The Earth surface is defined as the interface between the atmosphere and the underlying ocean or land. This later include all existing land covers types: vegetation, bare soil, water bodies, impervious surfaces like roads and urbanized areas.

Hydrometeorology is a part of meteorology which focus on studies of the exchanges of water and energy between the Earth surface and its atmosphere.

The water cycle involves precipitation, evapotranspiration, water stored in the soil, rivers and water bodies. The condensation of atmospheric water forms precipitation and release energy into the atmosphere. The evapotranspiration process combines both the evaporation of water at the Earth surface and the transpiration of the vegetation. It consumes energy, so-called latent heat, which is itself in balance with other energy and heat fluxes (namely, the net surface radiative flux, the sensible heat flux and the heat conduction flux exchanged between the atmosphere and the ground). Transpiration of the vegetation is also related to other physiological processes like respiration and photosynthesis involved in the carbon cycle. Other exchanges of mass (e.g. dust, trace gazes) are also participating to exchanges between the surface and the atmosphere. Finally, human activity can also contribute to those exchanges (e.g. addition of nutriments to the soil, crops irrigation).

The ‘land surface processes’ gather the different physical phenomena occurring at the continental Earth surface or, by extension, in its immediate neighboring: in the lower part of the atmospheric boundary-layer, in the vegetation layer and in the upper layers of the soil or water bodies. Together with the air advection, they impact directly weather conditions (air temperature and humidity, wind speed) in the lower part of the atmospheric boundary layer, as well as temperature and moister conditions at the surface and beneath (in the soil, water bodies and canopy layer).

Land surface processes are determinant for weather and climate which in turn impact them. They affect human life environment and activities. They condition directly and indirectly the society: the quality of habitat, the available resources for life as available food and drinking water, the possibilities to develop agricultural and other human activities are directly tributary of phenomenon occurring at the land surface.