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Evaluation of the Impact of observations on Blended Sea Surface Winds in a Two-Dimensional Variational Scheme Using Degrees of Freedom

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Journal of meteorological Research 2017年第6期31卷 1123-1132页

作者： Ting WANG Jie XIANG Jianfang FEI Yi WANG Chunxia LIU Yuanxiang LI Institute of Meteorology and Oceanography National University of Defense TechnologyNanjing 211101 key laboratory of Mesoscale Severe Weather of Ministry of Education Nanjing UniversityNanjing 210093 Guangdong Institute of Tropical and Marine Meteorology of China meteorological Administration Guangzhou 510080 School of Aeronautics andAstronautics Shanghai Jiao Tong UniversityShanghai 200240

This paper presents an evaluation of the observational impacts on blended sea surface winds from a two- dimensional variational data assimilation （2D-Var） scheme. We begin by briefly introducing the analysis sensitivity with respect to observations in variational data assimilation systems and its relationship with the degrees of freedom for signal （DFS）, and then the DFS concept is applied to the 2D-Var sea surface wind blending scheme. Two meth- ods, a priori and a posteriori, are used to estimate the DFS of the zonal （u） and meridional （v） components of winds in the 2D-Var blending scheme. The a posteriori method can obtain almost the same results as the a priori method. Because only by-products of the blending scheme are used for the a posteriori method, the computation time is re- duced significantly. The magnitude of the DFS is critically related to the observational and background error statistics. Changing the observational and background error variances can affect the DFS value. Because the observation error variances are assumed to be uniform, the observational influence at each observational location is related to the background error variance, and the observations located at the place where there are larger background error variances have larger influences. The average observational influence of u and v with respect to the analysis is about 40%, implying that the background influence with respect to the analysis is about 60%.

关键词： sea surface wind blending sensitivity observational influence degrees of freedom for signal

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EVALUATION OF CORRECTIONS ON TURBULENT FLUXES OBTAINED BY EDDY COVARIANCE METHOD IN HIGH WINDS

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Journal of Tropical Meteorology 2018年第2期24卷 176-184页

作者： BI Xue-yan WEN Bin ZHAO Zhong-kuo HUANG Jian LIU Chun-xia HUANG Hui-jun MAO Wei-kang WEN Guan-huan Guangzhou Institute of Tropical and Marine Meteorology China Meteorological AdministrationGuangzhou 5 I0080 China Zhanjiang meteorological Bureau Zhanjiang 524000 China

This paper investigates processing of fast-response data and corrections of turbulent fluxes obtained by using eddy covariance method based on data collected at an offshore observation tower during three Cold-intrusion(CI)events in the South China Sea in 2010. This study presents the data processing procedure in detail and compares frictional velocities(u*), sensible heat fluxes(H) and latent heat fluxes(LE) yielded by using different averaging periods and different coordinate rotation methods; evaluates the sonic temperature correction for sensible heat flux and the Webb correction for latent heat flux as a function of 10 m wind speed(u10) during the CIs. The results show(1) that the different averaging periods of 30 min and 10 min cause biases of u*(H, LE) within 5%(15%, 62%). The values of u*(H,LE) averaged from 30 mins are mostly larger than those averaged from 10 mins. We suggest that the averaging period of 10 min is not sufficiently long to capture all scale eddies and recommend 30 min averaging period in calculating turbulent fluxes using eddy covariance method during CIs;(2) that the values of u*(H, LE) obtained from double rotation(DR2) and those obtained from planar fit rotation(PF) have good agreements and correlation coefficients between them are larger than 0.99. Because PF method requires unchanged environment and it is easier to apply DR2 method, we suggest DR2 coordinate rotation method in processing fast-response data; and(3) that the median values of frictional velocity(sensible heat flux and latent heat flux) binned according to 2 m s^(-1) intervals of u_(10) increase(decrease,increase) by less than 9%(4%, 10%) by Coriolis corrections(sonic temperature corrections, Webb corrections), which decreases(decreases, increases) with increasing u10 when u10 are 5-17 m s^(-1).

关键词： processing of fast-response data averaging period coordinate rotation Coriolis correction sonic temperature correction Webb correction

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ASSESSMENT OF THE POEM2 MODEL FOR SIMULATING TROPICAL INTRASEASONAL OSCILLATION

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Journal of Tropical Meteorology 2018年第3期24卷 323-333页

作者： WANG Kuo MA Hao LI Juan GU Bo-hui WU Hao Zhejiang Climate Center Hangzhou 310017 China College of Atmospheric Sciences Lanzhou UniversityLanzhou 730000 China International Pacific Research Center University of Hawaii at ManoaHonolulu 96822 USA key laboratory of meteorological Disaster Ministry of Education(KLME)/Joint International Research Laboratory of Climate and Environment Change(ILCEC)/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters(CIC-FEMD)Earth System Modeling CenterNanjing University of Information Science and TechnologyNanjing 210044 China Hu'nan Climate Center Changsha 410118 China

The intraseasonal oscillation(ISO)of the atmosphere is closely related to weather and climate systems and is also an important aspect of extended numerical weather forecast *** phenomenon is significant in tropical regions and is one of the key indices for assessing the simulation capability of a climate *** better evaluate numerical model simulations of the tropical ISO using the 10-year historic data calculated by the POEM2 climate system model developed by the University of Hawaii in the U.S.,we utilized the methods of variance and power spectral analysis to compare and assess the simulation ability of this model for the ISO in tropical *** results showed that the simulated variance results for the 850 h Pa zonal wind and outgoing long-wave radiation(OLR)by POEM2 are overall consistent with the observed distribution pattern,and the simulated variance is relatively larger than the observed in the North Indian Ocean and West Pacific *** respect to the summer model,the winter model can better simulate the eastward propagation motion of the Madden-Julian oscillation(MJO)and the 850 h Pa zonal *** comparison,the summer model can better simulate the northward propagation motion of MJO and atmospheric precipitation than the winter *** eastward propagation speed of the simulated MJO signal is faster in the model than in the observation,and the high frequency region for the power spectra of meteorological element anomalies are concentrated in wavenumber 2-3 in the simulation and in wavenumber 1-2 in the *** multivariate combined empirical orthogonal function(EOF)results showed that this model can simulate the relationship between high-low level wind distributions and precipitation over the East Indian Ocean and the West Pacific,but the simulated signal is weaker than the *** lagging correlation of time coefficients between the first two EOFs from observation and simulation shows a similar ***,these resu

关键词： model diagnostics power spectrum analysis POEM2 model MJO

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Evaluation of the performance of linearly frequency modulated signals generated by heterodyning two free-running laser diodes

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Optoelectronics Letters 2021年第5期17卷 266-270页

作者： CHANG Meng-xu JIANG Li-zhong LIU Qing-bo XU Jing CHEN Yang Shanghai key laboratory of Multidimensional Information processing East China Normal UniversityShanghai200241China School of Artificial Intelligence and Automation Huazhong University of Science and TechnologyWuhan430074China Shanghai Radio Equipment Research Institute Shanghai200090China

A method to evaluate the influence of the laser linewidth on the linearly frequency-modulated(LFM)signals generated by heterodyning two free-running laser diodes(LDs)is *** Pearson correlation coefficient between the instantaneous frequency of the generated LFM signal and that of an ideal LFM signal is introduced to quantify the quality of the generated LFM *** closed-form solution of the correlation coefficient is given,which shows that the correlation coefficient is determined by the ratio of the LFM signal bandwidth to the square root of the total linewidth of the two LDs when the observation interval is *** results are also given,which proves the correctness of the theoretical results.

关键词： LFM Pearson Evaluation of the performance of linearly frequency modulated signals generated by heterodyning two free-running laser diodes

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Quasi-biennial oscillation signal detected in the stratospheric zonal wind at 55–65°N

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Atmospheric and Oceanic Science Letters 2016年第3期9卷 147-152页

作者： ZHANG Yu ZHOU Li-Bo State key laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry Institute of Atmospheric PhysicsChinese Academy of SciencesBeijingChina Department of Lower Atmosphere observation and Research Institute of Atmospheric PhysicsChinese Academy of SciencesBeijingChina College of Earth Science University of the Chinese Academy of SciencesBeijingChina

To investigate the impacts of the quasi-biennial oscillation （QBO） on high-latitude circulation and the Arctic vortex, stratospheric zonal wind at 55-65°N is analyzed. The seasonal cycle, solar cycle, and linear trend in the zonal wind at these latitudes are analyzed and removed, and the QBO signal is retrieved from the monthly zonal wind for the period 1979-2014. The zonal wind has a strong decreasing trend in winter, with a maximum decrease （less than -0.35 m s-1 yr-1） occurring within 70-100°E. The zonal wind has an in-phase response of 1.6 m s-1 to the solar cycle, with a maximum within 100-140°E. A clear QBO signal is detected in the zonal wind during the period 1979-2014, with an amplitude of 2.5 m s-1 and a period of 30 months. The latitudinal distribution of the QBO signal is inhomogeneous, with a maximum within 120-180°E and a minimum within 25-45°E.

关键词： Quasi-Biennial Oscillation zonal wind Arctic vortex

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Spectral evolution of NIR luminescence in a Yb^(3+)-doped photonic crystal fiber prepared by non-chemical vapor deposition

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Chinese Optics Letters 2013年第6期11卷 46-49页

作者：王超周桂耀韩颖王伟夏长明候蓝田 College of Information Science and Engineering Yanshan University key laboratory for Special Fiber and Fiber Sensor of Hebei Province Yanshan University laboratory of Nanophotonic Fanctional Materials and Devices South China Normal University State key laboratory of Metastable Materials Science and Technology Yanshan University laboratory of Nanophotonic Fanctional Materials and Devices South China Normal UniversityGuangzhou 510006China

Silica-based yb3＋-doped glass is prepared by non-chemical vapor deposition. The drawn photonic crystal fiber （PCF） has a strong absorption at 976 nm and emission wavelength of approximately 1 037 nm. The intensity and spectral lineshape of the near infrared （NIR） luminescence of the Yb3＋-doped PCF are recorded and discussed in terms of excitation power, excitation wavelength, fiber length, and Yba＋ ion concentration. The emission intensifies as the excitation power and Yb3＋ ion concentration increase. The intensity of the shorter wavelength side of the luminescence spectrum decreases as the length of the PCF increases.

关键词： Spectral evolution of NIR luminescence in a Yb PCF doped photonic crystal fiber prepared by non-chemical vapor deposition NIR

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Study on the Deconvolution Method and processing Flow of Airgun Source Data

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Earthquake Research in China 2016年第3期30卷 394-404页

作者： Zhai Qiushi Yao Huajian Wang Baoshan School of Earth and Space Sciences University of Science and Technology of China Hefei 230026 China Mengcheng National Geophysical Observatory Bozhou 233527 Anhui China key laboratory of Seismic observation and Geophysical Imaging Institute of Geophysics CEA Beijlng 100081 China

With its high repeatability,the airgun source has been used to monitor the temporal variations of subsurface structures. However,under different working conditions,there will be subtle differences in the airgun source signals. To some extent,deconvolution can eliminate changes of the recorded signals due to source variations. Generally speaking,in order to remove the airgun source wavelet signal and obtain the Green's functions between the airgun source and stations,we need to select an appropriate method to perform the deconvolution process for seismic waveform data. Frequency domain water level deconvolution and time domain iterative deconvolution are two kinds of deconvolution methods widely used in the field of receiver functions,etc. We use the Binchuan( in Yunnan Province,China) airgun data as an example to compare the performance of these two deconvolution methods in airgun source data processing. The results indicate that frequency domain water level deconvolution is better in terms of computational efficiency;time domain iterative deconvolution is better in terms of the signal-to-noise ratio( SNR),and the initial motion of P-wave is also clearer. We further discuss the sequence issue of deconvolution and stack for multiple-shot airgun data processing. Finally,we propose a general processing flow for the airgun source data to extract the Green 's functions between the airgun source and stations.

关键词： Artificial source Airgun source Deconvolution Data processing flow

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Radial velocity of ocean surface current estimated from SAR Doppler frequency measurements—a case study of Kuroshio in the East China Sea

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Acta Oceanologica Sinica 2021年第12期40卷 135-147页

作者： Lihua Wang Benwei Shi Yunxuan Zhou Hui Sheng Yanghua Gao Li Fan Ziheng Yang Department of Geography and Spatial Information Techniques/Center for Land and Marine Spatial Utilization and Governance Research Ningbo UniversityNingbo 315211China State key laboratory of Estuarine and Coastal Research East China Normal UniversityShanghai 200062China Chongqing Institute of meteorological Sciences Chongqing 401147China College of Resources and Environment Chengdu University of Information TechnologyChengdu 610225China

Ocean currents are a key element in ocean processes and in meteorology,affecting material transport and modulating climate change *** Doppler frequency shift information of the synthetic aperture radar(SAR)echo signal can reflect the dynamic characteristics of the sea surface,and has become an essential sea surface dynamic remote sensing *** have verified that the instantaneous Doppler frequency shift can realize the SAR detection of the sea surface ***,the validation of SAR-derived ocean current data and a thorough analysis of the errors associated with them remain *** this study,we derive high spatial resolution flow measurements for the Kuroshio in the East China Sea from SAR data using a theoretical model of shifts in Doppler frequency driven by ocean surface *** ocean multi observation(MOB)products and global surface Lagrangian drifter(GLD)data are used to validate the Kuroshio flow retrieved from the SAR *** show that the central flow velocity for the Kuroshio derived from the SAR is 0.4–1.5 m/*** error distribution between SAR ocean currents and MOB products is an approximate standard normal distribution,with the 90%confidence interval concentrated between–0.1 m/s and 0.1 m/*** analysis of SAR ocean current and GLD products,the correlation coefficient is 0.803,which shows to be significant at a confidence level of 99%.The cross-validation of different ocean current dataset illustrate that the SAR radial current captures the positions and dynamics of the Kuroshio central flow and the Kuroshio Counter Current,and has the capability to monitor current velocity over a wide range of values.

关键词： Doppler frequency radial velocity ocean current SAR Kuroshio

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Urdnet:A Cryo-EM Particle Automatic Picking Method

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Computers, Materials & Continua 2022年第7期72卷 1593-1610页

作者： Jianquan Ouyang Yue Zhang Kun Fang Tianming Liu Xiangyu Pan School of Computer Science&School of Cyberspace Science Xiangtan UniversityXiangtan411105China Hunan meteorological Information Center Hunan Meteorological BureauChangshaHunan410118China Department of Computer Science The University of GeorgiaAthensGeorgiaUSA

Cryo-Electron Microscopy(Cryo-EM)images are characterized by the low signal-to-noise ratio,low contrast,serious background noise,more impurities,less data,difficult data labeling,simpler image semantics,and relatively fixed structure,while U-Net obtains low resolution when downsampling rate information to complete object category recognition,obtains highresolution information during upsampling to complete precise segmentation and positioning,fills in the underlying information through skip connection to improve the accuracy of image segmentation,and has advantages in biological image processing like Cryo-EM *** article proposes A U-Net based residual intensive neural network(Urdnet),which combines point-level and pixel-level tags,used to accurately and automatically locate particles from cryo-electron microscopy images,and solve the bottleneck that cryo-EM Single-particle biologicalmacromolecule reconstruction requires tens of thousands of automatically picked *** 80S ribosome,HCN1 channel and TcdA1 toxin subunits,and other public protein datasets have been trained and tested on *** experimental results show that Urdnet could reach the same excellent particle picking performances as the mainstream methods of RELION,DeepPicker,and acquire the 3Dstructure of picked particleswith higher resolution.

关键词： Deep learning convolutional neural network particle picking cryo-electron microscopy single-particle reconstruction

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A New Statistical Downscaling Scheme for Predicting Winter Precipitation in China

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Atmospheric and Oceanic Science Letters 2013年第5期6卷 332-336页

作者： LIU Ying FAN Ke YAN Yu-Ping laboratory for Climate Studies National Climate Center China Meteorological Administration Institute of Atmospheric Physics Chinese Academy of Sciences Institute of Atmospheric Physics Chinese Academy of Sciences

An effective statistical downscaling scheme was developed on the basis of singular value decomposition to predict boreal winter(December-January-February)precipitation over *** variable geopotential height at 500 hPa(GH5)over East Asia,which was obtained from National Centers for Environmental Prediction’s Coupled Forecast System(NCEP CFS),was used as one predictor for the *** preceding sea ice concentration(SIC)signal obtained from observed data over high latitudes of the Northern Hemisphere was chosen as an additional *** downscaling scheme showed significantly improvement in predictability over the original CFS general circulation model(GCM)output in cross *** multi-year average spatial anomaly correlation coefficient increased from–0.03 to 0.31,and the downscaling temporal root-mean-square-error(RMSE)decreased significantly over that of the original CFS GCM for most China ***,large precipitation anomaly centers were reproduced with greater accuracy in the downscaling scheme than those in the original CFS GCM,and the anomaly correlation coefficient between the observation and downscaling results reached～0.6 in the winter of 2008.

关键词： statistical downscaling winter precipitation China Coupled Forecast System

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