Modelling convective processes during the suppressed phase of a Madden–Julian oscillation: Comparing single‐column models with cloud‐resolving models

Abstract

The role of convective processes in moistening the atmosphere during suppressed periods of the suppressed phase of a Madden-Julian oscillation is investigated in cloud-resolving model (CRM) simulations, and the impact of moistening on the subsequent evolution of convection is assessed as part of a Global Energy and Water Cycle Experiment Cloud System Study (GCSS) intercomparison project. The ability of single-column model (SCM) versions of a number of state-of-the-art climate and numerical weather prediction models to capture these convective processes is also evaluated. During the suppressed periods, the CRMs are found to simulate a maximum moistening around 3 km, which is associated with a predominance of shallow convection. All SCMs produce adequate amounts of shallow convection during the suppressed periods, comparable to that seen in CRMs, but the relatively drier SCMs have higher precipitation rates than the relatively wetter SCMs and CRMs. The relatively drier SCMs dry, rather than moisten, the lower troposphere below the melting level. During the transition periods, convective processes act to moisten the atmosphere above the level at which mean advection changes from moistening to drying, despite an overall drying effect for the column. The SCMs capture some essence of this moistening at upper levels. A gradual transition from shallow to deep convection is simulated by the CRMs and the wetter SCMs during the transition periods, but the onset of deep convection is delayed in the drier SCMs. This results in lower precipitation rates for these SCMs during the active periods, although much better agreement exists between the models at this time.

Precipitation distributions for explicit versus parametrized convection in a large‐domain high‐resolution tropical case study

“…This is associated with subgrid increments with significantly more moistening in the free troposphere and drying in the boundary layer as well as mid-tropospheric cooling; these are likely related to more shallow convection and/or evaporation of stratiform rainfall (although the relationship between subgrid terms and total increments can be complicated to explain). The subgrid moistening profiles at rain rates of 1.0 E−1 mm h −1 and 3.0 E−1 mm h −1 for the 4 km 3Dsmag run are similar to the suppressed period CSRM integrations in (Woolnough et al, 2010, their figure 8), although the magnitude in the 12 km param model is more similar to those profiles at 1.0 E−1 mm h −1 ; the precipitation in the CSRMs compared in the suppressed period of that study ranges from 4.0 E−2 to 1.0 E−1 mm h −1 . Interestingly, the lowest rain-rate bin in our Figure 8, with rain rates lower than those in the suppressed period CSRMs in Woolnough et al (2010), shows strong moistening at levels below 2 km for both model versions, somewhat lower than shown by the CSRMs (at somewhat higher rain rates) in that study.…”

ASoP (v1.0): a set of methods for analyzing scales of precipitation in general circulation models

“…These comparisons must take care to analyze observed and simulated data at comparable spatial and temporal scales, given our results on the effects of spatial and temporal averaging on the distributions and coherence of precipitation. Model development efforts to reduce or remove undesirable intermittency may involve single-column model experiments, in which the effects of changes in sub-gridscale physics can be isolated from feedbacks through the resolved dynamics (e.g., Satoh and Hayashi, 1992;Takata and Noda, 1997;Woolnough et al, 2010), although we stress that physics-dynamics coupling may have a substantial effect on the model behaviors and diagnostics presented here.…”

Overview of the Meso-NH model version 5.4 and its applications

“…Numerous studies have evaluated the KFB deep convection scheme in the 1D configuration and intercompared it with other schemes/models (e.g., Mallet et al, 1999;Bechtold et al, 2000;Xie et al, 2002;Bechtold et al, 2004;Guichard et al, 2004;Woolnough et al, 2010;5 Couvreux et al, 2015). Initiated under the Global Energy and Water Cycle Experiment (GEWEX) project with the GEWEX Cloud System Study (GCSS) working group Redelsperger et al, 2000;Stevens et al, 2001;Xie et al, 2002), many of these intercomparison studies involving Meso-NH have focused on deep and boundary layer clouds (Siebesma et al, 2003;Lenderink et al, 2004;Guichard et al, 2004;Woolnough et al, 2010;Varble et al, 2011;Fridlind et al, 2012;Varble et al, 2014a, b;Daleu et al, 2016a, b;Field et al, 2017). These studies have allowed progress in convection param-…”