DOI: 10.5194/hess-19-1787-2015
Scopus记录号: 2-s2.0-84928321990
论文题名: Stochastic bias correction of dynamically downscaled precipitation fields for Germany through Copula-based integration of gridded observation data
作者: Mao G ; , Vogl S ; , Laux P ; , Wagner S ; , Kunstmann H
刊名: Hydrology and Earth System Sciences
ISSN: 10275606
出版年: 2015
卷: 19, 期: 4 起始页码: 1787
结束页码: 1806
语种: 英语
Scopus关键词: Calibration
; Climate models
; Data flow analysis
; Mapping
; Mean square error
; Stochastic models
; Stochastic systems
; Transfer functions
; Weather forecasting
; Conditional distribution
; Correction approaches
; Dependence structures
; Marginal distribution
; Regional climate models
; Root mean square errors
; Statistical differences
; Weather research and forecasting models
; Distribution functions
; algorithm
; climate modeling
; data set
; mapping
; regional climate
; stochasticity
; weather forecasting
; Germany
英文摘要: Dynamically downscaled precipitation fields from regional climate models (RCMs) often cannot be used directly for regional climate studies. Due to their inherent biases, i.e., systematic over- or underestimations compared to observations, several correction approaches have been developed. Most of the bias correction procedures such as the quantile mapping approach employ a transfer function that is based on the statistical differences between RCM output and observations. Apart from such transfer function-based statistical correction algorithms, a stochastic bias correction technique, based on the concept of Copula theory, is developed here and applied to correct precipitation fields from the Weather Research and Forecasting (WRF) model. For dynamically downscaled precipitation fields we used high-resolution (7 km, daily) WRF simulations for Germany driven by ERA40 reanalysis data for 1971-2000. The REGNIE (REGionalisierung der NIEderschlagshöhen) data set from the German Weather Service (DWD) is used as gridded observation data (1 km, daily) and aggregated to 7 km for this application. The 30-year time series are split into a calibration (1971-1985) and validation (1986-2000) period of equal length. Based on the estimated dependence structure (described by the Copula function) between WRF and REGNIE data and the identified respective marginal distributions in the calibration period, separately analyzed for the different seasons, conditional distribution functions are derived for each time step in the validation period. This finally allows to get additional information about the range of the statistically possible bias-corrected values. The results show that the Copula-based approach efficiently corrects most of the errors in WRF derived precipitation for all seasons. It is also found that the Copula-based correction performs better for wet bias correction than for dry bias correction. In autumn and winter, the correction introduced a small dry bias in the northwest of Germany. The average relative bias of daily mean precipitation from WRF for the validation period is reduced from 10% (wet bias) to -1% (slight dry bias) after the application of the Copula-based correction. The bias in different seasons is corrected from 32% March-April-May (MAM), -15% June-July-August (JJA), 4% September-October-November (SON) and 28% December-January-February (DJF) to 16% (MAM), -11% (JJA), -1% (SON) and -3% (DJF), respectively. Finally, the Copula-based approach is compared to the quantile mapping correction method. The root mean square error (RMSE) and the percentage of the corrected time steps that are closer to the observations are analyzed. The Copula-based correction derived from the mean of the sampled distribution reduces the RMSE significantly, while, e.g., the quantile mapping method results in an increased RMSE for some regions. © Author(s) 2015. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/78551
Appears in Collections: 气候变化事实与影响
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作者单位: Institute of Meteorology and Climate Research (IMK-IFU), Karlsruhe Institute of Technology (KIT), Kreuzeckbahnstr. 19, Garmisch-Partenkirchen, Germany; Institute of Geography, University of Augsburg, Universitätsstr. 10, Augsburg, Germany; Siemens AG, Corporate Technology, Munich, Germany
Recommended Citation:
Mao G,, Vogl S,, Laux P,et al. Stochastic bias correction of dynamically downscaled precipitation fields for Germany through Copula-based integration of gridded observation data[J]. Hydrology and Earth System Sciences,2015-01-01,19(4)