Consider the following statements:
1. Troposphere varies in its thickness between equator and poles.
2. Stratosphere does not experience Normal Lapse Rate.
3. Ozone layer occurs in the Mesosphere.
4. Ionosphere lies between Stratosphere and Mesosphere
Which of these statements are correct?

Troposphere varies in its thickness between equator and poles. Near the equator, the troposphere is thicker than at the poles, since the spinning of the Earth tends to shift air towards the equator. The thickness of the troposphere also varies with season. Stratosphere does not experience Normal Lapse Rate. There it generally gets colder as you go higher due to the expansion of gases as the pressure decreases. Technically, the stratosphere has a negative 'lapse rate' (temperature increases with height), while the lower atmosphere's lapse rate is positive.