The 21-yr ensemble predictions of model precipitation and circulation in the East Asian and western North Pacific （Asia-Pacific） summer monsoon region （0°-50°N, 100° 150°E） were evaluated in ni...The 21-yr ensemble predictions of model precipitation and circulation in the East Asian and western North Pacific （Asia-Pacific） summer monsoon region （0°-50°N, 100° 150°E） were evaluated in nine different AGCM, used in the Asia-Pacific Economic Cooperation Climate Center （APCC） multi-model ensemble seasonal prediction system. The analysis indicates that the precipitation anomaly patterns of model ensemble predictions are substantially different from the observed counterparts in this region, but the summer monsoon circulations are reasonably predicted. For example, all models can well produce the interannual variability of the western North Pacific monsoon index （WNPMI） defined by 850 hPa winds, but they failed to predict the relationship between WNPMI and precipitation anomalies. The interannual variability of the 500 hPa geopotential height （GPH） can be well predicted by the models in contrast to precipitation anomalies. On the basis of such model performances and the relationship between the interannual variations of 500 hPa GPH and precipitation anomalies, we developed a statistical scheme used to downscale the summer monsoon precipitation anomaly on the basis of EOF and singular value decomposition （SVD）. In this scheme, the three leading EOF modes of 500 hPa GPH anomaly fields predicted by the models are firstly corrected by the linear regression between the principal components in each model and observation, respectively. Then, the corrected model GPH is chosen as the predictor to downscale the precipitation anomaly field, which is assembled by the forecasted expansion coefficients of model 500 hPa GPH and the three leading SVD modes of observed precipitation anomaly corresponding to the prediction of model 500 hPa GPH during a 19-year training period. The cross-validated forecasts suggest that this downscaling scheme may have a potential to improve the forecast skill of the precipitation anomaly in the South China Sea, western North Pacific and the East Asia Pacific regions, where the anomaly correlation coefficient （ACC） has been improved by 0.14, corresponding to the reduced RMSE of 10.4% in the conventional multi-model ensemble （MME） forecast.展开更多
Based on summer precipitation hindcasts for 1991-2013 produced by the Beijing Climate Center Climate System Model （BCC_CSM）, the relationship between precipitation prediction error in northeastern China （NEC） and ...Based on summer precipitation hindcasts for 1991-2013 produced by the Beijing Climate Center Climate System Model （BCC_CSM）, the relationship between precipitation prediction error in northeastern China （NEC） and global sea surface temperature is analyzed, and dynamic-analogue prediction is carried out to improve the summer precipitation prediction skill of BCC_CSM, through taking care of model historical analogue prediction error in the real-time output. Seven correction schemes such as the systematic bias correction, pure statistical correction, dynamic-analogue correction, and so on, are designed and compared. Independent hindcast results show that the 5-yr average anomaly correlation coefficient （ACC） of summer precipitation is respectively improved from -0. 13/0.15 to 0.16/0.24 for 2009-13/1991-95 when using the equally weighted dynamic-analogue correction in the BCC_CSM prediction, which takes the arithmetical mean of the correction based on regional average error and that on grid point error. In addition, probabilistic prediction using the results from the multiple correction schemes is also performed and it leads to further improved 5-yr average prediction accuracy.展开更多
A new approach to forecast the middle-lower reaches of the Yangtze River Valley summer rainfall in June―August(JJA) is proposed in this paper.The year-to-year increment of the middle-lower reaches of the Yangtze Rive...A new approach to forecast the middle-lower reaches of the Yangtze River Valley summer rainfall in June―August(JJA) is proposed in this paper.The year-to-year increment of the middle-lower reaches of the Yangtze River Valley is forecasted and hence the summer precipitation could be predicted.In this paper,DY is defined as the difference of a variable between the current year and the preceding year(year-to-year increment).YR denotes the seasonal mean precipitation rate of the middle-lower reaches of the Yangtze River Valley summer rainfall.After analyzing the atmospheric circulation anomalies in winter and spring that were associated with the DY of YR,six key predictors for the DY of YR have been identified.Then the forecast model for the DY of YR is established by using the multi-linear regression method.The predictors for the DY of YR are Antarctic Oscillation,the meridional wind shear between 850hPa and 200hPa over the Indo-Australian region,and so on.The prediction model shows a high skill for the hindcast during 1997-2006,with the average relative root mean square error is at 18%.The model can even reproduce the upward and downward trends of YR during 1984―1998 and 1998―2006.Considering that the current operational forecast models of the summer precipitation over the China region have the average forecast scores at 60%―70% and that the prediction skill for the middle-lower reaches of Yangtze River Valley summer precipitation remains quite limited up to now,thus this new approach to predict the year-to-year increment of the summer precipitation over the Yangtze River Valley(and hence the summer precipitation itself) has the potential to significantly increase the operational forecast skill of the summer precipitation.展开更多
利用BP-CCA方法并结合当前国际先进气候预测模式结果,探讨了如何建立对西南夏季降水具有较高预测技巧的统计降尺度模型及其可预报性来源。结果表明,将热带区域海表温度作为预测因子的降尺度模型的预测能力优于亚洲区域和热带区域500 h P...利用BP-CCA方法并结合当前国际先进气候预测模式结果,探讨了如何建立对西南夏季降水具有较高预测技巧的统计降尺度模型及其可预报性来源。结果表明,将热带区域海表温度作为预测因子的降尺度模型的预测能力优于亚洲区域和热带区域500 h Pa位势高度作为预测因子的模型。对模型可预报性来源的分析表明,热带区域海表温度作为预测因子的降尺度模型的预测能力年与年之间的差异主要受热带海表温度EOF第二模态的影响。该模态表现为在热带东南印度洋及西太平洋区域有正载荷值,而在热带中东太平洋区域有负载荷中心,其与影响西南夏季降水的菲律宾和海洋大陆西部对流有较好的相关,并且ECMWF和NCEP业务气候预测模式对其有较好的预测能力。展开更多
基金The National Nat-ural Science Foundation of China (NSFC), Grant Nos.90711003, 40375014the program of GYHY200706005, and the APCC Visiting Scientist Program jointly supportedthis work.
文摘The 21-yr ensemble predictions of model precipitation and circulation in the East Asian and western North Pacific （Asia-Pacific） summer monsoon region （0°-50°N, 100° 150°E） were evaluated in nine different AGCM, used in the Asia-Pacific Economic Cooperation Climate Center （APCC） multi-model ensemble seasonal prediction system. The analysis indicates that the precipitation anomaly patterns of model ensemble predictions are substantially different from the observed counterparts in this region, but the summer monsoon circulations are reasonably predicted. For example, all models can well produce the interannual variability of the western North Pacific monsoon index （WNPMI） defined by 850 hPa winds, but they failed to predict the relationship between WNPMI and precipitation anomalies. The interannual variability of the 500 hPa geopotential height （GPH） can be well predicted by the models in contrast to precipitation anomalies. On the basis of such model performances and the relationship between the interannual variations of 500 hPa GPH and precipitation anomalies, we developed a statistical scheme used to downscale the summer monsoon precipitation anomaly on the basis of EOF and singular value decomposition （SVD）. In this scheme, the three leading EOF modes of 500 hPa GPH anomaly fields predicted by the models are firstly corrected by the linear regression between the principal components in each model and observation, respectively. Then, the corrected model GPH is chosen as the predictor to downscale the precipitation anomaly field, which is assembled by the forecasted expansion coefficients of model 500 hPa GPH and the three leading SVD modes of observed precipitation anomaly corresponding to the prediction of model 500 hPa GPH during a 19-year training period. The cross-validated forecasts suggest that this downscaling scheme may have a potential to improve the forecast skill of the precipitation anomaly in the South China Sea, western North Pacific and the East Asia Pacific regions, where the anomaly correlation coefficient （ACC） has been improved by 0.14, corresponding to the reduced RMSE of 10.4% in the conventional multi-model ensemble （MME） forecast.
基金Supported by the Science and Technology Research Project of Liaoning Provincial Meteorological Bureau(201502)Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)+1 种基金Liaoning Province Agricultural Research and Industrialization Project(2015103038)China Meteorological Administration Special Public Welfare Research(GYHY201306021)
文摘Based on summer precipitation hindcasts for 1991-2013 produced by the Beijing Climate Center Climate System Model （BCC_CSM）, the relationship between precipitation prediction error in northeastern China （NEC） and global sea surface temperature is analyzed, and dynamic-analogue prediction is carried out to improve the summer precipitation prediction skill of BCC_CSM, through taking care of model historical analogue prediction error in the real-time output. Seven correction schemes such as the systematic bias correction, pure statistical correction, dynamic-analogue correction, and so on, are designed and compared. Independent hindcast results show that the 5-yr average anomaly correlation coefficient （ACC） of summer precipitation is respectively improved from -0. 13/0.15 to 0.16/0.24 for 2009-13/1991-95 when using the equally weighted dynamic-analogue correction in the BCC_CSM prediction, which takes the arithmetical mean of the correction based on regional average error and that on grid point error. In addition, probabilistic prediction using the results from the multiple correction schemes is also performed and it leads to further improved 5-yr average prediction accuracy.
基金Supported the National Natural Science Foundation of China (Grant Nos. 40631005,40620130113 and 40523001) the "Korea Enhanced Observing Program ofMeiyu Project"
文摘A new approach to forecast the middle-lower reaches of the Yangtze River Valley summer rainfall in June―August(JJA) is proposed in this paper.The year-to-year increment of the middle-lower reaches of the Yangtze River Valley is forecasted and hence the summer precipitation could be predicted.In this paper,DY is defined as the difference of a variable between the current year and the preceding year(year-to-year increment).YR denotes the seasonal mean precipitation rate of the middle-lower reaches of the Yangtze River Valley summer rainfall.After analyzing the atmospheric circulation anomalies in winter and spring that were associated with the DY of YR,six key predictors for the DY of YR have been identified.Then the forecast model for the DY of YR is established by using the multi-linear regression method.The predictors for the DY of YR are Antarctic Oscillation,the meridional wind shear between 850hPa and 200hPa over the Indo-Australian region,and so on.The prediction model shows a high skill for the hindcast during 1997-2006,with the average relative root mean square error is at 18%.The model can even reproduce the upward and downward trends of YR during 1984―1998 and 1998―2006.Considering that the current operational forecast models of the summer precipitation over the China region have the average forecast scores at 60%―70% and that the prediction skill for the middle-lower reaches of Yangtze River Valley summer precipitation remains quite limited up to now,thus this new approach to predict the year-to-year increment of the summer precipitation over the Yangtze River Valley(and hence the summer precipitation itself) has the potential to significantly increase the operational forecast skill of the summer precipitation.
文摘利用BP-CCA方法并结合当前国际先进气候预测模式结果,探讨了如何建立对西南夏季降水具有较高预测技巧的统计降尺度模型及其可预报性来源。结果表明,将热带区域海表温度作为预测因子的降尺度模型的预测能力优于亚洲区域和热带区域500 h Pa位势高度作为预测因子的模型。对模型可预报性来源的分析表明,热带区域海表温度作为预测因子的降尺度模型的预测能力年与年之间的差异主要受热带海表温度EOF第二模态的影响。该模态表现为在热带东南印度洋及西太平洋区域有正载荷值,而在热带中东太平洋区域有负载荷中心,其与影响西南夏季降水的菲律宾和海洋大陆西部对流有较好的相关,并且ECMWF和NCEP业务气候预测模式对其有较好的预测能力。
