东太平洋冷舌区海表面温度日变化特征的模拟研究

The Simulation Study of the Features of Diurnal Variation of Sea Surface Temperature in the Eastern Pacific Cold Tongue

本文通过分辨太阳辐射日变化,利用中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室(LASG/IAP)气候系统海洋环流模式(LICOM),模拟了东太平洋冷舌区海表面温度(SST)的日变化特征并研究了弱混合对其影响。采用理想的太阳辐射日变化强迫上层垂向分辨率为10m的海洋模式LI-COM,模拟出了SST日变化一些特征,同时海洋的上层流场也产生明显日变化。模拟的SST日变化振幅水平分布与观测接近,且受太阳辐射日变化振幅水平分布调制。在赤道中东太平洋区,模拟的SST日变化振幅(约为0.3～0.4℃)比观测偏小约0.1～0.2℃。模拟的SST日变化峰值出现在15～16时(当地标准时间),落后于太阳辐射峰值2～3个小时,接近观测。进一步减弱混合后,模拟的日变化振幅增加约0.1℃,更接近观测。这说明在东太平洋冷舌区SST日变化主要受太阳辐射日变化和垂直混合影响。此外,混合减小后,在太阳辐射日变化调制下,平均态(如混合层、温度和流场)也出现明显变化。在赤道东太平洋冷舌区北侧,弱混合导致混合层变浅,变浅使热量堆积进而使平均SST升高约0.3℃;在赤道东太平洋冷舌南侧,经向平流加强导致平均SST降低约0.2℃。

The features of diurnal variation of sea surface temperature （SST） are simulated in the LASG/IAP Cli- mate System Ocean Model （LICOM） by resolving the diurnal variation of solar radiation and the influence of weak mixing is investigated. Forced by the ideal diurnal variation of solar radiation, some features of diurnal variation of SST can be captured in LICOM with 10-m vertical resolution in the upper layers. The diurnal variation of solar radi- ation also results in diurnal variation of currents in the upper layers. The horizontal distribution of diurnal amplitudeof simulated SST is consistent with that of observed SST and modulated by the diurnal amplitude of solar radiation. In the eastern Pacific cold tongue, the diurnal amplitude of simulated SST is about 0. 3~C- 0. 4~C and 0. 1~C- 0. 2~C, smaller than that of observations. The peak of daily SST variation appears during 1500 - 1600 LST and lags 2 - 3 hours than the peak time of daily solar radiation, which is close to observation. After reducing mixing, the diurnal amplitude of SST variation increases in the equatorial eastern Pacific cold tongue, closer to observation. This indi- cates that the features of diurnal variation in the equatorial eastern Pacific cold tongue are mainly controlled by the diurnal variation of solar radiation and vertical mixing. After reducing mixing, under the modulation of solar radia- tion, the mean states including the mixed layer depth, temperatures and currents are obviously changed. In the northern part of the eastern Pacific cold tongue, the reduced mixing causes heat accumulation in the upper layers and then leads to an increase in SST about 0.3~C. While in the southern part, the enhanced meridional advection leads to a decrease in SST about 0.2~C.