E4DVar: Coupling an Ensemble Kalman Filter with Four-Dimensional Variational Data Assimilation in a Limited-Area Weather Prediction Model

Monthly Weather Review - Tập 140 Số 2 - Trang 587-600 - 2012
Meng Zhang1, Fuqing Zhang1
1Department of Meteorology, The Pennsylvania State University, University Park, Pennsylvania

Tóm tắt

A hybrid data assimilation approach that couples the ensemble Kalman filter (EnKF) and four-dimensional variational (4DVar) methods is implemented for the first time in a limited-area weather prediction model. In this coupled system, denoted E4DVar, the EnKF and 4DVar systems run in parallel while feeding into each other. The multivariate, flow-dependent background error covariance estimated from the EnKF ensemble is used in the 4DVar minimization and the ensemble mean in the EnKF analysis is replaced by the 4DVar analysis, while updating the analysis perturbations for the next cycle of ensemble forecasts with the EnKF. Therefore, the E4DVar can obtain flow-dependent information from both the explicit covariance matrix derived from ensemble forecasts, as well as implicitly from the 4DVar trajectory. The performance of an E4DVar system is compared with the uncoupled 4DVar and EnKF for a limited-area model by assimilating various conventional observations over the contiguous United States for June 2003. After verifying the forecasts from each analysis against standard sounding observations, it is found that the E4DVar substantially outperforms both the EnKF and 4DVar during this active summer month, which featured several episodes of severe convective weather. On average, the forecasts produced from E4DVar analyses have considerably smaller errors than both of the stand-alone EnKF and 4DVar systems for forecast lead times up to 60 h.

Từ khóa


Tài liệu tham khảo

Andersson, E., M. Fisher, R. Munro, and R. A. McNally, 2000: Diagnosis of background error for radiances and other observable quantities in a variational data assimilation scheme, and the explanation of a case of poor convergence. ECMWF Tech. Memo. 296, Reading, United Kingdom, 22 pp.

10.1175/1520-0493(2004)132<0897:ATVDAS>2.0.CO;2

10.1175/1520-0493(2000)128<0644:EOSAMF>2.0.CO;2

10.1175/1520-0493(2001)129<0420:ASWTET>2.0.CO;2

10.1256/qj.04.15

10.1175/2009MWR3157.1

10.1175/2009MWR3158.1

10.1002/qj.49712354414

10.1002/qj.49712051912

10.1175/1520-0493(2004)132<1982:WATRIT>2.0.CO;2

10.1029/94JC00572

10.1175/MWR3391.1

10.1175/2007MWR2120.1

10.1002/qj.49712555417

10.1175/1520-0493(2001)129<2089:IOTDFA>2.0.CO;2

10.1175/MWR3394.1

10.1029/2002GL015311

10.1175/1520-0493(2000)128<0619:FDVDAO>2.0.CO;2

10.1175/1520-0493(2000)128<2905:AHEKFV>2.0.CO;2

10.1175/1520-0450-34.1.3

10.1256/qj.05.132

10.1175/1520-0493(2004)132<0103:ARATIM>2.0.CO;2

10.1175/2008MWR2737.1

Huang, X.Y., X. Yang, N. Gustafsson, K. Mogensen, and M. Lindskog, 2002: Four-dimensional variational data assimilation for a limited area model. HIRLAM Tech. Rep. 57, 41 pp.

10.1175/2008MWR2577.1

10.1175/2008MWR2312.1

10.1175/2008MWR2699.1

10.1256/qj.02.132

10.1256/qj.02.131

10.1002/qj.49712657002

10.1175/MWR3352.1

10.1175/2007MWR2106.1

10.1175/2008MWR2270.1

10.1175/2010MWR3209.1

10.1007/11428848_107

10.1023/A:1022146015946

10.1175/1520-0493(1992)120<1747:TNMCSS>2.0.CO;2

10.1002/qj.49712455005

10.1256/smsqj.56414

Skamarock, W. C., J. B. Klemp, J. Dudhia, D. O. Gill, D. M. Barker, W. Wang, and J. G. Powers, 2005: A description of the advanced research WRF version 2. NCAR Tech. Note TN-468+STR, 88 pp.

10.1175//2555.1

10.1175/1520-0469(1997)054<1642:DAMRFD>2.0.CO;2

10.1002/qj.49712253012

10.1175/MWR2898.1

10.1175/MWR3187.1

10.1175/MWR3282.1

10.1175/2008MWR2444.1

10.1175/2008MWR2445.1

10.1175/2009MWR2923.1

10.1175/2007MWR2018.1

10.3402/tellusa.v57i4.14710

10.1175/1520-0493(2002)130<1617:MPOTSS>2.0.CO;2

10.1175/1520-0493(2004)132<1238:IOIEAO>2.0.CO;2

10.1175/MWR3101.1

10.1007/s00376-009-0001-8

10.1175/2010MWR3610.1

10.1034/j.1600-0870.1997.00002.x

10.1175/1520-0493(1996)124<2859:RATAOC>2.0.CO;2

10.1175/1520-0493(2002)130<1967:FDVDAF>2.0.CO;2

10.1175/MWR2891.1

Thông tin
Thông tin xuất bản

Monthly Weather Review

Tập 140 Số 2

587-600

Thông tin tác giả