Simulation of monsoon intraseasonal variability in NCEP CFSv2 and its role on systematic bias

We have evaluated the simulation of Indian summer monsoon and its intraseasonal oscillations in the National Centers for Environmental Prediction climate forecast system model version 2 (CFSv2). The dry bias over the Indian landmass in the mean monsoon rainfall is one of the major concerns. In spite...

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Bibliographic Details
Published in:Climate dynamics 2014-11, Vol.43 (9-10), p.2725-2745
Main Authors: Goswami, Bidyut B, Deshpande, Medha, Mukhopadhyay, P, Saha, Subodh K, Rao, Suryachandra A, Murthugudde, Raghu, Goswami, B. N
Format: Article
Language:English
Subjects:
climate models
Climate system
Climatology
Climatology. Bioclimatology. Climate change
coevolution
Convection
Earth and Environmental Science
Earth Sciences
Earth, ocean, space
Exact sciences and technology
External geophysics
Geophysics/Geodesy
heat
Heating
Meteorology
monsoon season
Monsoons
Oceanography
rain
Sea surface temperature
Seasons
Simulation
surface water temperature
Tidal waves
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Summary:We have evaluated the simulation of Indian summer monsoon and its intraseasonal oscillations in the National Centers for Environmental Prediction climate forecast system model version 2 (CFSv2). The dry bias over the Indian landmass in the mean monsoon rainfall is one of the major concerns. In spite of this dry bias, CFSv2 shows a reasonable northward propagation of convection at intraseasonal (30–60 day) time scale. In order to document and understand this dry bias over the Indian landmass in CFSv2 simulations, a two pronged investigation is carried out on the two major facets of Indian summer monsoon: one, the air–sea interactions and two, the large scale vertical heating structure in the model. Our analysis shows a possible bias in the co-evolution of convection and sea surface temperature in CFSv2 over the equatorial Indian Ocean. It is also found that the simulated large scale vertical heat source (Q1) and moisture sink (Q2) over the Indian region are biased relative to observational estimates. Finally, this study provides a possible explanation for the dry precipitation bias over the Indian landmass in the simulated mean monsoon on the basis of the biases associated with the simulated ocean–atmospheric processes and the vertical heating structure. This study also throws some light on the puzzle of CFSv2 exhibiting a reasonable northward propagation at the intraseasonal time scale (30–60 day) despite a drier monsoon over the Indian land mass.
ISSN:0930-7575
1432-0894
DOI:10.1007/s00382-014-2089-5