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Propagation and Mechanisms of the Quasi-Biweekly Oscillation over the Asian Summer Monsoon Region

Journal of Meteorological research 2017年第2期31卷 321-335页

作者： Meirong WANG Jun WANG Anmin DUAN Center of Data Assimilation for Research and Application/Key Laboratory of Meteorological Disaster of Ministry of Education Nanjing University of Information Science & TechnologyNanjing 210044 Plateau Atmosphere and Environment Key Laboratory of Sichuan Province Chengdu 610225 International Institute for Earth System Science Nanjing UniversityNanjing 210023 State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029

The propagation and underlying mechanisms of the boreal summer quasi-biweekly oscillation（QBWO）over the entire Asian monsoon region are investigated,based on ECMWF Interim reanalysis（ERA-Interim）data,GPCP precipitation data,and an atmospheric general circulation model（AGCM）.Statistical analyses indicate that the QBWO over the Asian monsoon region derives its main origin from the equatorial western Pacific and moves northwestward to the Bay of Bengal and northern India,and then northward to the Tibetan Plateau（TP）area,with a baroclinic vertical *** propagation of the QBWO is promoted by three main mechanisms：barotropic vorticity,boundary moisture advection,and surface sensible heating（SSH）.It is dominated by the barotropic vorticity effect when the QBWO signals are situated to the south of 20°*** the propagation taking place farther north toward the TP,the boundary moisture advection and SSH are the leading *** use an AGCM to verify the importance of SSH on the northward propagation of the *** simulations confirm the diagnostic conclusion that the equatorial western Pacific is the source of the ***,the model can accurately simulate the propagation pathway of the QBWO signals over the Asian monsoon ***,sensitivity experiments demonstrate that the SSH over northern India and the southern slope of the TP greatly contributes to the northward propagation of the QBWO as far as the TP area.

关键词： quasi-biweekly oscillation Asian monsoon region northward-propagating mechanism surface sensible heating atmospheric general circulation model

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Detection of radio-frequency interference signals from AMSR-E data over the United States with snow cover

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Frontiers of Earth Science 2016年第2期10卷 195-204页

作者： Chengcheng FENG Xiaolei ZOU Juan ZHAO Center of Data Assimilation for Research and Application Nanjing University of Information Science & Technology Nanjing 210044 China Earth System Science Interdisciplinary Center University of Maryland College Park MD 20740-3823 USA China Meteorological Administration Training Centre Beijing 100081 China

Radio Frequency Interference （RFI） causes severe contamination to passive and active microwave sensing observations and corresponding retrieval products. RFI signals should be detected and filtered before applying the microwave data to retrieval and data assimilation. It is difficult to detect RFI over land surfaces covered by snow because of the scattering effect of snow surface. The double principal component analysis （DPCA） method is adopted in this study, and its ability in identifying RFI signals in AMSR-E data over snow covered regions is investigated. Results show that the DPCA method can detect RFI signals effectively in spite of the impact of snow scattering, and the detected RFI signals persistent over time. Compared to other methods, such as PCA and normalized PCA, DPCA is more robust and suitable for operational application.

关键词： Radio Frequency Interference （RFI） AMSR-E double principal component analysis （DPCA）

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Quality control of AIRS total column ozone data within tropical cyclones

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Frontiers of Earth Science 2016年第2期10卷 222-235页

作者： Yin LIU Xiaolei ZOU Center of Data Assimilation for Research and Application Nanjing University of Information Science & Technology Nanjing 210044 China Key Laboratory of Meteorological Disaster of Ministry of Education Nanjing University of Information Science & Technology Nanjing 210044 China Earth System Science Interdisciplinary Center University of Maryland College Park MD 20740-3823 USA

The Atmospheric Infrared Sounder （AIRS） provides infrared radiance observations twice daily, which can be used to retrieve total column ozone with high spatial resolution. However, it was found that almost all of the ozone data within typhoons and hurricanes were flagged to be of bad quality by the AIRS original quality control （QC） scheme. This determination was based on the ratio of total precipitable water （TPW） error divided by TPW value, where TPW was an AIRS retrieval product. It was found that the difficulty in finding total column ozone data that could pass AIRS QC was related to the low TPW employed in the AIRS QC algorithm. In this paper, a new two-step QC scheme for AIRS total column ozone is developed. A new ratio is defined which replaces the AIRS TPW with the zonal mean TPW retrieved from the Advanced Microwave Sounding Unit. outliers when the new The first QC step is to remove ratio exceeds 33%. Linear regression models between total column ozone and mean potential vorticity are subsequently developed with daily updates, which are required for future applications of the proposed total ozone QC algorithm to vortex initialization and assimilation of AIRS data. In the second QC step, observations that significantly deviate from the models are further removed using a biweighting algorithm. Numerical results for two typhoon cases and two hurricane cases show that a large amount of good quality AIRS total ozone data is kept within Tropical Cyclones after implementing the proposed QC algorithm.

关键词： AIRS total column ozone total precipitablewater mean potential vorticity quality control

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ANALYSIS OF THE EFFECT OF 3DVAR AND ENSRF DIRECT assimilation OF RADAR data ON THE FORECAST OF A HEAVY RAINFALL EVENT

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Journal of Tropical Meteorology 2016年第3期22卷 413-425页

作者：刘寅何光鑫刘佳伟赵虹燕成玉 Jiangsu Meteorological Observation Center Nanjing 210009 China Jiangsu Institute of Meteorological Sciences Nanjing 210009 China Center for Data Assimilation Research and Application Nanjing University of Information Science & Technology Nanjing 210044 China Luhe Meteorological Bureau Nanjing 211599 China Qinhuangdao Municipal Meteorological Observatory Qinhuangdao 066000 China

The present study designs experiments on the direct assimilation of radial velocity and reflectivity data collected by an S-band Doppler weather radar(CINRAD WSR-98D) at the Hefei Station and the reanalysis data produced by the United States National centers for Environmental Prediction using the Weather research and Forecasting(WRF) model,the WRF model with a three-dimensional variational(3DVAR) data assimilation system and the WRF model with an ensemble square root filter(EnSRF) data assimilation *** addition,the present study analyzes a Meiyu front heavy rainfall process that occurred in the Yangtze-Huaihe River Basin from July 4 to July 5,2003,through numerical *** results show the following.(1) The assimilation of the radar radial velocity data can increase the perturbations in the low-altitude atmosphere over the heavy rainfall region,enhance the convective activities and reduce excessive simulated precipitation.(2) The 3DVAR assimilation method significantly adjusts the horizontal wind *** assimilation of the reflectivity data improves the microphysical quantities and dynamic fields in the *** addition,the assimilation of the radial velocity and reflectivity data can better adjust the wind fields and improve the intensity and location of the simulated radar echo bands.(3) The EnSRF assimilation method can assimilate more small-scale wind field information into the *** assimilation of the reflectivity data alone can relatively accurately forecast the rainfall *** addition,the assimilation of the radial velocity and reflectivity data can improve the location of the simulated radar echo bands.(4) The use of the 3DVAR and EnSRF assimilation methods to assimilate the radar radial velocity and reflectivity data can improve the forecast of precipitation,rain-band areal coverage and the center location and intensity of precipitation.

关键词： assimilation radar data heavy rainfall forecast numerical simulation

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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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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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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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Polarization signature from the FengYun-3 Microwave Humidity Sounder

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Frontiers of Earth Science 2014年第4期8卷 625-633页

作者： Xiaolei ZOU Xu CHEN Fuzhong WENG Center of Data Assimilation for Research and Application Nanjing University of Information Science & Technology Nanjing 210044 China Department of Earth Ocean and Atmospheric Sciences Florida State University FL 32306 USA National Environmental Satellite Data & Information Service National Oceanic and Atmospheric Administration College Park MD 20740 USA

Microwave Humidity Sounders （MHS） onboard NOAA- 15, - 16, - 17, - 18, - 19, and EUMETSAT MetOp-A/B satellites provide radiance measurements at a single polarization state at any of five observed frequen- cies. The Microwave Humidity Sounder （MWHS） onboard the FengYun-3 （FY-3） satellite has a unique instrument design that provides dual polarization measurements at 150 GHz. In this study, the MWHS polarization signal was investigated using observed and modeled data. It is shown that the quasi-polarization brightness temperatures at 150GHz display a scan angle dependent bias. Under calm ocean conditions, the polarization difference at 150 GHz becomes non-negligible when the scan angle varies from 10° to 45° and reaches a maximum when the scan angle is about 30°. Also, the polarization state is sensitive to surface parameters such as surface wind speed. Under clear-sky conditions, the differences between horizontal and vertical polarization states at 150GHz increase with decreasing surface wind speed. Therefore, the polarization signals from the cross-track scanning microwave measurements at window channels contain useful information about surface parameters. In addition, the availability of dual polarization measurements allows a one-to-one conversion from antenna brightness temperature to sensor brightness temperature ifa cross-polarization spill-over exists.

关键词： Microwave Humidity Sounder （MWHS）,polarization remote sensing surface properties

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Correction to "Fengyun-3B MicroWave Humidity Sounder (MWHS) data Noise Characterization and Filtering Using Principle Component Analysis" [Dec 12 4892-4902]

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IEEE Transactions on Geoscience and Remote Sensing 2013年第4期51卷 2484-2484页

作者： Xiaolei Zou Yuan Ma Zhengkun Qin Center of Data Assimilation for Research and Application Nanjing University of Information Science and Technology Nanjing China Department of Earth Ocean and Atmospheric Sciences Florida State University Tallahassee FL USA

In the above-named article [ibid., vol. 50, no. 12, pp. 4892-4902, Dec. 2012], Fig. 6 is incorrect. The correct one is printed here.

关键词： Principal component analysis Humidity Noise Atmospheric measurements

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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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