
Icing and Airspeed
Types of Icing: Clear Ice; Rime Icing; Mixed Icing
Icing Intensity: Light Icing; Moderate Icing; Severe Icing
Clouds and Icing
Special Icing Scenarios: Icing Due to Freezing Rain; Icing Due to Freezing Drizzle; Icing in non-Cloudy Air
Worksheet

AIR MASSES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-1

FRONTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-1

Formation of Fronts
Symbology of Fronts
Types of Fronts and Their Structure: Cold Front; Warm Front; Occlusions and Trowals; Quasi-Stationary Front; Upper Fronts
Fronts in North America
Terms and Fronts: Frontogenesis; Frontolysis; Wave; Cold sector; Warm sector
Worksheet

FRONTAL WEATHER . . . . . . . . . . . . . . . . . . . . . . 13-1

Cold Front Weather: Cold Fronts and Wind; Cold Fronts and Temperature; Cold Fronts and Moisture (dewpoint); Cold Front Clouds and Precipitation; Cold Fronts and Visibility; Cold Fronts and Pressure; Cold Fronts and Flight Problems
Warm Front Weather: Warm Fronts and Wind; Warm Fronts and Temperature; Warm Fronts and Moisture (dewpoint); Warm Front Clouds and Precipitation; Warm Fronts and Visibility; Warm Fronts and Pressure; Warm Fronts and Flight Problems; Warm Fronts and Freezing Rain
Some Questions
Weather at Trowals
Weather at Upper Fronts
Worksheet

SURFACE BASED LAYERS . . . . . . . . . . . . . . . . . . 14-1

Fog
Fog Types: Radiation Fog; Upslope Fog; Advection Fog; Steam Fog/Arctic Sea Smoke; Ice Fog; Frontal Fog
Haze and Smoke
Blowing Obstructions to Visibility: Blowing Sand (Dust); Blowing Snow
Obscured and Partially-Obscured Conditions
Worksheet

THUNDERSTORMS . . . . . . . . . . . . . . . . . . . . . . . . 15-1

Requirements for Thunderstorm Development
Development and Dissipation of Thunderstorms: Cumulus or Development Stage; Mature Stage; Dissipation Stage
Scenarios for Thunderstorm Development: Air Mass CB's; Frontal CB's
Severe Thunderstorm: Development; Rules of Thumb
Thunderstorm Hazards: Sudden Changes in Surface Pressure and Temperature; Gusts, Squalls and Gust Fronts; Turbulence; Wind Shear and Microbursts; Hail; Icing; Precipitation; Tornadoes; Lightning; Worksheet

SEVERE CONVECTIVE WEATHER: SQUALL LINES AND TORNADOES . . . . . . . . . . . . 16-1

HURRICANES . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-1

WORKSHEET SOLUTIONS . . . . . . . . . . . . . . . . . . . A-1