Identification of Ground Clutter with C-band Doppler Weather Radar

Li Feng; Liu Liping; Wang Hongyan; Yang Chuan

Vol.25, NO.2, 2014

Article Contents

Article Navigation > Journal of Applied Meteorological Science > 2014 > 25(2): 158-167

Li Feng, Liu Liping, Wang Hongyan, et al. Identification of ground clutter with C-band Doppler weather radar. J Appl Meteor Sci, 2014, 25(2): 158-167.

Citation:

Li Feng, Liu Liping, Wang Hongyan, et al. Identification of ground clutter with C-band Doppler weather radar. J Appl Meteor Sci, 2014, 25(2): 158-167.

Li Feng, Liu Liping, Wang Hongyan, et al. Identification of ground clutter with C-band Doppler weather radar. J Appl Meteor Sci, 2014, 25(2): 158-167.

Citation:

Li Feng, Liu Liping, Wang Hongyan, et al. Identification of ground clutter with C-band Doppler weather radar. J Appl Meteor Sci, 2014, 25(2): 158-167.

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Identification of Ground Clutter with C-band Doppler Weather Radar

1.
State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing 100081
2.
The 23rd Research Institute, China Aerospace Science & Industry Corporation, Beijing 100854

Received Date: 2013-03-05
Rev Recd Date: 2013-12-10
Publish Date: 2014-03-31

Abstract

Abstract

The application of radar data is negatively affected by echoes caused by ground clutter, meanwhile these echoes from ground clutter have significant effect on rainfall estimation and radar data assimilation. As a result, it is important to identify and discriminate these echoes, which is an absolutely necessary part of radar data quality control. The ground clutter identifying algorithms in operation are mostly based on S-band Doppler weather radar, the resolution and velocity scanning mode of which are different from those of C-band radar. Few researches are carried out to discuss whether the method based on S-band is applicable to the C-band radar or not. Based on the current algorithm used for the SA radar, one method is developed for the CC radar using the data observed by radars of Changzhi and Harbin. The statistical characteristics of clutter are analyzed using data collected during 2011, and the membership functions are improved for C-band Doppler weather radar.Results show that, for S-band and C-band Doppler weather radar, parameters about reflectivity of ground clutter are similar, and there are notable differences between ground clutter and precipitation echoes. For C-band ground clutter echoes, the parameter T_DBZ is greater than S-band. G_DBZ value of both kinds of radar is alike, mostly below 0. S_PIN value of ground clutter echoes is remarkably greater than that of precipitation echoes for both C-band and S-band radar. It shows that three parameters about reflectivity including T_DBZ, G_DBZ and S_PIN, can be used to identify and discriminate C-band radar ground clutter echoes.For C-band radar ground clutter and precipitation echoes, only M_DVE, associated with velocity, could be used to distinguish these two kinds of echoes. For M_DSW and S_DVE, there is no notable difference between ground clutter and precipitation. In contrast, two parameters of ground clutter are different from that of precipitation echoes for S-band radar. For S-band radar, M_DSW and S_DVE are both very small, mostly below 1. There are considerable numbers of values above 1 for two parameters of C-band radar. The spatial resolutions of two kinds of radars are different, which may result in the fact that M_DSW and S_DVE could not be used to distinguish ground clutter echoes from precipitation echoes. Besides, the velocity scan mode, the dual pulse repetition frequency may cause the phenomenon to some extent. It can also be caused by the different precisions of two kinds of radars. The velocity precision of S-band radar is 0.5 m·s^-1, while the velocity of C-band radar is 0.1 m·s^-1. For S-band radar, the velocity changes more smoothly than that of C-band radar. Compared with the method based on S-band radar, the identification accuracy of ground clutter is improved notably and the false detection of stratiform cloud echoes is also reduced obviously.
- ground clutter;
- fuzzy logical;
- quality control

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References(23)

Figures and Tables

图 1 2011年7月2日07:00长治雷达观测数据 (距离圈间隔50 km)

(a)0.5°仰角反射率因子, (b)0.5°仰角径向速度, (c) 0.5°仰角回波分类
(AP为地物，CA为晴空回波，SC为层状云，CC为对流云)

Fig. 1 PPI of Changzhi radar at 0700 BT 2 Jul 2011 (range rings at 50 km intervals)

(a) reflectivity at 0.5° elevation, (b) radial velocity at 0.5° elevation, (c) echo classify at 0.5° elevation
(AP shows ground clutter, CA shows clear air echoes, SC shows stratiform cloud, CC shows convective cloud)

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图 2 各参量的概率分布

(AP为地物，CC为对流云，SC为层状云)

Fig. 2 Probability distribution of characteristic parameters

(AP shows ground clutter, CC shows convective cloud, SC shows stratiform cloud)

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Fig. 3 Distribution of V_D (a) and percentage of V_D below some value (b)

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Fig. 4 Membership function of characteristic parameters

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图 5 2011年07月25日07:01哈尔滨雷达识别效果 (距离圈间隔50 km)

(a)0.5°仰角反射率因子, (b)0.5°仰角径向速度, (c)1.5°仰角反射率因子，(d)1.5°仰角径向速度, (e) MSA方法识别后0.5°仰角反射率因子, (f) MCC方法识别后0.5°仰角反射率因子

Fig. 5 PPI of Harbin radar at 0701 BT 25 Jul 2011(range rings at 50 km intervals)

(a) reflectivity at 0.5° elevation, (b) radial velocity at 0.5° elevation, (c) reflectivity at 1.5° elevation, (d) radial velocity at 1.5° elevation, (e) reflectivity at 0.5° elevation after echo identification with MSA, (f) reflectivity at 0.5° elevation after echo identification with MCC

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图 6 2011年7月2日07:05长治雷达识别效果

Fig. 6 PPI of Changzhi radar at 0705 BT 2 Jul 2011(range rings at 50 km intervals)

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图 7 2011年6月3日11:05哈尔滨雷达识别效果 (距离圈间隔50 km)

Fig. 7 PPI of Harbin radar at 1105 BT 3 Jun 2011(range rings at 50 km intervals)

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Table 1 Identifiable accuracy of each characteristic parameter (unit:%)

参量	总样本正确率	地物识别正确率	对流云误判率	层状云误判率
T_DBZ	98.4	97.0	1.84	0.12
G_DBZ	91.7	82.7	2.1	5.5
S_PIN	97.4	96.1	3.0	1.0
M_DVE	92.8	89.1	4.7	5.9

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Table 2 Identifiable accuracy for ground clutter echoes and false detection of precipitation echoes (unit:%)

识别方法	总样本正确率	地物识别正确率	对流云误判率	层状云误判率
MCC	99.2	97.8	0.31	0.03
MSA	87.4	62.3	0.03	0.18
MSC	98.5	97.9	1.64	0.69

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