The influence of the initial temperature field on sea ice simulations in the Bohai Sea in winter of 2015/2016

初始温度场对2015/2016年冬季渤海海冰数值模拟的影响

To assess the influence of the initial temperature field on ocean temperature and sea ice simulations,a climatological dataset(WOA18),a real-time varying dataset(SODA),and an analysis field obtained after applying the“vertical projection”assimilation scheme were selected to obtain the initial temperature field(the initial moment was December 1,2015)for use in the sea ice simulation of the HAMSOM ice-ocean coupled model,considering the Bohai Sea in the 2015/2016 winter.In this study,after using this assimilation scheme,the analysis initial temperature field showed significant improvement.The simulated SST results showed that the initial temperature field had a considerable effect on the SST results in the first 45 days of the model run;after this period,the effect became negligible and the model internal dynamics and atmospheric forcing became dominant.The simulated sea ice results showed that the ice area and ice edge distance(i.e.,the distance between the intersection of the central axis and the ice edge line and axis apex)results obtained in experiment E3 which used the analysis initial temperature field were improved by~14%and~35%,respectively,and those obtained in experiment E2 which used the real-time varying initial temperature field were improved by~10%and~22%,respectively,compared to the results of experiment E1 which used the climatological initial temperature field.

为了评估初始温度场对渤海海温和海冰数值模拟的影响,我们基于三种数据(气候态的WOA18数据集(实验E1),实时变化的再分析SODA数据集(实验E2),以及应用“垂向映射”同化方法后获得的温度分析场(实验E3))构造了三种初始温度场(初始时刻为2015年12月1日),用于模拟2015/2016年冬季渤海的海洋和海冰要素,所用模式为HAMSOM冰-海耦合模型。首先,通过对比这三种初始温度场,我们发现应用“垂向映射”同化方法得到的初始温度场相比于前两种初始温度场有明显的改进。其次,模拟得到的SST结果显示,初始温度场仅对模拟时段的前45天的模拟结果产生较显著的影响,之后,这种影响将忽略不计,模拟结果将主要受到模式内部的动力演变和大气强迫场的控制。海冰要素模拟结果表明,使用经过同化后的初始温度场(实验E3)得到的冰面积和冰外缘线离岸距离相比于使用气候态的初始温度场(实验E1)得到的结果分别改进了约14%和35%,而使用实时变化的初始温度场(实验E2)得到的冰面积和冰外缘线离岸距离相比于实验E1的结果分别改进了约10%和22%。