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Experimental Observation of Cumulative Second-Harmonic Generation of Circumferential Guided Wave Propagation in a Circular Tube 被引量:2
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作者 邓明晰 高广健 李明亮 《Chinese Physics Letters》 SCIE CAS CSCD 2015年第12期88-91,共4页
The experimental observation of cumulative second-harmonic generation of the primary circumferential guided wave propagation is reported. A pair of wedge transducers is used to generate the primary circumferential gui... The experimental observation of cumulative second-harmonic generation of the primary circumferential guided wave propagation is reported. A pair of wedge transducers is used to generate the primary circumferential guided wave desired and to detect its fundamental-frequency and second-harmonic amplitudes on the outside surface of the circular tube. The amplitudes of the fundamental waves and the second harmonics of the circumferential guided wave propagation are measured for different separations between the two wedge transducers. At the driving frequency where the primary and the double-frequency circumferential guided waves have the same linear phase velocities, the clear second-harmonic signals can be observed. The quantitative relationships between the second-harmonic amplitudes and circumferential angle are analyzed. It is experimentally verified that the second harmonics of primary circumferential guided waves do have a cumulative growth effect with the circumferential angle. 展开更多
关键词 LENGTH experimental observation of Cumulative Second-Harmonic Generation of Circumferential Guided Wave Propagation in a Circular Tube
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Experimental Observation of Cubic C_3N_4 Compound in Carbon Nitride Thin Films 被引量:1
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作者 Furen XIAO Dongli YU +2 位作者 Yongjun TIAN Julong HE Dongchun LI and Wenkui WANG(College of Materials Science and Chemical Engineering, Yanshan University, Qinhuangdao 066004, China To whom correspondence should be addressed E-mail: fhcl@ysu.edu.cn ) 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 1999年第5期480-482,共3页
Cubic C3N4 compound in the C-N thin films on Si and NaCl substrates was prepared by ion beam sputtering of a pure graphite target with discharge gas of pure N2. X-ray photoelectron spectroscopy indicated that nitrogen... Cubic C3N4 compound in the C-N thin films on Si and NaCl substrates was prepared by ion beam sputtering of a pure graphite target with discharge gas of pure N2. X-ray photoelectron spectroscopy indicated that nitrogen atoms combined with sp2- and sp3- coordinated C atoms in the film, respectively. X-ray diffraction, selected area electron diffraction and high-resolution electron microscopy were used to identify the cubic C3N4 phase. The results reconfirm the ab initio calculations on metastable structure in C-N compounds 展开更多
关键词 Thin experimental observation of Cubic C3N4 Compound in Carbon Nitride Thin Films Rev
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Experimental Observation of the Ground-State Geometric Phase of Three-Spin XY Model
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作者 周辉 李兆凯 +3 位作者 王恒岩 陈宏伟 彭新华 杜江峰 《Chinese Physics Letters》 SCIE CAS CSCD 2016年第6期1-5,共5页
The geometric phase has become a fundamental concept in many fields of physics since it was revealed. Recently, the study of the geometric phase has attracted considerable attention in the context of quantum phase tra... The geometric phase has become a fundamental concept in many fields of physics since it was revealed. Recently, the study of the geometric phase has attracted considerable attention in the context of quantum phase transition, where the ground state properties of the system experience a dramatic change induced by a variation of an external parameter. In this work, we experimentally measure the ground-state geometric phase of the three-spin XY model by utilizing the nuclear magnetic resonance technique. The experimental results indicate that the geometric phase could be used as a fingerprint of the ground-state quantum phase transition of many-body systems. 展开更多
关键词 of on it in experimental observation of the Ground-State Geometric Phase of Three-Spin XY Model is been that
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Experimental Observation of Phase Transition in Sb203 under High Pressure
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作者 耿爱辉 曹立华 +2 位作者 马艳梅 崔启良 万春明 《Chinese Physics Letters》 SCIE CAS CSCD 2016年第9期112-115,共4页
The in situ high-pressure behavior of the semiconductor antimony trioxide (Sb2O3) iS investigated by the Raman spectroscopy techniques and angle-dispersive synchrotron x-ray powder diffractfon in a diamond anvil cel... The in situ high-pressure behavior of the semiconductor antimony trioxide (Sb2O3) iS investigated by the Raman spectroscopy techniques and angle-dispersive synchrotron x-ray powder diffractfon in a diamond anvil cell up to 31.5 and 30.7 GPa, respectively. New peaks observed in the external lattice mode range in the Raman spectra at 13.5 GPa suggest that the structural phase transition occurs. The group mode (140 cm^-1) in Sb2O3 exhibits anomalous pressure dependence; that is, the frequency decreases gradually with the increasing pressure. High pressure synchrotron x-ray diffraction measurements at room temperature reveal that the transition from the orthorhombic structure to high-pressure new phase occurs at about 14.2 GPa, corresponding to the softening of the group optic mode (140cm^-1). 展开更多
关键词 of on AS experimental observation of Phase Transition in Sb203 under High Pressure SB in
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Experimental Observation of Bright and Dark Solitons Mode-Locked with Zirconia-Based Erbium-Doped Fiber Laser
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作者 A.M.Markom S.J.Tan +4 位作者 H.Haris M.C.Paul A.Dhar S.Das S.W.Harun 《Chinese Physics Letters》 SCIE CAS CSCD 2018年第2期25-28,共4页
We demonstrate the generation of dark and bright solitons with our homemade zirconia-based erbium-doped fiber and graphene oxide(GO) saturable absorber in anomalous dispersion region.The GO is fabricated using an ab... We demonstrate the generation of dark and bright solitons with our homemade zirconia-based erbium-doped fiber and graphene oxide(GO) saturable absorber in anomalous dispersion region.The GO is fabricated using an abridged Hummer's method,which is combined with polyethylene oxide to produce a composite film.The film is sandwiched between two optical ferrules and embedded in the laser cavity to enhance its birefringence and nonlinearity.The self-starting bright soliton is easily generated at pump power of 78 mW with the whole length cavity of 14.7 m.The laser produces the bright pulse train with repetition rate,pulse width,pulse energy and central wavelength being 13.9 MHz,0.6 ps,2.74 p J and 1577.46 nm,respectively.Then,by adding the 10 m of single mode fiber into the laser cavity,dark soliton pulse is produced.For the formation of dark pulse train,the measured repetition rate,pulse width,pulse energy and central wavelength are 8.3 MHz,20 ns and 4.98 p J and1596.82 nm,respectively.Both pulses operate in the anomalous region. 展开更多
关键词 Zr EDF experimental observation of Bright and Dark Solitons Mode-Locked with Zirconia-Based Erbium-Doped Fiber Laser
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Experimental Observation of Spin-Exchange in Ultracold Fermi Gases
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作者 彭鹏 黄良辉 +3 位作者 李东豪 孟增明 王鹏军 张靖 《Chinese Physics Letters》 SCIE CAS CSCD 2018年第3期18-21,共4页
We experimentally study the spin exchange collision in ultracold 40K Fermi gases. The quadratic Zeeman shift, trap potential and temperature of atomic cloud will influence on the spin changing dynamics. Dependences of... We experimentally study the spin exchange collision in ultracold 40K Fermi gases. The quadratic Zeeman shift, trap potential and temperature of atomic cloud will influence on the spin changing dynamics. Dependences of the spin components populations on the external bias magnetic field, the optical trap depth and the temperature of atomic cloud are experimentally investigated. The spin exchange from the initial states to the final state are observed for different initial states. This work shows an interesting process of reaching equilibrium by redistribution among the spin states with the spin exchange collision in an ultracold large-spin Fermi gas. 展开更多
关键词 experimental observation of Spin-Exchange in Ultracold Fermi Gases
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Experimental observation of rat's early-stage fracture healing with different kinds of nerve injuries
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作者 马昕 《外科研究与新技术》 2005年第3期182-182,共1页
To investigate the impact of different kinds of nerve injuries of early-stage fracture healing.Methods Three groups of rats were included in the experiment among which group 1 was inflicted with femoral fracture and T... To investigate the impact of different kinds of nerve injuries of early-stage fracture healing.Methods Three groups of rats were included in the experiment among which group 1 was inflicted with femoral fracture and T10 spinal cord transsection (SCI),group 2 was inflicted with femoral and peripheral nerve resection (PNR),and group 3 with simple femoral fracture as control group.Two weeks after operation the femoral bones were collected for X-ray checking and 2 more weeks later X-ray checking was performed again followed by pathomorphologic exams.Results X-ray result showed no massive calluses in the bones in the 2nd week postoperatively,while in the 4th week,callus appeared with larger size in group 3 than that of group 1 and with smaller size than that of group 2.It was the same with the result of pathomorphologic examining.Cortical bone bridges between fracture point and osteiod were also found in group 2 and there were less normal blood vessels and worse bone remodeling than that of group 3.There were relatively immature calluses with more fibroblast-like cells and disordered bone structure in group 2.Group 3 showed normal healing process and callus structure.Conclusion Early-stage bone fracture healing can be influenced significantly by different kinds of nerve injuries.6 refs,6 figs. 展开更多
关键词 experimental observation of rat’s early-stage fracture healing with different kinds of nerve injuries
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Experimental observation of Fano-like resonance in a whispering-gallery-mode microresonator in aqueous environment 被引量:5
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作者 YAN-LEI SHANG MING-YONG YE XIU-MIN LIN 《Photonics Research》 SCIE EI 2017年第2期119-123,共5页
We report on the transmission spectra of a sausage-like microresonator(SLM)in aqueous environment,where a fiber taper is used as a light coupler.The transmission spectra show an interesting dependence on the coupling ... We report on the transmission spectra of a sausage-like microresonator(SLM)in aqueous environment,where a fiber taper is used as a light coupler.The transmission spectra show an interesting dependence on the coupling position between the SLM and the fiber taper.When the SLM is moved along the fiber taper,the line shape can evolve periodically among symmetric dips,asymmetric Fano-like resonance line shapes,and symmetric peaks.A coupled-mode theory with feedback is developed to explain the observation.The observation of Fano-like resonance in aqueous environment holds great potential in biochemical sensing. 展开更多
关键词 mode experimental observation of Fano-like resonance in a whispering-gallery-mode microresonator in aqueous environment
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Experimental observation of surface phonon absorption in Zn fine particles coated with ZnO
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作者 Xu, JF Zhang, JR Du, YW 《Chinese Science Bulletin》 SCIE EI CAS 1997年第1期85-86,共2页
FINE particles have attracted much attention in the past few years due to their unique physical and chemical properties. For gas-evaporated fine metallic particles, a thin oxide layer is usually formed on their surfac... FINE particles have attracted much attention in the past few years due to their unique physical and chemical properties. For gas-evaporated fine metallic particles, a thin oxide layer is usually formed on their surface. According to Ruppin’s prediction, a dielectric coating on metallic particles should have a series of surface modes between ω<sub>TO</sub> and ω<sub>LO</sub>, the long-wavelength transverse and longitudinal optical phonon frequencies of the dielectric. The frequency of 展开更多
关键词 experimental observation of surface phonon absorption in Zn fine particles coated with ZnO mode
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Experimental Studies of Icing Resistanceand Observation of Icing Sleet in Heavy Icing Areaat Huangmaogeng Icing Observation Station
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作者 LiuYu XiongHaixing ChangZhineng 《Electricity》 1999年第4期35-37,共3页
关键词 experimental Studies of Icing Resistanceand observation of Icing Sleet in Heavy Icing Areaat Huangmaogeng Icing observation Station
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An Experimental Study on the Drag Property of High-Temperature Particles Falling into Cold Liquid Pool 被引量:1
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作者 李小燕 匡波 +1 位作者 杨燕华 徐济鋆 《Journal of Shanghai Jiaotong university(Science)》 EI 2003年第1期58-62,共5页
This experiment is to study the special resistant induced by the high-speed evaporation surrounding themoving high-temperature particles. An observable equipment was designed, in which the first 11 experiments wereper... This experiment is to study the special resistant induced by the high-speed evaporation surrounding themoving high-temperature particles. An observable equipment was designed, in which the first 11 experiments wereperformed by pouring one or several Zirconia spheres with various high-temperature and a diameter of 3~ 10 mminto a water pool. The particles falling-down speeds were recorded by high-speed photographic instrumentation,and pressures and water temperatures were measured. A comparison between the experiments with cold and hotspheres respectively, employing three different sphere types each, was presented. The experimental data, com-pared with the theory of the evaporation drag model, are nearly identical. 展开更多
关键词 vapor explosion high temperature particles contact with low temperature liquid evaporation drag model observable experiment equipment
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Observation system simulation experiments using an ensemble-based method in the northeastern South China Sea 被引量:1
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作者 GENG Wu CHENG Feng +9 位作者 XIE Qiang ZOU Xiaoli HE Weihong WANG Zhaozheng SHU Yeqiang CHEN Gengxin LIU Danian YE Dong WANG Ruiwen LIU Chuanyu 《Journal of Oceanology and Limnology》 SCIE CAS CSCD 2020年第6期1729-1745,共17页
An ensemble-based method for the observation system simulation experiment(OSSE)is employed to design optimal observation stations and assess the present observation stations in the northeastern South China Sea(SCS).We... An ensemble-based method for the observation system simulation experiment(OSSE)is employed to design optimal observation stations and assess the present observation stations in the northeastern South China Sea(SCS).We employed the 20-year(1992-2012)sea surface height(SSH)data to design an array to monitor the intraseasonal to interannual variability.The results show that the most key region was found located at the northwest of Luzon Island(LI)where the energetic Luzon cyclonic gyre(LCG)occurs;other key regions include the edge of the LCG,the northwest of the Luzon Strait(LS),and the southwest of Taiwan,China.By contrast,we found that the present observation stations might oversample at the northwest of the LS and undersample at the northwest of LI.In addition,the optimal stations perform better in a larger area than the present stations.In vertical direction,the key layer is located within the upper 200-m depth,of which the surface and subsurface layers are most valuable to the observing system. 展开更多
关键词 ASSIMILATION observation system simulation experiment(OSSE) ENSEMBLE South China Sea(SCS) Kalman filter
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Objective array design for three-dimensional temperature and salinity observation:Application to the South China Sea
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作者 Mengxue Qu Zexun Wei +2 位作者 Yanfeng Wang Yonggang Wang Tengfei Xu 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2022年第7期65-77,共13页
In this study,a moored array optimization tool(MAOT)was developed and applied to the South China Sea(SCS)with a focus on three-dimensional temperature and salinity observations.Application of the MAOT involves two ste... In this study,a moored array optimization tool(MAOT)was developed and applied to the South China Sea(SCS)with a focus on three-dimensional temperature and salinity observations.Application of the MAOT involves two steps:(1)deriving a set of optimal arrays that are independent of each other for different variables at different depths based on an empirical orthogonal function method,and(2)consolidating these arrays using a K-center clustering algorithm.Compared with the assumed initial array consisting of 17 mooring sites located on a 3°×3°horizontal grid,the consolidated array improved the observing ability for three-dimensional temperature and salinity in the SCS with optimization efficiencies of 19.03%and 21.38%,respectively.Experiments with an increased number of moored sites showed that the most cost-effective option is a total of 20 moorings,improving the observing ability with optimization efficiencies up to 26.54%for temperature and 27.25%for salinity.The design of an objective array relies on the ocean phenomenon of interest and its spatial and temporal scales.In this study,we focus on basin-scale variations in temperature and salinity in the SCS,and thus our consolidated array may not well resolve mesoscale processes.The MAOT can be extended to include other variables and multi-scale variability and can be applied to other regions. 展开更多
关键词 optimal array design observation system simulation experiment South China Sea empirical orthogonal function K-center clustering
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An Economical Approach to Four-dimensional Variational Data Assimilation 被引量:26
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作者 王斌 刘娟娟 +5 位作者 王曙东 成巍 刘娟 刘成思 Qingnong XIAO Ying-Hwa KUO 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2010年第4期715-727,共13页
Four-dimensional variational data assimilation (4DVar) is one of the most promising methods to provide optimal analysis for numerical weather prediction (NWP). Five national NWP centers in the world have successfu... Four-dimensional variational data assimilation (4DVar) is one of the most promising methods to provide optimal analysis for numerical weather prediction (NWP). Five national NWP centers in the world have successfully applied 4DVar methods in their global NWPs, thanks to the increment method and adjoint technique. However, the application of 4DVar is still limited by the computer resources available at many NWP centers and research institutes. It is essential, therefore, to further reduce the computational cost of 4DVar. Here, an economical approach to implement 4DVar is proposed, using the technique of dimension- reduced projection (DRP), which is called "DRP-4DVar." The proposed approach is based on dimension reduction using an ensemble of historical samples to define a subspace. It directly obtains an optimal solution in the reduced space by fitting observations with historical time series generated by the model to form consistent forecast states, and therefore does not require implementation of the adjoint of tangent linear approximation. To evaluate the performance of the DRP-4DVar on assimilating different types of mesoscale observations, some observing system simulation experiments are conducted using MM5 and a comparison is made between adjoint-based 4DVar and DRP-4DVar using a 6-hour assimilation window. 展开更多
关键词 4DVAR ADJOINT dimension reduction historical sample observing system simulation experiment
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The REMO Ocean Data Assimilation System into HYCOM(RODAS_H):General Description and Preliminary Results 被引量:1
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作者 Clemente Augusto Souza TANAJURA Alex Novaes SANTANA +3 位作者 Davi MIGNAC Leonardo Nascimento LIMA Konstantin BELYAEV XIE Ji-Ping 《Atmospheric and Oceanic Science Letters》 CSCD 2014年第5期464-470,共7页
The first version of the Brazilian Oceano- graphic Modeling and Observation Network (REMO) ocean data assimilation system into the Hybrid Coordi- nate Ocean Model (HYCOM) (RODAS H) has recently been constructed ... The first version of the Brazilian Oceano- graphic Modeling and Observation Network (REMO) ocean data assimilation system into the Hybrid Coordi- nate Ocean Model (HYCOM) (RODAS H) has recently been constructed for research and operational purposes. The system is based on a multivariate Ensemble Optimal Interpolation (EnOI) scheme and considers the high fre- quency variability of the model error co-variance matrix. The EnOl can assimilate sea surface temperature (SST), satellite along-track and gridded sea level anomalies (SLA), and vertical profiles of temperature (T) and salinity (S) from Argo. The first observing system experiment was carried out over the Atlantic Ocean (78°S-50°N, 100°W-20°E) with HYCOM forced with atmospheric reanalysis from 1 January to 30 June 2010. Five integra- tions were performed, including the control run without assimilation. In the other four, different observations were assimilated: SST only (A SST); Argo T-S profiles only (AArgo); along-track SLA only (A_SLA); and all data employed in the previous runs (A_All). The A_SST, A_Argo, and A_SLA runs were very effective in improv- ing the representation of the assimilated variables, but they had relatively little impact on the variables that were not assimilated. In particular, only the assimilation of S was able to reduce the deviation of S with respect to ob- servations. Overall, the A_All run produced a good analy- sis by reducing the deviation of SST, T, and S with respect to the control run by 39%, 18%, and 30%, respectively, and by increasing the correlation of SLA by 81%. 展开更多
关键词 ocean data assimilation ensemble optimalinterpolation observing system experiment HYCOM Atlantic Ocean
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Observation on Experimental Infection of Periodic Brugia Malayi in Man.
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《Chinese Medical Journal》 SCIE CAS CSCD 1995年第5期28-28,共1页
We described the results of ten-year obsevations on the clinical manifestarions,pathology,immunity to filariasis and aetiological bioloay of filariae in three volunteers(first author and his family members) who were... We described the results of ten-year obsevations on the clinical manifestarions,pathology,immunity to filariasis and aetiological bioloay of filariae in three volunteers(first author and his family members) who were inoculated experimentally with infective larvae of periodic Brugia malayi in 1981 and wthout use of any anti-filariasis drugs. 展开更多
关键词 observation on experimental Infection of Periodic Brugia Malayi in Man
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A Review of Advances in Lightning Observations during the Past Decade in Guangdong, China 被引量:8
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作者 ZHANG Yijun LU Weitao +7 位作者 CHEN Shaodong ZHENG Dong ZHANG Yang YAN Xu CHEN Liiwen DONG Wansheng DAN Jianru PAN Hanbo 《Journal of Meteorological Research》 SCIE CSCD 2016年第5期800-819,共20页
This paper reviews recent advances in understanding the physical processes of artificially triggered light- ning and natural lightning as well as the progress in testing lightning protection technologies, based on a s... This paper reviews recent advances in understanding the physical processes of artificially triggered light- ning and natural lightning as well as the progress in testing lightning protection technologies, based on a series of lightning field campaigns jointly conducted by the Chinese Academy of Meteorological Sciences and Guangdong Meteorological Bureau since 2006. During the decade-long series of lightning field experi- ments, the technology of rocket-wire artificially triggered lightning has been improved, and has successfully triggered 94 lightning flashes. Through direct lightning current waveform measurements, an average return stroke peak current of 16 kA was obtained. The phenomenon that the downward leader connects to the lateral surface of the upward leader in the attachment process was discovered, and the speed of the upward leader during the connection process being significantly greater than that of the downward leader was re- vealed. The characteristics of several return strokes in cloud-to-ground lighting have also been unveiled, and the mechanism causing damage to lightning protection devices (i.e., ground potential rise within the rated current) was established. The performance of three lightning monitoring systems in Guangdong Province has also been quantitatively assessed. 展开更多
关键词 LIGHTNING field observation experiment artificially triggered lightning lightning physical pro- cesses lightning protection
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Numerical Assessing Experiments on the Individual Component Impact of the Meteorological Observation Network on the "July 2000" Torrential Rain in Beijing 被引量:9
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作者 张朝林 陈敏 +2 位作者 郭英华 范水勇 仲跻芹 《Acta meteorologica Sinica》 SCIE 2006年第4期389-401,共13页
In an effort to assess the impact of the individual component of meteorological observations (ground-based CPS precipitable water vapor, automatic and conventional meteorological observations) on the torrential rain... In an effort to assess the impact of the individual component of meteorological observations (ground-based CPS precipitable water vapor, automatic and conventional meteorological observations) on the torrential rain event in 4-5 July 2000 in Beijing (with the 24-h accumulated precipitation reaching 240 mm), 24-h observation system experiments are conducted numerically by using the MM5/WRF 3DVAR system and the nonhydrostatic MM5 model. Results indicate that, because the non-conventional GPS observations are directly assimilated into the initial analyses by 3DVAR system, better initial fields and 24-h simulation for the severe precipitation event are achieved than those under the MM5/Litter_R objective analysis scheme. Further analysis also shows that the individual component of meteorological observation network plays their special positive role in the improvement of initial field analysis and forecasting skills. 3DVAR scheme with or without radiosonde and pilot observation has the most significant influence on numerical simulation, and automatic and conventional surface meteorological observations rank second. After acquiring the supplement information from the other meteorological observations, the ground-based GPS precipitable water vapor data can more obviously reflect initial field assimilation and precipitation forecast. By incorporating the groundbased CPS precipitable water vapor data into the 3DVAR analyses at the initial time, the threat scores (TS) with thresholds of 1, 5, 10, and 20 mm are increased by 1%-8% for 6- and 24-h accumulated precipitation observations, respectively. This work gives one helpful example that assesses the impact of individual component of the existing meteorological observation network on the high influence weather event using 3DVAR numerical system. 展开更多
关键词 three-dimensional variational data assimilation global positioning system (CPS) severe rainfall observation system experiment numerical weather prediction (NWP)
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Impact of Different Guidances on Sensitive Areas of Targeting Observations Based on the CNOP Method 被引量:8
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作者 谭晓伟 王斌 王栋梁 《Acta meteorologica Sinica》 SCIE 2010年第1期17-30,共14页
The conditional nonlinear optimal perturbations(CNOPs) obtained by a fast algorithm are applied to determining the sensitive area for the targeting observation of Typhoon Matsa in 2005 using an operational regional ... The conditional nonlinear optimal perturbations(CNOPs) obtained by a fast algorithm are applied to determining the sensitive area for the targeting observation of Typhoon Matsa in 2005 using an operational regional prediction model-the Global/Regional Assimilation and PrEdiction System(GRAPES).Through a series of sensitivity experiments,several issues on targeting strategy design are discussed,including the effectivity of different guidances to determine the sensitive area(or targeting area) and the impact of sensitive area size on improving the 24-h forecast.In this study,three guidances are used along with the CNOP to find sensitive area for improving the 24-h prediction of sea level pressure and accumulated rainfall in the verification region.The three guidances are based on winds only;on winds,geopotential height,and specific humidity;and on winds,geopotential height,specific humidity,and observation error,respectively.The distribution and effectivity of the sensitive areas are compared with each other,and the results show that the sensitive areas identified by the three guidances are different in terms of convergence and effectivity.All the sensitive areas determined by these guidances can lead to improvement of the 24-h forecast of interest. The second and third guidances are more effective and can identify more similar sensitive areas than the first one.Further,the size of sensitive areas is changed the same way for three guidances and the 24-h accumulated rainfall prediction is examined.The results suggest that a larger sensitive area can result in better prediction skill,provided that the guidance is sensitive to the size of sensitive areas. 展开更多
关键词 conditional nonlinear optimal perturbation(CNOP) targeting observations observational system sensitivity experiment(OSSE) Typhoon Matsa
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A Fast Algorithm for Solving CNOP and Associated Target Observation Tests 被引量:8
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作者 王斌 谭晓伟 《Acta meteorologica Sinica》 SCIE 2009年第4期387-402,共16页
Conditional Nonlinear Optimal Perturbation (CNOP) is a new method proposed by Mu et al. in 2003, which generalizes the linear singular vector (LSV) to include nonlinearity. It has become a powerful tool for studyi... Conditional Nonlinear Optimal Perturbation (CNOP) is a new method proposed by Mu et al. in 2003, which generalizes the linear singular vector (LSV) to include nonlinearity. It has become a powerful tool for studying predictability and sensitivity among other issues in nonlinear systems. This is because the CNOP is able to represent, while the LSV is unable to deal with, the fastest developing perturbation in a nonlinear system. The wide application of this new method, however, has been limited due to its large computational cost related to the use of an adjoint technique. In order to greatly reduce the computational cost, we hereby propose a fast algorithm for solving the CNOP based on the empirical orthogonal function (EOF). The algorithm is tested in target observation experiments of Typhoon Matsa using the Global/Regional Assimilation and PrEdiction System (GRAPES), an operational regional forecast model of China. The effectivity and feasibility of the algorithm to determine the sensitivity (target) area is evaluated through two observing system simulation experiments (OSSEs). The results, as expected, show that the energy of the CNOP solved by the new algorithm develops quickly and nonlinearly. The sensitivity area is effectively identified with the CNOP from the new algorithm, using 24 h as the prediction time window. The 24-h accumulated rainfall prediction errors (ARPEs) in the verification region are reduced significantly compared with the "true state," when the initial conditions (ICs) in the sensitivity area are replaced with the "observations." The decrease of the ARPEs can be achieved for even longer prediction times (e.g., 72 h). Further analyses reveal that the decrease of the 24-h ARPEs in the verification region is attributable to improved simulations of the typhoon's initial warm-core, upper level relative vorticity, water vapor conditions, etc., as a result of the updated ICs in the sensitivity area. 展开更多
关键词 fast algorithm CNOP (Conditional Nonlinear Optimal Perturbation) target observation OSSE (observing system simulation experiment)
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