WEEK 1 ENVR 1040 Meteorology Study Notes

ENVR 1040 Meteorology Study Notes

Course Overview

  • Welcome to the course on Meteorology.

  • Resources:
      - Reference Text: From the Ground Up
      - Aeronautical Information Manual (AIM)
      - AWWS (Nav Canada) weather website: flightplanning.navcanada.ca
      - Other weather websites as applicable
      - CX3 Flight Computer

  • Tonight's Lesson: Overview of The Atmosphere and Clouds.

Topics Covered

  • The Atmosphere

  • Clouds

  • Pressure and Wind

  • Humidity, Temperature and Stability

  • Air Masses and Fronts

  • Precipitation

  • Fog

  • Thunderstorms

  • Icing

  • Meteorology Reports and Forecasts

Evaluation Criteria

  • Quizzes (30% of final mark): Scheduled for Weeks 3, 5, 10, 12

  • Mid Term Examination (25% of final mark): Week 7

  • Final Examination (30% of final mark): Week 14

  • Class Participation (15% of final mark)

The Atmosphere

Composition

  • The atmosphere is primarily composed of:
      - 78% Nitrogen
      - 21% Oxygen
      - 1% Other Gases:
        - Argon
        - Carbon Dioxide
        - Water vapor
        - Other trace gases

Properties

  • Mobility:
      - The atmosphere exhibits movement, characterized by winds that can be comparable to large bodies of water like the ocean, but with greater freedom of motion in the air.

  • Expansion:
      - When air is forced to rise, the surrounding pressure decreases, allowing the rising air to expand and cool. This process can lead to cloud formation and subsequently precipitation.

  • Compression:
      - Conversely, if air descends, the surrounding pressure increases, causing the air to compress and warm. This warming can lead to the evaporation of any water droplets present.

Adiabatic Processes

  • Adiabatic refers to a process of cooling or heating that occurs without transfer of heat to or from the environment.
      - Rising air cools through adiabatic expansion.
      - Descending air warms through adiabatic compression.

Divisions of the Atmosphere

  • The atmosphere is categorized into several layers:
      - Troposphere: Extends from sea level to about 25,000 to 30,000 feet; where weather phenomena primarily occur.
      - Stratosphere: Above the troposphere, beginning at about 50,000 feet.
      - Mesosphere: Above the stratosphere.
      - Thermosphere: Extends beyond the mesosphere.
      - Exosphere: The outermost layer, essentially space.

Temperature Variations with Altitude

  • Temperature and pressure generally decrease with altitude in the troposphere. The tropopause is defined as the point where temperature stops decreasing and begins increasing in the stratosphere.

  • Specific temperatures at different altitudes include:
      - Top of the tropopause: ~-56°C
      - Stratopause: ~0°C at the top of the stratosphere.

Ozone Layer

  • Ozone Layer Definition:
      - A layer in the Earth's stratosphere containing a high concentration of ozone (O₃), which absorbs the majority of the Sun's harmful ultraviolet radiation.

  • Ozone Formation:
      - Ozone is formed by the combination of free oxygen molecules (O) with diatomic oxygen molecules (O₂) in the presence of ultraviolet (UV) light.

  • UV Light Interaction:
      - UV light between 100-315 nm is filtered through the processes of ozone creation and destruction.

Clouds

Classification

  • Clouds are classified based on their height and formation methods:
      - Height-Based Classification:
        - High Clouds: 16,500 to 45,000 feet (e.g., Cirrus, Cirrostratus)
        - Middle Clouds: 6,500 to 23,000 feet (e.g., Altostratus, Altocumulus)
        - Low Clouds: Surface to 6,500 feet (e.g., Stratus, Nimbostratus)
      - Formation-Based Classification:
        - Stratus: Horizontal layers
        - Cumulus: Vertical development
        - Nimbus: Associated with precipitation

Sky Condition in Aviation Weather

  • Expressed in eighths (or “oktas”) of sky covered by clouds, defined as follows:
      - Clear: 0 oktas (no clouds)
      - Few: 1-2 oktas
      - Scattered: 3-4 oktas
      - Broken: 5-7 oktas
      - Overcast: 8 oktas

  • Ceiling is defined when conditions are either Broken or Overcast.

Cloud Formation Processes

  • Clouds are formed through:
      1. Rising Air: Air expands and cools as it rises, leading to condensation at or past the dew point.
      2. Addition of Water Vapor: Water vapor is added until saturation (the air cannot hold any m     ore).

  • The primary reason for cloud formation is rising air due to uplifting mechanisms such as:
      - Orographic Lift: Air is lifted over mountains, cooling and condensing.
      - Convection: Uneven heating causes parcels of air to rise.
      - Frontal Lift: Warm air pushing upward over colder air, leading to cooling.
      - Turbulence: Wind stirring the air can also induce lifting.
      - Convergence: Air parcels moving toward each other may force the air upward, promoting cloud formation.

Summary

  • The course thus far has covered:
      - Atmosphere composition and structure
      - Basic properties of the atmosphere
      - Important concepts such as adiabatic processes
      - Cloud classification
      - The formation of clouds under various atmospheric conditions

  • Next Week's Topic: Pressure, and further understanding of interpreting Graphic Area Forecasts from the specified sections in From the Ground Up.

  • Reference additional resources via the Nav Canada weather website: flightplanning.navcanada.ca.