I develop this document while studying for my EASA ATPL exams. To accomplish this I studied the Oxford Manual and did the Aviation Exam database. The information is brief and easy to read. I believe it contains all the information you will need to pass your exam. I hope you like it and can use it t...
meteorology
ATPL
STUDENT
pilot
resume
all info you need to pass atpl exams
, Meteorology
Tropopause/Troposphere
• Troposphere
- Concerns aviators
• Tropopause
- Mid-latitudes ISA: 11km & -56.5°C
- Equator: 16km & -75°C
- Tropical (area around equator) tropopause 54000ft
- Separates troposphere with stratosphere
- Lower in summer, higher in winter
- Temp higher at poles
- Temp lapse rate changes abruptly
- Breaks: Core of jetstreams found here
- Area where temp change does not exceed 2/3 of 1°C/1000ft in altitude range of 6000ft
- Higher temperature of airmass = higher pressure & higher tropopause
• Stratosphere
- Ozone contained
- Layer absolutely stable
- Lower part temperature constant
• Stratopause
- 50km
• Determining Tropopause height with formula: 16km (winter) or 18km (Summer) x cos latitude
Temperature
• Insolation(Downward):
- Earth heating from heat energy from the sun, partly absorbed by atmosphere, partly reflected by clouds
mostly reaches surface
- Insolation max at noon
- Amount of heat depends on sun’s elevation & duration of insolation.
- Most significant warming is through convection(upward currents of air bringing heat) & condensation(release
of latent heat) of air
- Variation of solar energy at earth’s surface is the primary cause of weather
• Terrestrial radiation(Upward):
- Heat energy from the earth radiates to space/atmosphere/troposphere
- The clouds blocks radiation from slipping to space(from surface) i.e. clear nights = colder
- The main methods of heat transfer are through formation of clouds & outgoing long wave radiation.
• Inversion:
- Subsidence inversion is caused by an old pressure system.
- A valley inversion happens when cool dense air descends down valley slopes into basin.
- Main cause of terrestrial radiation is a cloud-free night in winter when the ground is dry. In winter, the ground
is colder than in summer, conduction cools the air above.
- Found commonly in stratosphere
• Diurnal variation:
- Highest temperature 2 hours after noon, lowest temperature half hour after sunrise.
- Highest diurnal variations: Deserts. Hot during day, cold at night.
- Lowest diurnal variations: Tropical areas.
- Variation is highest when sky clear & winds are weak.
- Variation bigger over larger land masses compared to the sea/other regions
- Wind increases difference in temperature between surface and 4ft (Mixing)
• Specific heat capacity:
- Amount of heat per unit mass required to raise the temperature by 1°C, i.e. higher specific heat = takes more time
to heat up
- Water has higher specific heat than land
- Grass less SH than concrete
- Rocks very low SH
• Isotherms: Tropical = 16000ft, Temperate = 6000ft, Polar = 0ft
, Pressure
• Amount of pressure decreasing with height, lessens with height/smaller at higher levels/larger at lower layers.
E.g. MSL 27ft/hPa, 18000ft/5.5km 50ft/hPa
• Rate of pressure decrease with height is greater in cold air (More compact vertical isobars)
• QFF: Current pressure at aerodrome converted to MSL & actual conditions, used in weather charts
• Isobars: Lines of equal pressure reduced to sea level, lines of equal QFF, same air pressure at given level
• Isohypse: True altitude of a pressure level
• Contour heights: True heights AMSL
• “LOW”: Area of low pressure compared to horizontal environments and “high” Vice versa
• SEE positive & negatives
If height is ABOVE MSL (+) and Temp is > ISA (+) then QNH > QFF
If height is BELOW MSL (-) and Temp is < ISA (-) then QNH > QFF
If height is ABOVE MSL (+) and Temp is < ISA (-) then QFF > QNH
If height is BELOW MSL (-) and Temp is > ISA (+) then QFF > QNH
AT MSL QFF is always = QNH = QFF
• 5 triple 1, 2 triple 3 & 4. 876543221
• Change in height H = 96 x T ÷ P, (Temp decrease, pressure increase to make isobars closer together)
Density
• Inversely proportional to temperature
Directly proportional to pressure
• There is lesser pressure & density in upper levels (Logic)
• Density = Pressure/constant x temperature
• Affected by altitude, temp & amount of water vapour
• High density altitude = low performance
• Density altitude: Altitude in standard atmosphere to which observed density corresponds
Altimetry
• Q-codes
- QFE: (Height) = Atmospheric pressure at the official aerodrome elevation
- QFF: QFE reduced to MSL according to actual conditions
- QNH:
1. Atmospheric pressure/QFE reduced to MSL using the values of the standard temperature/standard
temperature gradient
2. QNH = QFE + AD elevation in hPa
3. Difference between QNH & QFE is always the same
4. When airport is below MSL, QFE is always more than QNH
• TA: Transition altitude, altitude at which we refer vertical position in terms of altitude based on QNH
• TL: Transition level, lowest usable flight level
• ISA deviation negative = air is colder = true altitude less than indicated
• Always do pressure correction before temp correction then, determine if flying to lower or higher pressure
• 4% for every 10°C deviation always applied to true altitude OR height above the elevation
• 1 inch – 1000ft
• Pressure altimeter: Indicates altitude corresponding to difference between reference pressure & the pressure
where the instrument is. The distance between two isobaric surfaces in the standard atmosphere
• Best conditions for flight level to clear all obstacles: Temp >/= ISA, QNH > 1013
• To find lowest usable flight level from a MSA, Get lowest QNH and highest negative temperature
• To assume whether air mass is colder or warmer: Look at either given pressure or temperature
• Temperature correction must be done using the height from the station where the altimeter starts measuring
from
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller ThePilotPT. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $14.65. You're not tied to anything after your purchase.
