Topographic Influence on the MJO in the Maritime Continent

Abstract

This study demonstrates that during the passage of the MJO through the Maritime Continent in the boreal winter, the corresponding deep convection and near-surface wind anomalies tend to skirt around mountainous islands. Flow bifurcation around elongated mountainous islands, such as New Guinea, is clearly seen. Topographic blocking generates distinctive vorticity and convergence distributions in this specific domain. Mountain-wave-like structures are also observed throughout the Maritime Continent, with a clear spatial relationship with the high terrains in Sumatra, Sulawesi, and New Guinea. The existence of topography seems to create extra lifting and sinking within the large-scale circulation and thus the convective system exhibits quasi-stationary features near the major topography during the MJO passage through the Maritime Continent. It is suggested that resolving the detailed topographic effects may play a key role in simulating realistic characteristics of the MJO in the Maritime Continent.

Observing and understanding the Southeast Asian aerosol system by remote sensing: An initial review and analysis for the Seven Southeast Asian Studies (7SEAS) program

“…If one wishes to move from the qualitative to even the semi-quantitative, one must consider SEA's many highly interrelated climate and meteorological features. Nominally there are five atmospheric scales of concern over greater SEA, from largest to smallest: 1) Interannual features such as El Niño Southern Oscillation (ENSO Rasmusson and Wallace, 1983;Mcbride et al, 2003), ENSO Modoki (Ashok et al, 2007) and the Indian Ocean Dipole (IOD, Saji et al, 1999;Saji and Yamagata, 2003;Schott et al, 2009); 2) Seasonal migration of the Intertropical Convergence Zone (ITCZ) and its associated summer and winter monsoonal period and transitions (Chang et al, 2005a;Moron et al, 2009;Wang et al, 2009); 3) Intraseasonal synoptic phenomenon such as the 30-90day oscillation or the Madden Julian Oscillation (MJO) (Madden and Julian, 1971;Zhang, 2005;Wu and Hsu, 2009;Wu et al, 2009), the quasi-monthly oscillation , Borneo Vortex (Chang et al, 2005b), the west Sumatran low (Wu et al, 2009a), or at the most northern extent of our domain, the Meiyu front (Ding, 2002;Ding and Chan, 2005); 4) Wave and mesoscale features such as fronts and tropical cyclones (Goh and Chan, 2010) in northern SEA, and equatorial waves, such as the Kelvin, Rossby, and Easterly waves in the MC (Wheeler and Kiladis, 1999;Kiladis et al, 2009), tropical cyclones, or mid-level dry tongue (Ridout, 2002;Yasunaga et al, 2003;Zhang et al, 2003); and 5) Regional convection from localized weather phenomena, such as fair weather cumulus, orographically modified flows, thunderstorms, isolated small or trade convection, convective cold pools, sea breeze circulation, etc. (Schafer et al, 2001;Yang and Smith, 2006;Mahmud, 2009a,b;Mahmud, in press;Li et al, 2010;Sow et al, 2011;…”

Enhanced MJO-like Variability at High SST

“…This approach has the advantage of simplifying the analysis and highlighting any changes in dynamics. On the other hand, it immediately sacrifices certain features like seasonality and the influence of topography, which may be relevant to some studies (e.g., Wu and Hsu 2009). More subtle aspects of the MJO may also be affected.…”

Response of Sea Surface Temperature (Sst) and Chlorophyll-a on Madden Julian Oscillation (Mjo) in Indonesian Seas

“…Ditinjau dari posisi geografisnya, Indonesia diapit oleh dua benua luas (Asia dan Australia) dan dua samudra luas (Pasifik dan Hindia), serta menjadi pusat perpindahan massa air pada berbagai tingkat kedalaman. Wilayah Indonesia memiliki topografi yang kompleks sehingga menambah variabilitas laut-atmosfer di Laut Indonesia (Wu and Hsu, 2009). …”

“…Fenomena MJO memiliki periode dominan berkisar antara 40 hingga 60 hari atau masuk dalam periode intra-musiman, sehingga untuk mempertegas osilasi data pada periode tersebut diperlukan penapisan dengan kisaran frekuensi intra-musiman (Zhang and Dong, 2004;Wu and Hsu, 2009;Arguez et al, 2005). Penapisan data diharapkan dapat membatasi dampak dari fenomena osilasi musiman, tahunan, ataupun antar tahunan.…”