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Overview and New Opportunities for Multi-Source data assimilation

Journal of Meteorological research 2025年第1期39卷 1-25页

作者： Xiaolei ZOU Joint Center of Data Assimilation for Research and Application Nanjing University of Information Science&TechnologyNanjing210044China

The world witnessed an accelerated development of various types of meteorological observing technology,an evolution of numerical weather prediction(NWP)models from single atmospheric component to coupled multi-components of the earth system,as well as the multi graphics processing unit technology in computer sciences,a new era for rapidly advancing data assimilation science and technology development has *** multi-source data assimilation is important not only for NWP but also for further understanding of global and regional weather *** article firstly selectively reviews past methods of multi-source data *** opportunities are then discussed for future development of data assimilation system framework,for innovative uses of high-resolution observations,and for applications of artificial intelligence machine learning in meteorological data assimilation.

关键词： multi-source observations data assimilation innovative use of high-resolution observations

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Impacts of Vertical Resolution and Diurnally Varying Background Error Covariance on FY-4A/AGRI data assimilation over Land

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Monthly Weather Review 2025年第5期153卷 763-790页

作者： Li, Xin Zou, Xiaolei Xu, Xu Liu, Weiguang Nanjing Innovation Institute for Atmospheric Sciences Chinese Academy of Meteorological Sciences Jiangsu Meteorological Service Nanjing China Key Laboratory of Transportation Meteorology of CMA Jiangsu Key Laboratory of Severe Storm Disaster Risk Nanjing China Center of Data Assimilation for Research and Application Nanjing University of Information Science and Technology Nanjing China

This study aims at improving the assimilation of Fengyun-4A (FY-4A)/Advanced Geostationary Radiation Imager (AGRI) clear-sky surface-sensitive brightness temperature over land using the Weather research and Forecasting and the Gridpoint Statistical Interpolation three-dimensional variational data assimilation for summer convective cases over eastern China. We investigated the influences of the planetary boundary layer on the assimilation of FY-4A/AGRI surface-sensitive channels, focusing on model low-level vertical resolution and diurnal variation of background error covariance. The vertical levels are increased from 48 to 91 by adding more near-surface levels. First, stronger low-level vertical background error correlations of humidity and temperature are found during daytime than during nighttime. A total of five numerical experiments are then conducted to examine the impacts of FY-4A/AGRI assimilation with two vertical resolutions. The experiments WV48 and WV91 assimilate only the water vapor channels, and ALL48, ALL91, and ALL91M assimilate the water vapor and surface-sensitive channels. The diurnally varying background error covariance, which is estimated at 3-h intervals, is incorporated into ALL91M. The 6-h cycling data assimilation at 1-h interval prior to convection initiation is conducted for each of the seven cases. Overall, a comparison between WV48/WV91 and ALL48/ALL91M revealed a consistent positive impact of AGRI brightness temperature assimilation over land on convective precipitation forecasts. The added values of assimilating AGRI surface-sensitive channels are more pronounced by using the finer vertical resolution due to low-level humidity enhancements that are related to the rise of the planetary boundary layer. With the diurnally varying background error covariance, ALL91M outperformed ALL91 because of improved low-level analyzed structures that are associated with proper low-level vertical error correlations of humidity and thermal variables. ©

关键词： Snow

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Relationships of along-the-track local variations of GPS RO impact parameter to strong local vertical gradient of wet refractivity in the tropics

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Science China Earth Sciences 2021年第11期64卷 2015-2026页

作者： Shengpeng YANG Xiaolei ZOU Joint Center of Data Assimilation for Research and Application Nanjing University of Information Science&TechnologyNanjing 210044China

Atmospheric refractivity fields are more strongly affected by more water vapor in the tropical lower troposphere than *** this study,based on model simulations,we first collocated the radio occultation(RO)data in 2009 from the Constellation Observing System for Meteorology,Ionosphere,and Climate(COSMIC)with CloudSat cloud profiling radar *** then investigate where and why a RO ray path intersects with other simulated rays of impact heights above and/or below the impact height of the *** the European Centre for Medium-Range Weather Forecasts ERA5 reanalysis as input to a raytracing observation operator,we show that the simulated impact parameters could vary along the ray in the tropical lower *** brevity,an intersection of a GPS RO ray path with rays above it or below it or both will be called an impact *** overlapping simulated ray trajectories over the vertical and horizontal gradients of refractivity in 2D occultation planes,impact multipath occurrences are vividly *** results show that the impact multipath is caused mostly by strong local vertical gradients of atmospheric wet refractivity mostly within 300 km horizontal distances from their perigee *** impact multipath occurs more frequently below 5-km impact height,with a maximum occurrence around the 3.4 km impact height(about 1.8 km geometric height).It is shown that both the simulated impact multipath phenomena and locally strong vertical gradients of wet refractivity are found in both cloudy and clear-sky conditions,and most frequently in presences of stratocumulus clouds.

关键词： GPS RO Multipath Troposphere

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MUSHROOM CLOUD MEMORIES

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IEEE SPECTRUM 2014年第4期51卷 29-32页

作者： Cass, Stephen Center of Data Assimilation for Research and Application Nanjing University of Information Science and Technology Nanjing China

Few minutes from the gaudy energy of the Las Vegas Strip is a quiet museum dedicated to an age when nuclear fireballs lit up the Nevada desert like second suns. Starting in 1951, more than 1000 atomic devices were detonated at what is now called the Nevada National Security Site, about 100 kilometers north of Las Vegas. Detonations went underground in 1963 and were suspended completely in 1992. The National Atomic Testing Museum (NAT M) chronicles the history of the period, as well as some of the work at the site that continues to this day. · While many visitors will be drawn to the museum by the dark glamour of the atomic age, the museum is in truth a celebration of test and measurement engineering. For obvious reasons, minimal details are given regarding the nuclear bombs at the heart of the tests. So the focus is squarely on the equipment used to capture the nuances of the highly energetic yet incredibly brief operating lives of these devices. [ABSTRACT FROM AUTHOR]

关键词： NATIONAL museums ATOMIC bomb NUCLEAR weapons testing DISARMING of nuclear weapons NUCLEAR engineering

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GOES-16 ABI Brightness Temperature Observations Capturing Vortex Rossby Wave Signals during Rapid Intensification of Hurricane Irma(2017)

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Journal of Meteorological research 2024年第4期38卷 768-783页

作者： Yanyang HU Xiaolei ZOU Joint Center of Data Assimilation for Research and Application Nanjing University of Information Science&TechnologyNanjing 210044

Geostationary Operational Environmental Satellite-16(GOES-16) Advanced Baseline Imager(ABI) observations of brightness temperature(TB) are used to examine the temporal evolutions of convection-affected structures of Hurricane Irma(2017) during its rapid intensification(RI) period from 0600 to 1800 UTC 4 September *** ABI observations reveal that both an elliptical eye and a spiral rainband that originated from Irma's eyewall obviously exhibit wavenumber-2 TB *** elliptical eye underwent a counterclockwise rotation at a mean speed of a wavenumber-2 vortex Rossby edge wave from 0815 to 1005 UTC 4 *** the following about 2 hours(1025–1255 UTC 4 September),an inner spiral rainband originated from the eyewall and propagated at a phase speed that approximates the vortex Rossby wave(VRW) phase speed calculated from the aircraft reconnaissance *** the RI period of Irma,ABI TB observations show an on–off occurrence of low TB intrusions into the eye,accompanying a phase lock of eyewall TB asymmetries of wavenumbers 1 and 2 and an outward propagation of VRW-like inner spiral rainbands from the *** phase lock leads to an energy growth of Irma's eyewall *** the eye remained clear from 1415 to 1725 UTC 4 September,an inner spiral rainband that originated from a large convective area also had a VRW-like outward propagation,which is probably due to a vertical tilt of *** study suggests a potential link between convection sensitive GOES imager observations and hurricane dynamics.

关键词： Geostationary Operational Environmental Satellite(GOES)imager brightness temperature(TB) hurricane vortex Rossby wave(VRW)

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Development and Initial Assessment of a New Land Index for Microwave Humidity Sounder Cloud Detection

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Journal of Meteorological research 2016年第1期30卷 12-37页

作者：秦正坤邹晓蕾 Center of Data Assimilation for Research and Application Nanjing University of Information Science & Technology Earth System Science Interdisciplinary Center University of Maryland

This paper describes a new quality control （QC） scheme for microwave humidity sounder （MHS） data assimilation. It consists of a cloud detection step and an O-B （i.e., differences of brightness temperatures between observations and model simulations） check. Over ocean, cloud detection can be carried out based on two MHS window channels and two Advanced Microwave Sounding Unit-A （AMSU-A） window channels, which can be used for obtaining cloud ice water path （IWP） and liquid water path （LWP）, respectively. Over land, cloud detection of microwave data becomes much more challenging due to a much larger emission contribution from land surface than that from cloud. The current MHS cloud detection over land employs an 0-]3 based method, which could fail to identify cloudy radiances when there is mismatch between actual clouds and model clouds. In this study, a new MHS observation based index is developed for identifying MHS cloudy radiances over land. The new land index for cloud detection exploits the large variability of brightness temperature observations among MHS channels over different clouds, It is shown that those MHS cloudy radiances that were otherwise missed by the current O-B based QC method can be successfully identified by the new land index. An O-B check can then be employed to the remaining data after cloud detection to remove additional outliers with model simulations deviated greatly from observations. It is shown that MHS channel correlations are significantly reduced by the newly proposed QC scheme.

关键词： microwave humidity sounder cloud detection data assimilation

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A Velocity Dealiasing Scheme for C-band Weather Radar Systems

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Advances in Atmospheric Sciences 2014年第1期31卷 17-26页

作者： LI Gang HE Guangxin Xiaolei ZOU Peter Sawin RAY Center of Data Assimilation for Research and Application Nanjing University of Information Science & Technology Department of Earth Ocean and Atmospheric Sciences Florida State University

A dealiasing algorithm for radar radial velocity observed by C-band Doppler radars is presented as an extension of an existing S-band dealiasing algorithm. This has operational significance in that many portable and many commercial broadcast radars, as well as approximately one half of the Chinese weather radar network （CINRAD）, are C-band radars. With a wavelength of about 5 cm, the Nyquist interval of C-band radars is just about one half that of S-band radars （wavelength of about 10 cm） and thus has more velocity folding. The proposed algorithm includes seven modules to remove noisy data, find the starting radials, dealias velocities, and apply least squares error checking in both the radial and azimuth directions. The proposed velocity dealiasing method was applied to one widespread rain case and three strong convective cases from radars operating in China. It was found that, on average, 92.95% of the aliased radial velocity data could be correctly de-aliased by the algorithm, resulting in 96.65% of the data being valid.

关键词： Doppler radar aliasing radial velocity unfolding

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Quality control of specific humidity from surface stations based on EOF and FFT—— Case study

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Frontiers of Earth Science 2015年第3期9卷 381-393页

作者： Hong ZHAO Xiaolei ZOU Zhengkun QINl Center of Data Assimilation for Research and Application Nanjing University of Information Science & Technology Nanjing 210044 China Vlaryland College Park MD 20740-3-823 USA

Comparisons between observations and back- ground fields indicate that amplitude and phase differences in oscillations result in a non-Gaussian distribution in observation minus background vectors （OMB）. Empirical Orthogonal Function （EOF） quality control （QC） and Fast Fourier Transform （FFT） quality control are proposed from the perspective of data assimilation and are applied to the surface specific humidity from ground-based stations. The QC results indicate that the standard deviation between observations and background is reduced effectively, and the frequency distribution for the observation increment is closer to a normal distribution. The specific humidity outliers occur primarily in mountainous and coastal regions. Comparing the two QC methods, it is found that the EOF QC performs better than the FFT QC as it can keep large scale of fluctuation information from the original field, preventing these waves from entering into the residual field and being removed by the QC process.

关键词： specific humidity quality control EOF FFT

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Detection and Correction of AMSR-E Radio-Frequency Interference

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Acta meteorologica Sinica 2011年第5期25卷 669-681页

作者：吴莹翁富忠 Center of Data Assimilation for Research and Application Nanjing University of Information Science & Technology School of Remote Sensing Nanjing University of Information Science & Technology NOAA/NESDIS/Center for Satellite Application and Research Camp Springs MD 20746 USA

Radio-frequency interference （RFI） affects greatly the quality of the data and retrieval products from space-borne microwave radiometry. Analysis of the Advanced Microwave Scanning Radiometer on the Earth Observing System （AMSR-E） Aqua satellite observations reveals very strong and widespread RFI contam- inations on the C- and X-band data. Fortunately, the strong and moderate RFI signals can be easily identified using an index on observed brightness temperature spectrum. It is the weak RFI that is diffi- cult to be separated from the nature surface emission. In this study, a new algorithm is proposed for RFI detection and correction. The simulated brightness temperature is used as a background signal （B） and a departure of the observation from the background （O–B） is utilized for detection of RFI. It is found that the O–B departure can result from either a natural event （e.g., precipitation or flooding） or an RFI signal. A separation between the nature event and RFI is further realized based on the scattering index （SI）. A positive SI index and low brightness temperatures at high frequencies indicate precipitation. In the RFI correction, a relationship between AMSR-E measurements at 10.65 GHz and those at 18.7 or 6.925 GHz is first developed using the AMSR-E training data sets under RFI-free conditions. Contamination of AMSR-E measurements at 10.65 GHz is then predicted from the RFI-free measurements at 18.7 or 6.925 GHz using this relationship. It is shown that AMSR-E measurements with the RFI-correction algorithm have better agreement with simulations in a variety of surface conditions.

关键词： radio-frequency interference (RFI) RFI index RFI detection

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Impacts of Initial Conditions on Cloud-Resolving Model Simulations

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Advances in Atmospheric Sciences 2008年第5期25卷 737-747页

作者：高守亭 Xiaofan LI Laboratory of Cloud-Precipitation Physics and Severe Storms （ LACS） Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 Joint Center for Satellite Data Assimilation and NOAA/NESDIS/Center for Satellite Application and Research Camp Springs Maryland

Impacts of initial conditions on cloud-resolving model simulations are investigated using a series of sensitivity experiments. Five experiments with perturbed initial temperature, moisture, and cloud conditions are conducted and compared to the control experiment. The model is forced by the large-scale vertical velocity and zonal wind observed and derived from NCEP/Global data assimilation System （GDAS）. The results indicate that model predictions of rainfall are much more sensitive to the initial conditions than those of temperature and moisture. Further analyses of the surface rainfall equation and the moisture and cloud hydrometeor budgets reveal that the calculations of vapor condensation and deposition rates in the model account for the large sensitivities in rainfall simulations.

关键词： cloud-resolving model initial conditions sensitivity experiments

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