Projects:EASA PPL/Meteorology

Atmosphere

• Thermosphere
• Mesosphere
• Stratosphere: Upper level, temperature constant
• Tropopause:
  • Boundary layer, Avg 36090ft, -56.5°C
  • at equator: 55000ft, -75°C
  • at polar: 25000ft, -45°C
• Troposphere:
  • Half the mass of atmosphere is in the lower 5km

Lapse Rate

	per 1000ft	per 100m
Absolute instability	>3°
Dry Adiabatic Lapse Rate	3°	1°
conditionally stable	2-3°
Average Environmental Lapse Rate (ISA) 15° @ MSL	1.98°	0.65°
Saturated Adiabatic Lapse Rate (Central Europe)	1.8°	0.6°
stable	<2°
Dew point	0.5°

Altimetry

• Pressure altitude: Indicated altitude at 1013.25 hPa setting
• Density altitude: pressure altitude corrected for non-ISA temperatures (120ft per 1°C change from ISA)
• QNH: ..N.. nautical
• True altitude:
• Wind on hPa - Wind on height
• Wind off hPa - Wind off height
• High to low - beware below
• Low to High - up in the sky
• 1) Correct altitude for pressure: 1hPa = 27ft
• 2) Correct altitude for Temp: 1% per 2.5°C change from ISA
  • colder: indicated alt minus offset / warmer: indicated alt plus offset

Wind

• Mountain-valley:
  • Katabatic: at night down from the mountains
  • Anabatic: up the mountain by day
• Land-breeze: From land-to-water, during the night, weaker than sea-breeze
• Sea breeze: From the sea to land, during the day
• pressure gradient: diff between high and low
• straight isobar: pressure gradient force + coriolis force
• curved isobar: gradient wind: pressure gradient force + coriolis force + centrifugal force

• • Col: saddle point/neutral point

• Convective weather:
  • Thunderstorms, hail, tornados, wind gusts, heavy showers, lightning strikes
• Low pressure travelling in summer: between 45° - 70°

Air Masses

prefix	suffix
A = Arctic	m = maritime
P = Polar	c = continental
T = Tropical
E = Equatorial

Clouds

• Clouds:
  • AC - Altocumulus
  • AS - Alsostatus
  • CB - Cumulonimbus
  • CC - Cirrocumulus
  • CI - Cirrus
  • CS Cirrostratus
  • CU - Cumulus
  • NS - Nimbostratus (moderate to severe icing)
  • SC - Stratocumulus
  • ST - Stratus
  • Altocumulus lenticularis: mountain wave cloud, strong wind at right angle to the ridge, stable air

Fog

• Radiation fog: at night/early day, when the ground cools. wind <5kt
• Advection fog: warm, moist air over cooler ground/sea below, 10-15kt, can withstands 25kt winds
• Frontal fog: ahead of warm front

Other

• CAVOK: vis 10km+, no clouds below 5000 above GND