Globally, the hydrological cycle is characterized by the evaporation of about 500,000 cubic kilometers of water per year, of which 86% is from the oceans and 14% is from the continents [Quante and Matthias, 2006]. Most of the water that evaporates from the oceans (90%) is precipitated back into them, while the remaining 10% is transported to the continents, where the water precipitates. About two thirds of this precipitation is recycled over the continents, and only one third runs off directly into the oceans. Because societies rely on secure water resources, it is important to understand the processes that govern the atmospheric transport of moisture [Trenberth et al., 2003] and how they are related to precipitation over land. Research on these processes is also related to studies on the energetic coupling of the land-atmosphere system, as well as to paleoclimatology; studies on the latter aim to extract information on past states of the climate system from records such as those of ice cores and stalagmites.
