Xuejin Sun

PLA Army Engineering University

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Chuanliang Zhang

Xi'an Jiaotong University

Riwei Zhang

Facing Our Risk of Cancer Empowered

Yongbo Zhou

Nanjing University of Information Science and Technology

Liu L

Washington University in St. Louis

Haoran Li

Chinese Academy of Meteorological Sciences

Shaohui Li

Zhengzhou University

Taichang Gao

National University of Defense Technology

Qinghui Li

Huazhong Agricultural University

Shijun Zhao

Chongqing University

Junhao Zhou

National Yunlin University of Science and Technology

Cooperative Institutions

PLA Army Engineering University

National University of Defense Technology

Chinese Academy of Sciences

University of Chinese Academy of Sciences

China Meteorological Administration

Shanghai Jiao Tong University

Chinese Academy of Meteorological Sciences

Xi'an Jiaotong University

Shanghai University

Zhejiang University

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Retrieving cloud base heights via the combination of CloudSat and MODIS observations

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (2014)

Haoran Li Xuejin Sun

An algorithm for estimating cloud base height (CBH) based on the combination of cloud products from CloudSat (provides CBH) and Moderate resolution Imaging Spectroradiometer (MODIS) (provides cloud top pressure and cloud optical thickness) is presented. The relationship among cloud geometric parameters and the feasibility of estimating the CBH via combining CloudSat and MODIS observations is analyzed. When the cloud top pressure (CTP) and cloud optical thickness (COT) of a certain point have been obtained by MODIS, its CBH could be estimated by searching the similar point in CloudSat track, which shares the same CTP, COT and CBH with the estimating point. In the process of searching the most matching point, an adjusting factor is introduced to uniform the unit of CTP and COT. The retrieval accuracy of cloud base height is heavily relied on the CBH provided by Cloudsat and the best matching point. Dataexclusion experiments along the CloudSat track also show a nice performance without the Cloudsat cloud classification products. And the root mean-square-error is less than 2 km when the exclusion distance is less than 100 km. This method provides a new approach to render a 3D cloud structure in a wide field.

Moderate-resolution imaging spectroradiometer

Cloud base

Cloud top

10.1117/12.2067765

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Citations (6)

Localized Si–Au eutectic bonding around sunken pad for fabrication of a capacitive absolute pressure sensor

Sensors and Actuators A Physical (2013)

Qimin Liu Lidong Du Zhan Zhao Xiao Li Xuejin Sun

Eutectic bonding

Anodic bonding

Wafer Bonding

Leakage (economics)

Wire bonding

10.1016/j.sna.2013.07.013

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Citations (24)

On the Quantification of Thermodynamic Phases of Raining Clouds: Insights From Multi‐Year CloudSat and Ground‐Based Radar Observations Over Longmen, Southern China

Journal of Geophysical Research Atmospheres (2024)

Qinghui Li Haoran Li Xuejin Sun Zheng Ruan Liping Liu

Abstract The thermodynamic phase of clouds is fundamental to rain initiation and development. Although it is well established that majority of rainfall from mid‐ to‐high latitudes originates from ice, there is a lack of consensus on the major thermodynamic phase of raining clouds over low latitudes. Previous CloudSat‐based studies have yet reached consistent results on the fraction of ice‐phase raining clouds over Southern China. In this work, we found that CloudSat‐based approaches are subject to metrics used for flagging rainfall events, which may lead to different estimates. Analysis of multi‐year surface radar observations suggests that has diurnal variation and increases with rain rate, while the surface rainfall originating from warm clouds does not exceed 50 . Using disdrometer observations to flag surface rainfall events, we found that about 71 and 95 of surface rainfall events and rainfall accumulation come from cold clouds, respectively. In addition, the observed rainfall accumulations over Longmen are consistent with the fifth generation atmospheric reanalysis (ERA5), whereas the frequency of warm rainfall over Longmen is significantly underestimated in ERA5.

Disdrometer

10.1029/2024jd041824

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Relationship between wind observation accuracy and the ascending node of the sun-synchronous orbit for the Aeolus-type spaceborne Doppler wind lidar

Atmospheric measurement techniques (2021)

Chuanliang Zhang Xuejin Sun Wen Lu Yingni Shi Naiying Dou

Abstract. The launch and operation of the first spaceborne Doppler wind lidar (DWL), Aeolus, is of great significance for observing the global wind field. Aeolus operates on a sun-synchronous dawn–dusk orbit to minimize the negative impact of solar background radiation (SBR) on wind observation accuracy. Future spaceborne DWLs may not operate on sun-synchronous dawn–dusk orbits due to their observational purposes. The impact of the local time of ascending node (LTAN) crossing of sun-synchronous orbits on the wind observation accuracy was studied in this paper by proposing two given Aeolus-type spaceborne DWLs operating on the sun-synchronous orbits with LTANs of 15:00 and 12:00 LT. On these two new orbits, the increments of the averaged SBR received by the new spaceborne DWLs range from 39 to 56 mW m−2 sr−1 nm−1 under cloud-free skies near the summer and winter solstices, which will lead to uncertainties of 0.19 and 0.27 m s−1 in the increment of the averaged Rayleigh channel wind observations for 15:00 and 12:00 LT orbits using the instrument parameters of Aeolus with 30 measurements per observation and 20 laser pulses per measurement. This demonstrates that Aeolus operating on the sun-synchronous dawn–dusk orbit is the optimal observation scenario, and the random error caused by the SBR will be larger on other sun-synchronous orbits. Increasing the laser pulse energy of the new spaceborne DWLs is used to lower the wind observation uncertainties, and a method to quantitatively design the laser pulse energy according to the specific accuracy requirements is proposed in this study based on the relationship between the signal-to-noise ratio and the uncertainty of the response function of the Rayleigh channel. The laser pulse energies of the two new spaceborne DWLs should be set to 70 mJ based on the statistical results obtained using the method. The other instrument parameters should be the same as those of Aeolus. Based on the proposed parameters, the accuracies of about 77.19 % and 74.71 % of the bins of the two new spaceborne DWLs would meet the accuracy requirements of the European Space Agency (ESA) for Aeolus. These values are very close to the 76.46 % accuracy of an Aeolus-type spaceborne DWL when it is free of the impact of the SBR. Moreover, the averaged uncertainties of the two new spaceborne DWLs are 2.62 and 2.69 m s−1, which perform better than that of Aeolus (2.77 m s−1).

Dusk

Orbit (dynamics)

Solstice

10.5194/amt-14-4787-2021

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Citations (6)

VizieR Online Data Catalog: G203.7+11.5 21cm and 11cm intensity maps (Reich+, 2020)

VizieR Online Data Catalog (2020)

W. Reich P. Reich Xuejin Sun

Source

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Comparison of Cloud Properties from Ground-Based Infrared Cloud Measurement and Visual Observations

Journal of Atmospheric and Oceanic Technology (2013)

Liu L Xuejin Sun Taichang Gao Shijun Zhao

Abstract Cloud properties derived from the whole-sky infrared cloud-measuring system (WSIRCMS) are analyzed in relation to measurements of visual observations and a ceilometer during the period July–August 2010 at the Chinese Meteorological Administration Yangjiang Station, Guangdong Province, China. The comparison focuses on the performance and features of the WSIRCMS as a prototype instrument for automatic cloud observations. Cloud cover derived from the WSIRCMS cloud algorithm compares quite well with cloud cover derived from visual observations. Cloud cover differences between WSIRCMS and visual observations are within ±1 octa in 70.83% and within ±2 octa in 82.44% of the cases. For cloud-base height from WSIRCMS data and Vaisala ceilometer CL51, the comparison shows a generally good correspondence in the lower and midtroposphere up to the height of about 6 km, with some systematic difference due to different detection methods. Differences between the resulting cloud-type classifications derived from the WSIRCMS and from visual observations show that cumulus and cirrus are classified with high accuracy, but that stratocumulus and altocumulus are not. Stratocumulus and altocumulus are suggested to be treated as waveform cloud for classification purposes. In addition, it is considered an intractable problem for automatic cloud-measurement instruments to do cloud classification when the cloud amount is less than 2 octa.

Ceilometer

Cloud top

Cloud height

Cirrus

Cloud albedo

Cloud fraction

Cloud base

10.1175/jtech-d-12-00157.1

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Citations (24)

Texture Feature Extraction Method for Ground Nephogram Based on Hilbert Spectrum of Bidimensional Empirical Mode Decomposition

Journal of Atmospheric and Oceanic Technology (2014)

Xiaoying Chen Aiguo Song Jianqing Li Zhu Yi-min Xuejin Sun

Abstract It is important to recognize the type of cloud for automatic observation by ground nephoscope. Although cloud shapes are protean, cloud textures are relatively stable and contain rich information. In this paper, a novel method is presented to extract the nephogram feature from the Hilbert spectrum of cloud images using bidimensional empirical mode decomposition (BEMD). Cloud images are first decomposed into several intrinsic mode functions (IMFs) of textural features through BEMD. The IMFs are converted from two- to one-dimensional format, and then the Hilbert–Huang transform is performed to obtain the Hilbert spectrum and the Hilbert marginal spectrum. It is shown that the Hilbert spectrum and the Hilbert marginal spectrum of different types of cloud textural images can be divided into three different frequency bands. A recognition rate of 87.5%–96.97% is achieved through random cloud image testing using this algorithm, indicating the efficiency of the proposed method for cloud nephogram.

Hilbert spectral analysis

Mode (computer interface)

Feature (linguistics)

Hilbert R-tree

10.1175/jtech-d-13-00238.1

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Citations (3)

Strong THz generation and application on high energy density golden plasma

2020 IEEE International Conference on Plasma Science (ICOPS) (2024)

D. W. Zhang H. Z. Wu Xuejin Sun Zhihui Lyu Zengxiu Zhao

10.1109/icops58192.2024.10627074

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Reliability Evaluation of the Joint Observation of Cloud Top Height by FY-4A and HIMAWARI-8

Remote Sensing (2021)

Qinghui Li Xuejin Sun Xiaolei Wang

It is well known that the measurement of cloud top height (CTH) is important, and a geostationary satellite is an important measurement method. However, it is difficult for a single geostationary satellite to observe the global CTH, so joint observation by multiple satellites is imperative. We used both active and passive sensors to evaluate the reliability of joint observation of geostationary satellites, which includes consistency and accuracy. We analyzed the error of CTH of FY-4A and HIMAWARI-8 and the consistency between the two satellites and conducted research on the problem of missing measurement (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) has CTH data, but FY-4A/HIMAWARI-8 does not) of the two satellites. The results show that FY-4A and HIMAWARI-8 have good consistency and can be jointly observed, but the measurement of CTH of FY-4A and HIMAWARI-8 has large errors, and the error of FY-4A is greater than that of HIMAWIRI-8. The error of CTH is affected by the CTH, cloud optical thickness (COT) and cloud type, and the consistency between the two satellites is mainly affected by the cloud type. FY-4A and HIMAWARI-8 have the problem of missing measurement. The missing rate of HIMAWARI-8 is greater than that of FY-4A, and the missing rate is not affected by the CTH, COT and surface type. Therefore, although FY-4A and HIMAWARI-8 have good consistency, the error of CTH and the problem of missing measurement still limit the reliability of their joint observation.

Meteorological satellite

Cloud top

10.3390/rs13193851

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Citations (10)

Nickel–chromium alloy piezoresistive pressure sensor using eutectic bonding

Micro & Nano Letters (2012)

Lidong Du Zhanzheng Zhao Xiao Li Zhen Fang Qing Tian

A nickel–chromium (Ni–Cr) piezoresistive pressure sensor is presented, which has the advantages of low-cost and easy fabrication processes. In the designed sensor, Ni–Cr alloy (80:20 wt%), which can be fabricated using simple processes, is used as the strain-detecting material with a smaller but acceptable gauge factor. Eutectic-bonding technology, based on silver–tin (Ag–Sn) alloy, which contains 3.5 wt% Ag and has 20 µm thickness, is used as an alternative and easy bonding choice to complete the vacuum package. Normally, Ag–Sn alloy is mostly obtained by the electrochemical deposition method. However, here the Ag–Sn solder film is directly used as a bonding material. It reduces the fabrication difficulty of eutectic bonding of the proposed pressure sensor. By studying the processes of annealing of Ni–Cr fabrication and eutectic bonding with Ag–Sn, the authors complete the alloy piezoresistive atmosphere pressure sensor. Bonding quality is evaluated by inspection through the deflection of a diaphragm of silicon with more than 95% of the area successfully bonded. The pressure–voltage characteristic test results suggest a precision within 0.3% in square fitting. The temperature coefficient offset is 620 ppm/(°C free space optic (FSO)).

Eutectic bonding

Piezoresistive effect

10.1049/mnl.2012.0552

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Citations (5)