A Comparison of ETKF and Downscaling in a Regional Ensemble Prediction SystemReport as inadecuate




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1

College of Atmospheric Science, Nanjing University of Information & Science Technology, Nanjing 210044, China

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Center of Numerical Weather Prediction of CMA, Beijing 100081, China

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Key Laboratory of Meteorological Disaster, Ministry of Education College of Atmospheric Science, Nanjing University of Information & Science Technology, Nanjing 210044, China

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Center of Meteorological Service of Zhejiang, Hangzhou 310017, China





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Author to whom correspondence should be addressed.



Academic Editor: Anthony R. Lupo

Abstract Based on the operational regional ensemble prediction system REPS in China Meteorological Administration CMA, this paper carried out comparison of two initial condition perturbation methods: an ensemble transform Kalman filter ETKF and a dynamical downscaling of global ensemble perturbations. One month consecutive tests are implemented to evaluate the performance of both methods in the operational REPS environment. The perturbation characteristics are analyzed and ensemble forecast verifications are conducted; furthermore, a TC case is investigated. The main conclusions are as follows: the ETKF perturbations contain more power at small scales while the ones derived from downscaling contain more power at large scales, and the relative difference of the two types of perturbations on scales become smaller with forecast lead time. The growth of downscaling perturbations is more remarkable, and the downscaling perturbations have larger magnitude than ETKF perturbations at all forecast lead times. However, the ETKF perturbation variance can represent the forecast error variance better than downscaling. Ensemble forecast verification shows slightly higher skill of downscaling ensemble over ETKF ensemble. A TC case study indicates that the overall performance of the two systems are quite similar despite the slightly smaller error of DOWN ensemble than ETKF ensemble at long range forecast lead times. View Full-Text

Keywords: regional ensemble prediction system; initial condition perturbation keyword; ensemble transform Kalman filter; dynamical downscaling regional ensemble prediction system; initial condition perturbation keyword; ensemble transform Kalman filter; dynamical downscaling





Author: Hanbin Zhang 1, Jing Chen 2,* , Xiefei Zhi 3 and Yanan Wang 4

Source: http://mdpi.com/



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