The lowest layer of atmosphere, extending upto 10 miles in the tropics, is called the :

The troposphere extends from the Earth’s surface to a height of 6–10 mi (10–16 km), the

base of the stratosphere. It contains about

four-fifths of the mass of the whole atmosphere. It extends to 16?km above ground level at the equator, 11?km at 50?° N and S, and

9?km at the poles.