Predictable patterns and predictive skills of monsoon precipitation in Northern Hemisphere summer in NCEP CFSv2 reforecasts

Renhe Zhang,Zeng-Zhen Hu,Fang Wang,Bohua Huang,Wanqiu Wang,Zhiyan Zuo,Song Yang

doi:10.1007/s00382-013-1772-2

Abstract

The predictable patterns and predictive skills of monsoon precipitation in the Northern Hemisphere summer (June–July–August) are examined using reforecasts (1983–2010) from the National Center for Environmental Prediction Climate Forecast System version 2 (CFSv2). The possible connections of these predictable patterns with global sea surface temperature (SST) are investigated. The empirical orthogonal function analysis with maximized signal-to-noise ratio is used to isolate the predictable patterns of the precipitation for three regional monsoons: the Asian and Indo-Pacific monsoon (AIPM), the Africa monsoon (AFM), and the North America monsoon (NAM). Overall, the CFSv2 well predicts the monsoon precipitation patterns associated with El Nino-South Oscillation (ENSO) due to its good prediction skill for ENSO. For AIPM, two identified predictable patterns are an equatorial dipole pattern characterized by opposite variations between the equatorial western Pacific and eastern Indian Ocean, and a tropical western Pacific pattern characterized by opposite variations over the tropical northwestern Pacific and the Philippines and over the regions to its west, north, and southeast. For NAM, the predictable patterns are a tropical eastern Pacific pattern with opposite variations in the tropical eastern Pacific and in Mexico, the Guyana Plateau and the equatorial Atlantic, and a Central American pattern with opposite variations in the eastern Pacific and the North Atlantic and in the Amazon Plains. The CFSv2 can predict these patterns at least 5 months in advance. However, compared with the good skill in predicting AIPM and NAM precipitation patterns, the CFSv2 exhibits little predictive skill for AFM precipitation, probably because the variability of the tropical Atlantic SST plays a more important than ENSO in the AFM precipitation variation and the prediction skill is lower for the tropical Atlantic SST than the tropical Pacific SST.

Highlights

The progress of coupled ocean–atmosphere models and the corresponding data assimilation system makes seasonal climate predictions possible in the last decade or so (Wang et al 2001; Palmer et al 2004; Saha et al 2006; Molteni et al 2011)
Considering the pronounced precipitation variations in the three monsoon regions, the focus of this study is to investigate the predictable patterns of monsoon precipitation and their prediction skills in the Climate Forecast System version 2 (CFSv2) reforecasts
This study has examined the prediction skills and predictable patterns of monsoon precipitation patterns for Northern Hemisphere summer using reforecasts of the National Center for Environmental Prediction (NCEP) CFSv2

Summary

Introduction

The progress of coupled ocean–atmosphere models and the corresponding data assimilation system makes seasonal climate predictions possible in the last decade or so (Wang et al 2001; Palmer et al 2004; Saha et al 2006; Molteni et al 2011). The MSN EOF1 for LM5 is still the leading pattern (exceeding 37.7 % of total variance) in the CFSv2 reforecasts, the discrepancy between modeled pattern and observed pattern corresponds to large disagreement between the ensemble mean PC and the projected PC.

Results

Conclusion