Weather and Atmosphere Quiz
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Questions and Answers

What effect does cloud cover have on maximum temperature during the day?

  • It has no significant effect on T max.
  • It increases T max by trapping solar radiation.
  • It increases T max by enhancing surface wind.
  • It decreases T max by reflecting solar radiation. (correct)

How is density defined?

  • Mass per unit volume. (correct)
  • Pressure per unit volume.
  • Mass per unit area.
  • Volume per unit mass.

What happens to minimum temperature due to wind at night?

  • It increases due to turbulent mixing of cold air. (correct)
  • It increases because wind reduces cloud cover.
  • It stays the same regardless of wind.
  • It decreases because wind cools the surface.

What is the ISA density value expressed in grams per cubic meter?

<p>1225 g/m³ (B)</p> Signup and view all the answers

During the day, how does wind affect temperatures?

<p>It reduces maximum temperature by mixing warm and cold air. (D)</p> Signup and view all the answers

At what height do Cirrus clouds typically form?

<p>16,500 to 45,000 ft (B)</p> Signup and view all the answers

Which cloud type is associated with ice crystals and generally has nil icing?

<p>Cirrostratus (B)</p> Signup and view all the answers

What is the primary composition of Altocumulus clouds?

<p>Water droplets and ice crystals (B)</p> Signup and view all the answers

Which type of cloud is typically found 400 to 600 nautical miles ahead of a warm front?

<p>Cirrostratus (D)</p> Signup and view all the answers

What is the expected visibility associated with Cirrocumulus clouds?

<p>1000 m + (D)</p> Signup and view all the answers

What characteristic do Altocumulus clouds exhibit in terms of icing?

<p>Light to moderate icing (D)</p> Signup and view all the answers

In terms of turbulence, Cirrocumulus clouds have what kind of relationship?

<p>Light turbulence when present (C)</p> Signup and view all the answers

Which cloud type is known to significantly indicate turbulence?

<p>Altocumulus (A)</p> Signup and view all the answers

What is the atmospheric pressure at Mean Sea Level (MSL)?

<p>1013.25 hPa (D)</p> Signup and view all the answers

How does temperature change between 11 km and 20 km altitude?

<p>Temperature remains constant (B)</p> Signup and view all the answers

What unit is commonly associated with atmospheric pressure measurements?

<p>Pascal (Pa) (D)</p> Signup and view all the answers

What phenomenon explains the difference in atmospheric pressure above two altitudes?

<p>Weight of the air column (D)</p> Signup and view all the answers

Which device measures atmospheric pressure using a column of mercury?

<p>Mercury barometer (C)</p> Signup and view all the answers

What happens to temperature in the atmosphere between 20 km and 32 km altitude?

<p>Temperature increases at 0.3⁰C/1000ft (D)</p> Signup and view all the answers

What is the relationship between pressure and altitude?

<p>Pressure decreases with altitude (B)</p> Signup and view all the answers

How is the force exerted on a surface by the atmosphere quantified?

<p>Pressure = Force/Area (D)</p> Signup and view all the answers

What defines an Isothermal Layer in the atmosphere?

<p>Temperature remains the same with change in height (D)</p> Signup and view all the answers

What is the boiling point of water in the Celsius scale?

<p>100 degrees (D)</p> Signup and view all the answers

What is the primary purpose of anti-icing measures?

<p>To prevent the formation of ice (D)</p> Signup and view all the answers

Which of the following processes primarily heats the atmosphere from the ground up?

<p>Terrestrial Radiation (A)</p> Signup and view all the answers

Which factor is not involved in the heating of the atmosphere?

<p>Reflection of solar wind (D)</p> Signup and view all the answers

Which condition increases the risk of carburettor icing the most?

<p>Temperatures between -10°C and +25°C in cloud, fog, or precipitation (A)</p> Signup and view all the answers

What is the function of de-icing measures?

<p>To remove icing after it has formed (A)</p> Signup and view all the answers

What is the Environmental Lapse Rate (ELR) under ISA conditions?

<p>2⁰C/1000 ft (A)</p> Signup and view all the answers

What happens to the air in contact with the ground at night?

<p>It loses heat by conduction (A)</p> Signup and view all the answers

What should be checked during the 'Before/ During Takeoff' procedure regarding engine performance?

<p>Engine operation should be checked for stability (C)</p> Signup and view all the answers

What is the correct conversion factor from Fahrenheit to Celsius?

<p>C = (F - 32) × (5/9) (A)</p> Signup and view all the answers

Which of the following is NOT an example of anti-icing measure?

<p>De-icing fluids (A)</p> Signup and view all the answers

Which of the following statements about Conduction is true?

<p>It occurs when two bodies touch each other. (A)</p> Signup and view all the answers

What safety measure should be taken during taxiing on slippery surfaces?

<p>Allow greater than normal distances between airplanes (B)</p> Signup and view all the answers

What aspect of the aircraft may appear less bright due to weather conditions during pre-taxi checks?

<p>The displays (D)</p> Signup and view all the answers

What is a consequence of NOT checking flight controls and flaps before taxi?

<p>Potential restriction in control movement (C)</p> Signup and view all the answers

What is one effect of ice accretion on an aircraft's airframe?

<p>Loss of lift and increase in drag (A)</p> Signup and view all the answers

What can happen to the aircraft instruments when ice obstructs them?

<p>They can give erroneous readings (D)</p> Signup and view all the answers

What temperature conditions can lead to the formation of supercooled water droplets?

<p>Below 0°C down to -40°C or lower (D)</p> Signup and view all the answers

What can ice blocking the air intake of an engine result in?

<p>Complete engine failure (B)</p> Signup and view all the answers

How does icing affect the center of gravity (CG) of an aircraft?

<p>It can cause a change in CG position (A)</p> Signup and view all the answers

What type of ice formation occurs from water droplets freezing upon contact with a surface?

<p>Clear ice (A), Rime ice (B)</p> Signup and view all the answers

What effect does ice have on windscreens and canopies of an aircraft?

<p>It obscures the view (A)</p> Signup and view all the answers

What is the primary danger of icing affecting the propeller of an aircraft?

<p>Increased risk of control difficulties (B)</p> Signup and view all the answers

What occurs to water vapor in rising air during the process of condensation?

<p>It condenses into visible droplets, forming clouds. (A)</p> Signup and view all the answers

How does the latitude effect influence surface temperature?

<p>Equatorial regions receive more heat per unit area than polar regions. (B)</p> Signup and view all the answers

At what time is the highest temperature typically observed on Earth's surface?

<p>At approximately 1500 local time. (A)</p> Signup and view all the answers

What role does latent heat play during the condensation of water vapor?

<p>It adds to the heat of the atmosphere. (D)</p> Signup and view all the answers

What factor primarily contributes to the seasonal effect on temperature?

<p>Earth's axial tilt and its revolution around the Sun. (A)</p> Signup and view all the answers

What happens to air when heated through conduction?

<p>It expands and rises, creating convection currents. (D)</p> Signup and view all the answers

What characterizes diurnal temperature variation?

<p>There is a slight lag in heat transfer to the atmosphere. (C)</p> Signup and view all the answers

Which of the following statements about convection currents is true?

<p>They are caused by warm air rising and cold air sinking. (D)</p> Signup and view all the answers

What happens to the air during the mature stage of a thunderstorm?

<p>Air is drawn in from the sides and below. (B)</p> Signup and view all the answers

Which factor contributes to the speed of down drafts during precipitation in a thunderstorm?

<p>Evaporation of rain that absorbs latent heat. (A)</p> Signup and view all the answers

What are microbursts characterized by?

<p>Very strong down currents confined to a small region. (D)</p> Signup and view all the answers

What is the maximum possible speed of up currents during a thunderstorm?

<p>10,000 feet per minute. (C)</p> Signup and view all the answers

How long can a gust front be experienced ahead of a thunderstorm?

<p>13 to 17 nautical miles. (D)</p> Signup and view all the answers

What leads to the colder, denser air that accelerates down drafts in a thunderstorm?

<p>Cooling from evaporation of rain droplets. (C)</p> Signup and view all the answers

What typically results from the rising and falling water droplets in a thunderstorm?

<p>Build-up of static electricity within the cloud. (C)</p> Signup and view all the answers

What type of turbulence is expected in and around a mature thunderstorm?

<p>Extreme turbulence with both updrafts and downdrafts. (B)</p> Signup and view all the answers

What does the variable 'Td' represent in the height of cloud base formula?

<p>Dewpoint temperature (B)</p> Signup and view all the answers

Which statement accurately describes the formula for calculating the height of cloud base in meters?

<p>h = (T – Td) 125 (A)</p> Signup and view all the answers

What is the significance of the wind direction being reported in degrees true (°T) rather than magnetic (°M)?

<p>It indicates the angle relative to true north. (D)</p> Signup and view all the answers

Which term refers to a change in wind direction in a clockwise manner?

<p>Veering (A)</p> Signup and view all the answers

What does the wind velocity (W/V) include as a component?

<p>Both direction and speed (B)</p> Signup and view all the answers

When calculating the height of cloud base using the dewpoint formula, what does the value of 400 represent?

<p>Conversion factor to feet (B)</p> Signup and view all the answers

What unit is commonly used to express wind speed in aviation?

<p>Knots (C)</p> Signup and view all the answers

Which of the following best describes the concept of 'backing' in wind behavior?

<p>Wind shifts in an anticlockwise direction (D)</p> Signup and view all the answers

What characterizes the dissipating stage of a thunderstorm?

<p>Predominantly downdraughts and heavy precipitation (C)</p> Signup and view all the answers

Which of the following hazards is associated with thunderstorms?

<p>Hail and Icing (D)</p> Signup and view all the answers

What is a notable feature of the cloud structure during a thunderstorm's mature stage?

<p>The cloud expands to the tropopause (A)</p> Signup and view all the answers

What causes lightning formation in a thundercloud?

<p>Large variations in static charge within and around the cloud (D)</p> Signup and view all the answers

How long does the dissipating stage of a thunderstorm typically last?

<p>1½ to 2½ hours (D)</p> Signup and view all the answers

What kind of airflow is primarily present during the dissipating stage of a thunderstorm?

<p>Overwhelming downdraughts (D)</p> Signup and view all the answers

Which of the following is NOT a characteristic of thunderstorms?

<p>Stable and calm conditions (D)</p> Signup and view all the answers

What does the upper wind do to the cloud at the tropopause stage of a thunderstorm?

<p>Disperses the cloud to create an anvil formation (B)</p> Signup and view all the answers

When the temperature is colder than ISA, which statement is accurate regarding the relationship between true altitude and indicated altitude?

<p>Indicated altitude is higher than true altitude. (B)</p> Signup and view all the answers

What is the frequency of METAR issuance during aerodrome operations?

<p>Every half hour. (A)</p> Signup and view all the answers

In the decoded METAR, what does 'BKN025' signify about cloud cover?

<p>Clouds at 2500 feet with broken coverage. (A)</p> Signup and view all the answers

What does the 'QNH' value represent in a METAR report?

<p>Mean sea level pressure. (C)</p> Signup and view all the answers

How do TAFs differ from METARs in terms of their content?

<p>TAFs are forecasts for future weather at an aerodrome, METARs are actual conditions. (C)</p> Signup and view all the answers

In a TAF report, what does 'BECMG' imply?

<p>The weather conditions are expected to change. (B)</p> Signup and view all the answers

What does the term 'CB' refer to in meteorological messages?

<p>Cumulonimbus clouds that indicate severe weather. (B)</p> Signup and view all the answers

In a decoded TAF report, what does the notation 'PROB30' indicate?

<p>There is a 30% probability of temporary weather conditions. (A)</p> Signup and view all the answers

What is the Dry Adiabatic Lapse Rate (DALR) for dry air?

<p>3°C per 1000 ft (B)</p> Signup and view all the answers

What occurs when saturated air is forced to rise?

<p>It cools, causing condensation and latent heat release (A)</p> Signup and view all the answers

What defines atmospheric stability?

<p>Resistance to change in temperature and pressure (C)</p> Signup and view all the answers

What is the average value of the Saturated Adiabatic Lapse Rate (SALR)?

<p>1.5°C/1000 ft (A)</p> Signup and view all the answers

What is indicated by the dew point temperature?

<p>The temperature at which condensation first occurs (D)</p> Signup and view all the answers

Which scenario exemplifies an adiabatic process?

<p>Air cooling due to pressure decrease without heat transfer (A)</p> Signup and view all the answers

What determines the Environmental Lapse Rate (ELR)?

<p>It varies based on actual atmospheric conditions (A)</p> Signup and view all the answers

Which factor contributes to the instability of the air?

<p>Warmer air at ground level compared to upper layers (B)</p> Signup and view all the answers

What is the abbreviation for a cloud cover that indicates 5 to 7 oktas?

<p>BKN (B)</p> Signup and view all the answers

Which formula correctly represents the calculation for cloud base height when the dewpoint is not constant?

<p>H = (T – Td)400 (D)</p> Signup and view all the answers

Which cloud type is associated with a significant vertical extent and is typically described as heaped?

<p>Cumuliform (D)</p> Signup and view all the answers

What does the term 'cloud ceiling' refer to in meteorology?

<p>The height of the lowest cloud layer with more than 4 oktas (A)</p> Signup and view all the answers

How can stratiform clouds be best characterized?

<p>They have considerable horizontal extent with little vertical height (A)</p> Signup and view all the answers

What abbreviation represents sky clear conditions with 0 oktas of cloud cover?

<p>SKC (C)</p> Signup and view all the answers

What type of cloud is typically present only at high levels in the troposphere and appears wispy or fibrous?

<p>Cirriform (C)</p> Signup and view all the answers

Which option describes the term 'oktas' in relation to cloud cover?

<p>A way to quantify the amount of cloud cover (A)</p> Signup and view all the answers

What is the true altitude of an aircraft flying at 6000 feet with a QNH of 1008 hPa and a temperature of 8°C?

<p>6120 ft (C)</p> Signup and view all the answers

How is QNH approximately calculated if an aerodrome has an elevation of 1500 ft and a QFE of 965 hPa?

<p>1021 hPa (B)</p> Signup and view all the answers

What adjustment should be made to the indicated altitude when the actual temperature is colder than ISA conditions?

<p>Subtract altitude (C)</p> Signup and view all the answers

When using altimetry calculations, what is the equivalent feet for 1 hPa of pressure change?

<p>27 ft (C)</p> Signup and view all the answers

If an aircraft's indicated altitude is higher than its true altitude, under what condition is this likely occurring?

<p>When the temperature is warmer than ISA (A)</p> Signup and view all the answers

What is the proper formula to convert indicated altitude to true altitude in case of a temperature deviation from ISA?

<p>$4 ext{ ft} imes rac{ ext{altitude}}{1000} imes ext{deviation}$ (A)</p> Signup and view all the answers

What is the total pressure change if an aircraft flying at 3500 ft has a QNH of 1010 hPa and a QFE of 988 hPa?

<p>22 hPa (C)</p> Signup and view all the answers

How does pressure at sea level relate to the QNH when an airfield is elevated?

<p>QNH will be higher than sea level pressure (B)</p> Signup and view all the answers

What is the approximate slope of a warm front?

<p>1:150 (A)</p> Signup and view all the answers

What type of weather is generally expected just before a warm front passes?

<p>Increasing cloud cover with potential fog (D)</p> Signup and view all the answers

What is typically true about a cold front compared to a warm front?

<p>Cold fronts have a steeper slope of approximately 1:80. (D)</p> Signup and view all the answers

What weather condition is typically observed after the passage of a cold front?

<p>Marked improvement in weather with lower temperatures (D)</p> Signup and view all the answers

What occurs during an occlusion?

<p>A cold front catches up with a warm front. (C)</p> Signup and view all the answers

What type of precipitation is commonly associated with cold fronts?

<p>Showers of rain or even hail (B)</p> Signup and view all the answers

How does the visibility change as a warm front approaches?

<p>Visibility decreases and may lead to fog. (C)</p> Signup and view all the answers

What defines the movement speed difference between cold fronts and warm fronts?

<p>Cold fronts typically move faster than warm fronts. (D)</p> Signup and view all the answers

What atmospheric condition occurs when ELR is less than both SALR and DALR?

<p>Absolute Stability (B)</p> Signup and view all the answers

Which lapse rate indicates that the atmosphere is stable and prevents upward movement of air?

<p>Saturated Adiabatic Lapse Rate (SALR) (B)</p> Signup and view all the answers

In which condition would an atmosphere be considered conditionally unstable?

<p>DALR &gt; ELR &gt; SALR (B)</p> Signup and view all the answers

What is the required formula to determine the cloud base height if the dewpoint is constant?

<p>H = (T - Td) ÷ 3 x 1000 (A)</p> Signup and view all the answers

What happens to air that is colder than its surrounding environment?

<p>It is more dense and sinks. (B)</p> Signup and view all the answers

What is the consequence of having an Environmental Lapse Rate (ELR) greater than both DALR and SALR?

<p>The atmosphere is absolutely unstable. (D)</p> Signup and view all the answers

What type of stability exists when the DALR is less than the ELR and greater than the SALR?

<p>Conditional Stability (B)</p> Signup and view all the answers

At what conditions is the ELR considered neutral?

<p>ELR = DALR (D)</p> Signup and view all the answers

Which lapse rate is generally used to describe the cooling of air that is rising under dry conditions?

<p>Dry Adiabatic Lapse Rate (DALR) (B)</p> Signup and view all the answers

Which temperature scale has its freezing point at 32 degrees?

<p>Fahrenheit (B)</p> Signup and view all the answers

Which process primarily heats the atmosphere through radiation from the Earth's surface?

<p>Terrestrial Radiation (B)</p> Signup and view all the answers

Which factor correctly describes conduction between the air and the ground at night?

<p>Ground cooling causes air to lose heat. (A)</p> Signup and view all the answers

How is the freezing point of water expressed in the Kelvin scale?

<p>273 K (B)</p> Signup and view all the answers

Which statement about insolation is accurate?

<p>It refers to the portion of solar radiation that reaches the Earth’s surface. (A)</p> Signup and view all the answers

What temperature change occurs in the atmosphere as altitude increases?

<p>It decreases due to temperature lapse rate. (B)</p> Signup and view all the answers

What is a primary source of heat for the atmosphere?

<p>The Sun (B)</p> Signup and view all the answers

What is the main purpose of de-icing measures?

<p>To remove ice after it has formed (D)</p> Signup and view all the answers

Which of the following is NOT a condition conducive to the formation of carburettor icing?

<p>Low humidity conditions (A)</p> Signup and view all the answers

Which procedure should be performed prior to taxiing to ensure safe operations?

<p>Perform the engine start procedures (A)</p> Signup and view all the answers

What is an example of an anti-icing measure?

<p>Hot air systems on leading edges (A)</p> Signup and view all the answers

What should be checked for during the 'Before/ During Takeoff' procedure in relation to instruments?

<p>Stable engine operation indicators (C)</p> Signup and view all the answers

Which of the following is a correct procedure during taxiing on slippery surfaces?

<p>Taxi at reduced speed (C)</p> Signup and view all the answers

What happens to the displays during cold weather operations?

<p>They may appear less bright than normal (C)</p> Signup and view all the answers

Which of the following is a characteristic of hot air systems used as anti-icing measures?

<p>They are used to maintain surface temperature above freezing (B)</p> Signup and view all the answers

Flashcards

Mean Sea Level (MSL) pressure

The average atmospheric pressure at sea level, typically 1013.25 hPa (hectopascals).

Atmospheric pressure

The force exerted by the atmosphere per unit area.

SI unit for pressure

Pascal (Pa), which is equivalent to N/m² (Newtons per square meter).

1 bar

Equivalent to 100,000 Pa.

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Atmospheric pressure measurement

Measured using instruments like mercury barometers (using mercury) and aneroid barometers (using a sealed capsule).

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Temperature decrease with altitude

In the troposphere (up to 11 km), temperature generally decreases by 1.98⁰C for every 1000 ft or 6.5⁰C per kilometer.

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Constant temperature in the stratosphere

Between 11 km and 20 km altitude, the temperature stays consistently at -56.5°C.

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Temperature increase in the mesosphere

From 20 km to 32 km, the temperature increases at 0.3⁰C/1000ft or about 1⁰C per kilometer.

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Isothermal Layer

A layer in the atmosphere where the temperature remains constant with changes in altitude.

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Fahrenheit Scale

A temperature scale where water freezes at 32 degrees and boils at 212 degrees.

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Celsius Scale

A temperature scale where water freezes at 0 degrees and boils at 100 degrees.

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Kelvin Scale

An absolute temperature scale where 0 Kelvin is the absolute zero, the theoretical temperature at which all molecular motion stops.

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Insolation

The process of the Earth's surface absorbing solar radiation.

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Terrestrial Radiation

The process of the Earth's surface emitting long-wave radiation back into the atmosphere.

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Temperature Lapse Rate

The rate at which temperature decreases with increasing altitude in the atmosphere.

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Conduction

The transfer of heat through direct contact between objects.

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Density

A measure of how much mass is packed into a given volume. It's like how tightly packed the molecules are in a substance.

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Density Altitude

The altitude in the atmosphere where the air has the same density as at your current altitude. It's used to adjust for changes in air density.

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What is relative density?

A comparison of the density of a substance to the density of a reference substance, usually water. It tells you how much denser or less dense a substance is compared to water.

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How does wind affect temperature?

During the day, wind mixes warm air with cooler air above, lowering the maximum temperature. At night, wind mixes cold air with warmer air above, increasing the minimum temperature.

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How does cloud cover affect temperature?

During the day, clouds reflect some sunlight, lowering the maximum temperature. At night, clouds trap heat, raising the minimum temperature.

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Cirrus Clouds

High-altitude clouds composed of ice crystals, often appearing wispy or feathery. They are typically associated with fair weather and are found 16,500 ft to 45,000 ft.

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Cirrostratus Clouds

High-altitude clouds that form a thin, sheet-like veil across the sky, composed of ice crystals. They can cause a halo around the sun or moon.

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Cirrocumulus Clouds

High-altitude clouds that appear as small, white patches or ripples in the sky. They're composed of ice crystals and are often associated with turbulent conditions.

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Altocumulus Clouds

Mid-altitude clouds that form layers or patches of white or gray rounded masses. They can be composed of water droplets or ice crystals and are often associated with turbulence.

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Altostratus Clouds

Mid-altitude clouds that form a gray or bluish sheet across the sky, often covering the entire sky. They are composed of water droplets and are associated with widespread precipitation.

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Warm Front

A boundary between a warm air mass and a colder air mass, where the warmer air rises over the colder air. It is often associated with cirrus, cirrostratus, and altostratus clouds, warm temperatures, and precipitation.

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Turbulence

Irregular air movements that can cause aircraft to bump or shake. It's often associated with certain cloud types, such as cirrocumulus and altocumulus.

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Visibility

The distance at which objects can be clearly seen. Poor visibility is often associated with dense cloud formations.

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Icing Dangers

Ice buildup on aircraft can cause aerodynamic problems, affect instruments, reduce engine power, and create general hazards like obscured vision and landing gear issues.

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Supercooled Water Droplets (SWD)

Water droplets that remain liquid below 0°C. They can freeze instantly upon contact with a surface, like an aircraft.

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Icing Formation - Hoar Frost

Ice forming directly from water vapor in the air when the temperature is below 0°C.

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Icing Formation - Rime Ice

Ice forming when supercooled water droplets freeze on a surface.

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Icing Formation - Clear Ice

Transparent, hard ice formed when larger supercooled water droplets freeze slowly.

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Aerodynamic Effects of Icing

Ice buildup on an aircraft's surfaces can alter airflow, reducing lift and increasing drag, potentially causing loss of control.

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Instrument Effects of Icing

Ice can block pressure sensors, leading to inaccurate readings on airspeed, altitude, and other instruments.

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Engine Effects of Icing

Icing can block air intakes or form in carburetors, reducing engine power or causing complete failure.

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Carburetor Icing

Formation of ice in the carburetor, which can restrict airflow and affect engine performance.

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Carburetor Icing Conditions

Occurs in temperatures between -10°C and +25°C, in cloud, fog, or precipitation, at any power setting.

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Anti-icing Measures

Actions taken to prevent ice formation.

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De-icing Measures

Actions taken to remove ice after it has already formed.

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Anti-icing Examples

Kill-frost paste, heated windshields, hot air systems, anti-icing fluids.

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De-icing Examples

De-icing fluids, pulsating rubber boots, hot air systems, electrical heating systems.

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Pre-Taxi Inspection

Check for snow, ice, or frost on aircraft surfaces that could affect system operations.

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Taxiing in Icy Conditions

Increase taxiing distances, reduce speed, and be cautious of crosswinds.

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Condensation

As rising air cools, water vapor turns into liquid, forming clouds. This releases latent heat, further warming the atmosphere.

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Latitude Effect

The equator receives more solar energy per unit area, leading to hotter temperatures compared to the poles.

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Seasonal Effect

Earth's tilt causes changes in solar energy received throughout the year, causing seasons with varying temperatures.

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Diurnal Variation

Highest temperatures occur around 1500 hours (3pm) due to delayed heat transfer from the Earth's surface to the atmosphere.

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Adiabatic Process

The process of air cooling as it rises and warming as it sinks. This happens without heat exchange with the surroundings.

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Latent Heat

The energy released or absorbed during a change of state. In condensation, latent heat is released warming the atmosphere.

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Saturation (Air)

When air holds the maximum amount of water vapor possible at a given temperature. If cooled further, condensation occurs.

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Dew Point

The temperature at which air becomes saturated with water vapor. Any further cooling leads to condensation.

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Dry Adiabatic Lapse Rate (DALR)

Rate of cooling for dry, unsaturated air when forced to rise. It cools at a constant rate of 3°C per 1000 feet (1°C per 100 meters).

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Saturated Adiabatic Lapse Rate (SALR)

Rate of cooling for saturated air when forced to rise. It cools at a slower rate than DALR because condensation releases latent heat.

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Environmental Lapse Rate (ELR)

The actual rate at which temperature changes with altitude in a specific location. It is variable.

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Atmospheric Stability

Air's resistance to change. Stable air discourages vertical movement.

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Atmospheric Instability

Air that is warmer and less dense than its surroundings, leading to rising air. This promotes vertical movement.

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Cloud Base Height

The altitude at which condensation occurs, forming the base of a cloud.

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Cloud Base Height Formula

The formula used to calculate the height of the cloud base, considering surface temperature (T) and dewpoint (Td).

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Wind

Air in horizontal motion, characterized by direction and speed.

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Wind Velocity

A measure of wind speed and direction.

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Wind Direction

The direction from which the wind is blowing, typically expressed in degrees.

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Veering Wind

A change in wind direction to the right (clockwise).

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Backing Wind

A change in wind direction to the left (counterclockwise).

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Thunderstorm Stages

Thunderstorms go through three stages: cumulus, mature, and dissipating. The mature stage is characterized by heavy precipitation, strong down drafts, and lightning.

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Mature Stage Updrafts

In the mature stage, strong updrafts persist, reaching speeds of up to 10,000 feet per minute. This results in rapid cloud growth and intense turbulence within the storm.

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Mature Stage Downdrafts

During the mature stage, strong downdrafts are created by the falling precipitation. These downdrafts can reach speeds up to 2,400 feet per minute, bringing cold air to lower levels.

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Microbursts

Microbursts are concentrated downdrafts that occur in thunderstorms. They are localized, intense gusts of wind that can pose significant hazards to aviation.

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Macrobursts

Macrobursts are similar to microbursts but are larger in area, affecting a wider region. They are caused by the outflow of cold air from a thunderstorm.

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Thunderstorm Electricity

The movement of rising and falling water droplets in a thunderstorm creates static electricity. This usually results in positive charge at the top of the cloud and negative charge at the bottom, leading to lightning.

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Lightning

Lightning is a sudden release of electrical energy in a thunderstorm, caused by the buildup of static charges in the cloud. It occurs when the electric potential difference between the cloud and the ground becomes too great.

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Mature Thunderstorm Stage

The mature stage is characterized by heavy precipitation, strong updrafts and, most importantly, downdrafts.

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Dissipating Thunderstorm Stage

The dissipating stage features weaker updrafts and predominantly downdrafts, causing the storm to weaken and lose intensity.

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Thunderstorm Hazards

Thunderstorms bring various hazards, including wind shear, gust fronts, microbursts, hail and icing, static electricity, lightning, and even tornados.

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Static Electricity in Thunderstorms

Large variations in static charge within and around the storm cloud create electrical discharges, which manifest as lightning.

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Gust Front

A line of strong winds that spreads outward from a thunderstorm, creating a sudden and strong wind shift.

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TAF

A forecast of weather conditions at an airport for a specific period.

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True Altitude vs. Indicated Altitude

True altitude is the actual height above sea level, while indicated altitude is what an altimeter shows. When temperature is colder than standard, true altitude is lower than indicated altitude.

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Wind Variation

Wind direction can change within a given period, often expressed as a range of degrees.

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Cloud Coverage

The amount of the sky covered by clouds, expressed in oktas (eighths).

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Temperature and Dew Point

Temperature is the air's warmth, dew point is the temperature at which condensation occurs.

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Inversion

A situation where the air near the ground is colder than the air above, causing warm air to stay trapped above the cold air.

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Fahrenheit to Celsius

To convert Fahrenheit to Celsius, subtract 32, then multiply by 5/9.

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Celsius to Fahrenheit

To convert Celsius to Fahrenheit, multiply by 9/5, then add 32.

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True Altitude

The actual altitude of an aircraft above mean sea level.

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Indicated Altitude

The altitude shown on the altimeter, which is calibrated for ISA conditions.

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ISA Temperature

The standard temperature used in aviation calculations, where the temperature decreases by 2°C for every 1000 feet of altitude.

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Altitude Deviation from ISA

The difference between the actual air temperature and the ISA temperature at a given altitude.

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True Altitude Correction

Adjusting the indicated altitude to account for deviations from ISA temperature, adding 4 ft per 1000 ft for every 1°C warmer than ISA, and subtracting 4 ft per 1000 ft for every 1°C colder than ISA.

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Altimeter Calibration

The process of setting the altimeter to accurately indicate altitude based on atmospheric pressure and standard temperature conditions.

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What is atmospheric stability?

The atmosphere's resistance to vertical air movement. Stable air discourages rising or sinking air currents.

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What is atmospheric instability?

The tendency for air to rise due to being warmer and less dense than its surrounding environment. This promotes vertical movement.

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What is Absolute Stability?

When the ELR (Environmental Lapse Rate) is less than both the SALR (Saturated Adiabatic Lapse Rate) and DALR (Dry Adiabatic Lapse Rate) causing air to be very stable, making it resistant to rising or sinking.

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What is Absolute Instability?

When the ELR is greater than both the DALR and SALR, resulting in very unstable air, making it easy to rise and promotes strong updrafts.

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What is Conditional Instability?

A state where air is stable when unsaturated but becomes unstable when saturated. This means that rising air will only become unstable if it cools and condenses into clouds.

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What is the formula for calculating cloud base height?

H = (T – Td) ÷ 3 x 1000. Where T is the surface temperature (°C), Td is the dewpoint (°C), and H is the height of the cloud base in feet.

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What are the three stages of a thunderstorm?

Cumulus, mature, and dissipating. The mature stage is characterized by heavy precipitation, strong downdrafts, and lightning.

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What is a microburst?

A concentrated downdraft from a thunderstorm, creating a localized, intense gust of wind.

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What is the difference between true altitude and indicated altitude?

True altitude is the actual height above sea level, while indicated altitude is what an altimeter shows. When temperature is colder than standard, true altitude is lower than indicated altitude.

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What is a TAF?

A forecast of weather conditions at an airport for a specific period.

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Cold Front

A boundary where cold air replaces warm air, marked by a rapid drop in temperature, intense precipitation, and possible hail.

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Occluded Front

A front formed when a cold front overtakes a warm front, creating a complex weather system with variable precipitation and temperature changes.

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Front Slope

The angle at which a front rises into the atmosphere, affecting how quickly weather changes occur.

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ZONE Term

When the term "ZONE" is used, the region of interaction significantly expands, potentially reaching up to 300 nanometers.

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Warm Front Symbol

A semi-circle with half-barbs pointing in the direction of movement.

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Cold Front Symbol

Triangles with full barbs pointing in the direction of movement.

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Cumulonimbus Clouds

Tall, dense, vertically developed clouds associated with thunderstorms, heavy precipitation, and strong updrafts and downdrafts.

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Cloud Base

The height of the lowest part of a cloud above the ground, typically measured at the airport level.

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Ceiling

The height of the lowest layer of clouds that covers more than 4/8 of the sky. It's essentially the main cloud base.

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Cloud Classification

The way we categorize clouds based on their shape and form. There are three main types: Stratiform, Cumuliform, and Cirriform.

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Stratiform Cloud

A layered cloud with little vertical extent, but spreading horizontally. Think of a sheet or blanket.

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Cumuliform Cloud

A cloud with a distinct, heaped shape, often appearing fluffy or cotton-like. They have significant vertical extent.

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Cirriform Cloud

A high altitude cloud that's wispy and fibrous, composed of ice crystals. It's known for its delicate, hair-like appearance.

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Cloud Levels

Clouds are categorized by their height: Low, Middle, and High.

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Cloud Coverage (Okta)

A measurement of the amount of sky covered by clouds, expressed in eighths (oktas).

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Carburetor Icing Danger Zone

Carburetor icing is most dangerous within a temperature range of -10°C to +25°C, in cloud, fog, or precipitation, at any power setting.

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Anti-Icing vs. De-icing

Anti-icing measures prevent ice formation, while de-icing measures remove ice that has already formed.

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Anti-Icing Methods

Common anti-icing methods include kill-frost paste, heated windshields, hot air systems, and anti-icing fluids.

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De-icing Methods

De-icing methods include de-icing fluids, pulsating rubber boots, hot air systems, and electrical heating systems.

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Pre-Taxi Inspection for Icing

Before taxiing, carefully inspect areas where snow, ice, or frost could affect aircraft systems.

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Flight Controls and Icing

Check flight controls and flaps before takeoff to ensure they are free from icing and operate properly.

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Engine Start and Icing

Perform normal engine start procedures, but be aware that displays might appear less bright than usual due to icing.

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Study Notes

Meteorology One Course Summary

  • Course code: 6ENT1169
  • Course title: Navigation, Human Factors and Meteorology
  • Lecturer: Dr Ivan Sikora
  • University: University of Hertfordshire

Today's Lecture Content

  • The Atmosphere
  • Atmospheric Pressure
  • Altimetry
  • Pressure Systems
  • Temperature
  • Density
  • Humidity
  • Atmospheric Stability and Instability
  • EASA Part-FCL / eRules Dec 2021 (Subpart C)

What is Meteorology?

  • The science of Earth's atmosphere and the physical processes occurring within it.

Why study Meteorology?

  • Understanding aircraft flight performance and safety.
  • Predicting weather conditions for aircraft flight.
  • Aviation hazards associated with weather conditions.

The Atmosphere

  • A gaseous envelope surrounding the Earth.
  • Acts as a fluid.
  • Poor heat conductor.
  • Supports life only to a lower extent.
  • Properties vary vertically and horizontally in pressure, temperature, density, and humidity.
  • Composition: Major components by volume: Nitrogen (78.09%), Oxygen (20.95%), Argon (0.93%), Carbon dioxide (0.03%), and other trace elements. 

The Earth's Atmosphere

  • Layers:

    • Troposphere: 0 to 11 km; contains most of the atmosphere's mass; weather occurs here.
    • Tropopause: boundary between troposphere and stratosphere.
    • Stratosphere: 11 to 50 km (20-25 km altitude, ozone layer - important for absorbing UV radiation); stable atmospheric layer.
    • Stratopause: boundary between stratosphere and mesosphere.
    • Mesosphere: 50 to 80 km; temperature decreases with altitude.
    • Mesopause: boundary between mesosphere and thermosphere.
    • Thermosphere: 80 to 700+ km; temperature increases with altitude
    • Exosphere: outermost layer, extending outward into space

  • Environmental Lapse Rate (ELR): 6.5°C per kilometre in the troposphere.

International Standard Atmosphere (ISA)

  • A hypothetical atmosphere with consistently specified pressure, temperature, and density at different altitudes or flight levels.
  • Used as a standard reference in aviation calculations.
  • ISA values at Mean Sea Level (MSL) : 1013.25 mb = 1013.25 hPa = 29.92 inHg = 101325 N/m² = 760 mmHg

Atmospheric Pressure

  • Force per unit area exerted by the atmosphere.
  • Measured in Pascal (Pa), millibars (mb), or hectopascals (hPa).
  • Values varies with altitude. 
  •  760 mm Hg (millimeters of mercury) is the average value at sea level for standard atmospheric pressure.

Altimetry

  • Measurement of altitude using atmospheric pressure.
  • Altimeters measure atmospheric pressure.
  • QNH, QFE, Calculation methods.
  • ISA related calculations.

Pressure Systems

  • Depressions/Lows/Cyclones
  • Anticyclones/Highs
  • Troughs
  • Cols
  • Isobars and isallobars

Winds

  • Air in horizontal motion
  • Measured in knots (nautical miles per hour)
  • Direction: The direction from which the wind is blowing, given with respect to North.
  • Speed: The 'force' of the wind; generally measured in knots. 
  • Types: Veering, Backing, Gusts, Lulls, Squalls, Gales, Hurricanes, and Wind Gradient.
  • Forces: Pressure Gradient Force (PGF) and Coriolis Force.
  • Local winds: Sea breeze, Land breeze, and Valley/Ravine/Funnel winds Föhn winds: A warm, dry wind that flows down the leeward side of a mountain range.

Clouds

  • Visible collections of water droplets, ice crystals, or a mixture of both.
  • Classification based on height (low level, medium level and high level) and shape (cirriform, stratocumulus, cumuliform, convective).
  • Types: Cirrus, Cirrocumulus, Cirrostratus, Altocumulus, Altostratus, Stratus, Cumulus, Cumulonimbus. 

Thunderstorms

  • Conditions: High relative humidity, instability and a trigger to lift air.
  • Stages: Initial/Growth, Mature, and Dissipating.

Icing

  • Ice formation on aircraft surfaces
  • Types of Icing: Glaze, Rime, Mixed, and Hoar Frost.
  • Causes of Icing:
  • Effects and Dangers of Icing on Aircraft.
  • Prevention and Removal methods.

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Meteorology One PDF

Description

Test your knowledge of atmospheric phenomena and cloud types with this quiz. Explore how cloud cover influences temperature and the characteristics of various clouds, including their effects on visibility and turbulence. Perfect for students of meteorology and anyone interested in weather patterns.

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