Importance of cloud/precipitation processes on tropical intraseasonal oscillation

The tropical intraseasonal oscillation (ISO), also known as the Madden-Julian oscillation (MJO), is the important variability at the subseasonal time scale, and is a dominant mode in the tropical region with eastward periods of 30-60 days (Madden and Julian 1994). ISO is important because of its considerable influence on monsoon dynamics, generating active and break phases of convection during the South-East Asian and Australian monsoons, on general weather and climate variability and as an important part of the ENSO cycle (Kang et al. 1999; Hoyos and Webster 2007; Kim et al. 2010). However, these phenomena are known to be difficult to be captured in general circulation models (GCMs) (Lin et al. 2006; Seo and Wang 2010). Recently, progress in understanding the moist processes associated with the development and maintenance of MJO has been made by observational data (Benedict and Randall 2007) and modeling studies (Lee et al. 2003; Fu and Wang 2009; Seo and Wang 2010). Fu and Wang (2009) found that the detrainment from the convective updraft moistens the large-scale environment and induces the further development of the deep convective plumes. They also demonstrated that the convective detrainment of moisture to the stratiform clouds plays a key role in sustaining the MJO. Seo and Wang (2010) mentioned that the convective detrainment of moisture plays a key role in sustaining the ISO by inducing the characteristic heating profile. Thus, it is clear that not only cumulus parameterization scheme but also statiform cloud scheme is important to the ISO simulation. Also, both processes are significantly connected to the cloud-radiation interaction because cloudiness in the radiation algorithm is function of the relative humidity and mixing ratio. In this study, the cloudiness parameterization will be evaluated for ISO simulation in GCM. Also, the characteristics of wave propagation and intensity of the ISO in coupled climate model using improved cloudiness formula will be investigated.