[A-AS08] Processes of the Moist Atmosphere Across Scales

[AAS08-P09] Convective aggregation in deep convective gray zone mock-walker simulations

*Chun-Yian Su¹, John Peters² (1.National Taiwan University, 2.Penn State)

Keywords:tropical convection, deep convective gray zone, mock-walker simulations, radiative-convective equilibrium

To better understand the multi-scale interactions between cloud systems and the large-scale overturning circulations over tropical ocean, this study aims to investigate how deep convective processes modulate the response of convective aggregation to the increase of SST gradient. We’ve carried out CM1 convection-permitting RCE simulations with non-interactive prescribed SST gradients using different horizontal grid spacings at the deep convective gray zone (3 and 9 km) and different representations of deep convection (NoCP, RAS, URAS, and URASca). Preliminary results highlight the impact of convection representation on the response of convective aggregation to SST gradient. For example, the upward branches of the circulation are located away from maximum SSTs when the prescribed SST gradient (dSST) is smaller than 0.75 K in simulations at the 3 km horizontal grid spacing. In contrast, the upward branches co-locate with maximum SSTs when the dSST is larger than 1.0 K. Interestingly, the convective aggregation driven by the SST gradient takes place at a larger dSST when the 9 km horizontal grid spacing is used. Meanwhile, the upward branches are narrower and stronger in the simulations with a cumulus parameterization. The underlying mechanisms and their implications will be further discussed.