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Insights into Convective-scale Predictability in East China: Error Growth Dynamics and Associated Impact on Precipitation of Warm-Season Convective Events

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Advances in Atmospheric Sciences 2020年第8期37卷 893-911页

作者： Xiaoran ZHUANG Jinzhong MIN Liu ZHANG Shizhang WANG Naigeng WU Haonan ZHU Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Key Laboratory of Meteorological Disaster of EducationNanjing University of Information Science and TechnologyNanjing 210044China Jiangsu Meteorological Observatory Jiangsu Meteorological BureauNanjing 210008China Key Laboratory of Regional Numerical Weather Prediction Institute of Tropical and Marine MeteorologyChina Meteorological AdministrationGuangzhou 210044China Chongqing Climate Center Chongqing Meteorological BureauChongqing 401120China

This study investigated the regime-dependent predictability using convective-scale ensemble forecasts initialized with different initial condition perturbations in the Yangtze and Huai River basin(YHRB)of East *** scale-dependent error growth(ensemble variability)and associated impact on precipitation forecasts(precipitation uncertainties)were quantitatively explored for 13 warm-season convective events that were categorized in terms of strong forcing and weak *** forecast error growth in the strong-forcing regime shows a stepwise increase with increasing spatial scale,while the error growth shows a larger temporal variability with an afternoon peak appearing at smaller scales under weak *** leads to the dissimilarity of precipitation uncertainty and shows a strong correlation between error growth and precipitation across spatial *** lateral boundary condition errors exert a quasi-linear increase on error growth with time at the larger scale,suggesting that the large-scale flow could govern the magnitude of error growth and associated precipitation uncertainties,especially for the strong-forcing *** comparisons between scale-based initial error sensitivity experiments show evident scale interaction including upscale transfer of small-scale errors and downscale cascade of larger-scale ***,small-scale errors are found to be more sensitive in the weak-forcing regime than those under strong ***,larger-scale initial errors are responsible for the error growth after 4 h and produce the precipitation uncertainties at the meso-β-***,these results can be used to explain underdispersion issues in convective-scale ensemble forecasts and provide feedback for ensemble design over the YHRB.

关键词： convective-scale predictability error growth strong forcing weak forcing scale interaction

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Mesoscale Predictability of Mei-yu Heavy Rainfall

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Advances in Atmospheric Sciences 2009年第3期26卷 438-450页

作者：刘建勇谈哲敏 Key Lab of Mesoscale Severe Weather/MOE and School of Atmospheric SciencesNanjing UniversityNanjing 210093

Recently reported results indicate that small amplitude and small scale initial errors grow rapidly and subsequently contaminate short-term deterministic mesoscale forecasts. This rapid error growth is dependent on not only moist convection but also the flow regime. In this study, the mesoscale predictability and error growth of mei-yu heavy rainfall is investigated by simulating a particular precipitation event along the mei-yu front on 4- 6 July 2003 in eastern China. Due to the multi-scale character of the mei-yu front and scale interactions, the error growth of mei-yu heavy rainfall forecasts is markedly different from that in middle-latitude moist baroclinic systems. The optimal growth of the errors has a relatively wide spectrum, though it gradually migrates with time from small scale to mesoscale. During the whole period of this heavy rainfall event, the error growth has three different stages, which similar to the evolution of 6-hour accumulated precipitation. Multi-step error growth manifests as an increase of the amplitude of errors, the horizontal scale of the errors, or both. The vertical profile of forecast errors in the developing convective instability and the moist physics convective system indicates two peaks, which correspond with inside the mei-yu front, and related to moist The error growth for the mei-yu heavy rainfall is concentrated convective instability and scale interaction.

关键词： mesoscale predictability error growth scale interaction mei-yu front precipitation

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An Investigation into Effect of Randomly Distributed Small scale Vortices on Vortex Self-Organization

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Acta meteorologica Sinica 2008年第2期22卷 143-151页

作者：罗哲贤李春虎 Remote Sensing College Nanjing University of Information Science and Technology

Previous studies concerning the interaction of dual vortices have been made generally in the deterministic framework. In this paper, by using an advection equation model, eight numerical experiments whose integration times are 30 h are performed in order to analyze the interaction of dual vortices and the vortex self-organization in a coexisting system of deterministic and stochastic components. The stochastic components are introduced into the model by the way that the Iwayama scheme is used to produce the randomly distributed small-scale vortices which are then added into the initial field. The different intensity of the small-scale vortices is described by parameter K being 0.0, 0.4, 0.6, 0.8, and 1.0, respectively. When there is no small-scale vortex （K=0.0）, two initially separated meso-beta vortices rotate counterclockwise mutually, and their quasi-final flow pattern is still two separated vortices; after initially incorporating small-scale vortices （K=0.8, 1.0）, the two separated meso-beta vortices of initially same intensity gradually evolve into a major and a secondary vortex in time integration. The major vortex pulls the secondary one, which gradually evolves into the spiral band of the major vortex. The quasi-final flow pattern is a self-organized vortex with typhoon-like circulation, and the relative vorticity at its center increases with increasing in K value, suggesting that small-scale vortices feed the self-organized vortex with vorticity. This may be a possible mechanism responsible for changes in the strength of the self-organized vortex. Results also show that the quasi-final pattern not only relates with the initial intensity of the small-scale vortices, but also with their initial distribution. In addition, three experiments are also performed in the case of various boundary conditions. Firstly, the periodic condition is used on the E-W boundary, but the fixed condition on the S-N boundary; secondly, the fixed condition is set on all the bounda

关键词： vortex self-organization scale interaction tropical cyclone intensity change

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Recent Advance in Understanding the Dynamics of the Madden-Julian Oscillation

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Journal of Meteorological Research 2014年第1期28卷 1-33页

作者：李天明 International Pacific Research Center and Department of Meteorology School of Ocean and Earth Science and TechnologyUniversity of Hawaii at Manoa Key Laboratory of Meteorological Disaster and College of Atmospheric Science Nanjing University of Information Science & Technology

The Madden-Julian oscillation （MJO） is a dominant atmospheric low-frequency mode in the tropics. In this review article, recent progress in understanding the MJO dynamics is described. Firstly, the fundamental physical processes responsible for MJO eastward phase propagation are discussed. Next, a recent modeling result to address why MJO prefers a planetary zonal scale is presented. The effect of the seasonal mean state on distinctive propagation characteristics between northern winter and summer is discussed in a theoretical framework. Then, the observed precursor signals and the physical mechanism of MJO initiation in the western equatorial Indian Ocean are further discussed. Finally, scale interactions between MJO and higher- frequency eddies are delineated.

关键词： Madden-Julian oscillation (MJO) eastward phase propagation physical mechanism of MJOinitiation scale interaction

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A Simulation Study of the Mesoscale Convective Systems Associated with a Meiyu Frontal Heavy Rain Event

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Acta meteorologica Sinica 2009年第4期23卷 438-454页

作者：张进谈哲敏 Key Laboratory of Mesoscale Severe Weather/MOE and School of Atmospheric Sciences Nanjing University

In this study, evolution of the mesoscale convective systems （MCSs） within a Meiyu front during a particularly heavy rainfall event on 22 June 1999 in East China was simulated by using a nonhydrostatic numerical model ARPS （Advanced Regional Prediction System）. Investigations were conducted with emphasis on the impact of the interaction among multi-scale weather systems （MWSs） on the development of MCSs in the Meiyu frontal environment. For this case, the development of MCSs experienced three different stages. （1） The convections associated with MCSs were firstly triggered by the eastward-moving Southwest Vortex （SWV） from the Sichuan Basin, accompanying the intensification of the upper-level jet （ULJ） and the low-level jet （LLJ） that were approaching the Meiyu front. （2） Next, a low-level shear line （LSL） formed, which strengthened and organized the MCSs after the SWV decayed. Meanwhile, the ULJ and LLJ enhanced and produced favorable conditions for the MCSs development. （3） Finally, as the MCSs got intensified, a mesoscale convective vortex （MCV）, a mesoscale LLJ and a mesoscale ULJ were established. Then a coupled-development of MWSs was achieved through the vertical frontal circulations, which further enhanced the MCV and resulted in the heavy rainfall. This is a new physical mechanism for the formation of Meiyu heavy rainfall related to the SWV during the warm season in East China. In the three stages of the heavy rainfall, the vertical frontal circulations exhibited distinguished structures and played a dynamic role, and they enhanced the interaction among the MWSs. A further examination on the formation and evolution of the MCV showed that the MCV was mainly caused by the latent heat release of the MCSs, and the positive feedback between the MCSs and MCV was a key characteristic of the scale interaction in this case.

关键词： mesoscale convective systems (MCSs) Meiyu front mesoscale convective vortex (MCV) scale interaction

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Impacts of Randomly Distributed Small-scale Vortices on Typhoon Tracks

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Acta meteorologica Sinica 2010年第6期24卷 713-720页

作者：罗哲贤邹立尧 Remote Sensing School Nanjing University of Information Science & Technology

Impacts of small-scale vortices on typhoon or tropical cyclone（TC） tracks in a system of three components （an idealized subtropical high ridge,a TC,and small-scale vortices） were examined numerically using a barotropic primitive equation model and idealized initial *** small-scale vorticity fields were generated stochastically,where the number of initial small-scale vortices is *** the two fields,the number, size,structure as well as the total kinetic energy of the small-scale vortices were all the same,but their center coordinates were randomly *** experiments,named EXA and EXB,with the integration time of 56 h,were performed. Comparison of the integration outputs from the two experiments indicates that various small-scale vorticity fields involved could produce both various horizontal winds in the TC outer area and various intensities of the environmental steering for *** values of the environmental flow speed along the east-west direction are 7.8,8.2,and 8.7 m s^（-1） in EXA and 8.3,9.5,and 9.7 m s^（-1） in EXB at t = 24,36,and 48 h,respectively. The values along the south-north direction are 0.9,1.8,and 2.5 m s^（-1） in EXA and 2.3,2.3,and 5.9 m s^（-1） in EXB,*** various intensities of the environmental steering could lead to various TC center *** example,the difference between the coordinates of TC centers in EXA and EXB reaches 120 km at t = 48 h,which is about 56%of the prediction error of TC tracks in the northwestern Pacific region derived from eight operational models. Dynamics of the interplays between a subtropical high ridge and a TC in previous works has shown that when the TC was located equatorwards of the subtropical ridge,the relationship between the propagation of TC and the local absolute vorticity gradient was characterized by points scattered around their mean *** introducing the stochastic vorticity field into the model,the interplays among the subtropical high ridge,the TC,and small-scale

关键词： tropical cyclone tropical cyclone tracks scale interaction stochastic effects

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