Sea Surface Temperature（ SST） is a basic parameter in characterizing the ocean-atmosphere system and serves an important function in climate change. Many types of cloud-free

high-spatial

and temporal coverage merged SST products have been generated by the Group for High Resolution Sea Surface Temperature. These products provide important data sources that can be used in a wide variety of operational and scientific applications. However

differences are existed among these products

due to their specific research requirements

different blending algorithms

different satellite SST sources for blending

and quality control methods. Therefore

monitoring the quality of these products is necessary

particularly at shelf and coastal seas around China

which are characterized by complex atmospheric conditions and hydrodynamics. This study compares four types of merged SST products in the South China Sea and adjacent waters in the years 2008 and 2009.Four multi-satellite merged SST products—the Operational SST and Sea Ice Analysis（ OSTIA）

microwave / infrared optimally interpolated SST

microwave optimally interpolated SST

and new generation SST（ NGSST） —are validated with the Argo SST in the shelf sea and Argos SST in the shallow coast. The match-up data are collected on the same day and location. The Root Mean Square（ RMS）

bias

and correlation coefficients are calculated and used to quantify the errors. These products are projected into the same grid of NGSST using the nearest-neighbor sampling method for comparison. OSTIA is selected as the basis

and the relative differences between OSTIA and the other three products are computed and visualized using maps

box-plot

and time series plots.The statistical results show that the RMS between the merged SSTs and Argo temperature ranged between 0. 3 ℃ and 1. 0 ℃

whereas the bias ranged between- 0. 1 ℃ and 0. 6 ℃ in the shelf sea（ water depth > 80 m）. The other three merged SSTs were consistent with the in situ data in the coastal area

except for NGSST

which had a significantly warm bias（- 1 ℃） and the largest RMS（- 1. 5 ℃）. The bias and RMS of OSTIA were the smallest. An inter-comparison indicates no significant differences among the four merged SST products in the shelf sea. Their biases were within ± 0. 3 ℃. However

the deviation increases in shallow water. The largest bias was found in winter because of the poor weather conditions

whereas the smallest bias was found in summer.In summary

the four merged SST products were consistent with in situ data in the study region

except for the NGSST in the shallow coastal sea and the OSTIA product exhibited the best performance. This study has provided a reliable basis for the effective application of these merged SSTs with high spatial and temporal coverage in the South China Sea and its adjacent waters.