Cloud base height(CBH) is a crucial parameter for cloud radiative effect estimates, climate change simulations, and aviation guidance. However, due to the limited information on cloud vertical structures included in p...Cloud base height(CBH) is a crucial parameter for cloud radiative effect estimates, climate change simulations, and aviation guidance. However, due to the limited information on cloud vertical structures included in passive satellite radiometer observations, few operational satellite CBH products are currently available. This study presents a new method for retrieving CBH from satellite radiometers. The method first uses the combined measurements of satellite radiometers and ground-based cloud radars to develop a lookup table(LUT) of effective cloud water content(ECWC), representing the vertically varying cloud water content. This LUT allows for the conversion of cloud water path to cloud geometric thickness(CGT), enabling the estimation of CBH as the difference between cloud top height and CGT. Detailed comparative analysis of CBH estimates from the state-of-the-art ECWC LUT are conducted against four ground-based millimeter-wave cloud radar(MMCR) measurements, and results show that the mean bias(correlation coefficient) is0.18±1.79 km(0.73), which is lower(higher) than 0.23±2.11 km(0.67) as derived from the combined measurements of satellite radiometers and satellite radar-lidar(i.e., Cloud Sat and CALIPSO). Furthermore, the percentages of the CBH biases within 250 m increase by 5% to 10%, which varies by location. This indicates that the CBH estimates from our algorithm are more consistent with ground-based MMCR measurements. Therefore, this algorithm shows great potential for further improvement of the CBH retrievals as ground-based MMCR are being increasingly included in global surface meteorological observing networks, and the improved CBH retrievals will contribute to better cloud radiative effect estimates.展开更多
In recent years, ground-based micro-deformation monitoring radar has attracted much attention due to its excellent monitoring capability. By controlling the repeated campaigns of the radar antenna on a fixed track, gr...In recent years, ground-based micro-deformation monitoring radar has attracted much attention due to its excellent monitoring capability. By controlling the repeated campaigns of the radar antenna on a fixed track, ground-based micro-deformation monitoring radar can accomplish repeat-pass interferometry without a space baseline and thus obtain highprecision deformation data of a large scene at one time. However, it is difficult to guarantee absolute stable installation position in every campaign. If the installation position is unstable, the stability of the radar track will be affected randomly, resulting in time-varying baseline error. In this study, a correction method for this error is developed by analyzing the error distribution law while the spatial baseline is unknown. In practice, the error data are first identified by frequency components, then the data of each one-dimensional array(in azimuth direction or range direction) are grouped based on numerical distribution period, and finally the error is corrected by the nonlinear model established with each group.This method is verified with measured data from a slope in southern China, and the results show that the method can effectively correct the time-varying baseline error caused by rail instability and effectively improve the monitoring data accuracy of groundbased micro-deformation radar in short term and long term.展开更多
Doppler weather radar has important applications in measuring the intrinsic factors of cloud, rainfall and various convective weather occurrences. Among them, CINRAD/CB Doppler weather radar is based on the requiremen...Doppler weather radar has important applications in measuring the intrinsic factors of cloud, rainfall and various convective weather occurrences. Among them, CINRAD/CB Doppler weather radar is based on the requirements of the China Meteorological Administration and many units have been provided. The modulator is a critical part of the transmitter’s high voltage, where high voltage, high current, and energy conversion are concentrated. It is therefore necessary to redesign the transmitter modulator cooling system protection. This article describes the new design of hardware and software solutions. The fan is a DV5214/2N DC fan from Ebmpapst, Germany. The speed is up to 5000 rpm, the power is 18.5 W, and the single fan current is about 0.8 A. It is powered by 28 V. The protection board uses a DC/DC module to output a 5 V voltage and a 3.3 V voltage adjustment chip LM1117. The embedded web software is based on the TCP/IP protocol stack provided by MICROCHIP. After the cooling system is designed and installed in the radar station in Xi’an, China and other places, after long-term operation, the comprehensive test shows that the system runs well.展开更多
When multiple ground-based radars(GB-rads)are utilized together to resolve three-dimensional(3-D)deformations,the resolving accuracy is related with the measurement geometry constructed by these radars.This paper focu...When multiple ground-based radars(GB-rads)are utilized together to resolve three-dimensional(3-D)deformations,the resolving accuracy is related with the measurement geometry constructed by these radars.This paper focuses on constrained geometry analysis to resolve 3-D deformations from three GB-rads.The geometric dilution of precision(GDOP)is utilized to evaluate 3-D deformation accuracy of a single target,and its theoretical equation is derived by building a simplified 3-D coordinate system.Then for a 3-D scene,its optimal accuracy problem is converted into determining the minimum value of an objective function with a boundary constraint.The genetic algorithm is utilized to solve this constrained optimization problem.Numerical simulations are made to validate the correctness of the theoretical analysis results.展开更多
Ground-based synthetic aperture radar(GB-SAR) has been successfully applied to the ground deformation monitoring.However, due to the short length of the GB-SAR platform, the scope of observation is largely limited. Th...Ground-based synthetic aperture radar(GB-SAR) has been successfully applied to the ground deformation monitoring.However, due to the short length of the GB-SAR platform, the scope of observation is largely limited. The practical applications drive us to make improvements on the conventional linear rail GB-SAR system in order to achieve larger field imaging. First, a turntable is utilized to support the rotational movement of the radar.Next, a series of high-squint scanning is performed with multiple squint angles. Further, the high squint modulation phase of the echo data is eliminated. Then, a new multi-angle imaging method is performed in the wave number domain to expand the field of view. Simulation and real experiments verify the effectiveness of this method.展开更多
A new method of single sample polarization filtering is proposed. The algorithm is fast and suitable for the polarization processing of stationary or nonstationary polarized disturbed signals with one or more independ...A new method of single sample polarization filtering is proposed. The algorithm is fast and suitable for the polarization processing of stationary or nonstationary polarized disturbed signals with one or more independent disturbances. A ground wave polarimetric radar with the ability of radio disturbance suppression is then introduced. Some numerical results demonstrate the effectiveness of single sample polarization filtering method for ground wave polarimetric radar.展开更多
面向安防区域的入侵监测过程包括区域边界的入侵报警和区域内部的入侵跟踪。然而,现有的入侵探测雷达技术难以兼顾区域边界和内部的同时监测,并且存在多入侵探测距离分辨率低和抗干扰能力弱的缺陷。提出并实验验证了一种面向入侵监测的...面向安防区域的入侵监测过程包括区域边界的入侵报警和区域内部的入侵跟踪。然而,现有的入侵探测雷达技术难以兼顾区域边界和内部的同时监测,并且存在多入侵探测距离分辨率低和抗干扰能力弱的缺陷。提出并实验验证了一种面向入侵监测的复合式随机码雷达系统。该雷达系统结合了基于泄漏电缆的导波雷达和基于喇叭天线的一发多收雷达。前者用于实现区域边界的入侵报警,后者继而负责区域内部的入侵跟踪,最终实现监测区域的全面覆盖并消除监测盲区。此外,该雷达系统采用高速、正交的随机码信号作为上述两种雷达的发射信号。实验结果表明所提出的雷达系统不仅可以实现多个入侵者的同时报警和跟踪,而且具有强抗干扰能力。受益于随机码信号的高速率和自相关特性,导波雷达和一发多收雷达可以分别实现30 cm和15 cm的高距离分辨率,且抗干扰容限可以达到33.5 d B。展开更多
In order to explain theoretically the observational biases of reflectivity and structure of precipitation systems by TRMM Precipitation Radar (TRMM PR) and ground-based radar,the effects of wavelengths,incident direct...In order to explain theoretically the observational biases of reflectivity and structure of precipitation systems by TRMM Precipitation Radar (TRMM PR) and ground-based radar,the effects of wavelengths,incident direction of radar waves and radar beam width on the reflectivity observation are simulated.The results show that the error due to the different wavelength and incident direction of radar wave is within 2.0 dB,TRMM PR can observe a larger reflectivity than ground-based radar in echo center.TRMM PR smoothes the cloud structure,overestimates and underestimates reflectivity by 3-5 dB in strong and week echo areas,respectively.Beam width and long distance from TRMM PR to target cause it to overestimate the large echo area and area integrated rainfall amount,and to underestimate the averaged refleetivity.The theoretical results above can only explain part of observational facts,meaning that the comparison of observation results between TRMM PR and ground-based radar is complicated,the attenuation of radar wave within precipitation area is the main factor to affect the observed result.展开更多
基金funded by the National Natural Science Foundation of China (Grant Nos. 42305150 and 42325501)the China Postdoctoral Science Foundation (Grant No. 2023M741774)。
文摘Cloud base height(CBH) is a crucial parameter for cloud radiative effect estimates, climate change simulations, and aviation guidance. However, due to the limited information on cloud vertical structures included in passive satellite radiometer observations, few operational satellite CBH products are currently available. This study presents a new method for retrieving CBH from satellite radiometers. The method first uses the combined measurements of satellite radiometers and ground-based cloud radars to develop a lookup table(LUT) of effective cloud water content(ECWC), representing the vertically varying cloud water content. This LUT allows for the conversion of cloud water path to cloud geometric thickness(CGT), enabling the estimation of CBH as the difference between cloud top height and CGT. Detailed comparative analysis of CBH estimates from the state-of-the-art ECWC LUT are conducted against four ground-based millimeter-wave cloud radar(MMCR) measurements, and results show that the mean bias(correlation coefficient) is0.18±1.79 km(0.73), which is lower(higher) than 0.23±2.11 km(0.67) as derived from the combined measurements of satellite radiometers and satellite radar-lidar(i.e., Cloud Sat and CALIPSO). Furthermore, the percentages of the CBH biases within 250 m increase by 5% to 10%, which varies by location. This indicates that the CBH estimates from our algorithm are more consistent with ground-based MMCR measurements. Therefore, this algorithm shows great potential for further improvement of the CBH retrievals as ground-based MMCR are being increasingly included in global surface meteorological observing networks, and the improved CBH retrievals will contribute to better cloud radiative effect estimates.
基金supported by the National Key R&D Program of China (2018YFC1508502)the National Natural Science Foundation of China (41601569,61661043,61631011)the Science and Technology Innovation Guidance Project of Inner Mongolia Autonomous Region (2019GG139,KCBJ2017,KCBJ 2018014,2019ZD022)。
文摘In recent years, ground-based micro-deformation monitoring radar has attracted much attention due to its excellent monitoring capability. By controlling the repeated campaigns of the radar antenna on a fixed track, ground-based micro-deformation monitoring radar can accomplish repeat-pass interferometry without a space baseline and thus obtain highprecision deformation data of a large scene at one time. However, it is difficult to guarantee absolute stable installation position in every campaign. If the installation position is unstable, the stability of the radar track will be affected randomly, resulting in time-varying baseline error. In this study, a correction method for this error is developed by analyzing the error distribution law while the spatial baseline is unknown. In practice, the error data are first identified by frequency components, then the data of each one-dimensional array(in azimuth direction or range direction) are grouped based on numerical distribution period, and finally the error is corrected by the nonlinear model established with each group.This method is verified with measured data from a slope in southern China, and the results show that the method can effectively correct the time-varying baseline error caused by rail instability and effectively improve the monitoring data accuracy of groundbased micro-deformation radar in short term and long term.
文摘Doppler weather radar has important applications in measuring the intrinsic factors of cloud, rainfall and various convective weather occurrences. Among them, CINRAD/CB Doppler weather radar is based on the requirements of the China Meteorological Administration and many units have been provided. The modulator is a critical part of the transmitter’s high voltage, where high voltage, high current, and energy conversion are concentrated. It is therefore necessary to redesign the transmitter modulator cooling system protection. This article describes the new design of hardware and software solutions. The fan is a DV5214/2N DC fan from Ebmpapst, Germany. The speed is up to 5000 rpm, the power is 18.5 W, and the single fan current is about 0.8 A. It is powered by 28 V. The protection board uses a DC/DC module to output a 5 V voltage and a 3.3 V voltage adjustment chip LM1117. The embedded web software is based on the TCP/IP protocol stack provided by MICROCHIP. After the cooling system is designed and installed in the radar station in Xi’an, China and other places, after long-term operation, the comprehensive test shows that the system runs well.
基金supported by the National Natural Science Foundation of China(61960206009,61971037,31727901)the Natural Science Foundation of Chongqing+1 种基金China(2020jcyj-jq X0008)Chongqing Key Laboratory of Geological Environment Monitoring and Disaster Early-warning in Three Gorges Reservoir Area(ZD2020A0101)。
文摘When multiple ground-based radars(GB-rads)are utilized together to resolve three-dimensional(3-D)deformations,the resolving accuracy is related with the measurement geometry constructed by these radars.This paper focuses on constrained geometry analysis to resolve 3-D deformations from three GB-rads.The geometric dilution of precision(GDOP)is utilized to evaluate 3-D deformation accuracy of a single target,and its theoretical equation is derived by building a simplified 3-D coordinate system.Then for a 3-D scene,its optimal accuracy problem is converted into determining the minimum value of an objective function with a boundary constraint.The genetic algorithm is utilized to solve this constrained optimization problem.Numerical simulations are made to validate the correctness of the theoretical analysis results.
基金supported by the National Natural Science Foundation of China(61801007)the Beijing Natural Science Foundation(4194075)。
文摘Ground-based synthetic aperture radar(GB-SAR) has been successfully applied to the ground deformation monitoring.However, due to the short length of the GB-SAR platform, the scope of observation is largely limited. The practical applications drive us to make improvements on the conventional linear rail GB-SAR system in order to achieve larger field imaging. First, a turntable is utilized to support the rotational movement of the radar.Next, a series of high-squint scanning is performed with multiple squint angles. Further, the high squint modulation phase of the echo data is eliminated. Then, a new multi-angle imaging method is performed in the wave number domain to expand the field of view. Simulation and real experiments verify the effectiveness of this method.
文摘A new method of single sample polarization filtering is proposed. The algorithm is fast and suitable for the polarization processing of stationary or nonstationary polarized disturbed signals with one or more independent disturbances. A ground wave polarimetric radar with the ability of radio disturbance suppression is then introduced. Some numerical results demonstrate the effectiveness of single sample polarization filtering method for ground wave polarimetric radar.
文摘面向安防区域的入侵监测过程包括区域边界的入侵报警和区域内部的入侵跟踪。然而,现有的入侵探测雷达技术难以兼顾区域边界和内部的同时监测,并且存在多入侵探测距离分辨率低和抗干扰能力弱的缺陷。提出并实验验证了一种面向入侵监测的复合式随机码雷达系统。该雷达系统结合了基于泄漏电缆的导波雷达和基于喇叭天线的一发多收雷达。前者用于实现区域边界的入侵报警,后者继而负责区域内部的入侵跟踪,最终实现监测区域的全面覆盖并消除监测盲区。此外,该雷达系统采用高速、正交的随机码信号作为上述两种雷达的发射信号。实验结果表明所提出的雷达系统不仅可以实现多个入侵者的同时报警和跟踪,而且具有强抗干扰能力。受益于随机码信号的高速率和自相关特性,导波雷达和一发多收雷达可以分别实现30 cm和15 cm的高距离分辨率,且抗干扰容限可以达到33.5 d B。
基金the Project of National Fundamental Research Planning"Research on the formation mechanism and the prediction theory of hazardous weather over China"(G1998040909)Doctoral Start-up Foundation Project in Chinese Academy of Meteorological Sciences
文摘In order to explain theoretically the observational biases of reflectivity and structure of precipitation systems by TRMM Precipitation Radar (TRMM PR) and ground-based radar,the effects of wavelengths,incident direction of radar waves and radar beam width on the reflectivity observation are simulated.The results show that the error due to the different wavelength and incident direction of radar wave is within 2.0 dB,TRMM PR can observe a larger reflectivity than ground-based radar in echo center.TRMM PR smoothes the cloud structure,overestimates and underestimates reflectivity by 3-5 dB in strong and week echo areas,respectively.Beam width and long distance from TRMM PR to target cause it to overestimate the large echo area and area integrated rainfall amount,and to underestimate the averaged refleetivity.The theoretical results above can only explain part of observational facts,meaning that the comparison of observation results between TRMM PR and ground-based radar is complicated,the attenuation of radar wave within precipitation area is the main factor to affect the observed result.
