Why are there few/no clouds in the stratosphere?

Question

stratosphere

Answer 1

Because the stratosphere is much more stable than the troposphere. The stratosphere contains the ozone layer and it aborbs heat which warms as height increases. Another factor is that the stratosphere has very little water vapor, and that is why very few or no clouds are located there.

Answer 2

More than ninety five percent of the water vapour is confined to the troposphere only.Further the temperature increases with height in the stratosphere which does not allow convection currents that are required for the vertical growth of the clouds.Availability of condensation nuclei(dust particle,smoke particles salt particles etc) which are required for the condensation of the water vapour into water droplets which constitute the cloud are less  at that level.