Validation and Evaluation of Ocean Calibration Accuracy of FY-3G Precipitation Measurement Radar

Yuan Mei; Yin Honggang; Shang Jian; Jiang Baisen; Yang Runfeng; Gu Songyan; Zhang Peng

doi:10.11898/1001-7313.20240502

Vol.35, NO.5, 2024

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Article Navigation > Journal of Applied Meteorological Science > 2024 > 35(5): 526-537

Yuan Mei, Yin Honggang, Shang Jian, et al. Validation and evaluation of ocean calibration accuracy of FY-3G precipitation measurement radar. J Appl Meteor Sci, 2024, 35(5): 526-537. DOI: 10.11898/1001-7313.20240502.

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Yuan Mei, Yin Honggang, Shang Jian, et al. Validation and evaluation of ocean calibration accuracy of FY-3G precipitation measurement radar. J Appl Meteor Sci, 2024, 35(5): 526-537. DOI: 10.11898/1001-7313.20240502.

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Validation and Evaluation of Ocean Calibration Accuracy of FY-3G Precipitation Measurement Radar

DOI: 10.11898/1001-7313.20240502

Yuan Mei^{1, 2, 3},
Yin Honggang^{1, 2, 3},
Shang Jian^{1, 2, 3
,
,},
Jiang Baisen⁴,
Yang Runfeng⁴,
Gu Songyan^{1, 2, 3},
Zhang Peng⁵

1.
National Satellite Meteorological Center/National Center for Space Weather, Beijing 100081
2.
Innovation Center for Fengyun Meteorological Satellite, Beijing 100081
3.
Key Laboratory of Radiometric Calibration and Validation for Environmental Satellites, Beijing 100081
4.
Beijing Research Institute of Telemetry, Beijing 100076
5.
Meteorological Observation Center, CMA, Beijing 100081

Received Date: 2024-03-17
Rev Recd Date: 2024-05-06
Publish Date: 2024-09-30

Abstract

Abstract

FY-3G precipitation satellite launched in April 2023 is the first dedicated precipitation measurement satellite in China. The dual-frequency precipitation measurement radar (PMR) is the core instrument on the satellite. Because the backscattering performance of the vast ocean area is relatively stable, the calibration accuracy of the on-orbit radar can be tested by studying the backscattering cross-section of the sea surface. FY-3G PMR level 1 data in July 2023 and GPM DPR (global precipitation measurement, dual-frequency precipitation radar) level 2A data are used to analyze the mean value and mean square error of the global sea surface backscattering cross section under no-rain conditions to evaluate the radar performance. At the same time, the theoretical model of ocean surface backscattering is studied to simulate the sea surface backscattering cross-section under the condition of no rain, and the sea surface backscattering cross-section is compared with the actual radar measurement, so as to realize the preliminary evaluation of FY-3G PMR calibration accuracy. Furthermore, the accuracy of FY-3G PMR calibration is evaluated by the ocean calibration test results of GPM DPR data. Test results of ocean calibration accuracy show that when the incidence angle of FY-3G PMR Ku-band is less than 15°, the deviation between the observed value and the model simulation value is small. The deviation of FY-3G PMR ranges from 1.65 to 2.73 dB, while the standard deviation ranges from 0.74 to 1.82 dB. The deviation of FY-3G PMR Ka-band at an 18° incidence is less than 0.27 dB, and the standard deviation of the deviation is 3.49 dB. The calibration deviation of FY-3G PMR and GPM DPR is relatively constant, with the difference is primarily attributed to the backscattering statistical characteristics of the data itself. The stability of the backscattering data of FY-3G PMR Ku- and Ka-band sea surfaces at each incidence angle is comparable to that of GPM DPR. Gas attenuation is not considered at the moment. In the future, the impact of gas attenuation on the Ku- and Ka-band ocean calibration accuracy validation will be further evaluated, and the systematic deviation of FY-3G PMR will be corrected.
- precipitation measurement radar;
- FY-3G;
- backscattering cross section;
- ocean calibration;
- accuracy validation

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References(36)

Figures and Tables

Fig. 1 Monthly mean of sea surface backscattering cross section in Jul 2023

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Fig. 1 Monthly mean of sea surface backscattering cross section in Jul 2023

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Fig. 2 Statistical histogram of sea surface backscattering cross section at 0° incidence angle of FY-3G PMR and GPM DPR in Jul 2023

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Fig. 2 Statistical histogram of sea surface backscattering cross section at 0° incidence angle of FY-3G PMR and GPM DPR in Jul 2023

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Fig. 3 Probability density of different sea surface backscattering intensity of FY-3G PMR and GPM DPR in Jul 2023

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Fig. 3 Probability density of different sea surface backscattering intensity of FY-3G PMR and GPM DPR in Jul 2023

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Fig. 4 Mean square errors of monthly and orbit mean of sea surface backscattering cross section in Jul 2023

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Fig. 4 Mean square errors of monthly and orbit mean of sea surface backscattering cross section in Jul 2023

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Fig. 5 Ocean calibration results of FY-3G PMR and GPM DPR at different wind speed intervals in Jul 2023

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Fig. 5 Ocean calibration results of FY-3G PMR and GPM DPR at different wind speed intervals in Jul 2023

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Table 1 Main performance indexes of FY-3G PMR

参数	Ku波段	Ka波段
工作中心频率	13.35 ± 0.01 GHz	35.55 ± 0.01 GHz
极化	HH	HH
脉冲体制	短脉冲	短脉冲/脉冲压缩
扫描方式	交轨方向一维扫描	交轨方向一维扫描
距离方向观测范围	-5~18 km(海拔)	-5~18 km(海拔)
6 dB距离分辨率	≤ 250 m	≤ 250 m
单程3 dB波束宽度	0.7°±0.02°	0.7°±0.02°
观测刈幅	300 km	300 km
最小可检测降水强度	0.5 mm·h^-1 (18 dBZ)	0.2 mm·h^-1 (12 dBZ)
辐射精度	≤ ±1 dB (3σ)	≤ ±1 dB (3σ)

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Table 1 Main performance indexes of FY-3G PMR

参数	Ku波段	Ka波段
工作中心频率	13.35 ± 0.01 GHz	35.55 ± 0.01 GHz
极化	HH	HH
脉冲体制	短脉冲	短脉冲/脉冲压缩
扫描方式	交轨方向一维扫描	交轨方向一维扫描
距离方向观测范围	-5~18 km(海拔)	-5~18 km(海拔)
6 dB距离分辨率	≤ 250 m	≤ 250 m
单程3 dB波束宽度	0.7°±0.02°	0.7°±0.02°
观测刈幅	300 km	300 km
最小可检测降水强度	0.5 mm·h^-1 (18 dBZ)	0.2 mm·h^-1 (12 dBZ)
辐射精度	≤ ±1 dB (3σ)	≤ ±1 dB (3σ)

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Table 2 FY-3G PMR and GPM DPR ocean calibration evaluation results (Ku-band typical incidence angle) in Jul 2023

仪器	入射角/(°)	观测值/dB	模拟值/dB	平均偏差/dB	偏差标准差/dB
FY-3G PMR	-18	0.37	-2.37	2.74	3.20
	-15	3.72	2.07	1.65	1.82
	-10	9.33	7.63	1.70	1.68
	-5	12.04	10.36	1.68	0.74
	0	13.71	11.48	2.23	1.26
	5	12.77	10.36	2.41	0.74
	10	10.32	7.58	2.73	1.74
	15	4.62	2.06	2.55	1.82
	18	2.98	-2.38	5.36	3.17
GPM DPR	-18	-0.69	-3.39	2.70	3.41
	-15	2.65	1.39	1.26	2.08
	-10	7.98	7.39	0.59	2.27
	-5	11.45	10.39	1.06	1.24
	0	12.93	11.63	1.30	1.95
	5	11.53	10.45	1.09	1.21
	10	8.12	7.49	0.63	2.23
	15	2.67	1.54	1.13	2.10
	18	-0.58	-3.22	2.64	3.39

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Table 2 FY-3G PMR and GPM DPR ocean calibration evaluation results (Ku-band typical incidence angle) in Jul 2023

仪器	入射角/(°)	观测值/dB	模拟值/dB	平均偏差/dB	偏差标准差/dB
FY-3G PMR	-18	0.37	-2.37	2.74	3.20
	-15	3.72	2.07	1.65	1.82
	-10	9.33	7.63	1.70	1.68
	-5	12.04	10.36	1.68	0.74
	0	13.71	11.48	2.23	1.26
	5	12.77	10.36	2.41	0.74
	10	10.32	7.58	2.73	1.74
	15	4.62	2.06	2.55	1.82
	18	2.98	-2.38	5.36	3.17
GPM DPR	-18	-0.69	-3.39	2.70	3.41
	-15	2.65	1.39	1.26	2.08
	-10	7.98	7.39	0.59	2.27
	-5	11.45	10.39	1.06	1.24
	0	12.93	11.63	1.30	1.95
	5	11.53	10.45	1.09	1.21
	10	8.12	7.49	0.63	2.23
	15	2.67	1.54	1.13	2.10
	18	-0.58	-3.22	2.64	3.39

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Table 3 FY-3G PMR and GPM DPR ocean calibration evaluation results (Ka-band typical incidence angle) in Jul 2023

仪器	入射角/(°)	观测值/dB	模拟值/dB	平均偏差/dB	偏差标准差/dB
FY-3G PMR	-18	-3.59	-2.30	-1.29	3.51
	-15	-0.45	2.06	-2.51	2.00
	-10	4.83	7.63	-2.80	2.02
	-5	8.28	10.38	-2.10	1.02
	0	9.52	11.49	-1.97	1.57
	5	8.86	10.38	-1.52	1.02
	10	5.33	7.62	-2.29	2.01
	15	1.13	2.13	-1.00	2.01
	18	-1.98	-2.25	0.27	3.49
GPM DPR	-18	-1.72	-2.85	1.13	3.40
	-15	1.56	1.73	-0.17	1.99
	-10	6.94	7.46	-0.52	2.04
	-5	10.09	10.32	-0.23	1.04
	0	11.21	11.47	-0.26	1.46
	5	10.15	10.35	-0.20	1.03
	10	6.90	7.51	-0.61	2.02
	15	1.72	1.81	-0.09	1.98
	18	-1.44	-2.77	1.33	3.36

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Table 3 FY-3G PMR and GPM DPR ocean calibration evaluation results (Ka-band typical incidence angle) in Jul 2023

仪器	入射角/(°)	观测值/dB	模拟值/dB	平均偏差/dB	偏差标准差/dB
FY-3G PMR	-18	-3.59	-2.30	-1.29	3.51
	-15	-0.45	2.06	-2.51	2.00
	-10	4.83	7.63	-2.80	2.02
	-5	8.28	10.38	-2.10	1.02
	0	9.52	11.49	-1.97	1.57
	5	8.86	10.38	-1.52	1.02
	10	5.33	7.62	-2.29	2.01
	15	1.13	2.13	-1.00	2.01
	18	-1.98	-2.25	0.27	3.49
GPM DPR	-18	-1.72	-2.85	1.13	3.40
	-15	1.56	1.73	-0.17	1.99
	-10	6.94	7.46	-0.52	2.04
	-5	10.09	10.32	-0.23	1.04
	0	11.21	11.47	-0.26	1.46
	5	10.15	10.35	-0.20	1.03
	10	6.90	7.51	-0.61	2.02
	15	1.72	1.81	-0.09	1.98
	18	-1.44	-2.77	1.33	3.36

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