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王鹏飞, 丁兆敏, 林鹏飞, 黄刚. 时间滑动相关方法在SST可预报性及可信计算时间研究中的应用[J]. 气候与环境研究, 2015, 20(3): 245-256. DOI: 10.3878/j.issn.1006-9585.2014.14141
引用本文: 王鹏飞, 丁兆敏, 林鹏飞, 黄刚. 时间滑动相关方法在SST可预报性及可信计算时间研究中的应用[J]. 气候与环境研究, 2015, 20(3): 245-256. DOI: 10.3878/j.issn.1006-9585.2014.14141
WANG Pengfei, DING Zhaomin, LIN Pengfei, HUANG Gang. Application of the Sliding Temporal Correlation Approach to the Studies of Predictability and Reliable Computation Time of Sea Surface Temperature[J]. Climatic and Environmental Research, 2015, 20(3): 245-256. DOI: 10.3878/j.issn.1006-9585.2014.14141
Citation: WANG Pengfei, DING Zhaomin, LIN Pengfei, HUANG Gang. Application of the Sliding Temporal Correlation Approach to the Studies of Predictability and Reliable Computation Time of Sea Surface Temperature[J]. Climatic and Environmental Research, 2015, 20(3): 245-256. DOI: 10.3878/j.issn.1006-9585.2014.14141

时间滑动相关方法在SST可预报性及可信计算时间研究中的应用

Application of the Sliding Temporal Correlation Approach to the Studies of Predictability and Reliable Computation Time of Sea Surface Temperature

  • 摘要: 将时间滑动相关方法STC(sliding temporal correlation)用于研究混沌系统和海洋环流模式的可信计算时间RCT(reliable computation time), Lorenz混沌系统的数值试验表明用STC求得的可预报时间和可信计算时间, 与使用传统误差限方法所得结果一致, 证明了其有效性。对海洋环流模式LICOM和NEMO的研究发现:1. 当海洋模式以非耦合的方式运行时, 试验的结果表明其海表温度SST的可信计算时间较长, 平均达到6个月以上, 这主要是由于海洋模式的运行过程中, 采用恢复性边界条件使模拟结果不会太过偏离观测值。对于强迫场从1月开始的试验, LICOM模式的SST可信计算时间在赤道东太平洋和西北太平洋地区存在RCT低值区, 其数值不超过2个月。而NEMO模式在赤道太平洋地区全是RCT高值区, NEMO模式的RCT低值区域出现在赤道外的太平洋和大西洋中纬度地区, 强迫场从7月开始的试验, RCT纬向平均分布与1月有相反的形式。2. 海洋模式以耦合方式运行时, 由于去掉了恢复边界条件作用, 海洋模式预报的SST可信计算时间明显减小, 年平均RCT为1个月左右。按季节平均得到的RCT变化不大, 在30~40天之间, RCT的大值区春季位于南半球, 而秋季位于北半球, 可达2个月以上。耦合模式中所模拟的500 hPa高度场的RCT与单独运行的大气模式所得结果相差不大, 仍在2周以内。3. 无论是按季节平均还是按海区平均所得到的RCT分布, 都在30~60天左右, 只有极少数区域在特定季节可以达到80天以上, 这说明在海气耦合模式中, 由于计算不确定造成的可预报上限一般不超过2~3个月, 这比使用资料分析得到可预报期限短很多, 因此根据木桶原理, RCT可能是制约海气耦合模式SST预报能力的一个重要因素。

     

    Abstract: The sliding temporal correlation (STC) approach is applied to the study of reliable computation time (RCT) for chaotic numeric systems and general oceanic circulation models. The numeric experiments in the Lorenz chaotic system indicate that the maximal prediction time and RCT calculated by STC well agree with those calculated using the classic error approach. This indicates that the STC approach may be applied to this study. Therefore, this approach is applied to examine the RCT of sea surface temperature (SST) simulated by two uncoupled LICOM and NEMO oceanic models and a coupled model using NEMO as its oceanic component. It is found that the mean RCT of SST extends to about six months in the two uncoupled oceanic models. This relatively long RCT is due to the adoption of surface boundary restore conditions that revert the numeric results to the observed values. Using external forcing data from January, low RCT values (under two months) in simulations are located in the equatorial Pacific and Northwest Pacific for the LICOM model. High RCT values for the NEMO model are located in the equatorial Pacific and low RCT values in the off-equatorial Pacific and in the middle latitudes of the Atlantic. Simulations using external forcing data from July show the reverse zonal mean RCT pattern to those from January. In addition, when using the coupled model (NEMO model coupled with other components such as atmosphere), the restore surface boundary condition is not used. The mean annual RCT in the coupled model decreases significantly to around one month. Seasonal variation in RCT is small, and the commonly seasonal mean RCT is about 30-40 days. In spring, a long RCT (over two months) is found mainly in the Southern Hemisphere and in autumn, mainly in the Northern Hemisphere. The RCT of 500 hPa geopotential height in the coupled model is about two weeks, which is close to that simulated by the uncoupled AGCM model. Moreover, the seasonal mean or regional mean RCT is generally in the range of 30-60 days and only in a few small regions, and in specific seasons, the RCT is longer than 80 days. This indicates that in the coupled model, the maximal prediction time is limited to 2-3 months for SST due to computational uncertainty. These average RCTs are shorter than the predictable time obtained by observation data (about eight months). Thus, due to the cask principle, the RCT may be an important reason to restrict the predictable time length of SST in the coupled model.

     

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