Ans. The tropopause is the boundary region that is located between the troposphere and the stratosphere region. This is the coldest layer of the atmosphere, here the lapse rate changes from positive (which is in the troposphere) towards negative (located in the stratosphere), this is defined as the tropopause region.The tropopause acts as the boundary of the Earth's atmosphere which is between the troposphere and the stratosphere region. This is a thermodynamic gradient of the stratification layer, here marks the end of the troposphere. It lies at 17 kilometers (11 mi) above the equatorial regions, and approximately it is 9 kilometers (5.6 mi) over the polar regions.