ISSN 1006-9895

CN 11-1768/O4

Evaluation and Correction of the East Asian Summer Monsoon Simulated by MRI Coupled Ocean–Atmosphere General Circulation Model
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    Abstract:

    Based on the monthly precipitation data of Climate Prediction Center Merged Analysis of Precipitation (CMAP),the NCEP reanalysis data,the Extended Reconstruction Sea Surface Temperature (ERSST) from National Oceanic and Atmospheric Administration (NOAA),and the output of the MRI-CGCM (Meteorological Research Institute Coupled Ocean-Atmosphere General Circulation Model) of Japan Meteorological Agency,the ability of MRI-CGCM to simulate precipitation in the East Asian Summer Monsoon (EASM) region is evaluated from the perspective of the climatology,the primary modes of Empirical Orthogonal Function (EOF) and the interannual variation of the EASM.The multiple linear regression equation is established by the relationship between the observed East Asian Summer Monsoon index (EASMI) and the simulated principal component (PC),and applied to correct the EASMI (PC correction method).Results show that the MRI-CGCM can reasonably reproduce the basic EASM rainfall and low-level wind fields.However,the simulated western North Pacific anticyclone is weaker and eastward-shifted than normal,which leads to the underestimation of rainfall over the subtropical region.MRI-CGCM can capture the first leading EOF mode (EOF1) of the EASM rainfall and the corresponding wind fields in lower levels over the EASM region and the decaying phase of El Niño.The EOF1 space Correlation Coefficient (ACC) between the simulation and observation is 0.72.The interannual variability of EOF1 is reasonably simulated,and the correlation coefficient between the first component (PC1) of MRI-CGCM simulation and observation is 0.41.The simulated EOF1 well reflects the observed characteristics of EOF1.However,the simulated Mei-yu rainbelt over eastern China shifts southward,which is closely related to the southward shift of the western North Pacific anticyclone.The model ability for the simulation of the second leading EOF mode (EOF2) decreases significantly compared to that for the EOF1.The EOF2 ACC between simulation and observation is 0.36.MRI-CGCM can well reproduce the EOF2 that corresponds to the developing phase of El Niño.However,the simulated western North Pacific anticyclone shifts southward abnormally,which leads to the southward shift of the rain belt.The simulated Mei-yu rain belt over China is located in the middle and lower reaches of the Yangtze River,which is contrary to the observation that little rain occurs over this region.The spatial distribution and interannual variability of summer precipitation and temperature anomalies in eastern China are well simulated.The mean ACC between the simulated and observed summer precipitation (temperature) is 0.74(0.68).The mean predict score (PS) of simulated summer precipitation over eastern China,the Yangtze-Huaihe River valley and southern China are 69,70,and 68,respectively,which are higher than the average PS (65) of the operational summer precipitation prediction.The mean PS of summer mean temperature in eastern China is 74.Improvements in the PC corrected EASMI are reflected in the correlation coefficient,the anomaly sign consistency rate,the weaker magnitude of the simulated EASMI,and the southward shift of the Mei-yu rain belt.The correlation coefficient between the corrected EASMI and observed EASMI increases from 0.51 to 0.65,the anomaly sign consistency rate changes from 84% to 91%,the standard deviation increases from 0.75 to 1.3,the number of years with greater than one standard deviation changes from 6 to 12,and the locations of the western North Pacific anticyclone and Mei-yu rain belt corresponding to the corrected EASMI are more consistent with observations.

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History
  • Received:April 27,2015
  • Revised:
  • Adopted:
  • Online: November 19,2016
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