We are very grateful for the insights provided by Anna Trevisan, Arlindo da Silva, and Fuqing Zhang. Takemasa Miyoshi and Kayo Ide and other members of the University of Maryland Weather and Chaos Group, Ross Hoffman (AER), and Xiang-Yu Huang (NCAR Data Assimilation Test Center) made very helpful suggestions. We also appreciate the comments and suggestions of the three reviewers and of the editor, Herschel Mitchell, and Adrienne Norwood’s English proofreading. Shu-Chih Yang is sponsored by Taiwan National Science Council Grants 97-2111-m-008-25 and 98-2111-m-008-014, and the NCU Development Program for the Top-Ranked University sponsored by the Ministry of Education. Eugenia Kalnay acknowledges support from NASA Grants NNX08AD40G and NN07AM97G and DOE Grant DEFG0207ER64437.
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