基于CESM气候模式的ENSO后报试验
An ENSO hindcast experiment using CESM
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摘要: 基于美国国家大气研究中心(NCAR)开发的通用地球系统模式(CESM),本文设计了nudging次表层海温的同化方案,进行了后报实验。对1982-2011年后报结果的分析表明,通过nudging同化,模式对ENSO现象有一定的模拟和预报能力,对赤道太平洋SST、纬向风、降水等海洋、大气要素等的后报结果与GODAS和NCEP再分析资料较接近,可以较好地重现历次厄尔尼诺和拉尼娜事件中异常东传的过程,超前1、3、6个月时,模式预报的Niño3指数与CPC指数的相关性分别达到0.88、0.81、0.70。但模式同时也表现出一定的春季预报障碍,秋季起报的后报效果最好,春季最差。对1982/1983和1997/1999两个厄尔尼诺事件的分析表明,模式后报的纬向风、热通量、风应力等大气变量的响应较实际滞后,而海洋的变化与实际情况相似,这与我们的同化方案设置有关,即模式只同化了次表层海温,进而强迫大气的响应,从而导致大气的变化较滞后。Abstract: An ENSO forecast system based on the Community Earth System Model (CESM) released by the National Center for Atmospheric Research (NCAR) is developed. We use a simple sub-surface sea temperature nudging scheme to generate realistic SST distribution. Hindcast results for the period 1982-2011 show a high predictability of ENSO. All past El Niño and La Niña events,including the strong 1997/1998 warm episode,are successfully predicted with SST,zonal wind and precipitation matching well with GODAS and NCEP datasets. The correlation coefficient of Niño3 index scores 0.88,0.81 and 0.70 at the 1-,3-and 6-month lead time respectively. However,the model shows a "spring prediction barrier" with the best predictability in autumn and the worst in spring. The comparisons of zonal wind,heat flux,SST anomaly,wind stress and sub-surface temperature of 1982/1983 and 1997/1999 demonstrate that the atmospheric response is latter than that of the ocean,which is in contrast with observing and reanalysis data. This is due to the ocean-only data assimilation scheme,which forces a delayed atmospheric response.
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Key words:
- CESM /
- nudging /
- ENSO hindcast
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