Mean state and interannual variability of the Indian summer monsoon simulation by NCEP CFSv2

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• 作者：Ravi P. Shukla ; Bohua Huang
• 刊名：Climate Dynamics
• 出版年：2016
• 出版时间：June 2016
• 年：2016
• 卷：46
• 期：11-12
• 页码：3845-3864
• 全文大小：4,220 KB
• 刊物类别：Earth and Environmental Science
• 刊物主题：Earth sciences
  Geophysics and Geodesy
  Meteorology and Climatology
  Oceanography
  
• 出版者：Springer Berlin / Heidelberg
• ISSN：1432-0894
• 卷排序：46

文摘

The capability of the National Centers for Environmental Prediction climate forecast system version 2 (CFSv2) in simulating the Indian summer monsoon (ISM) is evaluated in the context of the global monsoon in the Indo-Pacific domain and its variability. Although the CFSv2 captures the ISM spatial structure qualitatively, it demonstrates a severe dry bias over the Indian subcontinent. The weaker model monsoon may be related to an excessive surface convergence over the equatorial Indian Ocean, which reduces the moisture transport toward the Indian subcontinent. The excessively low equatorial pressure is in turn a part of a tropical-wise bias with the largest errors in the central and eastern equatorial Pacific associated with the cold sea surface temperature bias and an overly strong inter-tropical convergence zone. In this sense, the model bias in the tropical Pacific influences those in the Indian Ocean-ISM region substantially. The leading mode of the June–September averaged CFSv2 rainfall anomalies covering the ISM and its adjacent oceanic regions is qualitatively similar to that of the observations, characterized by a spatial pattern of strong anomalies over either side of the Indian peninsula as well as center of opposite sign over Myanmar. However, the model fails to reproduce the northward expansion of rainfall anomalies from Myanmar, leading to opposite anomalies over northeast India and Himalayas region. A substantial amount of the anomalous fluctuation is attributed to the El Niño and the Southern Oscillation (ENSO), although the model variability depends more strongly on ENSO. The active regional influences in the observations may contribute to its baroclinic vertical structure of the geopotential height anomalies in the ISM region, compared with the predominantly barotropic one in CFSv2. Model ENSO deficiencies also affects its ISM simulation significantly.KeywordsIndian summer monsoonNCEP CFSv2Interannual variabilityEOF analysis