Parameterization in a
weather or
climate model within
numerical weather prediction refers to the method of replacing processes that are too small-scale or complex to be physically represented in the model by a simplified process. This can be contrasted with other processes—e.g., large-scale flow of the atmosphere—that are explicitly resolved within the models. Associated with these parameterizations are various
parameters used in the simplified processes. Examples include the descent rate of raindrops, convective clouds, simplifications of the atmospheric
radiative transfer on the basis of
atmospheric radiative transfer codes, and
cloud microphysics. Radiative parameterizations are important to both atmospheric and oceanic modeling alike. Atmospheric emissions from different sources within individual grid boxes also need to be parameterized to determine their impact on
air quality.