Provides the theoretical and practical framework for a two-dimensional temperature model. The vertically integrated mass balance equations of an existing two-dimensional flow-reaction simulation model are shown to apply to temperature modeling. Terms contributing to the total heat flux across the water surface are described and approximated by empirical relations that, in turn, are integrated into the temperature model through an equilibrium temperature and heat exchange coefficient. The sensitivity of these parameters to the meteorological variables is discussed in the context of a preliminary calculation. Tables are given for the heat exchange coefficient and equilibrium temperature. Finally, expressions are derived for the relative isobaric slope as a function of chlorinity and temperature. 58 pp. Ref.