A hydrologically useful station precipitation model: 1. Formulation

A one‐dimensional, physically based precipitation model is formulated. Particular emphasis is placed on its utility for real‐time river flow forecasting. Thus, the model is in state‐space form, suitable for use with modern estimation theory techniques, and it uses only operationally readily available, meteorological variables as its input. Parameterization of the model components is based on well‐established observations and theories on water vapor condensation, precipitation mechanisms, and subcloud evaporation of falling hydrometeors. Model input consists of ground level station temperature, pressure, and dewpoint temperature observations. The model predicts the spatially averaged, ground surface precipitation rate in the characteristic area determined by the spatial scales of the input. The water equivalent mass condensed in a cloud column defined by the characteristic area is the model state. Key physical parameters in the formulation are the pressure at the cloud top, the height‐averaged updraft velocity, and the inverse of the average diameter of the hydrometeors at cloud base.