AWH 6-3

Chapter 6, Water Vapor 6-3 6.2.4 Deposition Deposition is the phase transition by which vapor (a gas) is changed into a solid without passing through the liquid phase. In the atmosphere, deposition of water occurs when vapor (a gas) in a sub-freezing cloud changes into ice crystals (solid). 6.2.5 Condensation Condensation is the phase transition by which vapor (a gas) is changed into a liquid. In the atmosphere, condensation may appear as clouds, fog, mist, dew, or frost, depending upon the physical conditions of the atmosphere. 6.2.6 Transportation Transportation is the movement of solid, liquid, and gaseous water through the atmosphere. Without this movement, the water evaporated over the ocean would not precipitate over land. 6.2.7 Precipitation Precipitation results when tiny condensation particles grow in the atmosphere through collision and coalescence and then fall to the Earth’s surface. 6.2.8 Runoff Runoff occurs when there is excessive precipitation and the ground is saturated (i.e., cannot absorb any more water). This runoff flows into streams and rivers and eventually back into the sea. Evaporation of this runoff into the atmosphere begins the hydrologic cycle over again. Some of the water percolates into the soil and into the ground water, only to be drawn into plants again for transpiration to take place. 6.2.9 Infiltration Infiltration is the movement of water into the ground from the surface. 6.2.10 Groundwater Flow Groundwater flow is the flow of water underground in aquifers. The water may return to the surface in springs or eventually seep into the oceans. 6.2.11 Plant Uptake Plant uptake is water taken from the groundwater flow and soil moisture. 6.3 Saturation Saturation is the maximum possible quantity of water vapor that an air parcel can hold at any given temperature and pressure. The term “saturated air” means an air parcel has all of the water vapor it can hold, while “unsaturated air” means an air parcel can hold more water vapor.