Question

Define how does heat transfer in between
land area and, water sources in day time
and night time .​

Answer 1

Water–air heat exchange

Concerning the heat exchange between a river and its environment, the heat exchange between water and atmosphere is the most significant (Evans et al. 1998; Webb and Zhang 1999). Its intensity depends on water temperature and external meteorological and hydrological conditions, and it is influenced by many processes (Chapra 2008; Edinger 1974; Rutherford et al. 1993) which may be divided into two groups:

Processes independent of water temperature, i.e.,

Shortwave solar radiation—radiation emitted by the sun (also called shortwave radiation or solar radiation);

Longwave atmospheric radiation—radiation that water receives from the atmosphere (also called thermal radiation); sometimes, it is calculated together with other sources of the longwave radiation from surrounding terrain like, for example, radiation from vegetation;

Processes dependent on water temperature, i.e.,

Longwave water back radiation—radiation emitted by the water surface (also called longwave back radiation);

evaporation and condensation—there are processes with matter changes from one state to another; evaporation is the loss of water to the atmosphere in the form of water vapour, and it is associated with the heat loss from the water surface, while the condensation is the reverse process;

conduction and convection—processes that take place at the border of water and air if they have different temperatures.

Those processes have been schematically presented in Fig. 1. Note that other processes may also be taken into account but their role usually become significant only in some specific cases.