4. The Earth Atmosphere might be described as a Thermodynamic
Medium in a Gravitational Field and in Hydrostatic Equilibrium
set by Solar Radiation. Since Solar Radiation and Atmospheric
Reradiation varies diurnally and annually and with latitude and
longitude, the Standard Atmosphere is only an approximation.
SOLO
4
Earth Atmosphere
The purpose of the Standard Atmosphere has been defined by
the World Metheorological Organization (WMO).
The accepted standards are the COESA (Committee on
Extension to the Standard Atmosphere) US Standard Atmosphere
1962, updated by US Standard Atmosphere 1976.
5. The basic variables representing the thermodynamics state of
the gas are the Density, ρ, Temperature, T and Pressure, p.
SOLO
5
Earth Atmosphere
The Density, ρ, is defined as the mass, m, per unit volume, v,
and has units of kg/m3
.
v
m
v ∆
∆
=
→∆ 0
limρ
The Temperature, T, with units in degrees Kelvin ( ͦ K). Is a
measure of the average kinetic energy of gas particles.
The Pressure, p, exerted by a gas on a solid surface is defined as
the rate of change of normal momentum of the gas particles
striking per unit area.
It has units of N/m2
. Other pressure units are millibar (mbar),
Pascal (Pa), millimeter of mercury height (mHg)
S
f
p n
S ∆
∆
=
→∆ 0
lim
kPamNbar 100/101 25
==
( ) mmHginHgkPamkNmbar 00.7609213.29/325.10125.1013 2
===
The Atmospheric Pressure at Sea Level is:
6. 6
Earth Atmosphere
Physical Foundations of Atmospheric Model
The Atmospheric Model contains the values of
Density, Temperature and Pressure as function
of Altitude.
Atmospheric Equilibrium (Barometric) Equation
In figure we see an atmospheric
element under equilibrium under
pressure and gravitational forces
( )[ ] 0=⋅+−+⋅⋅⋅− APdPPHdAg gρ
or
( ) gg HdHgPd ⋅⋅=− ρ
In addition, we assume the atmosphere to be a thermodynamic fluid. At altitude
bellow 100 km we assume the Equation of an Ideal Gas
where
V – is the volume of the gas
N – is the number of moles in the volume V
m – the mass of gas in the volume V
R* - Universal gas constant
TRNVP ⋅⋅=⋅ *
V
m
M
m
N == ρ&
MTRP /*
⋅⋅= ρ
8. We must make a distinction between:
- Kinetic Temperature (T): measures the molecular kinetic energy
and for all practical purposes is identical to thermometer
measurements at low altitudes.
- Molecular Temperature (TM): assumes (not true) that the
Molecular Weight at any altitude (M) remains constant and is
given by sea-level value (M0)
SOLO
8
Earth Atmosphere
T
M
M
TM ⋅= 0
To simplify the computation let introduce:
- Geopotential Altitude H
- Geometric Altitude Hg
Newton Gravitational Law implies: ( )
2
0
+
⋅=
gE
E
g
HR
R
gHg
The Barometric Equation is ( ) gg HdHgPd ⋅⋅=− ρ
The Geopotential Equation is defined as HdgPd ⋅⋅=− 0ρ
This means that g
gE
E
g Hd
HR
R
Hd
g
g
Hd ⋅
+
=⋅=
2
0
Integrating we obtain g
gE
E
H
HR
R
H ⋅
+
=
9. 9
Earth Atmosphere
Atmospheric Constants
Definition Symbol Value Units
Sea-level pressure P0 1.013250 x 105
N/m2
Sea-level temperature T0 288.15 ͦ K
Sea-level density ρ0 1.225 kg/m3
Avogadro’s Number Na 6.0220978 x 1023
/kg-mole
Universal Gas Constant R* 8.31432 x 103
J/kg-mole -ͦ K
Gas constant (air) Ra=R*/M0 287.0 J/kg--ͦ
K
Adiabatic polytropic constant γ 1.405
Sea-level molecular weight M0 28.96643
Sea-level gravity acceleration g0 9.80665 m/s2
Radius of Earth (Equator) Re 6.3781 x 106
m
Thermal Constant β 1.458 x 10-6
Kg/(m-s-ͦ K1/2)
Sutherland’s Constant S 110.4 ͦ K
Collision diameter σ 3.65 x 10-10
m
10. 10
Earth Atmosphere
Physical Foundations of Atmospheric Model
Atmospheric Equilibrium Equation
HdgPd ⋅⋅=− 0ρ
At altitude bellow 100 km we assume t6he
Equation of an Ideal Gas
TRMTRP a
MRR
a
aa
⋅⋅=⋅⋅=
=
ρρ
/
*
*
/
Hd
TR
g
P
Pd
a
⋅=− 0
Combining those two equations we obtain
Assume that T = T (H), i.e. function of Geopotential Altitude only.
The Standard Model defines the variation of T with altitude based on
experimental data. The 1976 Standard Model for altitudes between 0.0 to 86.0 km
is divided in 7 layers. In each layer dT/d H = Lapse-rate is constant.
11. 11
Earth Atmosphere
Layer
Index
Geopotential
Altitude Z,
km
Geometric
Altitude Z;
km
Molecular
Temperature T,
ͦ K
0 0.0 0.0 288.150
1 11.0 11.0102 216.650
2 20.0 20.0631 216.650
3 32.0 32.1619 228.650
4 47.0 47.3501 270.650
5 51.0 51.4125 270.650
6 71.0 71.8020 214.650
7 84.8420 86.0 186.946
1976 Standard Atmosphere : Seven-Layer Atmosphere
Lapse Rate
Lh;
ͦ K/km
-6.3
0.0
+1.0
+2.8
0.0
-2.8
-2.0
12. 12
Earth Atmosphere
Physical Foundations of Atmospheric Model
• Troposphere (0.0 km to 11.0 km).
We have ρ (6.7 km)/ρ (0) = 1/e=0.3679, meaning that 63% of the atmosphere
lies below an altitude of 6.7 km.
( )
Hd
HLTR
g
Hd
TR
g
P
Pd
aa
⋅
⋅+
=⋅=−
0
00
kmKLHLTT /3.60
−=⋅+=
Integrating this equation we obtain
( )∫∫ ⋅
⋅+
=−
H
a
P
P
Hd
HLTR
g
P
PdS
S 0 0
0 1
0
( )
0
00
lnln
0
T
HLT
RL
g
P
P
aS
S ⋅+
⋅
⋅
−=
Hence
aRL
g
SS H
T
L
PP
⋅
−
⋅+⋅=
0
0
0
1
and
−
⋅=
⋅
1
0
0
0
g
RL
S
S
a
P
P
L
T
H
13. 13
Earth Atmosphere
Physical Foundations of Atmospheric Model
Hd
TR
g
P
Pd
Ta
⋅=− *
0
Integrating this equation we obtain
( )T
TaS
S
HH
TR
g
P
P
T
−⋅
⋅
−= *
0
ln
Hence
( )T
Ta
T
HH
TR
g
SS ePP
−⋅
⋅
−
⋅=
*
0
and
S
STTa
T
P
P
g
TR
HH ln
0
*
⋅
⋅
+=
∫∫ =−
H
HTa
P
P T
S
TS
Hd
TR
g
P
Pd
*
0
• Stratosphere Region (HT=11.0 km to 20.0 km).
Temperature T = 216.65 ͦ K = TT* is constant (isothermal layer), PST=22632
Pa
14. 14
Earth Atmosphere
Physical Foundations of Atmospheric Model
( )[ ] Hd
HHLTR
g
Hd
TR
g
P
Pd
SSTaa
⋅
−⋅+⋅
=⋅=− *
00
( ) ( ) PaPHPkmKLHHLTT SSSSSST 5474.9,/0.1
*
===−⋅−=
Integrating this equation we obtain
( )[ ]∫∫ ⋅
−⋅+
=−
H
H SSTa
P
P S
S
SS
Hd
HHLTR
g
P
Pd
*
0 1
( )[ ]
*
*
0
lnln
T
ST
aSSS
S
T
HHLT
RL
g
P
P −⋅+
⋅
⋅
=
Hence ( )
aRL
g
S
T
S
SSS HH
T
L
PP
⋅
−
−⋅+⋅=
0
*
1
and
−
⋅+=
⋅
1
0
* g
RL
SS
S
S
T
S
aS
P
P
L
T
HH
Stratosphere Region (HS=20.0 km to 32.0 km).
15. 15
Earth Atmosphere
1962 Standard Atmosphere from 86 km to 700 km
Layer Index Geometric
Altitude
km
Molecular
Temperature
K
Kinetic
Temperature
K
Molecular
Weight
Lapse
Rate
K/km
7 86.0 186.946 186.946 28.9644 +1.6481
8 100.0 210.65 210.02 28.88 +5.0
9 110.0 260.65 257.00 28.56 +10.0
10 120.0 360.65 349.49 28.08 +20.0
11 150.0 960.65 892.79 26.92 +15.0
12 160.0 1110.65 1022.20 26.66 +10.0
13 170.0 1210.65 1103.40 26.49 +7.0
14 190.0 1350.65 1205.40 25.85 +5.0
15 230.0 1550.65 132230 24.70 +4.0
16 300.0 1830.65 1432.10 22.65 +3.3
17 400.0 2160.65 1487.40 19.94 +2.6
18 500.0 2420.65 1506.10 16.84 +1.7
19 600.0 2590.65 1506.10 16.84 +1.1
20 700.0 2700.65 1507.60 16.70
16. 16
Earth Atmosphere
1976 Standard Atmosphere from 86 km to 1000 km
Geometric Altitude Range: from 86.0 km to 91.0 km (index 7 – 8)
78
/0.0
TT
kmK
Zd
Td
=
=
Geometric Altitude Range: from 91.0 km to 110.0 km (index 8 – 9)
2/12
8
2
8
2/12
8
1
1
−
−
−
−
⋅−=
−
−⋅+=
a
ZZ
a
ZZ
a
A
Zd
Td
a
ZZ
ATT C
kma
KA
KTC
9429.19
3232.76
1902.263
−=
−=
=
Geometric Altitude Range: from 110.0 km to 120.0 km (index 9 – 10)
( )
kmK
Zd
Td
ZZLTT Z
/0.12
99
+=
−⋅+=
Geometric Altitude Range: from 120.0 km to 1000.0 km (index 10 – 11)
( ) ( )
( )
( )
+
+
⋅−=
+
+
⋅−⋅=
⋅−⋅−−=
∞
∞∞
ZR
ZR
ZZ
kmK
ZR
ZR
TT
Zd
Td
TTTT
E
E
E
E
10
10
10
10
10
/
exp
ξ
λ
ξλ
KT
kmR
km
E
1000
10356766.6
/01875.0
3
=
×=
=
∞
λ
19. References
SOLO
19
S. Hermelin, “Air Vehicle in Spherical Earth Atmosphere”
Frank J, Regan, Satya M. Anandakrishnan, “Dynamics of Atmospheric Re-Entry”,
AIAA Education Series, 1993
R.P.G. Collinson, “Introduction to Avionics”, Chapman & Hall, Inc., 1996, 1997, 1998
Earth Atmosphere
John D. Anderson, “Flight”, 4th
Ed., McGraw Hill, 2000,
Ch. 3, “The Standard Atmosphere”
20. 20
SOLO
Technion
Israeli Institute of Technology
1964 – 1968 BSc EE
1968 – 1971 MSc EE
Israeli Air Force
1970 – 1974
RAFAEL
Israeli Armament Development Authority
1974 – 2013
Stanford University
1983 – 1986 PhD AA
21. 21
Earth Atmosphere
Polytropic Process
A Polytropic Process is a Thermodynamic Process that is reversible and obeys the
relation:
where P is the pressure, V is the volume, n the Polytropic Index, and C is a constant.
CVP n
=⋅
The equation is a valid characterization of a thermodynamic process assuming that
the process is quasi-static and the values of the heat capacities, Cp and CV , are
almost constant when n is not zero or infinity. (In reality, Cp and CV are actually
functions of temperature and pressure, but are nearly constant within small changes
of temperature).
Polytropic
Index
Relation Effects
n = 0 P V0
=Const Equivalent to an isobaric process (constant pressure)
n = 1 P V = N k T
(constant)
Equivalent to an isothermal process (constant temperature)
1 < n < γ - A quasi-adiabatic process such as internal combustion engine
during expansion. Or in vapor compression refrigeration during
compression.
n = γ - γ = Cp/CV is the adiabatic index, yielding an adiabatic process
(no heat transferred)
n = ∞ - Equivalent to an isochoric process (constant volume)
22. Earth Atmosphere
Explanation of the Thermal Gradient in the Atmospheric Layers by the
Polytropic Process
A Polytropic Process is a Thermodynamic Process that is reversible and obeys the
relation:
where P is the pressure, V is the volume, n the Polytropic Index, and C is a constant.
n
n
nn
C
V
M
CPMCCVP ρ000 =
=⇒==⋅
Equation of an Ideal Gas MTRP /*
⋅⋅= ρ
Take the Logarithmic Differentiation of those two equations
ρ
ρd
P
Pd
n
=⋅
1
T
Tdd
P
Pd
+=
ρ
ρ
By eliminating d ρ/ρ we obtain T
Td
n
n
P
Pd
⋅
−
=
1
We have
gggg Hd
Td
T
P
n
n
Hd
P
T
Td
n
n
Hd
P
P
Pd
Hd
Pd
⋅⋅
−
=⋅⋅
−
=⋅=
11
23. Earth Atmosphere
Explanation of the Thermal Gradient in the Atmospheric Layers by the
Polytropic Process (continue – 1)
( )g
g
Hg
Hd
Pd
⋅=− ρBarometric Equation
gg Hd
Td
T
P
n
n
Hd
Pd
⋅⋅
−
=
1
( ) *
1
RT
MP
Hd
Pd
Hg gg ⋅
⋅
=⋅−=ρ
Molecular Temperature (TM) versus Kinetic Temperature (T) T
M
M
TM ⋅= 0
( )
*
000 11
R
MHg
n
n
Hd
Pd
P
T
M
M
n
n
Hd
Td
M
M
Hd
Td g
ggg
M
⋅
⋅
−
−=⋅⋅⋅
−
=⋅=
( )
*
01
R
MHg
n
n
Hd
Td g
g
M
⋅
⋅
−
−=
This equation gives a relation between dTM/dHg , the Polytropic Exponent n and
g (Hg).
24. Earth Atmosphere
Explanation of the Thermal Gradient in the Atmospheric Layers by the
Polytropic Process (continue – 2)
( )
*
01
R
MHg
n
n
Hd
Td g
g
M
⋅
⋅
−
−=
The Temperature Gradient dTM/dHg , determine the Stability of the Stratification
in the Stationary Atmosphere.
The Stratification is more stable when the temperature decrease with increasing
height become smaller.
For dTM/dHg = 0 when n = 1, the Atmosphere is Isothermal and has a very stable
stratification.
For n = γ = 1.405, the stratification is Adiabatic (Isentropic) with dTM/dHg =-0.98
ͦK per 100 m [-9.8 ͦ K per km]. This stratification is indiferent because an air
volume moving upward for a certain distance cools off through expansion at just
the same rate as the temperature drops with height. This air volume maintains the
temperature of the ambient air and is, therefore, in an indifferent equilibrium at
every altitude.
25. Earth Atmosphere
Explanation of the Thermal Gradient in the Atmospheric Layers by the
Polytropic Process (continue – 3)
Geopotential Altitude
H, km
0,0
11.0
20,0
32.0
47,0
51.0
71.0
84.8520
Thermal Lapse-rate
L, ͦK/km
-6.5
+0.0
+1.0
+2.8
+0.0
-2.8
-2.0
Polytropic Exponent
n
1.2350
1.0000
0.9716
0.9242
1.0000
1.0893
1.0622
Variation of the Polytropic Exponent with Altitude
26. Earth Atmosphere
Explanation of the Thermal Gradient in the Atmospheric Layers by the
Polytropic Process (continue – 4)
( )
*
01
R
MHg
n
n
Hd
Td g
g
M
⋅
⋅
−
−=
( )g
g
Hg
Hd
Pd
⋅=− ρBarometric Equation
Equation of an Ideal Gas MTRP /*
⋅⋅= ρ
( )
M
T
R
HdHg
P
Pd gg
⋅
⋅
=−
*
( )
( )
( )
( )gM
gg
M
R
R
gM
gg
T
M
M
T
HTR
HdHg
HTR
HdHgM
P
Pd
M
⋅
⋅
−=
⋅
⋅⋅
−=
=⋅=
0
*
0
*
0
( ) gg HdHgHdg ⋅=⋅0
Relation between Geopotential Altitude H, Geometric Altitude Hg.
( )
( ) ( )gMgM
gg
HTR
Hdg
HTR
HdHg
P
Pd
⋅
⋅
−=
⋅
⋅
−= 0
27. Earth Atmosphere
Explanation of the Thermal Gradient in the Atmospheric Layers by the
Polytropic Process (continue – 5)
Let carry the integration in two cases:
( )
( ) ( )gMgM
gg
HTR
Hdg
HTR
HdHg
P
Pd
⋅
⋅
−=
⋅
⋅
−= 0
( ) ( ) ( ) ( )
mxb
HbgRHgRHgHg gEgEgg
/10139.3:
1/21/1
7
00
2
0
−
−
=
⋅−⋅=−⋅≈+⋅=
1. The Non-isothermal layer with LZ:=dT/dHg ≠ 0
2. The Isothermal layer with LZ:=dT/dHg = 0
( )
( )∫∫ −+
⋅⋅−
−=
g
ig iiii
H
H ggZM
gg
P
P
HHLT
HdHb
R
g
P
Pd 10
( ) ( )
( )iZMM
i
Z
Z
L
T
b
LR
g
gg
M
Z
ii
ZZLTT
ZZ
LR
bg
HH
TR
L
P
P
ii
i
i
iZ
iM
iZ
i
i
i
−⋅+=
−⋅
⋅
⋅
⋅
+−⋅
⋅
==
−⋅+⋅
⋅
−
0
1
exp1
0
ρ
ρ
1
( ) ( ) ii
i
MMZi
M
i
ii
TTLZZ
b
TR
ZZg
P
P
==
−⋅+⋅
⋅
−⋅
−== &0
2
1exp 0
ρ
ρ
2
29. 29
Layer
Level
Name
Base
Geopotential
Height
h (in km)
Base
Geometric
Height
z (in km)
Lapse
Rate
(in °C/km)
Base
Temperature
T (in °C)
Base
Atmospheric
Pressure
p (in Pa)
0 Troposphere 0.0 0.0 -6.5 +15.0 101325
1 Tropopause 11.000 11.019 +0.0 -56.5 22632
2 Stratosphere 20.000 20.063 +1.0 -56.5 5474.9
3 Stratosphere 32.000 32.162 +2.8 -44.5 868.02
4 Stratopause 47.000 47.350 +0.0 -2.5 110.91
5 Mesosphere 51.000 51.413 -2.8 -2.5 66.939
6 Mesosphere 71.000 71.802 -2.0 -58.5 3.9564
7 Mesopause 84.852 86.000 — -86.2 0.3734
Earth Atmosphere
ICAO_Standard_Atmosphere
30. 30
Layer
Level
Name
Base
Geopotential
Height
h (in km)
Base
Geometric
Height
z (in km)
Lapse
Rate
(in °C/km)
Base
Temperature
T (in °C)
Base
Atmospheric
Pressure
p (in Pa)
0 Troposphere 0.0 0.0 -6.5 +15.0 101325
1 Tropopause 11.000 11.019 +0.0 -56.5 22632
2 Stratosphere 20.000 20.063 +1.0 -56.5 5474.9
3 Stratosphere 32.000 32.162 +2.8 -44.5 868.02
4 Stratopause 47.000 47.350 +0.0 -2.5 110.91
5 Mesosphere 51.000 51.413 -2.8 -2.5 66.939
6 Mesosphere 71.000 71.802 -2.0 -58.5 3.9564
7 Mesopause 84.852 86.000 — -86.2 0.3734
Earth Atmosphere
ICAO_Standard_Atmosphere
31. 31
Earth Atmosphere
There are two different equations for computing pressure at various height regimes
below 86 km (or 278,400 feet). The first equation is used when the value of
Standard Temperature Lapse Rate is not equal to zero; the second equation is used
when standard temperature lapse rate equals zero.
where
= Static pressure (pascals)
= Standard temperature (K)
= Standard temperature lapse rate -0.0065 (K/m) in ISA
= Height above sea level (meters)
= Height at bottom of layer b (meters; e.g., = 11,000 meters)
=Universal gas constant for air: 8.31432 N·m /(mol·K)
= Gravitational acceleration (9.80665 m/s2
)
= Molar mass of Earth's air (0.0289644 kg/mol)
( )
bLR
Mg
bbb
b
b
hhLT
T
PP
⋅
⋅
−⋅+
⋅=
*
0
( )
⋅
−⋅⋅−
⋅=
b
b
b
TR
hhMg
PP *
0
exp
Equation 1:
Equation 2:
32. 32
Earth Atmosphere
There are two different equations for computing pressure at various height regimes
below 86 km (or 278,400 feet).
Subscript b
Height above sea level
hb
Static pressure
Standard
temperature
Tb
(K)
Temperature lapse rate
Lb
(m) (ft) (Pascals) (inHg) (K/m) (K/ft)
0 0 0 101325.00 29.92126 288.15 -0.0065 -0.0019812
1 11,000 36,089 22632.10 6.683245 216.65 0.0 0.0
2 20,000 65,617 5474.89 1.616734 216.65 0.001 0.0003048
3 32,000 104,987 868.02 0.2563258 228.65 0.0028 0.00085344
4 47,000 154,199 110.91 0.0327506 270.65 0.0 0.0
5 51,000 167,323 66.94 0.01976704 270.65 -0.0028 -0.00085344
6 71,000 232,940 3.96 0.00116833 214.65 -0.002 -0.0006096