Cloud-Radiative Effects on the Coastal Diurnal Cycle Over the Maritime Continent

The diurnal cycle is one of the predominant components of atmospheric variations, yet the latest global circulation models continue to struggle with accurately representing the timing and strength of peak diurnal rainfall over land and ocean. Clouds alter how radiation is distributed throughout the atmosphere and surface, directly affecting diurnal convective triggering mechanisms. Additionally, results from idealized simulations suggest cloud-radiative effects influence the strength and local circulation of convection over open ocean environments. However, it is not clear how cloud-radiative effects influence coastal convection, specifically their influence on nocturnal offshore propagating convection.
This study will employ the Weather Research and Forecasting (WRF) model, a full physics model, to simulate the diurnal cycle over the Maritime Continent, a region where a strong diurnal signal and coastal propagation of convection exists. The 10-day long control simulation during the 2015 Pre-Years of Maritime Continent field campaign shows similar large-scale propagation of convection between the model and observed results, with a positive rain rate bias existing over land. Coastal analysis over the western coast of Sumatra and northern coast of Borneo shows a clear offshore propagation of convection similar to the observed. Offshore propagating days are subjected to additional experimentation, where cloud-radiative effects are turned off before convection is initiated over land (~12 LT); and before convection propagates offshore (~20 LT). These additional experiments will test the sensitivity of off-shore propagation of convection to cloud-radiative interactions, highlighting the importance of cloud-radiative effects on storm structure and strength.