Water vapor cools and relative humidity of the air increases as it rises in the atmosphere. Atmospheric circulation patterns may redistribute the saturated air prior to precipitation. Water balance on earth. The majority of earth's water is in the oceans. Most of the rest returns to the atmosphere by evaporation or through the transpiration of plants.
Land areas receive more moisture by precipitation than they supply by evaporation.
The difference is made up by evaporation from oceans. A slim fraction of water falling as precipitation infiltrates below the surface through bedrock or soils to form groundwater . Some of the soil moisture is lost to evaporation or taken up by vegetation and the remainder recharges the groundwater system. Groundwater flow is termed percolation and occurs at rates from meters per day to millimeters per year. Consequently the residence time for groundwater may be measured in intervals of weeks or thousands of years.