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Barotropic Processes Associated with the Development of the Mei-yu Precipitation System

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Advances in Atmospheric Sciences 2016年第5期33卷 593-598页

作者： Tingting li xiaofan li School of Earth Sciences Zhejiang University

The barotropic processes associated with the development of a precipitation system are investigated through analysis of cloud-resolving model simulations of Mei-yu torrential rainfall events over eastern China in mid-June 2011. During the model integration period, there were three major heavy rainfall events： 9–12, 13–16 and 16–20 June. The kinetic energy is converted from perturbation to mean circulations in the first and second period, whereas it is converted from mean to perturbation circulations in the third period. Further analysis shows that kinetic energy conversion is determined by vertical transport of zonal momentum. Thus, the prognostic equation of vertical transport of zonal momentum is derived, in which its tendency is associated with dynamic, pressure gradient and buoyancy processes. The kinetic energy conversion from perturbation to mean circulations in the first period is mainly associated with the dynamic processes. The kinetic energy conversion from mean to perturbation circulations in the third period is generally related to the pressure gradient processes.

关键词： tropical cyclone–trough interaction upper troposphere eddy momentum flux convergence

Dependence of the Accuracy of Precipitation and Cloud Simulation on Temporal and Spatial Scales

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Advances in Atmospheric Sciences 2009年第6期26卷 1108-1114页

作者：高守亭 xiaofan li Laboratory of Cloud-Precipitation Physics and Severe Storms 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 USA

Precipitation and associated cloud hydrometeors have large temporal and spatial variability, which makes accurate quantitative precipitation forecasting difficult. Thus, dependence of accurate precipitation and associated cloud simulation on temporal and spatial scales becomes an important issue. We report a cloud- resolving modeling analysis on this issue by comparing the control experiment with experiments perturbed by initial temperature, water vapor, and cloud conditions. The simulation is considered to be accurate only if the root-mean-squared difference between the perturbation experiments and the control experiment is smaller than the standard deviation. The analysis may suggest that accurate precipitation and cloud simulations cannot be obtained on both fine temporal and spatial scales simultaneously, which limits quanti- tative precipitation forecasting. The accurate simulation of water vapor convergence could lead to accurate precipitation and cloud simulations on daily time scales, but it may not be beneficial to precipitation and cloud simulations on hourly time scales due to the dominance of cloud processes.

关键词： temporal and spatial scales cloud and rainfall simulations cloud-resolving model initial con-ditions

Kinetic Energy Budgets during the Rapid Intensification of Typhoon Rammasun (2014)

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Advances in Atmospheric Sciences 2023年第1期40卷 78-94页

作者： Xin QUAN xiaofan li Key Laboratory of Geoscience Big Data and Deep Resource of Zhejiang Province School of Earth SciencesZhejiang UniversityHangzhouZhejiang 310027China

In this study,Typhoon Rammasun(2014)was simulated using the Weather Research and Forecasting model to examine the kinetic energy during rapid intensification(RI).Budget analyses revealed that in the inner area of the typhoon,the conversion from symmetric divergent kinetic energy associated with the collocation of strong cyclonic circulation and inward flow led to an increase in the symmetric rotational kinetic energy in the lower *** increase in the symmetric rotational kinetic energy in the mid and upper troposphere resulted from the upward transport of symmetric rotational kinetic energy from the lower *** the outer area,both typhoon and Earth’s rotation played equally important roles in the conversion from symmetric divergent kinetic energy to symmetric rotational kinetic energy in the lower *** decrease in the symmetric rotational kinetic energy in the upper troposphere was caused by the conversion to asymmetric rotational kinetic energy through the collocation of symmetric tangential rotational winds and the radial advection of asymmetric tangential rotational winds by radial environmental winds.

关键词： Typhoon Rammasun(2014) rapid intensification kinetic energy budget symmetric and asymmetric winds divergent and rotational circulations environmental flows

Radiative Effects on Torrential Rainfall during the Landfall of Typhoon Fitow(2013)

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Advances in Atmospheric Sciences 2016年第1期33卷 101-109页

作者： lingyun LOU xiaofan li School of Earth Sciences Zhejiang University

Cloud microphysical and rainfall responses to radiative processes are examined through analysis of cloud-resolving model sensitivity experiments of Typhoon Fitow（2013） during *** budget analysis shows that the increase in the mean rainfall caused by the exclusion of radiative effects of water clouds corresponds to the decrease in accretion of raindrops by cloud ice in the presence of radiative effects of ice clouds,but the rainfall is insensitive to radiative effects of water clouds in the absence of radiative effects of ice *** increases in the mean rainfall resulting from the removal of radiative effects of ice clouds correspond to the enhanced net *** increases（decreases） in maximum rainfall caused by the exclusion of radiative effects of water clouds in the presence（absence） of radiative effects of ice clouds,or the removal of radiative effects of ice clouds in the presence（absence） of radiative effects of water clouds,correspond mainly to the enhancements（reductions） in net *** mean rain rate is a product of rain intensity and fractional rainfall *** radiation-induced difference in the mean rain rate is related to the difference in rain *** radiation-induced difference in the maximum rain rate is associated with the difference in the fractional coverage of maximum rainfall.

关键词： radiative effects rainfall maximum rainfall rain intensity fractional rainfall coverage net condensation hydrometeor change

Monte-Carlo based random passive energy beamforming for reconfigurable intelligent surface assisted wireless power transfer

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Digital Communications and Networks 2023年第3期9卷 667-676页

作者： Ziyang Lu Yubin Zhao xiaofan li School of Microelectronics Science and Technology Sun Yat-Sen UniversityZhuhai519082China School of Intelligent System Science and Engineering Jinan UniversityZhuhai519070China

Reconfigurable intelligent surface(RIS)employs passive beamforming to control the wireless propagation channel,which benefits the wireless communication capacity and the received energy efficiency of wireless power transfer(WPT)*** beamforming schemes are classified as discrete and non-convex integer program-ming *** this paper,we propose a Monte-Carlo(MC)based random energy passive beamforming of RIS to achieve the maximum received power of electromagnetic(EM)WPT ***,the Gibbs sampling and re-sampling methods are employed to generate phase shift vector *** the sample with the maximum received power is considered the optimal *** order to adapt to the application scenarios,we develop two types of passive beamforming algorithms based on such MC sampling *** first passive beamforming uses an approximation of the integer programming as the initial sample,which is calculated based on the channel *** the second one is a purely randomized algorithm with the only total received power *** proposed methods present several advantages for RIS control,e.g.,fast convergence,easy implementation,robustness to the channel noise,and limited feedback requirement,and they are applicable even if the channel information is *** to the simulation results,our proposed methods outperform other approxi-mation and genetic *** our methods,the WPT system even significantly improves the power effi-ciency in the nonline-of-sight(NLOS)environment.

关键词： Reconfigurable intelligence surface Wireless power transfer Monte-carlo algorithm Passive beamforming Gibbs sampling

Water Vapor,Cloud,and Surface Rainfall Budgets Associated with the Landfall of Typhoon Krosa(2007):A Two-Dimensional Cloud-Resolving Modeling Study

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Advances in Atmospheric Sciences 2009年第6期26卷 1198-1208页

作者：岳彩军寿绍文 xiaofan li Shanghai Typhoon Institute China Meteorological Administration Shanghai 200030 Laboratory of Typhoon Forecast Technique/China Meteorological Administration Shanghai 200030 School of Atmospheric Sciences Nanjing University of Information Science and Technology Nanjing 210044 joint Center for Satellite Data Assimilation and NOAA/NESDIS/Center for Satellite Applications and Research Camp Springs Maryland USA

Water vapor, cloud, and surface rainfall budgets associated with the landfall of Typhoon Krosa on 6-8 October 2007 are analyzed based on a two-dimensional cloud-resolving model simulation. The model is integrated with imposed zonally-uniform vertical velocity, zonal wind, horizontal temperature, and vapor advection from NCEP/Global Data Assimilation System （GDAS） data. The simulation data that are validated with observations are examined to study physical causes associated with surface rainfall processes during the landfall. The time- and domain-mean analysis shows that when Krosa approached the eastern coast of China on 6 October, the water vapor convergence over land caused a local atmospheric moistening and a net condensation that further produced surface rainfall and an increase of cloud hydrometeor concentration. Meanwhile, latent heating was balanced by advective cooling and a local atmospheric warming. One day later, the enhancement of net condensation led to an increase of surface rainfall and a local atmospheric drying, while the water vapor convergence weakened as a result of the landfall-induced deprivation of water vapor flux. At the same time, the latent heating is mainly compensated the advective cooling. Further weakening of vapor convergence on 8 October enhanced the local atmospheric drying while the net condensation and associated surface rainfall was maintained. The latent heating is balanced by advective cooling and a local atmospheric cooling.

关键词： budget cloud-resolving modeling Typhoon Krosa

A Review of Cloud-Resolving Model Studies of Convective Processes

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Advances in Atmospheric Sciences 2008年第2期25卷 202-212页

作者： Xiaoqing WU xiaofan li Department of Geological and Atmospheric Sciences Iowa State University Ames Iowa USA Joint Center for Satellite Data Assimilation and NOAA/NESDIS/Center for Satellite Applications and Research Camp Springs Maryland USA

Convective processes affect large-scale environments through cloud-radiation interaction, cloud micro- physical processes, and surface rainfall processes. Over the last three decades, cloud-resolving models （CRMs） have demonstrated to be capable of simulating convective-radiative responses to an imposed large-scale forcing. The CRM-produced cloud and radiative properties have been utilized to study the convective- related processes and their ensemble effects on large-scale circulations. This review the recent progress on the understanding of convective processes with the use of CRM simulations, including precipitation processes; cloud microphysical and radiative processes; dynamical processes; precipitation efficiency; diurnal variations of tropical oceanic convection; local-scale atmosphere-ocean coupling processes; and tropical convective-radiative equilibrium states. Two different ongoing applications of CRMs to general circulation models （GCMs） are discussed： replacing convection and cloud schemes for studying the interaction between cloud systems and large-scale circulation, and improving the schemes for climate simulations.

关键词： cloud-resolving models (CRMs) convective processes simulations of convection and clouds

An Analysis of Thermally-Related Surface Rainfall Budgets Associated with Convective and Stratiform Rainfall

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Advances in Atmospheric Sciences 2011年第5期28卷 1099-1108页

作者：周玉淑 xiaofan li Laboratory of Cloud-Precipitation Physics and Severe Storms Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 NOAA//NESDIS/Center for Satellite Applications and Research Camp Springs Maryland

Both water vapor and heat processes play key roles in producing surface *** the water vapor effects of sea surface temperature and cloud radiative and microphysical processes on surface rainfall have been investigated in previous studies,the thermal effects on rainfall are analyzed in this study using a series of two-dimensional equilibrium cloud-resolving model experiments forced by zonally-uniform,constant,large-scale zonal wind and zero large-scale vertical *** analysis of thermally-related surface rainfall budget reveals that the model domain mean surface rain rate is primarily associated with the mean infrared cooling *** rainfall and transport of hydrometeor concentration from convective regions to raining stratiform regions corresponds to the heat divergence over convective regions,whereas stratiform rainfall corresponds to the transport of hydrometeor concentration from convective regions and heat divergence over raining stratiform *** heat divergence over convective regions is mainly balanced by the heat convergence over rainfall-free regions,which is,in turn,offset by the radiative cooling over rainfall-free *** sensitivity experiments of rainfall to the effects of sea surface temperature and cloud radiative and microphysical processes show that the sea surface temperature and cloud processes affect convective rainfall through the changes in infrared cooling rate over rainfall-free regions and transport rate of heat from convective regions to rainfall-free regions.

关键词： surface rainfall infrared cooling heat divergence cloud-resolving model simulation

Physical processes associated with movement of maximum wind of Typhoon Rammasun(2014)

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Frontiers of Earth Science 2023年第2期17卷 407-416页

作者： Xin QUAN xiaofan li Guoqing ZHAI Key Laboratory of Geoscience Big Data and Deep Resource of Zhejiang Province School of Earth SciencesZhejiang UniversityHangzhou 310027China

In this study,the movement of the maximum wind of Typhoon Rammasun(2014)was measured by the radial movement of the maximum symmetric rotational kinetic *** weather research and forecasting(WRF)model was used to simulate Typhoon Rammasun,and validated simulation data for the lower troposphere were analyzed to examine the physical processes responsible for the radial movement of the maximum *** radii,where maximum symmetric rotational kinetic energy and its maximum tendency were located,were compared to explain radial *** tendency in the lower troposphere is controlled by the flux convergence of symmetric rotational kinetic energy and the conversion from symmetric divergent kinetic energy to symmetric rotational kinetic energy,as well as frictional dissipation in the symmetric rotational kinetic energy *** inward movement before rapid intensification(RI)resulted from radial flux convergence;cyclonic circulation develops while moving *** maximum symmetric rotational kinetic energy and RI were caused by the conversion,which was observed to be proportional to the symmetric rotational kinetic *** increased terrain-induced friction dissipation,which led to outward movement and ended the RI.

关键词： typhoon radial movement of maximum wind symmetric rotational kinetic energy rapid intensification kinetic energy budget flux convergence conversion