Yale professor Ron Smith continues his course The Atmosphere, the Ocean and Environmental Change with a lecture on atmospheric stability and moisture. He explains the lapse rate, the rate at which air cools with altitude, and how it determines whether a lifted air parcel keeps rising or sinks back, the basis of atmospheric stability and instability. Smith covers the diurnal cycle of the adiabatic lapse rate, then turns to temperature inversions, where cooler air sits near the ground beneath warmer air aloft, trapping pollutants in a boundary layer near the surface. The final chapters shift to moisture, introducing how water vapor enters the atmosphere and the processes by which air becomes saturated. Recorded in fall 2011 as part of Yale's Open Yale Courses series, the lecture is organized into six chapters covering roughly forty five minutes, moving from a recap of atmospheric mixing through stability, inversions, and saturation.