Tropopause

The tropopause is the boundary between the troposphere and the stratosphere, marking where the temperature stops falling with height. The lapse rate drops to 2 degrees Celsius per kilometer or less, ending the well-mixed, weather-producing troposphere below. Its height varies with latitude and season, near 16 to 18 km over the tropics and 8 to 10 km over the poles, with a break in between where the jet streams sit. The strong stability above it caps deep convection, so cumulonimbus anvils spread out at the tropopause. It also limits the vertical extent of mid-latitude and tropical storm systems.