Tropopause The boundary layer between the troposphere and stratosphere, where an abrupt change in temperature lapse rate usually occurs. It is defined as the lowest level at which the lapse rate decreases to 2 °C km-1 or less, provided that the average lapse rate between this level and all higher levels within 2 km does not exceed 2 °C km-1. Occasionally, a second tropopause may be found if the lapse rate above the first tropopause exceeds 3 °C km-1. |
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