There are several different cloud microphysics parameterization schemes. They note that modifications to the microphysics scheme dramatically impacted the hurricane intensity. In this sense, it bridges the transition from simplicity of microphysics to complexity of macrophysics. They then inserted a vortex with varying microphysics schemes and noted that the tracks diverged. They used the microphysics scheme from NASA Goddard Space Flight Center. Cloud microphysics describe the structure and properties of clouds on the microscopic scale. Typically, microphysics schemes will use a mass-weighted average for the fall velocity. The bulk microphysics models are much faster than the bin models but are less accurate.