Water Vapor, Clouds, and Convective Storms in the Atmosphere

Water vapor in the atmosphere rarely exceeds 5% of surface air, and cloud droplets and ice are only 1/250 of total atmospheric water. However, the variability in water vapor and its condensed form, clouds, play vital roles in modulating weather and climate. In convective rainstorms, air-sea interaction and boundary layer turbulence determine the amount of moisture supplied to the bottom of storms. Slight variations in water vapor significantly alter the available potential energy for convection as air parcels rise in the atmosphere. Clouds cover 70% of the sky on average. Though being light in mass, their radiative effects are potent forcing to the atmosphere. Depending on the location and amount of cloud droplets and ice, convection in the atmosphere may organize as homogeneous random cells or in a clustered form where an intense large-scale system arises accompanied by dry air surrounding the system. In this discussion, I will demonstrate those powerful effects of water vapor and clouds with real cases and idealized numerical simulations. Detailed physical and dynamic processes will be explained and discussed.