Inclusion of the radiative effect of deep convective clouds in the Eta model simulations

• Published in: Quarterly journal of the Royal Meteorological Society 2024-04, Vol.150 (761), p.1809-1830
• Main Authors: Campos, Diêgo de Andrade, Chou, Sin Chan, Bottino, Marcus Jorge, Gomes, Jorge Luís, Lyra, André
• Format: Article
• Language: English
• Subjects: Atmospheric models; atmospheric radiation; BMJ; Cloud cover; Cloud water; Clouds; Condensates; Convective activity; Convective clouds; Convective instability; Convective precipitation; Cumulus clouds; Diurnal cycle; Energy budget; Eta model; Microphysics; Net radiation; Parameterization; Parameters; Precipitation; Radiation; Radiation balance; Radiation-cloud interactions; Radiative transfer; RRTM; Solar radiation; Terrestrial radiation
• ISSN: 0035-9009; 1477-870X
• DOI: 10.1002/qj.4673

Convective clouds play an important role in the local energy budget by directly interacting with solar and terrestrial radiation. However, radiation parameterization schemes of atmospheric models generally consider clouds produced from microphysics schemes or some other grid saturation criteria. Deep convective parameterization schemes tend to rain out the convective cloud before the radiation scheme perceives its water load. This may be a source of the positive bias of the incoming solar radiation at the surface. The objective of this work is to include the effects of deep convective clouds in the radiation scheme of the regional Eta model and to evaluate the impacts on the net radiative energy and other meteorological variables. The radiation scheme is the Rapid Radiative Transfer Model. The work is developed in four stages. The positive bias in the incoming solar radiation was diagnosed in the first stage. In the second stage, the parameters of the convective parameterization scheme were modified to increase convective precipitation. In the third stage, the parameters of the microphysics scheme were modified to increase explicit clouds. In the fourth and last stage, in addition to the previous modifications, the condensates from the convective parameterization were input into the radiation scheme. The runs were performed for a period of one summer rainy month with intense convective activity over South America. Including deep convective cloud condensates into the radiation scheme improved the cloud cover, the diurnal cycle of the surface net radiation, and the 2‐m temperature. However, the reduction of the net radiation at the surface caused the reduction of the available energy for convective instability and, consequently, the precipitation reduction. The results show the importance of including cumulus cloud water load in the radiative scheme for bias reduction in the radiative energy components. This work aimed at evaluating the Eta model using the Rapid Radiative Transfer Model for General circulation models (RRTMG) radiation scheme under cloudy‐sky conditions and verifying the effect of deep convective clouds on the radiation scheme. The work shows the need for the assessment of the interactions between convective and microphysics schemes with the radiation scheme, and for the step‐by‐step tests from the EtaR control run, no clear effects of deep convective clouds, up to the EtaR‐CMX run, with deep convective clouds effects.