Calculate the average environmental lapse rate as C per kilometer: height above surface in kilometers ...

The lapse rate is the rate at which the temperature changes as the altitude changes. It is calculated by the following expressions:

Lapse rate = - (change in temperature)/ (change in altitude)

It can also be written as,

lapse rate = - (final temperature - initial temperature) / (final altitude - initial altitude)

In this question, initial altitude or height = 0 km, final altitude = 12 km, initial temperature = 12 degrees C and final temperature = -54 degrees C.

Substituting the values in the equation, we get:

lapse rate = - (-54 - 12) / (12 - 0) C/km = -66/12 C/km = -5.5 C/km

Thus, the lapse rate is -5.5 C/km, that is with each km rise in altitude, the temperature will fall by 5.5 degrees C.

At a height of 2 km, the temperature = temperature at ground level + height x lapse rate

= 12 + 2 x -5.5 = 12 - 11 C = 1 degrees C.

Hope this helps.