Research of sea surface gust calculation method based on dual-frequency precipitation radar data
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摘要: 海面阵风对海洋资源利用、海洋研究以及海上运输与工程安全具有重要意义。但目前观测手段有限,海面阵风数据缺失严重。林静等基于HY-2B雷达高度计C、Ku波段后向散射系数的差值对海面风速进行修正,计算得到星下点的阵风风速,但观测范围较小。本文在此基础上,选用观测原理与雷达高度计相似的全球降雨观测计划(GPM)搭载的双频降雨雷达(DPR),利用其Ku、Ka波段后向散射系数的差值,并以ERA5海面风速作为观测值,对海面风速进行修正计算,得到阵风风速,以扩展观测范围并提高观测效率。结果表明:计算得到的阵风风速与ERA5阵风风速对比,相关系数(R)为0.96,均方根误差(RMSE)为1.79 m/s,平均偏差(Bias)为0.73 m/s,标准差(Std)为1.64 m/s;与同时期的NDBC浮标数据对比,R为0.91,RMSE为1.50 m/s,Bias为−0.15 m/s,Std为1.50 m/s,说明降雨雷达反演的阵风可靠性较好。进一步使用NDBC浮标海面风速代替ERA5海面风速后,R提高至0.95,RMSE降低至1.10 m/s,Bias为−0.07 m/s,Std为1.50 m/s,反演结果得到提高,说明精确的海面风速对阵风计算结果有较好的影响。Abstract: Sea surface gusts play a critical role in the utilization of ocean resources, marine research, and the safety of maritime transportation and offshore construction. However, current observation methods are limited, resulting in significant data gaps in surface gust measurements. Lin Jing et al. corrected sea surface wind speeds based on the difference in backscattering coefficients between the C and Ku bands observed by the HY-2B radar altimeter, thereby deriving gust wind speeds at nadir points, although the spatial coverage remained relatively limited. Building upon this approach, the present study employs the Dual-frequency Precipitation Radar (DPR) aboard the Global Precipitation Measurement (GPM) mission, whose observational principles are similar to those of radar altimeters. By utilizing the difference in Ku- and Ka-band backscattering coefficients and using ERA5 sea surface wind speed as a reference, surface wind speeds are corrected to retrieve gust speeds, aiming to expand observation coverage and improve observational efficiency. Validation against ERA5 gust data yields a correlation coefficient (r) of 0.96, a root mean square error (RMSE) of 1.79 m/s, a mean bias (Bias) of 0.73 m/s, and a standard deviation (Std) of 1.64 m/s. Comparison with simultaneous NDBC buoy observations shows an r of 0.91, an RMSE of 1.50 m/s, a Bias of −0.15 m/s, and a Std of 1.50 m/s, indicating that gust wind speeds retrieved from DPR data demonstrate good reliability. Furthermore, by replacing ERA5 sea surface wind speeds with NDBC buoy measurements, the r increases to 0.95, the RMSE decreases to 1.10 m/s, the Bias is −0.07 m/s, and the Std remains at 1.50 m/s, further improving the retrieval results. These findings highlight that accurate sea surface wind speeds have a significant positive impact on the accuracy of gust wind retrievals.
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表 1 ERA5与NDBC浮标匹配分析结果和浮标位置信息
Tab. 1 Matching analysis results of ERA5 and NDBC buoy and specific information of buoys
NDBC
浮标站点纬度 经度 距离/
km匹配对
数量ERA5与浮标
海面风速ERA5与浮标
阵风风速R RMSE/
(m·s−1)R RMSE/
(m·s−1)41002 31.76°N 74.94°W 6.15 2155 0.81 1.94 0.81 2.19 41040 14.54°N 53.14°W 12.92 2197 0.82 1.34 0.81 1.51 41044 21.58°N 58.63°W 15.39 2146 0.73 1.74 0.76 1.82 41048 31.83°N 69.57°W 11.33 2134 0.90 1.07 0.87 1.46 42001 25.93°N 89.66°W 12.04 2052 0.91 1.30 0.90 1.59 44011 41.09°N 66.56°W 11.57 1200 0.69 2.28 0.73 2.49 46005 46.14°N 131.09°W 13.77 2150 0.75 2.15 0.78 2.26 46066 52.77°N 155.01°W 1.78 2060 0.82 1.96 0.85 2.16 46080 57.91°N 150.13°W 12.32 1979 0.85 1.84 0.86 2.10 51001 24.48°N 162.03°W 5.05 2153 0.74 1.66 0.78 1.68 表 2 2020年6−8月阵风风速反演结果表
Tab. 2 Gust wind speed retrieval results from June to August 2020
时间 匹配对数量 R RMSE/
(m·s−1)Bias/
(m·s−1)Std/
(m·s−1)2020年6月 1933334 0.96 1.79 0.73 1.64 2020年7月 2071620 0.96 1.77 0.70 1.63 2020年8月 1529099 0.96 1.81 0.76 1.64 2020年6月至2020年8月 5534053 0.96 1.79 0.73 1.64 -
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