ACCESS evaluation of convective cloud system properties over the Northern Australian region

 
Poster PDF

Authors

Hanh Nguyen — Centre for Australian Weather and Climate Research
Vickal Vikash Kumar — Monash University
Alain Protat — Australian Bureau of Meterology

Category

Modeling

Description

In order to evaluate the representation of clouds and convection in the Australian Community Climate and Earth-System Simulator (ACCESS) forecast model within different large-scale forcings, the variability of the statistical properties of convective clouds over Darwin is investigated in the context of different phases of the Madden-Julian Oscillation (MJO). This study makes use of data sets from the ACCESS model, cloud radar and lidar measurements from the ARM Facility’s Darwin site, and the C-band polarimetric radar (C-POL) observations. Vertical profiles of the frequency of occurrence of the convective clouds over a two wet-seasons interval (2005–2007), together with the diurnal cycles, are composited onto these large-scale atmospheric regimes and phases of the MJO. The frequency of occurrence of convective clouds tends to peak too early in ACCESS compared to the ARM and C-POL observations, although the proportion of the vertical compared to the ARM and C-POL observations is in fairly good agreement. This strong bias is also observed in the diurnal cycle of the convective cloud system for all regimes. In addition, the diurnal cycle of model data reveals a notable occurrence of low-level clouds that is not seen in the ARM observations. These biases are observed as well in all of the large-scale regimes and MJO phases.