Atmosphere Lecture 2 ME EN 415 Andrew Ning aning@byu.edu UCAR - PowerPoint PPT Presentation

Atmosphere Lecture 2 ME EN 415 Andrew Ning aning@byu.edu

UCAR

Altitude Geometric Altitude: Absolute Altitude: Pressure Altitude: Geopotential Altitude:

Altimeters

International Standard Atmosphere Geopotential Temperature Altitude (km) Gradient (K/km) Altitude 0 -6.5 11 0.0 20 +1.0 32 +2.8 47 0.0 51 -2.8 71 -2.0 84.8520 Temperature

Sea Level Properties 288 . 15 K T SL 1 . 01325 × 10 5 Pa P SL 1 . 79 × 10 − 5 kg/m-s µ SL 9 . 80665 m/s 2 g

Hydrostatics

Isothermal Layers

Gradient Layers

Curve Fit 1 + exp(35 . 75 − 3 . 25 h ) + exp( − 3 . 0 + 0 . 0003 h 3 ) ⇥ ⇤ T ( h ) = T SL − 71 . 5 + 2 . 0 ln 0 . 0015 h 2 ✓ ◆ P ( h ) = P SL exp − 0 . 118 h − 1 − 0 . 018 h + 0 . 0011 h 2 (h in km, T in K) applicable for altitudes below 47 km modified slightly from: Mark Drela, Flight Vehicle Aerodynamics

Upper Atmosphere NRLMSISE-00 (up to 1000 km)

Upper Atmosphere NRLMSISE-00 (up to 1000 km) or for a simple approximation during atmospheric entry: P gh (reasonable up to 140 km) = exp − RTm P SL

Create Your Own P, T, ρ = atmosphere( h )

More Comprehensive Databases ERA Interim dataset https://earth.nullschool.net