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Spurious Dianeutral Mixing in a Global Ocean Model Using Spherical Centroidal Voronoi Tessellations

Journal of Ocean University of China 2016年第6期15卷 923-935页

作者： ZHAO Shimei LIU Yudi college of meteorology and Oceanography People's Liberation Army University of Science and Technology

In order to quantitatively evaluate the spurious dianeutral mixing in a global ocean model MPAS-Ocean （Model for Prediction Across Scales） using a spherical centroidal voronoi tessellations developed jointly by the National Center for Atmospheric Research and the Los Alamos National Laboratory in the United States, we choose z＊ vertical coordinate system in MPAS-Ocean, in which all physical mixing processes, such as convection adjustment and explicit diffusion parameter schemes, are omitted, using a linear equation of state. By calculating the Reference Potential Energy （RPE）, front revolution position, time rate of RPE change, probability density function distribution and dimensionless parameter 2＂, from the perspectives of resolution, viscosity, Horizontal Grid Reynolds Number （HGRN）, Rea, and momentum transmission scheme, using two ideal cases, overflow and baroclinic eddy channel, we qualitatively analyze the simulation results by comparison with the three non-isopycnal models in Ilicak et al. （2012）, i.e., MITocM, MOM, and ROMS. The results show that the spurious dianeutral mixing in the MPAS-Ocean increases over time. The spurious dianeutral transport is proportional to the HGRN directly and is reduced by increasing the lateral viscosity or using a finer resolution to control HGRN. When the HGRN is less than 10, spurious transport is reduced significantly. When using the proper viscosity closure, MPAS-Ocean performs better than MIT6c and MOM, closely to ROMS, in the 2D case without rotation, and much better than the above-mentioned three ocean models under the condition of 3D space with rotation due to the cell area difference between the hexa- gon cell and the quadrilateral cell with the same resolution. Both the Zalesak （1979） flux corrected transport scheme and Leith closure in MPAS-Ocean play an excellent role in reducing spurious dianeutral mixing. The performance of Leith scheme is preferable to the condition of three-dimensional baroclinic eddy.

关键词： MPAS-Ocean spurious dianeutral mixing Reference Potential Energy (RPE) Leith scheme Horizontal Grid Rey-nolds Number (HGRN)

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A Recognition Method of Hydrometeor in Tropical Cyclones by Using the GPM Dual-Frequency Precipitation Radar

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Journal of Tropical meteorology 2021年第2期27卷 161-168页

作者： QIAO Jun-qi AI Wei-hua HU Xiong HU Shen-sen YAN Wei college of meteorology and Oceanography National University of Defense TechnologyNanjing 211101 China

In this paper,we propose a fuzzy logic algorithm to recognize the types of hydrometeors by using Ka and Ku reflectivity factors,temperature thresholds and an asymmetric t-form membership *** identifiable types of hydrometeors include snow,graupel,mixed-phase particles,large raindrops,and small *** reflectivity detection data of Ka and Ku with attenuation correction is from dual-frequency precipitation radar onboard the global precipitation measurement *** temperature data from the European Centre for Medium-range Weather Forecasts are used to identify the hydrometeors,and the identified hydrometeors are compared with the vertical profiles of phase from official level-2 DPR *** results show that the identified hydrometeors are reasonable and reveal the evolution process of tropical cyclones,which can be further applied to the study of precipitation microphysical process and artificial precipitation.

关键词： GPM DPR hydrometeor tropical cyclones fuzzy logical phase

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Relationship between the Tibetan Plateau-tropical Indian Ocean thermal contrast and the South Asian summer monsoon

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Frontiers of Earth Science 2021年第1期15卷 151-166页

作者： Xiaoqing LUO Jianjun XU Yu ZHANG Kai LI South China Sea Institute of Marine meteorology Guangdong Ocean UniversityZhanjiang 524088China college of Ocean and meteorology Guangdong Ocean UniversityZhanjiang 524088China Maritime college Guangdong Ocean UniversityZhanjiang 524088China

The impact of land-sea thermal contrast on the South Asian summer monsoon(SASM)was investigated by calculating the atmospheric heat sources(AHS)and baroclinic component with ERA5 data for the period *** diagnostic and statistical methods,it was found that the thermal contrast between the Tibetan Plateau(TP)and the tropical Indian Ocean(TIO)affects the South Asian monsoon circulation through the meridional temperature gradient in the upper *** seasonal changes of the AHS of the TP and TIO are *** summer,the TP is the strongest at the same latitude whereas the TIO is the weakest,and the thermal contrast is the most *** heat sources of the TP and TIO are located on the north and south side of the strong baroclinic area of the SASM region,respectively,and both of which are dominated by deep convective heating in the upper *** TP-TIO regional meridional thermal contrast index(QI)based on the AHS,and the SASM index(MI)based on baroclinicity were found to be strongly positively *** years of abnormally high QI,the thermal contrast between the TP and TIO is strong in summer,which warms the upper troposphere over Eurasia and cools it over the *** stronger temperature gradient enhances the baroclinicity in the troposphere,which results in a strengthening of the low-level westerly airflow and the upper-level easterly *** anomalous winds strengthen the South Asian high(SAH),with the warmer center in the upper troposphere,and the enhanced Walker circulation over the equatorial Indian ***,the anomalous circulation leads to much more precipitation over the SASM *** influence of abnormally low QI is almost the opposite.

关键词： Tibetan Plateau tropical Indian Ocean atmosphere heat sources South Asian summer monsoon atmosphere baroclinic component

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The optimal retrieval of ocean color constituent concentrations based on the variational method

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Journal of Hydrodynamics 2013年第1期25卷 62-71页

作者： YU Hong FAN Zhe DU Hua-dong college of meteorology and Oceanography PLA University of Science and Technology Meteorological Center of Air Force Command in Nanjing Military Region

In this paper, a new approach to the optimal retrieval of the ocean color based on the variational method is developed by setting up a rational target functional combining with the Broydor Fletcher, Goldfarb, Shanno （BFGS） optimal algorithm. The numerical tests and the exemplary retrievals are carried out and compared with the statistical retrievals and the optimal retrievals based on the genetic algorithm. The results show that this approach enjoys a higher accuracy as compared to the statistical method and a higher efficiency as compared to the genetic algorithm. The optimal retrieval method presented in this paper provides a new idea for the ocean color inversion and could also be used as a reference for the direct assimilation of the satellite data into the ecological models.

关键词： ocean color optimal retrieval variational method Broydor Fletcher Goldfarb Shanno (BFGS) algorithm

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Sensitivity of Cyclone Tracks to the Initial Moisture Distribution:A Moist Potential Vorticity Perspective

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Advances in Atmospheric Sciences 2005年第6期22卷 807-820页

作者： Zuohao CAO Da-Lin ZHANG Meteorological Service of Canada Ontario Canada Department of meteorology University of Maryland College Park Maryland USA

In this study, the characteristics of moist potential vorticity （MPV） in the vicinity of a surface cyclone center and their physical processes axe investigated. A prognostic equation of surface absolute vorticity is then used to examine the relationship between the cyclone tracks and negative MPV （NMPV） using numerical simulations of the life cycle of an extratropical cyclone. It is shown that the MPV approach developed herein, i.e., by tracing the peak NMPV, can be used to help trace surface cyclones during their development and mature stages. Sensitivity experiments are conducted to investigate the impact of different initial moisture fields on the effectiveness of the MPV approach. It is found that the lifetime of NMPV depends mainly on the initial moisture field, the magnitude of condensational heating, and the advection of NMPV. When NMPV moves into a saturated environment at or near a cyclone center, it can trace better the evolution of the surface cyclone due to the conservative property of MPV. It is also shown that the NMPV generation is closely associated with the coupling of large potential temperature and moisture gradients as a result of frontogenesis processes. Analyses indicate that condensation, confluence and tilting play important but different roles in determining the NMPV generation. NMPV is generated mainly through the changes in the strength of baroclinicity and in the direction of the moisture gradient due to moist and/or dry air mass intrusion into the baroclinic zone.

关键词： cyclone tracks moist potential vorticity mid-latitude cyclones

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Some progress on ocean data assimilation in China: Introduction of the special section “Ocean Data Assimilation”

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Acta Oceanologica Sinica 2022年第2期41卷 1-2页

作者： Huizan Wang Yan Chen Weimin Zhang college of meteorology and Oceanography National University of Defense TechnologyChangsha 410073China

This special section is the scientific legacy of the 13th National Ocean Data Assimilation and Numerical Simulation Conference of China,which was held in Changsha,China during December 3–4,2020 with more than 160 participants from 35 units in *** continued a series of National Ocean Data Assimilation conferences which began in 2003,which played an important role in the development of ocean data assimilation in *** this 13th conference,there were 41 oral presentations and 15 posters,which focused on ocean data assimilation methods,ocean reanalysis data,developments and operational application of ocean data assimilation systems,assimilation of new type ocean observations,ocean targeted observation analysis,coupled data assimilation,ocean models and parameter estimation,*** conference was hosted by National University of Defense Technology,and cohosted by the Institute of Atmospheric Physics of Chinese Academy of Sciences,the South China Sea Institute of Oceanology of Chinese Academy of Sciences,the Second Institute of Oceanography of the Ministry of Natural Resources,Ocean University of China,Tianjin University and Hohai University.

关键词： China ocean assimilation

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Multi-decadal Changes of the Impact of El Niño Events on Tibetan Plateau Summer Precipitation

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Journal of Atmospheric Science Research 2024年第1期7卷 90-105页

作者： Weinan Jiang Ning Cao Riga Aze Jianjun Xu college of Ocean and meteorology Guangdong Ocean UniversityZhanjiangGuangdong524088China CMA-GDOU Joint Laboratory for Marine meteorology Guangdong Ocean UniversityZhanjiangGuangdong524088China South China Institute of Marine meteorology(SIMM) Guangdong Ocean UniversityZhanjiangGuangdong524088China Shenzhen Institute of Guangdong Ocean University ShenzhenGuangdong518108China

Precipitation on the Tibetan Plateau(TP)has an important effect on the water supply and demand of the downstream *** recent climate change,the multi-decadal variations of the impact of El Niño-Southern Oscillation(ENSO)events on regional climate were *** this work,the authors investigated the changes in summer precipitation over TP during *** the multi-decadal scale,the authors found that the inhabiting impact of El Niño events on the TP summer precipitation has strengthened since the late *** main factor contributing to this phenomenon is the significant amplification in the decadal amplitude of El Niño during 1978-2019 accompanied by a discernible escalation in the frequency of El Niño *** phenomenon induces anomalous perturbations in sea surface temperatures(SST)within the tropical Indo-Pacific region,consequently weakening the atmospheric vapor transport from the western Pacific to the ***,conspicuous anomalies in subsidence motion are observed longitudinally and latitudinally across the TP which significantly contributes to a curtailed supply of atmospheric *** results bear profound implications for the multi-decadal prediction of the TP climate.

关键词： Tibetan plateau Summer precipitation ENSO Multi-decadal changes Climate variability

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RISK ANALYSIS AND MANAGEMENT OF URBAN RAINSTORM WATER LOGGING IN TIANJIN

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Journal of Hydrodynamics 2006年第5期18卷 552-558页

作者： HAN Su-qin XIE Yi-yang LI Da-ming LI Pei-yan SUN Mei-ling college of Environmental Science and Engineering Nankai University Tianjin 300071 China Tianjin Meteorology Institute Tianjin 300074 China Tianjin meteorology Institute Tianjin 300074 China School of Civil Engineering Tianjin University Tianjin 300072 China

The risk analysis of urban rainstorm water logging facing Tianjin city by using methods of probability, investigation and numerical simulation was carried out in this article. Firstly, a mathematical model for the urban rainstorm water logging was established on the basis of one- and two-dimensional unsteady flow theory and the technique of non-structural irregular grid division, Secondly, the precipitation over heavy rain was divided into seven grades, the experiential expression of frequency and rain grades was got according to the observed rainfall from May 1918 to October 1998. Thirdly, the mathematical model was used to simulate various rain process according to the features of the rainstorm and the draining rule, based on the simulated maximum water depths, 3 class of disaster extents were established, the disaster risks were mainly in Class Ⅰ and Class Ⅱ, The risk analysis of water logging on traffic were primarily evaluated, and finally, some management and mitigation measures of the urban rainstorm water logging disaster were discussed.

关键词： urban rainstorm water logging mathematical model traffic disaster risk analysis,Tianjin

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Multi-Temporal Detection of Rice Phenological Stages Using Canopy Spectrum

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Rice science 2014年第2期21卷 108-115页

作者： WANG Lin ZHANG Fu-cun JING Yuan-shu JIANG Xiao-dong YANG Shen-bin HAN Xiao-mei Jiangsu Key Laboratory of Agricultural meteorology College of Applied MeteorologyNanjing University of Information Science& Technology

Information on rice phenology is essential for yield estimation and crop management. To test the ability of remote sensing in detecting multiple phenological stages, paddy rice canopy spectrum was measured by a hand-held radiometer. Normalized difference vegetation index （NDVI） was calculated from spectrum, and the slope of NDVI was obtained as its difference. We evaluated the response of NDVI and its slope to rice growth with a comparison of two late-season rice cultivars. The results showed that NDVI and its slope curves had distinct variation corresponding to rice development and they could be used as cultivar-independent phenological indicators. The dates of flooding and transplanting, tillering, panicle development, heading and flowering, maturity, harvest stages, and even field management practices, could be deduced from these indicators. ‘NDVI ≤ 0’ could be used as a single threshold for the detection of flooding and transplanting. The largest spike in the curve of the NDVI slope indicated the duration of tillering stage. The next spike corresponded to panicle development. The heading and flowering stage was characterized by the maximum NDVI and the change of NDVI slope from positive to negative. At the maturity stage, NDVI decreased continuously, and its slope fluctuated just below zero. When rice grains were completely mature and ready for harvest, NDVI decline was accelerated. At harvest, NDVI slope reached its minimum value. The distinction between heading and maturity stages was obscure, most likely due to NDVI saturation at high biomass. The study might provide references for paddy rice phenology determination through remote sensing images.

关键词： ground remote sensing normalized difference vegetation index (NDVI) NDVI slop ricephenology

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Monitoring of ducting by using a ground-based GPS receiver

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Chinese Physics B 2013年第2期22卷 575-579页

作者：盛峥方涵先 college of meteorology and Oceangraphy PLA University of Science and Technology Sate Key Laboratory of Space Weather Chinese Academy of Sciences

In this paper,we describe the estimation of low-altitude refractivity structure from simulation and real ground-based GPS *** vertical structure of the refractive environment is modeled using three parameters,i.e.,duct height,duct thickness,and duct *** refractivity model is implemented with a priori constraints on the duct height,thickness,and strength,which might be derived from soundings or numerical weather-prediction models.A ray propagation model maps the refractivity structure into a replica *** fields are compared with the simulation observed data using a squarederror objective function.A global search for the three environmental parameters is performed using a genetic *** inversion is assessed by comparing the refractivity profiles from the radiosondes to those *** technique could provide near-real-time estimation of the ducting *** results suggest that ground-based GPS provides significant atmospheric refractivity information,despite certain fundamental limitations of ground-based *** are typically launched just a few times ***,estimates of temporally and spatially varying refractivity that assimilate GPS delays could substantially improve over-estimates caused by using radiosonde data alone.

关键词： global positioning system ducting genetic algorithm radio remote sensing

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