Hydrophysics

a branch of geophysics in which the physical processes taking place in the water envelope (hydrosphere) of the earth are studied. Among the general problems covered by hydrophysics are the molecular structure of water in all three of its states (liquid, solid, and gaseous); the physical properties of water, snow, and ice, including thermal (thermal conductivity and heat capacity), radiation, electrical, radioactive, acoustic, and mechanical (elasticity and viscosity); the processes occurring in bodies of water, both dynamic (currents, waves, and tides) and thermal (heating and cooling of bodies of water, evaporation and condensation, the formation and thawing of ice and snow); and the propagation, absorption, and scattering of light in layers of water, snow, and ice.

Hydrophysics is subdivided into marine physics and the physics of land waters. The latter studies the rivers, lakes, reservoirs, underground waters, and other bodies of water on the continents in connection with the problems of land hydrology, as well as the thermal and dynamic processes involved in the changes of moisture reserves in river basins (in the upper layer, or root zone, of the soil and at the surface, in the snow cover, in glaciers, and in snowflakes). Progress has also been made on the problems of turbulent motion of water, the movement of alluvium by turbulent flows, and the interaction between a stream and its channel. This set of problems has become a special discipline, stream dynamics. The thermal characteristics of freshwater ponds, such as the principles of the formation and growth of surface and frazil ice and the thermal balance of bodies of water and the snow cover, have been very extensively treated.

Marine physics deals with the processes that occur in the seas and oceans: the dynamics of ocean currents; tidal, surface, and internal waves; the interaction between an ocean and the atmosphere; and the thermal characteristics, acoustics, and optics of the seas.