Troposphere

Figs. 2.5 and 2.6 (in section Standard Atmosphere) show that the atmospheric temperature decreases linearly over a distance of 11 km from the sealevel. This region is called the Troposphere. In this region temperature is given by,

$$T~=~T_a~-~\beta z$$ (2.24)

where $T_a$ is the sealevel temperature and $\beta$ is called the Lapse Rate, which in the Troposphere is 0.00650 K/m. Substituting this value of T in Eq.1.24 and simplifying one gets for pressure in the Troposphere,

$$p~=~p_a \left( 1~-~{{\beta z} \over {T_a}} \right)^{g/R\beta}$$ (2.25)

$p_a$ is the sealevel pressure. Using the values of $T_a$ and $p_a$ from the Table, one finds a temperature of $-56.5 ^0 C$ and a pressure of 23 kPa at the edge of Troposphere (i.e. at an altitude of 11 km). The exponent $g/R\beta$ is dimensionless and is equal to 5.26 for air.