Parameterization of the Elevated Convection With a Unified Convection Scheme (UNICON) and Its Impacts on the Diurnal Cycle of Precipitation.

To improve the simulation of nocturnal precipitation, we develop a parameterization for the elevated convection that is launched from the level of maximum grid‐mean moist static energy, when grid‐mean vertical flow is upward at the launching interface. The parameterized elevated convection is forced by both cold pool‐driven and partially resolved external mesoscale organized flows. Properties of the external mesoscale flow are estimated from grid‐mean vertical velocity and three dimensional advection tendencies of temperature and moisture. The new parameterization is implemented into a unified convection scheme (UNICON) and tested for both the single‐column case at the Southern Great Plain (SGP) site in US and in global simulations. At the SGP site, the parameterized elevated convection strengthens nocturnal convection, increases nocturnal precipitation, and better simulates the observed diurnal cycle of precipitation. It appears that the elevated and surface‐based convections interact with each other by stabilizing the atmospheric column, which affects subsequent convection. Global simulation shows that the elevated convection mostly occurs over the continents during the night, and also over the oceanic mid‐latitude warm air advection and storm track regions during summer. Without degrading global mean climate, the elevated convection improves the simulation of nocturnal precipitation in the mid‐US but simulates somewhat strong nocturnal precipitation in northeastern Asia. It seems that a key to simulate observed nocturnal precipitation is to appropriately parameterize the impacts of external organized flow on the elevated convection. Plain Language Summary: Precipitation has a strong diurnal cycle as a result of complex interactions between the atmosphere and the surface through moist convection. The diurnal cycle of precipitation has a significant impact on surface energy and water budgets, and its accumulated effect may appear even on the climate timescale. However, most general circulation models (GCM) poorly simulate the observed diurnal cycle of precipitation. Particularly, it has been difficult to simulate nocturnal precipitation over the central US during summer. To improve the simulation of nocturnal precipitation, we develop a new parameterization for the elevated convection. Both single‐column and global test simulations show that the new parameterization increases nocturnal precipitation and better simulates the observed diurnal cycle of precipitation. Our research will contribute to improving the performance of GCM and so better simulating current and future climates. Key Points: To improve the simulation of nocturnal precipitation, we develop a parameterization for the elevated convectionIn the mid‐US, the new parameterization increases nocturnal precipitation and better simulates the observed diurnal cycle of precipitationA key to simulate observed nocturnal precipitation is to parameterize the impacts of external mesoscale flow on the elevated convection [ABSTRACT FROM AUTHOR]