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Meteorology
3.3.5.7 Variation of air pressure with height .................................................. 231
3.3.6 Altimeter ................................................................................................... 232
3.3.6.1 Altimeters ............................................................................................. 232
3.3.6.2 Transition layers, transition altitude and transition level .................... 235
3.3.6.3 QNH, QFF, QFE, QNE ............................................................................ 236
3.3.6.4 Pressure altitude and density altitude ................................................. 238
3.3.6.5 Air density and flight performance ...................................................... 245
3.3.6.6 Venturi effect ....................................................................................... 245
3.4 Pressure and wind ...................................................................................... 246
3.4.1 High pressure and low pressure .............................................................. 246
3.4.1.1 The globale wind system and high-pressure and low-pressure belts .. 247
3.4.2 Atmospheric movement .......................................................................... 248
3.4.2.1 Pressure Gradient Force....................................................................... 248
3.4.2.2 Coriolis Force ........................................................................................ 249
3.4.2.3 The Polar Front ..................................................................................... 250
3.4.2.4 The Jet Stream ...................................................................................... 251
3.4.2.5 The independence of high- and low-pressure systems ....................... 251
3.4.3 The Earth’s surface and the geostrophic wind ........................................ 253
3.4.3.1 The geotrophic wind ............................................................................ 253
3.4.3.2 Surface wind ......................................................................................... 254
3.4.3.3 Pressure Gradient Force....................................................................... 255
3.4.4 Local winds .............................................................................................. 257
3.4.4.1 Sea breeze ............................................................................................ 257
3.4.4.2 Land breeze .......................................................................................... 257
3.4.4.3 The Föhn wind ...................................................................................... 258
3.4.4.4 Rotor winds in the mountains .............................................................. 258
3.4.4.5 Valley winds and mountain winds ....................................................... 259
3.4.5 Mechanical and og thermal turbulence .................................................. 260
3.4.5.1 Mechanical turbulence ........................................................................ 260
3.4.5.2 Thermal turbulence .............................................................................. 260
3.4.6 CB’s and gust fronts ................................................................................. 260
3.4.7 Microburst ............................................................................................... 262
3.4.8 Wind in relation to flying ......................................................................... 262
3.4.8.1 Wind speed and wind direction - given in METAR ............................... 263
Flight Theory PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 208
