A Method for Significant Wave Height Estimation From Circularly Polarized X-Band Coastal Marine Radar Images

摘要

Circularly polarized X-band coastal marine radar data have been used to develop the algorithm for estimating significant wave height (H-S) in the Tallinn Bay in the Gulf of Finland directly from radar images. Since sea state in the Tallinn Bay is mainly dominated by slight (WMO-3) windsea, the traditional methods where backscatter intensity variance spectrum is transferred to wave spectrum do not resolve wave height retrievals with sufficient accuracy. In contrast, an empirical method which uses only image spectrum and its parameters has proven to be applicable under these conditions. A wave height retrieval algorithm was developed for the short steep wind sea using image spectrum parameters in addition to Grey level co-occurrence matrix (GLCM) statistics of the radar signal intensity. In total, 1678 collocation pairs from October 18, 2016 to November 14, 2016 were used in the algorithm tuning process. The HS results from radar images were collocated with in situ data from three buoys representing variable meteo-marine conditions. The comparison of radar-derived HS with measured HS shows high agreement with a correlation coefficient r of 0.78 (RMSE-0.23 m) for tuning data set. The method validation with independent data sets from January and June showed high correlation values of 0.82 (RMSE-0.26 m) and 0.89 (RMSE-0.25 m) correspondingly. In case of HS > 0.5 m, the validation resulted in higher correlation (over 0.93) and lower RMSE (from 0.15 to 0.21 m). The spatial variability of wave height from radar imagery is demonstrated based on the commonly occurring north-western storm.