Journal of Tropical Oceanography >
Accuracy analysis of the retrieved wind from HY-2B scatterometer
Copy editor: LIN Qiang
Received date: 2019-12-17
Request revised date: 2020-05-12
Online published: 2020-05-13
Supported by
National Natural Science Foundation of China(41876204)
National Natural Science Foundation of China(41476152)
Scientific Project of Guangdong Polytechnic of Industry and Commerce(2017-Z-5)
Copyright
Spaceborne microwave scatterometer is the most efficient instrument to measure the global ocean surface wind. The successfully launched HY-2B scatterometer is an important guarantee to continue the measurement of global ocean surface wind. In this paper, we use the European Center for Medium-Range Weather Forecasts (ECMWF) reanalysis wind data, Tropical Atmosphere Ocean Array (TAO) and National Data Buoy Center (NDBC) buoy wind data to estimate the accuracy of the HY-2B retrieved wind. Our statistical results show that at speed range from 4 to 24 m·s-1, the retrieved wind speed root mean square error (RMSE) with respect to the ECMWF wind speed is 1.58 m·s-1, and the direction RMSE is 15.34°, while the speed and direction RMSEs with respect to the TAO buoys located in the open ocean are 1.06 m·s-1 and 15.98°, respectively. Thus, the retrieved wind well satisfies the operational precision requirement of the HY-2B scatterometer, that is, the speed and direction RMSEs should be better than 2 m·s-1 and 20.00°, respectively, for the open ocean. Moreover, the NDBC buoys are mainly located in immediate offshore areas, HY-2B wind speed and direction RMSEs are 1.60 m·s-1and 19.14°, respectively, which shows that HY-2B scatterometer has good ability to measure wind of offshore sea areas. We also reveal that the retrieved wind error varies with wind speed and cross track position of wind vector cell, which will provide the users with reference for the effective application of HY-2B wind product.
CHEN Kehai , XIE Xuetong , ZHANG Jinlan , ZOU Juhong , ZHANG Yi . Accuracy analysis of the retrieved wind from HY-2B scatterometer[J]. Journal of Tropical Oceanography, 2020 , 39(6) : 30 -40 . DOI: 10.11978/2019138
表1 HY-2B与ECMWF的风矢量偏差统计Tab. 1 Statistics of wind vector deviation of HY-2B vs ECMWF |
风速区间/( m·s-1 ) | HY-2B~ECMWF风速误差 | HY-2B~ECMWF风向误差 | ||||||
---|---|---|---|---|---|---|---|---|
偏差均值/(m·s-1) | 绝对偏差均值/( m·s-1) | 均方根误差/(m·s-1) | 绝对偏差小于2m·s-1的比例/% | 偏差均值 | 绝对偏差均值 | 均方根 误差 | 绝对偏差小于20°的比例/% | |
0~4 | 1.43 | 1.80 | 2.01 | 68.90 | 0.48° | 38.99° | 52.60° | 38.81 |
4~24 | 0.27 | 1.18 | 1.58 | 84.85 | 0.78° | 11.53° | 15.34° | 83.40 |
图3 HY-2B与ECMWF的风矢量偏差概率分布情况a. 风速绝对偏差累积概率; b. 风速绝对偏差小于2m·s-1的比例随风速的变化; c. 风向绝对偏差累计概率; d. 风向绝对偏差小于20°的比例随风速的变化 Fig. 3 Probability distribution of HY-2B vs ECMWF wind vector deviation: a) cumulative distribution of speed absolute deviation; b) ratio of speed absolute deviation within 2 m·s-1 varying with speed; c) cumulative distribution of direction absolute deviation; d) ratio of direction absolute deviation within 20° varying with speed |
表2 HY-2B与TAO浮标的风矢量偏差统计Tab. 2 Statistics of wind vector deviation of HY-2B vs TAO buoys |
风速区间 /(m·s-1) | 匹配数据数目 | 异常点数 目(比例/%) | HY-2B~TAO风速误差 | HY-2B~TAO风向误差 | ||||||
---|---|---|---|---|---|---|---|---|---|---|
偏差均值 /(m·s-1) | 绝对偏差均值/(m·s-1) | 均方根误差/(m·s-1) | 绝对偏差小 于2 m·s-1的比例/% | 偏差 均值 | 绝对偏 差均值 | 均方 根误差 | 绝对偏差小于20°的比例/% | |||
0~4 | 296 | 0 (0%) | 1.02 | 1.34 | 1.74 | 81.16 | -2.93° | 42.90° | 59.84° | 42.12 |
4~13* | 1613 | 35(2.22%) | 0.49 | 0.77 | 1.03 | 94.67 | 1.78° | 11.13° | 14.98° | 86.68 |
注: *TAO浮标位于赤道附近(纬度15°S—15°N), 赤道风速低, 这里TAO风速只统计到13m·s-1 |
表3 HY-2B与NDBC浮标的风矢量偏差统计Tab. 3 Statistics table of wind vector deviation of HY-2B vs NDBC buoys |
风速区间/( m·s-1) | 匹配数据数目 | 异常点数目 (比例) | HY-2B与NDBC的风速误差 | HY-2B与NDBC的风向误差 | ||||||
---|---|---|---|---|---|---|---|---|---|---|
偏差均值/(m·s-1) | 绝对偏差均值/(m·s-1) | 均方根误差/(m·s-1) | 绝对偏差小于2m·s-1的比例/% | 偏差 均值 | 绝对偏差均值 | 均方根误差 | 绝对偏差小于20°的比例/% | |||
0~4 | 308 | 0(0%) | 1.30 | 1.65 | 1.85 | 69.80 | 3.60° | 49.24° | 64.02° | 29.87 |
4~13* | 1442 | 24(1.70%) | 0.34 | 1.15 | 1.54 | 85.36 | 4.20° | 15.31° | 20.07° | 75.95 |
4~24 | 1772 | 31(1.79%) | 0.25 | 1.20 | 1.60 | 83.14 | 5.06° | 14.86° | 19.14° | 76.73 |
注: * 增加4~13m·s-1风速区间是为了与TAO浮标对比。 |
图6 HY-2B与浮标(TAO、NDBC)的风矢量散点图a. HY-2B与TAO的风速散点图; b. HY-2B与TAO的风向散点图; c. HY-2B与NDBC的风速散点图; d. HY-2B与NDBC的风向散点图 Fig. 6 Wind scatter plot of HY-2B vs buoy (TAO, NDBC ). a) speed scatter plot of HY-2B vs TAO; b) direction scatter plot of HY-2B vs TAO; c) speed scatter plot of HY-2B vs NDBC; d) direction scatter plot of HY-2B vs NDBC |
图7 HY-2B与浮标(TAO、NDBC)的风矢量偏差直方图a. HY-2B与TAO的风速偏差直方图; b. HY-2B与TAO的风向偏差直方图; c. HY-2B与NDBC的风速偏差直方图; d. HY-2B与NDBC的风向偏差直方图 Fig. 7 Wind deviation histogram of HY-2B vs buoys ( TAO, NDBC ): a) speed deviation histogram of HY-2B vs TAO; b) direction deviation histogram of HY-2B vs TAO; c) speed deviation histogram of HY-2B vs NDBC; d) direction deviation histogram of HY-2B vs NDBC |
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