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A Tri-mode of Mock-Walker Cells

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Advances in Atmospheric Sciences 2024年第4期41卷 671-679页

作者： Han QIN Ji NIE Zhiyong MENG laboratory for climate and ocean-atmosphere studies Department of Atmospheric and Oceanic SciencesSchool of PhysicsPeking UniversityBeijing 100871China China Meteorological Administration Tornado Key laboratory Foshan 528061China

This work uses cloud-resolving simulations to study mock-Walker cells driven by a specified sea surface temperature(SST).The associated precipitation in the mock-Walker cells exhibits three different modes,including a single peak of precipitation over the SST maximum(mode 1),symmetric double peaks of precipitation straddling the SST maximum(mode 2),and a single peak of precipitation on one side of the SST maximum(mode 3).The three modes are caused by three distinct convective activity center migration traits.Analyses indicate that the virtual effect of water vapor plays an important role in differentiating the three modes.When the SST gradient is large,the virtual effect may be strong enough to overcome the temperature effect,generating a low-level low-pressure anomaly below the ascending branch of the Walker cell off the center.The results here highlight the importance of the virtual effect of water vapor and its interaction with convection and large-scale circulation in the Walker circulation.

关键词： Walker circulation cloud-resolving simulation virtual effect

Widening and weakening of the Hadley circulation under global warming

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Science Bulletin 2018年第10期63卷 640-644页

作者： Yongyun Hu Han Huang Chen Zhou laboratory for climate and ocean-atmosphere studies Department of Atmospheric and Oceanic SciencesSchool of PhysicsPeking University School of Atmospheric Sciences Nanjing University

The Hadley circulation is one of the most important atmospheric circulations.Widening of the Hadley circulation has drawn extensive studies in the past decade.The key concern is that widening of the Hadley circulation would cause poleward shift of the subtropical dry zone.Various metrics have been applied to measure the widening of the tropics.What are responsible for the observed widening trends of the Hadley circulation? How anthropogenic and natural forcings caused the widening? How the widening results in regional climatic effects? These are the major questions in studing the widening of the Hadley circulation.While both observations and simulations all show widening of the Hadley circulation in the past few decades,there are no general agreements of changes in the strength of the Hadley circulation.Although some reanalysis datasets show strengthening of the Hadley circulation,it was shown that the strengthening trend could be artificial,and simulations show weakening of the Hadley circulation for global greenhouse warming.In the present paper,we shall briefly review the major progresses of studies in trends in width and strength of the Hadley circulation.We address answers to these questions,clarify inconsistent results,and propose ideas for future studies.

关键词：发行量温暖度量标准副热带地区性显示数据集模拟

Three-dimensional spiral structure of tropical cyclone under four-force balance

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Chinese Physics B 2014年第6期23卷 644-648页

作者：刘式适付遵涛刘式达 Department of Atmospheric and oceanic Sciences and Laboratory for Climate and Ocean–Atmosphere Studies School of Physics Peking University

The steady axis-symmetrical atmosphere dynamical equations are used for describing spiral structure of tropical cyclones under four-force （pressure gradient force, Coriolis force, centrifugal force, and friction force） balance, and the dynamical systems of three-dimensional （3D） velocity field are introduced. The qualitative analysis of the dynamical system shows that there are down 3D spiral structures in eye of tropical cyclone and tropical cyclone is 3D counterclockwise up spiral structure. These results are consistent with the observed tropical cyclone on the weather map.

关键词： tropical cyclones spiral structure dynamical systems four-force balance

The Characteristics of Turbulence Structure and Transfer over the Middle Area of the Tibetan Plateau

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Atmospheric and oceanic Science Letters 2013年第2期6卷 67-73页

作者： LI Fu-Yu LI Xiao-Lan ZHANG Hong-Sheng Department of Atmospheric and oceanic Sciences & laboratory for climate and ocean-atmosphere studies Peking University

In this paper, turbulent data obtained from the Damxung site during the Secondary Tibetan Plateau Science Experiment (TIPEX) in 1998 are used to study the characteristics of the turbulent spectra, turbulence transport, and the dissipation rates of turbulent kinetic energy, temperature variance, and humidity variance in the middle area of the Tibetan Plateau. The turbulent spectra of wind velocity, potential temperature, and humidity satisfy the-2/3 power law in the high frequency range. Horizontal transportation of heat and water vapor is negligible compared with vertical transportation under strong unstable conditions, and as the stability parameter z/L increases (where z is the observational height, and L is the Monin Obukhov length), horizontal transportation becomes dominant under near-neutral, neutral, and stable conditions. The non-dimensional temperature and humidity variances are 20% less than the temperature and humidity gradient variances. These deficits appear to increase as the absolute stability parameter increases. Moreover, the effects of turbulence transportation and pressure variance exist throughout the entire stability region.

关键词：湍流结构青藏高原中部地区温度变化率稳定性参数湿度梯度转让垂直运输

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潘吉亚超大陆时期的哈德雷环流

Science Bulletin 2023年第10期68卷 1060-1068,M0004页

作者：张诗妍胡永云杨军李想康婉莹张健刘永岗聂绩 laboratory for climate and ocean-atmosphere studies Department of Atmospheric and Oceanic SciencesSchool of PhysicsPeking UniversityBeijing 100871China Department of Earth Atmosphericand Planetary SciencesMassachusetts Institute of TechnologyCambridge MA 02139USA

潘吉亚超大陆时期,是地球历史上的一个独特阶段.在约2.5亿年前,全球大陆汇聚成一块从南极延伸至北极的超级大陆,其面积约占地球表面积的35%,与现代大陆面积(约30%)相比要大得多.此时地球处于温室气候,全球平均地面温度约为26℃,二氧化... 详细信息

潘吉亚超大陆时期,是地球历史上的一个独特阶段.在约2.5亿年前,全球大陆汇聚成一块从南极延伸至北极的超级大陆,其面积约占地球表面积的35%,与现代大陆面积(约30%)相比要大得多.此时地球处于温室气候,全球平均地面温度约为26℃,二氧化碳浓度远高于现代.本文通过气候模拟研究了这一地质时期的哈德雷环流.结果表明,潘吉亚的哈德雷环流强度较弱,边界纬度较宽.一个最为显著的特征是,北半球和南半球冬季的哈德雷环流上升支分别位于23°S和18°N,比现代的上升支远离赤道得多.这是副热带较大的陆地面积以及与之相关的极高温度造成的.

关键词： Hadleycir culation Pangea supercontinent climate simulations Hothouse climate Greenhouse gases

气溶胶散射性增强对恒河平原季风降水减少的贡献

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Science Bulletin 2023年第21期68卷 2629-2638,M0006页

作者：应同李婧姜中景刘冠宇张震宇张璐董悦明赵传峰 Department of Atmospheric and oceanic Sciences School of PhysicsPeking UniversityBeijing 100871China laboratory for climate and ocean-atmosphere studies Department of Atmospheric and Oceanic SciencesSchool of PhysicsPeking UniversityBeijing 100871China Environmental and climate Sciences Department Brookhaven National LaboratoryUpton NY 11973USA

气溶胶的气候效应存在着很大的不确定性.由于散射性与吸收性气溶胶具有明显不同乃至相反的辐射强迫,二者之间的相对比例决定了气溶胶整体的辐射效应.通过结合观测数据与全球气候模式模拟,本研究表明,1980年以来吸收性与散射性气溶胶的... 详细信息

气溶胶的气候效应存在着很大的不确定性.由于散射性与吸收性气溶胶具有明显不同乃至相反的辐射强迫,二者之间的相对比例决定了气溶胶整体的辐射效应.通过结合观测数据与全球气候模式模拟,本研究表明,1980年以来吸收性与散射性气溶胶的相对比例变化在南亚北部,尤其是恒河平原的夏季风降水变化中起到了重要作用.散射性气溶胶比例的增加,或吸收性气溶胶比例的减少,表现为气溶胶单次散射反照率SSA的上升,能够导致对流层上部大气的显著冷却,抑制抬升运动,从而导致局地的降水减少.对第六次耦合模式比较计划CMIP6历史模拟的进一步分析表明,新一代气候模式对南亚北部SSA增加的低估可能是导致该地区降水模拟偏差的重要来源之一.

关键词：气溶胶单次散射反照率辐射效应辐射强迫吸收性全球气候模式耦合模式相对比例

Impact of assimilating Taiwan＇s coastal radar radial velocity on forecasting Typhoon Morakot (2009) in southeastern China using a WRF-based EnKF

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Science China Earth Sciences 2017年第2期60卷 315-327页

作者： YUE Jian MENG ZhiYong laboratory for climate and ocean-atmosphere studies Department of Atmospheric and Oceanic Sciences School of Physics Peking University Beij'ing 100871 China

This study explores for the first time the impact of assimilating radial velocity(Vr)observations from a single or multiple Taiwan's coastal radars on tropical cyclone(TC)forecasting after landfall in the Chinese mainland by using a Weather Research and Forecasting model(WRF)-based ensemble Kalman filter(EnKF)data assimilation system.Typhoon Morakot(2009),which caused widespread damage in the southeastern coastal regions of the mainland after devastating Taiwan,was chosen as a case study.The results showed that assimilating Taiwan's radar Vr data improved environmental field and steering flow and produced a more realistic TC position and structure in the final EnKF cycling analysis.Thus,the subsequent TC track and rainfall forecasts in southeastern China were improved.In addition,better observations of the TC inner core by Taiwan's radar was a primary factor in improving TC rainfall forecast in the Chinese mainland.

关键词：东南沿海地区中国东南部预测模型径向速度 WRF 台湾雷达吸收

The Predictability of a Squall Line in South China on 23 April 2007

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Advances in Atmospheric Sciences 2013年第2期30卷 485-502页

作者：吴多常孟智勇严大春 laboratory for climate and ocean-atmosphere studies Department of Atmospheric and Oceanic Sciences School of PhysicsPeking University

This study investigated the predictability of a squall line associated with a quasi-stationary front on 23 April 2007 in South China through deterministic and probabilistic forecasts. Our results show that the squallline simulation was very sensitive to model error from horizontal resolution and uncertainties in physical parameterization schemes. At least a 10-km grid size was necessary to decently capture this squall line. The simulated squall line with a grid size of 4.5 km was most sensitive to long-wave radiation parameterization schemes relative to other physical schemes such as microphysics and planetary boundary layer. For a grid size from 20 to 5 km, a cumulus parameterization scheme degraded the squall-line simulation （relative to turning it off）, with a more severe degradation to grid size -10 km than 〉10 km. The sensitivity of the squall-line simulation to initial error was investigated through ensemble forecast. The performance of the ensemble simulation of the squall line was very sensitive to the initial error. Approximately 15% of the ensemble members decently captured the evolution of the squall line, 25% failed, and 60% dislocated the squall line. Using different combinations of physical parameterization schemes for different members can improve the probabilistic forecast. The lead time of this case was only a few hours. Error growth was clearly associated with moist convection development. A linear improvement in the performance of the squall line simulation was observed when the initial error was decreased gradually, with the largest contribution from initial moisture field.

关键词： squall line predictability South China ensemble moisture

Soil Moisture Effects on Sand Saltation and Dust Emission Observed over the Horqin Sandy Land Area in China

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Journal of Meteorological Research 2014年第3期28卷 444-452页

作者：李晓岚张宏升 laboratory for climate and ocean-atmosphere studies Department of Atmospheric and Oceanic SciencesSchool of Physics Peking University

In this study, the eff ects of soil moisture on sand saltation and dust emission over the Horqin Sandy Land area are investigated, based on observations of three dust events in 2010. The minimum friction velocity initiating the motion of surface particles, namely, the threshold friction velocity, is estimated to be 0.34, 0.40, and 0.50 m s？1 under the very dry, dry, and wet soil conditions, respectively. In comparison with the observations during the dust events under the very dry and dry soil conditions, the dust emission fl ux during the wet event is smaller, but the saltation activities of sand particles （d≧50 μm） are stronger. The size distributions of airborne dust particles （0.1≦d≦20 μm） show that concentrations of the fi ner dust particles （0.1≦d≦0.3 μm） have a secondary peak under dry soil conditions, while they are absent under wet soil conditions. This suggests that the surface soil particle size distribution can be changed by soil moisture. Under wet soil conditions, the particles appear to have a larger size, and hence more potential saltating particles are available. This explains the occurrence of stronger saltation processes observed under wet soil conditions.

关键词： soil moisture sand saltation dust emission Horqin Sandy Land area