Water Cycles - Hydrogeology: Objectives, Methods, Applications - page 21

experiences a surplus (Figure 7). The tilt of the Earth's axis, the spatial
distribution of continents and oceans, variations in elevation, atmospheric
circulation, and ocean currents all locally modify this scenario to produce
the different climates present on Earth and thus defi ne the highly variable
quantities of precipitation and evapotranspiration.
Figure 7 Radiation budget by geographic position.
Due to heating by solar radiation, water from the oceans and from
the surface of continents passes into the gaseous phase and rises into the
atmosphere, where it condenses to form raindrops (Figure 8). It falls back
into the oceans and onto land in the form of rain or snow. The annual volume
Figure 8 External water cycle.