运用CSEOF方法分析南海表面温度季节与年际变化

Seasonal and Interannual Variation of the Sea Surface Temperature in the South China Sea Deduced by CSEOF Analysis

本文基于粗分辨率卫星数据和中尺度分辨率ROMS模型数据,通过一种较新的循环平稳经验正交函数(CSEOF)方法,分析南海表面温度的季节变化与年际变化,其中南海表面温度的第一模态和第二模态分别代表南海温度的季节变化信号和随ENSO变化的信号。卫星与模型的第一模态的空间分布较为一致,南海北部相对南部具有更强的季节变化,第一模态时间序列主成分与Nino3指数具有一定相关性,但相关系数小于30%。卫星与模型第二模态时间序列主成分与Nino3相关性较高,均大于50%,落后Nino3指数7个月。通过对比模型与卫星结果发现,中尺度过程的引入仅使第二模态空间分布更为复杂,而对第一模态的季节变化及与ENSO信号的相关性并没有显著影响。赤道太平洋温度异常通过大气环流无延迟的影响南海的云层覆盖和蒸发,进而影响南海表面的短波辐射和潜热通量,混合层中垂向混合和夹带过程可能是阻碍南海表面温度过快响应净热通量改变的原因。

Using satellite data and ROMS model output,the seasonal and interannual variation of the surface temperature in the South China Sea is analyzed with the cyclostationary empirical orthogonal function(CSEOF)method.The results show that the first and second modes represent the seasonal and ENSO-related variation of the sea surface temperature respectively.The spatial pattern of the first mode shows greater amplitude of the variation in the northern South China Sea.The correlation between the principal component and Nino3 index is less than 30%for the first mode while exceeds 50%for the second mode with Nino3 index 7 months leading.By comparing the model and satellite results,we found the mesoscale processes generally have an insignificant impact on the seasonal variation and ENSO correlation of the surface temperature.The equatorial Pacific temperature anomaly affects the cloud cover and evaporation of the South China Sea through the atmospheric circulation synchronously,and then the short wave radiation and latent heat flux on the surface of the South China Sea will be affected.The vertical mixing and entrainment process in the mixed layer may be the reason that hinders net heat flux influences the surface temperature of the South China Sea so fast.