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Zhiyong Meng and Fuqing Zhang

implemented at the University of Washington in January 2005 ( Torn and Hakim 2008a ). The 2-yr performance of this system was found to have slightly larger errors of wind and temperature fields, but smaller errors in moisture in comparison to deterministic output of different operational forecast models ( Fig. 2 ). Fig . 2. The performance of a quasi-operational WRF-EnKF system implemented at the University of Washington in comparison to selected operational forecasts in terms of RMS error (solid) and

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Thomas M. Hamill and Jeffrey S. Whitaker

approximately 2.4 days. This model is obviously much simpler than the operational numerical weather prediction models currently in use; the resolution is lower, there is no terrain, no land or water, and no atmospheric moisture. In fact, while this model is capable of supporting internal gravity waves, it does not produce an external mode. These simplifications should be kept in mind while interpreting the results and their implications for operational numerical weather prediction. b

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Takuya Kawabata, Tohru Kuroda, Hiromu Seko, and Kazuo Saito

, P. , J. N. Thepaut , and A. Hollingsworth , 1994 : A strategy for operational implementation of 4D-Var, using an incremental approach . Quart. J. Roy. Meteor. Soc. , 120 , 1367 – 1387 . Dee , D. P. , and A. M. Da Silva , 2003 : The choice of variable for atmospheric moisture analysis . Mon. Wea. Rev. , 131 , 155 – 171 . Doms , G. , and U. Schaettler , 1999 : The nonhydrostatic limited area model LM of DWD . Part I. Scientific Documentation, DWD, 172 pp . Dudhia , J

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Mark Buehner and Ahmed Mahidjiba

the implicitly restarted Lanczos method was used. The optimization time interval is 48 h and the total energy norm ( Zadra et al. 2004 ) with the moisture term neglected is used to define the norms at both the initial and optimization times. The SVs were computed on a global grid with a horizontal grid spacing of 3° in latitude and longitude and 28 vertical levels. In this study, the only physical parameterization included in the tangent-linear and adjoint models is the simplified boundary layer

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