Question

Why there is more atmosphere in the lower level of the atmosphere

Answer 1

This causes the atmosphere to be concentrated at the Earth's surface and thin rapidly with height. Air pressure is a measure of the weight of the molecules above you. As you move up in the atmosphere there are fewer molecules above you, so the air pressure is lower. ... Temperature decreases with height in the troposphere.

Answer 2

there is more molecules of the air in the lower level of atmosphere . as we move upper the atmosphere , air molecules becomes lesser and lesser , so air presser become lower.

that's why there is more atmosphere in the lower of the atmosphere.