The jet aircrafts fly very easily and smoothly in the lower stratosphere. What could be the appropriate explanation?

Thee are no clouds or water vapour in the lower stratosphere.

There are no vertical winds in the lower stratosphere.

Which of the above statements given above is/are correct in this context?

Question

The jet aircrafts fly very easily and smoothly in the lower stratosphere. What could be the appropriate explanation?

Thee are no clouds or water vapour in the lower stratosphere.
There are no vertical winds in the lower stratosphere.

Which of the above statements given above is/are correct in this context?

Accepted Answer

Both 1 and 2 While many smaller, private, or propeller planes operate exclusively in the lower troposphere, the long-haul commercial jet aircraft often fly in the lower stratosphere (altitude) to avoid weather and reduce fuel consumption as detailed below: First, the air in the stratosphere is much thinner than the air at lower altitudes, so that aeroplanes experience less air resistance and less drag and can therefore fly smoothly, more efficiently, and at higher cruising speeds. Hardly does the noise produced by them at this altitude reach the ground. In contrast, the troposphere, which literally means zone of ‘mixing', contains over 75% mass of the total atmosphere and almost all of its water vapor — explaining why almost all weather phenomena like clouds, frost, rainfall, thunder, lightning, etc. occur in this layer. Secondly, the lower stratosphere is also relatively stable and free from turbulence than the air at lower altitudes because vertical air movements are inhibited by the temperature inversion in the stratosphere. Tropopause, whose temperature is -50℃, marks the end of decrease in temperature at normal lapse rate. The cold airmasses at tropopause are cooler and denser than the air at lower altitudes and therefore, they always tend to subside rather than rise further. Due to the absorption of UV radiation by ozone molecules, the temperature in the stratosphere (between 15-50 km altitudes increases with altitude and reaches 0℃ at stratopause. This temperature inversion neither allow the cold airmasses of lower altitudes to rise nor does it allow the warmer air masses of higher altitudes to subside. This means atmospheric stability with little vertical mixing of air in the troposphere. However, horizontal air currents, known as jet streams, act as tailwinds for jet aircraft while flying west-to-east but act as severe headwinds while flying east-to-west.