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Interdecadal Variations of ENSO around 1999/2000

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Journal of meteorological research 2017年第1期31卷 73-81页

作者： Zeng-Zhen HU Arun KUMAR Bohua HUANG Jieshun ZHU Hong-Li REN Climate Prediction Center NCEP/NWS/NOAA5830 University Research CourtCollege ParkMD 20740USA Department of Atmospheric Oceanic and Earth Sciences and Center for Ocean-Land-Atmosphere StudiesGeorge Mason University4400 University DriveFairfaxVA 22030USA Laboratory for Climate Studies&CMA-NJU Joint Laboratory for Climate Prediction Studies National Climate CenterChina Meteorological AdministrationBeijing 100081China

This paper discusses the interdecadal changes of the climate in the tropical Pacific with a focus on the correspond- ing changes in the characteristics of the E1 Nifio-Southern Oscillation （ENSO）. Compared with 1979-1999, the whole tropical Pacific climate system, including both the ocean and atmosphere, shifted to a lower variability regime after 1999/2000. Meanwhile, the frequency of ENSO became less regular and was closer to a white noise process. The lead time of the equatorial Pacific＇s subsurface ocean heat content in preceding ENSO decreased remarkably, in addition to a reduction in the maximum correlation between them. The weakening of the correlation and the shorten- ing of the lead time pose more challenges for ENSO prediction, and is the likely reason behind the decrease in skill with respect to ENSO prediction after 2000. Coincident with the changes in tropical Pacific climate variability, the mean states of the atmospheric and oceanic components also experienced physically coherent changes. The warm an- omaly of SST in the western Pacific and cold anomaly in the eastern Pacific resulted in an increased zonal SST gradi- ent, linked to an enhancement in surface wind stress and strengthening of the Walker circulation, as well as an in- crease in the slope of the thermocline. These changes were consistent with an increase （a decrease） in precipitation and an enhancement （a suppression） of the deep convection in the western （eastern） equatorial Pacific. Possible con- nections between the mean state and ENSO variability and frequency changes in the tropical Pacific are also dis- cussed.

关键词： ENSO interdecadal variation amplitude suppression frequency change mean state

Conjugate Gradient Algorithm in the Four-Dimensional Variational Data Assimilation System in GRAPES

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Journal of meteorological research 2018年第6期32卷 974-984页

作者： Yongzhu LIU Lin ZHANG Zhihua LIAN National meteorological Center Beijing 100081

Minimization algorithms are singular components in four-dimensional variational data assimilation(4DVar).In this paper,the convergence and application of the conjugate gradient algorithm(CGA),which is based on the Lanczos iterative algorithm and the Hessian matrix derived from tangent linear and adjoint models using a non-hydrostatic framework,are investigated in the 4DVar ***,the influence of the Gram-Schmidt orthogonalization of the Lanczos vector on the convergence of the Lanczos algorithm is *** results show that the Lanczos algorithm without orthogonalization fails to converge after the ninth iteration in the 4DVar minimization,while the orthogonalized Lanczos algorithm converges ***,the convergence and computational efficiency of the CGA and quasi-Newton method in batch cycling assimilation experiments are compared on the 4DVar platform of the Global/Regional Assimilation and Prediction System(GRAPES).The CGA is 40%more computationally efficient than the quasi-Newton method,although the equivalent analysis results can be obtained by using either the CGA or the quasi-Newton ***,the CGA based on Lanczos iterations is better for solving the optimization problems in the GRAPES 4DVar system.

关键词： numerical weather prediction Global/Regional Assimilation and Prediction System four-dimensional variation conjugate gradient algorithm Lanczos algorithm

Characteristics of Near Surface Winds over Different Underlying Surfaces in china: Implications for Wind Power Development

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Journal of meteorological research 2019年第2期33卷 349-362页

作者： Xi GONG Rong ZHU Lianshou CHEN Nanjing University of Information Science & Technology Chinese Academy of meteorological Sciences National Climate Center china meteorological Administration

Accurate wind and turbulence information are essential to wind energy research and utilization, among which wind shear and turbulence intensity/scale have seldom been investigated. In this paper, the observational data from the100-m high wind towers in Xilinhot in Inner Mongolia(2009–10; grassland region), Huanghua in Hebei Province(2009–10; coastal flat region), and Xingzi County in Jiangxi Province(2010–11; mountain–lake region) are used to study the variations in near surface winds and turbulence characteristics related to the development of local wind energy over different underlying surfaces. The results indicate that(1) the percentage of the observed wind shear exponents exceeding 0.3 for the grassland region is 6%, while the percentage is 13% for the coastal flat region and 10%for the mountain–lake region. In other words, if the wind speed at 10 m is 10 ms^(–1), the percentage of the wind speed at 100 m exceeding 20 ms^(–1) for the grassland region is 6%, while the percentage is 13% for the coastal flat region and 10% for the mountain–lake region.(2) In terms of the turbulent intensity in the zonal, meridional, and vertical directions(I_u, I_v, and I_w, respectively), the frequencies of I_v/I_u < 0.8 in the grassland, coastal flat, and mountain–lake regions are 23%–29%, 32%–38%, and 30%–37%, respectively. Additionally, the frequencies of I_w/I_u < 0.5 in the grassland, coastal flat, and mountain–lake regions are 45%–75%, 52%–70%, and 43%–53%, respectively. The frequencies of I_v/I_u < 0.8 and Iw/I_u < 0.5 in each region mean that I_u is large and the air flow is unstable and fluctuating,which will damage the wind turbines. Therefore, these conditions do not meet the wind turbine design requirements,which must be considered separately.(3) At 50-and 70-m heights, the value of the turbulence scale parameter Λ in the grassland region is greater than that in the coastal flat region, and the latter is greater than that in the mountain–lake region. Therefore, under

关键词： wind energy underlying surface wind shear exponent turbulence turbulent intensity

Change of parameters of BCC/RCG-WG for daily non-precipitation variables in china： 1951-1978 and 1979-2007

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Journal of Geographical Sciences 2013年第4期23卷 579-594页

作者：廖要明 Laboratory for Climate Studies/National Climate Center CMA Beijing 100081 China State Key Laboratory of Earth Surface Processes and Resource Ecology School of Geography Beijing Normal University Beijing 100875 China

Parameters of weather generator BCC/RCG-WG for daily non-precipitation variables including maximum temperature, minimum temperature and sunshine hours at 669 stations in china are estimated using history daily records from 1951 to 1978 and from 1979 to 2007 respectively. The changes in the parameters for the two periods are revealed to explore the impact of climate change on these parameters. The results show that the parameters of the non-precipitation variables have experienced different changes. While the annual means and the amplitudes of the seasonal cycle show a clear change, the interannual variability, the timings of the seasonal cycles, and the temporal correlations for each variable remain practically unchanged. This indicates that climate changes in china over the last 57 years are mainly reflected in variations in the means and in the strength of the seasonal cycles. The changed parameters have implications for the stationary assumption implied in the parameter estimation and use of the weather generator for climate change studies.

关键词： BCC/RCG-WG weather generator daily non-precipitation variables climate change parameters china

Changes in classified precipitation in the urban, suburban, and mountain areas of Beijing

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Advances in Climate Change research 2017年第4期8卷 279-285页

作者： YUAN Yu-Feng ZHAI Pan-Mao LI Jian CHEN Yang Key Laboratory of meteorological Disaster of Ministry of Education Collaborative Innovation Center on Forecast and Evaluation of Meteorological DisastersNanjing University of Information Science and Technology Nanjing 210044 China State Key Laboratory of Severe Weather Chinese Academy of Meteorological Sciences Beijing 100081 China

In this paper, based on hourly precipitation observations in 1977e2013 in the Beijing area, china, hourly precipitation in summer (June?August) is classified into three categories: light (below the 50th percentile values), moderate (the 50th to 95th percentile values), and heavy (above the 95th percentile values). Results reveal that both light and moderate precipitation decreased significantly during the research period and thereby caused the decrease in summer totals. By contrast, pronounced trends failed to be detected in the heavy category. Since 2004, the contribution of heavy rainfall to the summer total precipitation in the urban area increased as compared to the suburban area, which is opposite to light rainfall. There are obvious differences in the diurnal variations of classified precipitation. Light precipitation shows a double peak structure in the early morning and at night, while moderate and heavy rainfall show a single peak at night. Light precipitation at the early morning peak time decreased significantly in the whole Beijing area. Compared with the suburban area, light precipitation in the urban area occurred less frequently whereas heavy precipitation occurred more frequently at evening peak time after 2004. The asymmetry of the rainfall is obvious, especially, for heavy precipitation. The asymmetry of heavy precipitation events in the urban area exhibits a significant increasing trend.

关键词： Hourly precipitation Classified precipitation Diurnal variation Asymmetry Beijing

Re-evaluating the vertical mass-flux profiles of aeolian sediment at the southern fringe of the Taklimakan Desert, china

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Journal of Arid Land 2015年第6期7卷 765-777页

作者： XUE Jie LEI Jiaqiang LI Shengyu GUI Dongwei MAO Donglei ZHOU Jie State Key Laboratory of Desert and Oasis Ecology Xinjiang Institute of Ecology and Geography Chinese Academy of Sciences Cele National Station of Observation and research for Desert-Grassland Ecosystem Xinjiang Institute of Ecology and GeographyChinese Academy of Sciences Key Laboratory of Biogeography and Bioresource in Arid Land Xinjiang Institute of Ecology and Geography Chinese Academy of Sciences University of Chinese Academy of Sciences

Reliable estimation of the mass-flux profiles of aeolian sediment is essential for predicting sediment transport rates accurately and designing measures to cope with wind-erosion. Vertical mass-flux profiles from seventeen wind-erosion events were re-evaluated using five typical models based on observed data obtained from a smooth bare field at the southern fringe of the Taklimakan Desert, china. The results showed that the exponential-function model and the logarithmic-function model exhibited the poorest fit between observed and predicted mass-flux profiles. The power-function model and the modified power-function model improved the fit to field data to an equivalent extent, while the five-parameter combined-function model with a scale constant（σ） of 0.00001 m（different from the σ value proposed by Fryear, which represented the height above which 50% of the total mass flux occurred） was verified as the best for describing the vertical aeolian sediment mass-flux profiles using goodness of fit（R2） and the Akaike Information Criterion（AIC） values to evaluate model performance. According to relationships among model parameters, the modified power model played a prominent explanatory role in describing the vertical profiles of the observed data, whereas the exponential model played a coordinating role. In addition, it was found that the vertical profiles could not be extrapolated using the five selected models or easily estimated using an efficient model without field observations by a near-surface sampler at 0 to 0.05 m.

关键词： vertical profile mass flux aeolian sediment wind erosion Taklimakan Desert

Development of a Global Historic Monthly Mean Precipitation Dataset

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Journal of meteorological research 2016年第2期30卷 217-231页

作者：杨溯徐文慧许艳李庆祥 National meteorological Information Center China Meteorological Administration

Global historic precipitation dataset is the base for climate and water cycle *** have been several global historic land surface precipitation datasets developed by international data centers such as the US National Climatic Data Center(NCDC),European Climate Assessment & Dataset project team,Met Office,etc.,but so far there are no such datasets developed by any research institute in *** addition,each dataset has its own focus of study region,and the existing global precipitation datasets only contain sparse observational stations over china,which may result in uncertainties in East Asian precipitation *** order to take into account comprehensive historic information,users might need to employ two or more ***,the non-uniform data formats,data units,station IDs,and so on add extra difficulties for users to exploit these *** this reason,a complete historic precipitation dataset that takes advantages of various datasets has been developed and produced in the National meteorological Information Center of *** observations from 12 sources are aggregated,and the data formats,data units,and station IDs are *** stations with the same ID are identified,with duplicated observations *** test,correlation coefficient test,significance t-test at the95%confidence level,and significance F-test at the 95%confidence level are conducted first to ensure the data *** those datasets that satisfy all the above four criteria are integrated to produce the china meteorological Administration global precipitation(CGP) historic precipitation dataset version *** contains observations at 31 thousand stations with 1.87 x 107 data records,among which 4152 time series of precipitation are longer than 100 *** dataset plays a critical role in climate research due to its advantages in large data volume and high density of station network,compared to other *** the Penalized Maximal

关键词： global precipitation observation historic data

Evaluation of the NMC Regional Ensemble Prediction System During the Beijing 2008 Olympic Games

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Acta meteorologica Sinica 2011年第5期25卷 568-580页

作者：李晓莉田华邓国 The Center of Numerical Weather Prediction China Meteorological Administration

Based on the B08RDP（Beijing 2008 Olympic Games Mesoscale Ensemble Prediction research and Development Project） that was launched by the World Weather research Programme（WWRP） in 2004,a regional ensemble prediction system（REPS） at a 15-km horizontal resolution was developed at the National meteorological Center（NMC） of the china meteorological Administration（CMA）.Supplementing to the forecasters＇ subjective affirmation on the promising performance of the REPS during the 2008 Beijing Olympic Games（BOG）,this paper focuses on the objective verification of the REPS for precipitation forecasts during the BOG *** use of a set of advanced probabilistic verification scores,the value of the REPS compared to the quasi-operational global ensemble prediction system（GEPS） is assessed for a 36-day period（21 July-24 August 2008）.The evaluation here involves different aspects of the REPS and GEPS,including their general forecast skills,specific attributes（reliability and resolution）,and related economic *** results indicate that the REPS generally performs significantly better for the short-range precipitation forecasts than the GEPS,and for light to heavy rainfall events,the REPS provides more skillful forecasts for accumulated 6-and 24-h *** further identifying the performance of the REPS through the attribute-focused measures,it is found that the advantages of the REPS over the GEPS come from better reliability（smaller biases and better dispersion） and increased ***,evaluation of a decision-making score reveals that a much larger group of users benefits from using the REPS forecasts than using the single model（the control run） forecasts,especially for the heavy rainfall events.

关键词： regional ensemble prediction ensemble verification probabilistic scores

Numerical study of the effects of local atmospheric circulations on a pollution event over Beijing–Tianjin–Hebei, china

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Journal of Environmental Sciences 2015年第4期27卷 9-20页

作者： Yucong Miao Shuhua Liu Yijia Zheng Shu Wang Bicheng Chen Hui Zheng Jingchuan Zhao Department of Atmospheric and Oceanic Sciences School of Physics Peking University Department of Meteorology The Pennsylvania State University University Park Key Laboratory of Regional Climate–Environment research for Temperate East Asia Institute of Atmospheric PhysicsChinese Academy of Sciences Department of Atmospheric Sciences Yunnan University

Currently, the Chinese central government is considering plans to build a trilateral economic sphere in the Bohai Bay area, including Beijing, Tianjin and Hebei（BTH）, where haze pollution frequently occurs. To achieve sustainable development, it is necessary to understand the physical mechanism of the haze pollution there. Therefore, the pollutant transport mechanisms of a haze event over the BTH region from 23 to 24 September 2011 were studied using the Weather research and Forecasting model and the FLEXible-PARTicle dispersion model to understand the effects of the local atmospheric circulations and atmospheric boundary layer structure. Results suggested that the penetration by sea-breeze could strengthen the vertical dispersion by lifting up the planetary boundary layer height（PBLH） and carry the local pollutants to the downstream areas; in the early night, two elevated pollution layers（EPLs） may be generated over the mountain areas： the pollutants in the upper EPL at the altitude of 2–2.5 km were favored to disperse by long-range transport, while the lower EPL at the altitude of 1 km may serve as a reservoir, and the pollutants there could be transported downward and contribute to the surface air *** intensity of the sea–land and mountain–valley breeze circulations played an important role in the vertical transport and distribution of pollutants. It was also found that the diurnal evolution of the PBLH is important for the vertical dispersion of the pollutants,which is strongly affected by the local atmospheric circulations and the distribution of urban areas.

关键词： Air pollution Sea–land breeze circulation Mountain–valley breeze circulation WRF model FLEXPART model