Asian summer monsoon simulated by a global cloud‐system‐resolving model: Diurnal to intra‐seasonal variability

[1] Interaction of convection and circulation is key to the Asian summer monsoon, but difficult to represent in global models. Here we report results from simulations for the summer of 2004 by a global cloud-system-resolving model, NICAM. At both 14- and 7-km horizontal resolution, NICAM simulates the observed monsoon circulation patterns, and the northward propagation of precipitation. The 7-km run simulates summer-mean precipitation maxima in narrow bands along the western Ghats, Himalayan foothills, the Arakan Yoma highlands, and the Annamite range. Precipitation 1) is modulated by orography, 2) is affected by synoptic-scale systems, and 3) displays a pronounced diurnal cycle, especially over Indo-China, with its strong/weak signal propagating westward/eastward in the wet/dry phase of the intraseasonal oscillation. This set of simulations captures these intraseasonal changes of the Indian monsoon with high fidelity from June to early July. NICAM exhibits a positive bias in precipitation over the Indian Ocean, common to atmospheric models with prescribed sea surface temperature. This calls for the inclusion of ocean-atmosphere coupling process to improve monsoon simulation skills.

[1]  B. Goswami.  Interannual Variations of Indian Summer Monsoon in a GCM: External Conditions versus Internal Feedbacks , 1998 .

[2]  H. Niino,et al.  An Improved Mellor–Yamada Level-3 Model: Its Numerical Stability and Application to a Regional Prediction of Advection Fog , 2006 .

[3]  S. Yokoi,et al.  Geographical Distribution of Variance of Intraseasonal Variations in Western Indochina as Revealed from Radar Reflectivity Data , 2008 .

[4]  Paquita Zuidema,et al.  Convective Clouds over the Bay of Bengal , 2003 .

[5]  W. Liu,et al.  Role of Narrow Mountains in Large-Scale Organization of Asian Monsoon Convection* , 2006 .

[6]  J. Shukla,et al.  Intraseasonal and Seasonally Persisting Patterns of Indian Monsoon Rainfall , 2007 .

[7]  A. Kitoh,et al.  Modulation of Tropical Intraseasonal Oscillations by Ocean–Atmosphere Coupling , 2006 .

[8]  Bin Wang,et al.  Differences of Boreal Summer Intraseasonal Oscillations Simulated in an Atmosphere–Ocean Coupled Model and an Atmosphere-Only Model* , 2004 .

[9]  Hiroaki Miura,et al.  A Simulated Preconditioning of Typhoon Genesis Controlled by a Boreal Summer Madden-Julian Oscillation Event in a Global Cloud-system-resolving Model , 2009 .

[10]  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 .

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

[12]  T. Yasunari,et al.  A Climatological Monsoon Break in Rainfall over Indochina—A Singularity in the Seasonal March of the Asian Summer Monsoon , 2006 .

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

[14]  Hiroaki Miura,et al.  Characteristics of Cloud Size of Deep Convection Simulated by a Global Cloud Resolving Model over the Western Tropical Pacific( The International Workshop on High-Resolution and Cloud Modeling, 2006) , 2008 .

[15]  Hiroshi L. Tanaka,et al.  Characteristics of Internal Inertial Gravity Waves and Inertial Waves in the Lower Stratosphere Obse , 1990 .

[16]  M. Satoh,et al.  Resolution Dependency of the Diurnal Cycle of Convective Clouds over the Tibetan Plateau in a Mesoscale Model( The International Workshop on High-Resolution and Cloud Modeling, 2006) , 2008 .

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

[18]  K. V. Ramesh,et al.  Indian Ocean‐monsoon coupled interactions and impending monsoon droughts , 2006 .

[19]  M. Sugi,et al.  Internal Feedbacks from Monsoon–Midlatitude Interactions during Droughts in the Indian Summer Monsoon , 2009 .

[20]  H. Tomita,et al.  Importance of the subgrid-scale turbulent moist process: Cloud distribution in global cloud-resolving simulations , 2010 .

[21]  Hiroaki Miura,et al.  Global cloud‐system‐resolving model NICAM successfully simulated the lifecycles of two real tropical cyclones , 2008 .

[22]  Bin Wang,et al.  Ensemble Simulations of Asian–Australian Monsoon Variability by 11 AGCMs* , 2004 .

[23]  Olive Heffernan.  They say they want a revolution , 2008, Nature.

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

[25]  M. Hoerling,et al.  Advancing dynamical prediction of Indian monsoon rainfall , 2005 .

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

[27]  Li Tao,et al.  Impact of Atmosphere-Ocean Coupling on the Predictability of Monsoon Intraseasonal Oscillations , 2007 .