Homogenization and trend analysis of 1960–2015 in situ sea surface temperature observations along the coast of China

Sea surface temperature(SST)measurements from 26 coastal hydrological stations of China during 1960–2015 were homogenized and analyzed in this study.The homogenous surface air temperature(SAT)series from meteorological stations which were highly correlated to SST series was used to construct the reference series.Monthly mean SST series were then derived and subjected to a statistical homogeneity test,called penalized maximal t test.Homogenized monthly mean SST series were obtained by adjusting all significant change points which were supported by historic metadata information.Results show that the majority of break points are caused by instrument change and station relocation,which accounts for about 61.3%and 24.2%of the total break points,respectively.The regionally averaged annual homogeneous SST series from the 26 stations shows a warming trend(0.19℃ per decade).This result is consistent with that based on the homogenized annual mean SAT at the same region(0.22℃ per decade),while the regionally averaged mean original SST series from the same stations shows a much weaker warming of 0.09℃ per decade for 1960–2015.This finding suggests that the effects of artificial change points on the result of trend analysis are remarkable,and the warming rate from original SST observations since 1960 may be underestimated.Thus a high quality homogenized observation is crucial for robust detection and assessment of regional climate change.Furthermore,the trends of the seasonal mean homogenized SST were also analyzed.This work confirmed that there was an asymmetric seasonal temperature trends in the Chinese coastal water in the past decades,with the largest warming rate occurring in winter.At last,the significant warming in winter and its relationships to the variability of three large-scale atmospheric modes were investigated.