A New Comprehensive Cloud Macrophysics Scheme With a Prognostic Dual‐Triangular PDF.

To improve cloud simulation in a general circulation model, we develop a new cloud macrophysics scheme that treats detrained cumulus generated by convective detrainment process separately from pure stratus; prognoses two symmetric triangular probability density functions of total specific humidity for each detrained cumulus and pure stratus; and diagnoses both cloud fraction and cloud condensate in all liquid, ice, and mixed‐phases in a consistent and unified way without any adjustment to remove empty or very dense cloud. Supersaturation is allowed within ice cloud. The new scheme ("NEW") is compared with the previous model ("OLD") using single‐column simulations for subtropical marine stratocumulus (DYCOMS2) and continental deep convection (ARM97) cases. In DYCOMS2, both NEW and OLD produce vertical profiles of grid‐mean cloud condensate similar to large‐eddy simulation. In ARM97, compared with OLD, NEW simulates less sporadic vertical profiles of in‐cloud condensates, due to consistent diagnosis of cloud fraction and cloud condensate; more continuously‐varying detrained cumulus with time, due to prognostic treatment of detrained cumulus; and ice cloud fraction and ice condensate similar to those of OLD, in spite of completely different treatment of ice cloud processes. The global performance of NEW is similar to OLD with improved relative humidity. Compared to OLD, NEW simulates more and improved cloud condensate, but less and degraded cloud fraction, particularly, in the lower troposphere. Detrained cumulus is moister and colder and has a larger moisture variance than pure stratus. Overall, NEW simulates stronger condensation‐deposition rates than OLD, due in part to the separate treatment of detrained cumulus and pure stratus. Plain Language Summary: This study suggests a new cloud parameterization scheme in a general circulation model that can represent clouds in nature in a realistic way. Our new cloud scheme separates two types of stratus, called detrained cumulus and pure stratus, by using a set of prognostic equations. Moreover, both liquid, ice, and mixed‐phase clouds are treated in a consistent way. We found that the new scheme successfully operates for two single‐column simulations for subtropical marine stratocumulus and continental deep convection cases. In addition, we performed the global simulation and found that the new scheme simulated more cloud condensate but less cloud fraction than the old scheme with some improvements. Key Points: We develop a new cloud macrophysics scheme by prognosing two triangular probability density functions for each detrained cumulus and pure stratusThe new scheme computes both cloud fraction and cloud condensate in all liquid, ice, and mixed‐phases in a consistent and unified wayThe new scheme simulates more cloud condensate but less cloud fraction than the old scheme with improved relative humidity and global performance [ABSTRACT FROM AUTHOR]