The presence of embedded convection in stratiform clouds strongly affects ice microphysical properties and precipitation formation.In situ aircraft measurements,including upward and downward spirals and horizontal pen...The presence of embedded convection in stratiform clouds strongly affects ice microphysical properties and precipitation formation.In situ aircraft measurements,including upward and downward spirals and horizontal penetrations,were performed within both embedded convective cells and stratiform regions of a mixedphase stratiform cloud system on 22 May 2017.Supercooled liquid water measurements,particle size distributions,and particle habits in different cloud regions were discussed with the intent of characterizing the riming process and determining how particle size distributions vary from convective to stratiform regions.Significant amounts of supercooled liquid water,with maxima up to 0.6 g m−3,were observed between−3℃ and−6℃ in the embedded convective cells while the peak liquid water content was generally less than 0.1 g m−3 in the stratiform regions.There are two distinct differences in particle size distributions between convective and stratiform regions.One difference is the significant shift toward larger particles from upper−15℃ to lower−10℃ in the convective region,with the maximum particle dimensions increasing from less than 6000μm to over 1 cm.The particles larger than 1 cm at−10℃ are composed of dendrites and their aggregates.The other difference is the large concentrations of small particles(25–205μm)at temperatures between−3℃ and−5℃ in the convective region,where rimed ice particles and needles coexist.Needle regions are observed from three of the five spirals,but only the cloud conditions within the convective region fit into the Hallett-Mossop criteria.展开更多
Vertical distributions of aerosol optical properties based on aircraft measurements over the Loess Plateau were measured for the first time during a summertime aircraft campaign, 2013 in Shanxi, China. Data from four ...Vertical distributions of aerosol optical properties based on aircraft measurements over the Loess Plateau were measured for the first time during a summertime aircraft campaign, 2013 in Shanxi, China. Data from four flights were analyzed. The vertical distributions of aerosol optical properties including aerosol scattering coefficients(σsc), absorption coefficients(σab),Angstr?m exponent(α), single scattering albedo(ω), backscattering ratio(βsc), aerosol mass scattering proficiency(Q sc) and aerosol surface scattering proficiency(Q sc′) were obtained. The mean statistical values of σsc were 77.45 Mm-1(at 450 nm), 50.72 Mm-1(at 550 nm), and32.02 Mm-1(at 700 nm). The mean value of σab was 7.62 Mm-1(at 550 nm). The mean values ofα, βsc and ω were 1.93, 0.15, and 0.91, respectively. Aerosol concentration decreased with altitude. Most effective diameters(ED) of aerosols were less than 0.8 μm. The vertical profiles of σsc,, α, βsc, Q sc and Q sc′ showed that the aerosol scattering properties at lower levels contributed the most to the total aerosol radiative forcing. Both α and βsc had relatively large values, suggesting that most aerosols in the observational region were small particles. The mean values of σsc, α, βsc, Q sc, Q sc′, σab and ω at different height ranges showed that most of the parameters decreased with altitude. The forty-eight hour backward trajectories of air masses during the observation days indicated that the majority of aerosols in the lower level contributed the most to the total aerosol loading, and most of these particles originated from local or regional pollution emissions.展开更多
Operations in assembling and joining large size aircraft components are changed to novel digital and flexible ways by digital measurement assisted alignment.Positions and orientations(P&O)of aligned components are ...Operations in assembling and joining large size aircraft components are changed to novel digital and flexible ways by digital measurement assisted alignment.Positions and orientations(P&O)of aligned components are critical characters which assure geometrical positions and relationships of those components.Therefore,evaluating the P&O of a component is considered necessary and critical for ensuring accuracy in aircraft assembly.Uncertainty of position and orientation(U-P&O),as a part of the evaluating result of P&O,needs to be given for ensuring the integrity and credibility of the result;furthermore,U-P&O is necessary for error tracing and quality evaluating of measurement assisted aircraft assembly.However,current research mainly focuses on the process integration of measurement with assembly,and usually ignores the uncertainty of measured result and its influence on quality evaluation.This paper focuses on the expression,analysis,and application of U-P&O in measurement assisted alignment.The geometrical and algebraical connotations of U-P&O are presented.Then,an analytical algorithm for evaluating the multi-dimensional U-P&O is given,and the effect factors and characteristics of U-P&O are discussed.Finally,U-P&O is used to evaluate alignment in aircraft assembly for quality evaluating and improving.Cases are introduced with the methodology.展开更多
A large planar microphone array, which consists of 111 microphones, was successfully developed. The positions of 111 microphones in the array were determined by a random optimization procedure for the largest possible...A large planar microphone array, which consists of 111 microphones, was successfully developed. The positions of 111 microphones in the array were determined by a random optimization procedure for the largest possible amplification and dynamic range. The beam pattern of planar array was obtained by numerical calculation. This planar array was applied to measure a two-dimensional mapping of the sound sources on landing aircraft. It is shown that important airframe noise sources can be identified. The spectra and directivity of any interested noise source can also be obtained by this measurement.展开更多
基金the National Key Research and Development Program of China(Grant Nos.2019YFC1510300 and 2018YFC1507900)the National Natural Science Foundation of China(Grant Nos.41575131).
文摘The presence of embedded convection in stratiform clouds strongly affects ice microphysical properties and precipitation formation.In situ aircraft measurements,including upward and downward spirals and horizontal penetrations,were performed within both embedded convective cells and stratiform regions of a mixedphase stratiform cloud system on 22 May 2017.Supercooled liquid water measurements,particle size distributions,and particle habits in different cloud regions were discussed with the intent of characterizing the riming process and determining how particle size distributions vary from convective to stratiform regions.Significant amounts of supercooled liquid water,with maxima up to 0.6 g m−3,were observed between−3℃ and−6℃ in the embedded convective cells while the peak liquid water content was generally less than 0.1 g m−3 in the stratiform regions.There are two distinct differences in particle size distributions between convective and stratiform regions.One difference is the significant shift toward larger particles from upper−15℃ to lower−10℃ in the convective region,with the maximum particle dimensions increasing from less than 6000μm to over 1 cm.The particles larger than 1 cm at−10℃ are composed of dendrites and their aggregates.The other difference is the large concentrations of small particles(25–205μm)at temperatures between−3℃ and−5℃ in the convective region,where rimed ice particles and needles coexist.Needle regions are observed from three of the five spirals,but only the cloud conditions within the convective region fit into the Hallett-Mossop criteria.
基金supported partially by the Ministry of Science and Technology of China under its national key project on global change studies (No.2013CB955804)the Special Fund for doctorate programs in Chinese Universities (No.20113228110002)+1 种基金the Public Meteorology Special Foundation of MOST (No.GYHY201306065)the Shanxi Meteorological Bureau Key Research Projects (No.SXKZDTC20140605)
文摘Vertical distributions of aerosol optical properties based on aircraft measurements over the Loess Plateau were measured for the first time during a summertime aircraft campaign, 2013 in Shanxi, China. Data from four flights were analyzed. The vertical distributions of aerosol optical properties including aerosol scattering coefficients(σsc), absorption coefficients(σab),Angstr?m exponent(α), single scattering albedo(ω), backscattering ratio(βsc), aerosol mass scattering proficiency(Q sc) and aerosol surface scattering proficiency(Q sc′) were obtained. The mean statistical values of σsc were 77.45 Mm-1(at 450 nm), 50.72 Mm-1(at 550 nm), and32.02 Mm-1(at 700 nm). The mean value of σab was 7.62 Mm-1(at 550 nm). The mean values ofα, βsc and ω were 1.93, 0.15, and 0.91, respectively. Aerosol concentration decreased with altitude. Most effective diameters(ED) of aerosols were less than 0.8 μm. The vertical profiles of σsc,, α, βsc, Q sc and Q sc′ showed that the aerosol scattering properties at lower levels contributed the most to the total aerosol radiative forcing. Both α and βsc had relatively large values, suggesting that most aerosols in the observational region were small particles. The mean values of σsc, α, βsc, Q sc, Q sc′, σab and ω at different height ranges showed that most of the parameters decreased with altitude. The forty-eight hour backward trajectories of air masses during the observation days indicated that the majority of aerosols in the lower level contributed the most to the total aerosol loading, and most of these particles originated from local or regional pollution emissions.
基金support of National Natural Science Foundation of China (No.50905010)Fund of National Engineering and Research Center for Commercial Aircraft Manufacturing (No.SAMC12-JS-15-044)
文摘Operations in assembling and joining large size aircraft components are changed to novel digital and flexible ways by digital measurement assisted alignment.Positions and orientations(P&O)of aligned components are critical characters which assure geometrical positions and relationships of those components.Therefore,evaluating the P&O of a component is considered necessary and critical for ensuring accuracy in aircraft assembly.Uncertainty of position and orientation(U-P&O),as a part of the evaluating result of P&O,needs to be given for ensuring the integrity and credibility of the result;furthermore,U-P&O is necessary for error tracing and quality evaluating of measurement assisted aircraft assembly.However,current research mainly focuses on the process integration of measurement with assembly,and usually ignores the uncertainty of measured result and its influence on quality evaluation.This paper focuses on the expression,analysis,and application of U-P&O in measurement assisted alignment.The geometrical and algebraical connotations of U-P&O are presented.Then,an analytical algorithm for evaluating the multi-dimensional U-P&O is given,and the effect factors and characteristics of U-P&O are discussed.Finally,U-P&O is used to evaluate alignment in aircraft assembly for quality evaluating and improving.Cases are introduced with the methodology.
基金the Bundesministerium fur Bildung und Forschung (BMBF) of Germany.
文摘A large planar microphone array, which consists of 111 microphones, was successfully developed. The positions of 111 microphones in the array were determined by a random optimization procedure for the largest possible amplification and dynamic range. The beam pattern of planar array was obtained by numerical calculation. This planar array was applied to measure a two-dimensional mapping of the sound sources on landing aircraft. It is shown that important airframe noise sources can be identified. The spectra and directivity of any interested noise source can also be obtained by this measurement.