Xinghua Zhou (First Institute of Oceanography, State Oceanic Administration,Qingdao, China)

This work presents the first calibration results for the HY-2A, Jason-2&3 Sentinel-3A and the SARAL/AltiKa altimetric missions by using the permanent calibration facilities on the Qianli Yan islet (China). Qianli Yan is located in the Yellow Sea and only 3 km from the Jason-2 and SARAL/AltiKa crossover point and 20~25km from the HY-2A and Sentinel-3A track. Analysis of the HY-2A, Jason-2 and SARAL/AltiKa waveform data and geophysical data over the Qianli Yan calibration area has proven that the altimeters and microwave radiometers are not contaminated by the mainland or the islet. The accuracies of the regional geoid model provided by the First Institute of Oceanography (FIO) and the DTU10 MSS model were assessed by a GNSS buoy experiment. The results indicated that the FIO model is suitable for altimeter calibration in the Qianli Yan area. In summary, the absolute biases the altimeters at the Qianli Yan Cal/Val site in China have been estimated as +1.9cm±0.3cm (Jason-2), 0.96cm±0.5cm(Jason-3), -3.92cm±1.3cm (Sentinel-3A), −4.56cm±0.6cm (SARAL) and −27±3cm (HY-2A), respectively. The results also indicated that the bias of the Jason-2&3 and Saral instrument showed no specific trend, whereas the absolute bias of the HY-2A altimeter presented a significant trend (from −14cm to -91cm) during the two-year period (2013–2015) with the drift velocity estimated to be -51cm/a .