Diurnal Convection Peaks over the Eastern Indian Ocean off Sumatra during Different MJO Phases

The authors investigated diurnal convection peak characteristics over the eastern Indian Ocean off the island of Sumatra during different phases of the Madden-Julian oscillation (MJO). During MJO phases 2 to 3 (P2 and P3) defined by Wheeler and Hendon (2004), prominent diurnal variation in convection was observed by satellites when moderate low-level westerly winds were dominant over the eastern Indian Ocean. The diurnal convection peaks were prominent over the island of Sumatra in the evening, while migrations of the convection toward the Indian Ocean were observed in the early morning. By using the Global Positioning System around the western region offshore of Sumatra, a significant reduction in water vapor was observed from evening until midnight, compensating for the upward motion over the island. During midnight to early morning, the water vapor in-creased in the western offshore region as the convections migrated from the island. This prominent diurnal varia-tion confirmed the result from a numerical experiment by Miura et al. (2007) using the Nonhydrostatic ICosahe-dral Atmospheric Model (NICAM).During P2 to P3, the atmosphere over the eastern Indian Ocean contains abundant water vapor, while the Maritime Continent is fairly well heated by solar radiation under calm conditions. This situation should be favor-able for the development of two diurnal convection peaks: the evening convection over the land induced by solar radiative heating and the midnight convection over the ocean triggered by convergence of the low-level westerly wind and the land breeze.

[1]  M. Fujita,et al.  Morning Precipitation Peak over the Strait of Malacca under a Calm Condition , 2010 .

[2]  Ping Liu,et al.  An MJO Simulated by the NICAM at 14- and 7-km Resolutions , 2009 .

[3]  Hiroaki Miura,et al.  Diurnal Cycle of Precipitation in the Tropics Simulated in a Global Cloud-Resolving Model , 2009 .

[4]  Y. Takayabu,et al.  An Evaluation of the Reproducibility of the Madden-Julian Oscillation in the CMIP3 Multi-Models , 2009 .

[5]  M. Hara,et al.  Why a Large Amount of Rain Falls over the Sea in the Vicinity of Western Sumatra Island during Nighttime , 2009 .

[6]  M. Satoh,et al.  Multi-scale Organization of Convection in a Global Numerical Simulation of the December 2006 MJO Event Using Explicit Moist Processes , 2009 .

[7]  M. Hara,et al.  Assessment of the Diurnal Cycle of Precipitation over the Maritime Continent Simulated by a 20 km Mesh GCM Using TRMM PR Data , 2009 .

[8]  Hirohiko Masunaga,et al.  A joint satellite and global cloud‐resolving model analysis of a Madden‐Julian Oscillation event: Model diagnosis , 2008 .

[9]  Fujio Kimura,et al.  Verification of precipitable water vapor estimated from shipborne GPS measurements , 2008 .

[10]  Masaki Satoh,et al.  Nonhydrostatic icosahedral atmospheric model (NICAM) for global cloud resolving simulations , 2008, J. Comput. Phys..

[11]  Hiroaki Miura,et al.  A Madden-Julian Oscillation Event Realistically Simulated by a Global Cloud-Resolving Model , 2007, Science.

[12]  T. Yasunari,et al.  Propagating diurnal disturbances embedded in the Madden‐Julian Oscillation , 2007 .

[13]  Eric J. Fetzer,et al.  Modulation of the diurnal cycle of tropical deep convective clouds by the MJO , 2006 .

[14]  Bin Wang,et al.  Vertical Moist Thermodynamic Structure and Spatial-Temporal Evolution of the MJO in AIRS Observations , 2006 .

[15]  Philip J. Rasch,et al.  Tropical Intraseasonal Variability in 14 IPCC AR4 Climate Models. Part I: Convective Signals , 2006 .

[16]  T. Yasunari,et al.  Time-space characteristics of diurnal rainfall over borneo and surrounding oceans as observed by TRMM-PR , 2006 .

[17]  F. Murata,et al.  Diurnal cycle of cloud system migration over Sumatera Island , 2005 .

[18]  Christian Rocken,et al.  Atmospheric water vapor and geoid measurements in the open ocean with GPS , 2005 .

[19]  M. Wheeler,et al.  An All-Season Real-Time Multivariate MJO Index: Development of an Index for Monitoring and Prediction , 2004 .

[20]  Hirofumi Tomita,et al.  A new dynamical framework of nonhydrostatic global model using the icosahedral grid , 2004 .

[21]  Kwang-Yul Kim,et al.  Propagation and initiation mechanisms of the Madden-Julian oscillation , 2003 .

[22]  Hiroyuki Hashiguchi,et al.  Diurnal Land-Sea Rainfall Peak Migration over Sumatera Island, Indonesian Maritime Continent, Observed by TRMM Satellite and Intensive Rawinsonde Soundings , 2003 .

[23]  B. Hoskins,et al.  The organization of tropical convection by intraseasonal sea surface temperature anomalies , 2001 .

[24]  T. Ohsawa,et al.  Diurnal Variations of Convective Activity and Rainfall in Tropical Asia , 2001 .

[25]  H. Hendon.  Impact of Air-Sea Coupling on the Madden-Julian Oscillation in a General Circulation Model , 2000 .

[26]  Richard H. Johnson,et al.  Trimodal Characteristics of Tropical Convection , 1999 .

[27]  W. Grabowski.  Toward Cloud Resolving Modeling of Large-Scale Tropical Circulations: A Simple Cloud Microphysics Parameterization , 1998 .

[28]  T. Nitta,et al.  Diurnal variation of convective activity over the tropical western pacific , 1994 .

[29]  Thomas M. Smith,et al.  Improved Global Sea Surface Temperature Analyses Using Optimum Interpolation , 1994 .

[30]  P. R. Julian,et al.  Observations of the 40-50-day tropical oscillation - a review , 1994 .

[31]  K. Lau,et al.  Multiscale Phenomena in the Tropical Atmosphere over the Western Pacific , 1992 .

[32]  P. R. Julian,et al.  Description of Global-Scale Circulation Cells in the Tropics with a 40–50 Day Period , 1972 .

[33]  P. R. Julian,et al.  Detection of a 40–50 Day Oscillation in the Zonal Wind in the Tropical Pacific , 1971 .

[34]  F. Kimura,et al.  Diurnal Variation of Rainfall and Precipitable Water over Siberut Island off the Western Coast of Sumatra Island , 2008 .