Within a grid cell the clouds and other small-scale phenomena create fluctuations in the radiation field. It is important that the temporal domain over which the statistical properties are described be appropriate. The statistical properties of the cloud field that the parameterization of the field preserves must include the essential elements. For example, a model may preserve fractional cloudiness but not the average surface heating rate. Such a model would fail to treat adequately the temporal parameterization.
Temporal resolution is also important for the experimental verification of radiative models.
Radiative processes are characterized by the time scales required for the atmosphere to change its thermal structure or its cloud distribution. It is the integration of these processes over the meteorological time scale that is important. This can be as small as several minutes for cloud properties. In addition, the range of physical conditions that control the transfer of radiation through the atmosphere can be observed over time. A long-term measurement system, with carefully chosen sites, would enable exploration of the full domain of the radiative transfer codes and their parameterizations.