A Multiscale Model for the Intraseasonal Impact of the Diurnal Cycle over the Maritime Continent on the Madden–Julian Oscillation

Abstract

The eastward-propagating Madden–Julian oscillation (MJO) typically exhibits complex behavior during its passage over the Maritime Continent, sometimes slowly propagating eastward and other times stalling and even terminating there with large amounts of rainfall. This is a huge challenge for present-day numerical models to simulate. One possible reason is the inadequate treatment of the diurnal cycle and its scale interaction with the MJO. Here these two components are incorporated into a simple self-consistent multiscale model that includes one model for the intraseasonal impact of the diurnal cycle and another one for the planetary/intraseasonal circulation. The latter model is forced self-consistently by eddy flux divergences of momentum and temperature from a model for the diurnal cycle with two baroclinic modes, which capture the intraseasonal impact of the diurnal cycle. The MJO is modeled as the planetary-scale circulation response to a moving heat source on the synoptic and planetary scales. The results show that the intraseasonal impact of the diurnal cycle during boreal winter tends to strengthen the westerlies (easterlies) in the lower (upper) troposphere in agreement with the observations. In addition, the temperature anomaly induced by the intraseasonal impact of the diurnal cycle can cancel that from the symmetric–asymmetric MJO with convective momentum transfer, yielding stalled or suppressed propagation of the MJO across the Maritime Continent. The simple multiscale model should be useful for the MJO in observations or more complex numerical models.

Intraseasonal Variability of the Diurnal Cycle of Precipitation in the Philippines

“…Inclusion of the diurnal cycle dramatically improves the representation of the MJO in a general circulation model (Slingo et al 2003, Bernie et al 2008, indicating that understanding this interaction could be important for an understanding of the MJO. There is also evidence that the diurnal cycle can precondition the atmosphere for MJO propagation, and modulate it through diurnally generated gravity waves (Raupp andSilva Dias 2009, Majda andQ. Yang 2016).…”

The Multiscale Impacts of Organized Convection in Global 2‐D Cloud‐Resolving Models

“…Thus, multiscale models describe an alternative mechanism than diabatic feedbacks for the large‐scale organization of tropical convection. These multiscale models highlight the central role of vertically tilted synoptic‐scale anomalies (Biello & Majda, , , Majda & Biello, ) and the upscale impact of the diurnal cycle through eddy flux divergence of temperature (Majda & Yang, ; Yang & Majda, ). In so doing, they can explain many of the observed characteristics of the MJO.…”

Possible Role of the Diurnal Cycle in Land Convection in the Barrier Effect on the MJO by the Maritime Continent

“…The diurnal cycle is a prominent feature of the MC (Houze et al, 1981;Mori et al, 2004;Yamanaka, 2016). Connected to the MJO over the MC (Ichikawa & Yasunari, 2008;Peatman et al, 2014;Suzuki, 2009) as well as over the open ocean (Chen & Houze, 1997;Sakaeda et al, 2017;Sui & Lau, 1992;Tian et al, 2006), the diurnal cycle has been considered a possible reason for the barrier effect (Hagos et al, 2016;Majda & Yang, 2016;Neale & Slingo, 2003;Tung et al, 2014;Wang & Li, 1994;Zhang & Hendon, 1997). One possible role of the diurnal cycle in the barrier effect is through a competition between convection over land and over water of the MC.…”