Calibration and Validation of Reprocessed HY-2A Altimeter Wave Height Measurements Using Data from Buoys, Jason-2, Cryosat-2, and SARAL/AltiKa

Abstract

The Haiyang-2A (HY-2A) satellite is China’s first ocean dynamic environment satellite, and the radar altimeter is one of its main payloads. In this study the HY-2A altimeter sensor interim geophysical dataset records (SIGDR) data are reprocessed to obtain better significant wave height (Hs) measurements over a period of more than four years (from 1 October 2011 to 15 March 2016). The reprocessed HY-2A Hs measurements are calibrated and validated using National Data Buoy Center (NDBC) buoys and several operating altimeters: Joint Altimetry Satellite Oceanography Network-2 (Jason-2), CryoSat-2, and Satellite with Argos Data Collection System and Ka-Band Altimeter (SARAL/ALtiKa) The final results of buoys and cross-altimeter comparisons show that the accuracy of the reprocessed HY-2A Hs measurements is significantly improved with respect to the Hs measurements in the operational HY-2A interim geophysical data record (IGDR) publicly distributed by the National Satellite Ocean Application Service (NSOAS), State Oceanic Administration (SOA) of China. Compared with the NDBC Hs measurements, the reprocessed HY-2A Hs measurements show a root-mean-square error (RMSE) of 0.215 m with a positive bias of 0.117 m. After calibrating with the two-branched corrections, the RMSE for the reprocessed HY-2A Hs measurements is reduced to 0.173 m, which is lower than those for the calibrated HY-2A IGDR, Jason-2, Cryosat-2, and SARAL measurements with an RMSE of 0.278, 0.233, 0.239, and 0.184 m, respectively. Long-term validation of the altimeter Hs measurements shows that the reprocessed HY-2A Hs measurements after calibration are stable with respect to the buoys and three other altimeters over the entire period. The reprocessed HY-2A Hs measurements are expected to improve the practical applicability of HY-2A Hs measurements significantly.

New wind-wave climate records in the Western Mediterranean Sea

“…This satellite altimeter observation database contains data since July 2019 from six missions of the most recent altimetry satellites, which include AltiKa, Cryosat-2, Jason-3, Sentinel-3A, Sentinel-3B and CFOSAT with a very high spatial resolution; the observations between each measurement in the same orbit is 7 km. The observations from these satellites have been evaluated against buoy measurements by several researchers (Hithin et al 2015;Kumar et al 2015;Jiang et al 2018;Yang and Zhang 2019;Ribal and Young 2019;Hauser et al 2020) on a global scale and have proved the high quality of the SWH data provided by these satellites. In this study, the total period of satellite measurements provided by CMEMS was used, from July 2019 to the time of analysis on 31/03/2020.…”

Validation of 7 Years in-Flight HY-2A Calibration Microwave Radiometer Products Using Numerical Weather Model and Radiosondes

“…Before March 2016, the HY-2A orbit height was 971 km and the revisiting time was 14 days. After that, the orbit height changed to 973 km and the revisiting time switched to 168 days [15]. HY-2A was firstly designed for 3 years, while it is still operating now.…”

“…HY-2A CMR played an important role in SSH and wave height measurements for the past 7 years after launching [2,15], but a comprehensive evaluation has not been conducted. As the accuracy of CMR WTC is extremely important for RA, such kind of validation is in need.…”

Pemanfaatan Satelit Altimetri Untuk Verifikasi Tinggi Gelombang Signifikan Ocean Forecast System (Ofs) – Model BMKG

“…Hal ini menjadi tantangan tersendiri sebab mau tidak mau harus dikembangkan teknik tersendiri agar data yang dihasilkan dapat digunakan lebih lanjut. Beberapa referensi menunjukkan sedikit sekali satelit altimetri digunakan sebagai sebagai alat verifikasi suatu model [10,11].…”

“…penelitian lebih cenderung membandingkan data in situ dengan satelit altimetri pada berbagai skala. Sebagai contoh satelit altimetri China HY-2A memperoleh RMSE dan bias SWH yang cukup baik untuk periode 2011-2016 masingmasing sebesar 0,215 m dan 0,117 m dibandingkan dengan pengukuran bouy [11].…”