Recently, an explicit cloud prediction scheme was added to the Eta and Meso Eta models. This scheme explicitly represents cloud liquid water and cloud ice in the model's prognostic equations. Additionally, this scheme produces explicit, three-dimensional forecasts of both cloud fraction and water content, which are used to link the hydrologic cycle to the radiation parameterization package in the model. Clouds are produced in this scheme from large-scale condensation processes, just like in the previous scheme. Clouds in this scheme consist of either liquid droplets or ice particles, depending on the temperature of the cloud.
Condensation occurs in the model at two different percentages.
This higher value over water is due to the fact that condensation can occur much easier over the ocean than on land, especially in the lower atmosphere, because of the availability of moisture. These percentages allow for sub-grid variations in the relative humidity field. Six major microphysical processes are used in the parameterization of precipitation production from clouds. Because of the differences in the two types of schemes, forecasters will need to interpret the output of relative humidities produced in each model differently. This difference in relative humidity values is mainly due to two processes.