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Extended Range Forecast Experiment for Rainfall Based on the Real-time Intraseasonal Oscillation
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摘要: 利用代表南海夏季风季节内振荡特征的850 hPa纬向风EOF分解的前两个主成分，定义南海夏季风季节内振荡指数，并利用美国国家环境预测中心第2代气候预报系统 (NCEP Climate Forecast System Version 2, NCEP/CFSv2) 提供的1982—2009年逐日回算预报场计算了南海夏季风季节内振荡指数的预报值，用于我国南方地区持续性强降水的预报试验。试验结果表明：利用南海夏季风季节内振荡实时监测指数与模式直接预报降水量相结合的统计动力延伸预报方法，能够有效提高季节内降水分量的预报效果。同时，该方法能够避免末端数据损失，修正了对模式预报降水直接进行带通滤波而导致的负相关现象，并起到消除模式系统误差的作用。
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关键词:
- 南海夏季风季节内振荡;
- 实时监测指数;
- 延伸预报;
- NCEP/CFSv2
Abstract: 1 State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing 1000812 Beijing Meteorological Observatory, Beijing 100089Intraseasonal oscillation (ISO) in South China Sea summer monsoon (SCSSM) plays a key role in controlling the intraseasonal variations of rainfalls over southern China, and it can be described with the leading pair of empirical orthogonal functions (EOFs) for the 110°-120°E averaged 850 hPa zonal wind (U850). An index for monitoring the SCSSM ISO is built on a pair of principal component (PC) time series of EOFs mentioned above, and then the NCEP Climate Forecast System Version 2 (NCEP/CFSv2) hindcasts and stepwise regression statistical method are employed, to explore extended range forecast (ERF) of rainfall intraseasonal variations.First, southern China is divided into three regions using rotated empirical orthogonal functions (REOFs), where the incidence rate of regionally persistent heavy rainfall (RPHR) is closely linked to the intraseasonal variation in rainfall. Based on the spatial structure of the first three REOFs, three intraseasonal rainfall indices are constructed by averaging the 30-60-day filtered precipitation over the typical regions and taken as predictands. Second, EOF1 of the 850 hPa zonal wind over the SCS and southern China mainly represent the ISO mode controlling the intraseasonal rainfall south of the Yangtze River, while EOF2 leads to the intraseasonal out-of-phase rainfall over South China and the Yangtze-Huai River Basins. Projection of the daily data onto the leading pair EOFs of 850 hPa zonal wind yields PC time series that serves as an effective filter for ISO without the need for bandpass filtering and making the PC time series two effective indices for real-time use. The pair of PC time series that form indices are called real-time indices for SCSSM ISO. Finally, 28 years of NCEP/CFSv2 reforecasts are used which include wind at 850 hPa and grid values of rainfall extending up to 30-day lead time. Characteristics of SCSSM ISO are also found similar to observations in the NCEP/CFSv2 reforecasts. Forecast models are built on the historical reforecast values of indices (predictors) and rainfall time series (predictands), and use forecast values of indices to predict the future values of rainfall time series varying mostly on the intraseasonal time scale. This method can significantly improve the ERF results (10-30 days) of intraseasonal variations of rainfalls in southern China, reduce system errors, avoid losses of forecasting data and correct negative correlations between forecasts and observations caused by bandpass filtering. -
图 1 1981—2010年4—9月逐日降水量场30~60 d低频分量REOF分解的前3个主模态及区域划分 (粗黑曲线为长江)
(a) REOF1, (b) REOF2, (c) REOF3, (d) 区域划分示意图
Fig. 1 The first three REOF modes of the 30-60-day bandpass filtered precipitation over southern China for the period between 1 Apr and 30 Sep from 1981 to 2010 with three typical regions (the bold solid curve represents the Yangtze River)
(a) REOF1, (b) REOF2, (c) REOF3, (d) a map of three typical regions
图 2 对110°~120°E平均的850 hPa纬向风场在赤道至35°N进行EOF分解后得到的前3个主成分的Morlet小波变换和小波功率谱
(a) PC1的小波变换，(b) PC1的小波功率谱，(c) PC2的小波变换，(d) PC2的小波功率谱，(e) PC3的小波变换，(f) PC3的小波功率谱
Fig. 2 Morlet wavelet analysis and spectral of PCs of three leading EOFs of 850 hPa zonal wind averaged in 110°-120°E
(a) wavelet of PC1, (b) spectral of PC1, (c) wavelet of PC2, (d) spectral of PC2, (e) wavelet of PC3, (f) spectral of PC3
图 4 1982—2009年各年南海夏季风爆发日至爆发后30 d 3个子区域30~60 d低频降水分量拟合值与观测值相关系数
Fig. 4 Correlation coefficients between 30-60-day bandpass filtered rainfall of fitted vaules and observations of three areas from the SCSSM onset to 30 days after from 1982 to 2009
图 5 1982—2009年自南海夏季风爆发日至爆发后30 d 3个子区域逐日降水观测值与NCEP/CFSv2预报值以及两种预报方案预报值相关系数 (28年平均值)
Fig. 5 Avergerd correlation coefficients between observation and NCEP/CFSv2 forecast rainfall of three areas from the SCSSM onset to 30 days after from 1982 to 2009(average of 28 years)
图 7 预报降水与观测降水的均方根误差
Fig. 7 Root mean square error (RMSE) between observation and forecast
图 8 2000年5月12日—8月3日华南地区 (a) 和1998年5月22日—8月29日江淮地区 (b) 观测降水距平、观测降水低频分量、预报试验降水结果、NCEP/CFSv2模式直接预报降水量30~60 d低频分量
(横坐标上方黑色粗短线标注持续性强降水时间段)
Fig. 8 Rainfall anomaly during 12 May-3 Aug in 2000 over South China (a) and during 22 May-29 Aug in 1998 over Yangtze-Huai River Basins (b) with 30-60-day bandpass filtered rainfall of observation, forecast vaule of experiment, 30-60-day bandpass filtered rainfall of NCEP/CFSv2 output
(thick short line near the x-axis labelling the time of RPHR)
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[1] Yamamoto R, Sakurai Y.Long term intensification of extremely heavy rainfall intensity in recent 100 years.World Resour Rev, 1999, 11:271-281. [2] Osborn T J, Hnhne M, Jones P D, et al.Observed trends in the daily intensity of United Kingdom precipitation.Int J Climatol, 2000, 20:347-364. doi: 10.1002/(ISSN)1097-0088 [3] 江志红, 丁裕国, 陈威霖.21世纪中国极端降水事件预估.气候变化研究进展, 2007, 3(4):202-207. http://www.cnki.com.cn/Article/CJFDTOTAL-QHBH200704005.htm [4] 鲍名.近50年我国持续性暴雨的统计分析及其大尺度环流背景.大气科学, 2007, 31(5):779-792. http://www.cnki.com.cn/Article/CJFDTOTAL-DQXK200705002.htm [5] 钱维宏.气候变化与中国极端事件图集.北京:气象出版社, 2011:147-151. [6] 陈官军, 魏凤英, 巩远发.NCEP/CFS模式对东亚地区夏季延伸预报的检验评估.应用气象学报, 2010, 21(6):659-670. doi: 10.11898/1001-7313.20100603 [7] Lo F, Hendon H H.Empirical prediction of the Madden-Julian oscillation.Mon Wea Rev, 2000, 128:2528-2543. doi: 10.1175/1520-0493(2000)128<2528:EERPOT>2.0.CO;2 [8] Hendon H H, Liebmann B, Newman M, et al.Medium-range forecast errors associated with active episodes of the Madden-Julian Oscillation.Mon Wea Rev, 2000, 128:69-86. doi: 10.1175/1520-0493(2000)128<0069:MRFEAW>2.0.CO;2 [9] 杨秋明.初夏亚洲季风区环流低频振荡与长江下游持续暴雨.应用气象学报, 1992, 4(3):320-326. http://qikan.camscma.cn/jams/ch/reader/view_abstract.aspx?file_no=19930355&flag=1 [10] 徐国强, 藏建升, 周伟灿.1998年京津冀夏季风的低频振荡与降水的特征.应用气象学报, 2001, 12(3):297-306. http://qikan.camscma.cn/jams/ch/reader/view_abstract.aspx?file_no=20010341&flag=1 [11] 杜良敏, 柯宗建.一种适用于延伸期过程事件预报的检验方法.应用气象学报, 2013, 24(6):686-694. doi: 10.11898/1001-7313.20130605 [12] 纪忠萍, 高晓容, 谷德军, 等.广东低温阴雨的低频振荡及环流特征.应用气象学报, 2013, 24(1):32-42. doi: 10.11898/1001-7313.20130104 [13] 杨蓉, 巩远发, 谢启玉, 等.1997—1998年青藏高原大气低频振荡及对降水影响.应用气象学报, 2015, 26(4):397-408. doi: 10.11898/1001-7313.20150402 [14] Chen Guanjun, Wei Fengying, Zhou Xiuji.Intraseasonal oscillation of the South China Sea summer monsoon and its influence on the regionally persistent heavy rain over Southern China.J Meteor Res, 2014, 28(2):213-229. doi: 10.1007/s13351-014-3063-1 [15] 陈官军, 魏凤英.基于低频振荡特征的夏季江淮持续性降水延伸预报方法.大气科学, 2012, 36(3):633-644. doi: 10.3878/j.issn.1006-9895.2011.11111 [16] Kalnay E, Kanamitsu M, Kistler R, et al.The NCEP/NCAR 40-year reanalysis project.Bull Amer Meteor Soc, 1996, 77:437-470. doi: 10.1175/1520-0477(1996)077<0437:TNYRP>2.0.CO;2 [17] Saha Suranjana, Coauthors.The NCEP climate forecast system version 2.J Climate, 2014, 27:2185-2208. doi: 10.1175/JCLI-D-12-00823.1 [18] Saha Suranjana, Coauthors.The NCEP climate forecast system reanalysis.Bull Amer Meteor Soc, 2010, 91:1015-1057. doi: 10.1175/2010BAMS3001.1 [19] Murakami T, Nakazawa T, He J.On the 40-50 day oscillations during the 1979 Northern Hemisphere summer.Ⅰ:Phase propagation.J Meteor Soc Japan, 1984, 62:440-468. doi: 10.2151/jmsj1965.62.3_440 [20] 吕宏忠, 张先恭, 丁一汇.赤道地区向西传播的40天周期低频波.气象学报, 1991, 49(2):29-38. http://www.cnki.com.cn/Article/CJFDTOTAL-QXXB199101003.htm [21] 梁建茵, 吴尚森, 游积平.南海夏季风的建立及强度.热带气象学报, 1999, 15(2):97-105. http://www.cnki.com.cn/Article/CJFDTOTAL-RDQX199902000.htm [22] Mao J Y, Chan J C L.Intraseasonal variability of the South China Sea summer monsoon.J Climate, 2005, 18:2388-2402. doi: 10.1175/JCLI3395.1 [23] 孙丹, 琚建华, 吕俊梅.2003年东亚季风季节内振荡对我国东部地区降水的影响.热带气象学报, 2008, 24(6):641-648. http://www.cnki.com.cn/Article/CJFDTOTAL-RDQX200806008.htm [24] 梁建茵, 吴尚森.南海西南季风爆发日期及其影响因子.大气科学, 2002, 26(5):829-844. http://www.cnki.com.cn/Article/CJFDTOTAL-RDQX200801007.htm [25] Torrence C, Compo G P.A practical guide to wavelet analysis.Bull Amer Meteor Soc, 1998, 79:61-78. doi: 10.1175/1520-0477(1998)079<0061:APGTWA>2.0.CO;2 [26] 魏凤英.现代气候统计诊断与预测技术 (第2版).北京:气象出版社, 2007:71-75. -
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