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Investigation into the Formation, Structure, and Evolution of an EF4 Tornado in East China Using a High-Resolution Numerical Simulation

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Journal of Meteorological Research 2018年第2期32卷 157-171页

作者： Dan YAO Haile XUE Jinfang YIN Jisong SUN Xudong LIANG Jianping GUO State Key Laboratory of severe weather Chinese Academy of Meteorological Sciences

Devastating tornadoes in China have received growing attention in recent years, but little is known about their formation, structure, and evolution on the tornadic scale. Most of these tornadoes develop within the East Asian monsoon regime, in an environment quite different from tornadoes in the U.S. In this study, we used an idealized, highresolution（25-m grid spacing） numerical simulation to investigate the deadly EF4（Enhanced Fujita scale category 4）tornado that occurred on 23 June 2016 and claimed 99 lives in Yancheng, Jiangsu Province. A tornadic supercell developed in the simulation that had striking similarities to radar observations. The violent tornado in Funing County was reproduced, exceeding EF4（74 ms–1）, consistent with the on-site damage survey. It was accompanied by a funnel cloud that extended to the surface, and exhibited a double-helix vorticity structure. The signal of tornado genesis was found first at the cloud base in the pressure perturbation field, and then developed both upward and downward in terms of maximum vertical velocity overlapping with the intense vertical vorticity centers. The tornado＇s demise was found to accompany strong downdrafts overlapping with the intense vorticity centers. One of the interesting findings of this work is that a violent surface vortex was able to be generated and maintained, even though the simulation employed a free-slip lower boundary condition. The success of this simulation, despite using an idealized numerical approach, provides a means to investigate more historical tornadoes in China.

关键词： tornado Cloud Model version 1(CM1) vertical vorticity updraft helicity double-helix structure hazardous wind

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Applications of Wavelet Analysis in Differential Propagation Phase Shift Data De-noising

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Advances in Atmospheric Sciences 2014年第4期31卷 825-835页

作者： HU Zhiqun LIU Liping State Key Laboratory of severe weather Chinese Academy of Meteorological Sciences

Using numerical simulation data of the forward differential propagation shift （ΦDP） of polarimetric radar,the principle and performing steps of noise reduction by wavelet analysis are introduced in *** from the multiscale analysis,various types of noises can be identified according to their characteristics in different scales,and suppressed in different resolutions by a penalty threshold strategy through which a fixed threshold value is applied,a default threshold strategy through which the threshold value is determined by the noise intensity,or a ΦDP penalty threshold strategy through which a special value is designed for ΦDP ***,a hard-or soft-threshold function,depending on the de-noising purpose,is selected to reconstruct the *** the three noise suppression strategies and the two signal reconstruction functions,and without loss of generality,two schemes are presented to verify the de-noising effect by dbN wavelets：（1） the penalty threshold strategy with the soft threshold function scheme （PSS）; （2） the ΦDP penalty threshold strategy with the soft threshold function scheme （PPSS）.Furthermore,the wavelet de-noising is compared with the mean,median,Kalman,and finite impulse response （FIR） methods with simulation data and two actual *** results suggest that both of the two schemes perform well,especially when ΦDP data are simultaneously polluted by various scales and types of noises.A slight difference is that the PSS method can retain more detail,and the PPSS can smooth the signal more successfully.

关键词： polarimetric radar wavelet analysis differential propagation phase shift de-noising

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An Assessment of CAMS-CSM in Simulating Land–Atmosphere Heat and Water Exchanges

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Journal of Meteorological Research 2018年第6期32卷 862-880页

作者： Guo ZHANG JiANDuo LI Xinyao RONG Yufei XIN Jian LI Haoming CHEN Jingzhi SU Lijuan HUA State Key Laboratory of severe weather Chinese Academy of Meteorological Sciences

The Chinese Academy of Meteorological Sciences(CAMS)has been devoted to developing a climate system model(CSM)to meet demand for climate simulation and prediction for the East Asian *** this study,we evaluated the performance of CAMS-CSM in regard to sensible heat flux(H),latent heat flux(LE),surface temperature,soil moisture,and snow depth,focusing on the Atmospheric Model Intercomparison Project experiment,with the aim of participating in the Coupled Model Intercomparison Project phase *** systematically assessed the simulation results achieved by CAMS-CSM for these variables against various reference products and ground observations,including the FLUXNET model tree ensembles H and LE data,climate Prediction Center soil moisture data,snow depth climatology data,and Chinese ground observations of snow depth and winter surface *** compared these results with data from the ECMWF Interim reanalysis(ERA-Interim)and Global Land Data Assimilation System(GLDAS).Our results indicated that CAMS-CSM simulations were better than or comparable to ERA-Interim reanalysis for snow depth and winter surface temperature at regional scales,but slightly worse when simulating total column soil *** root-mean-square differences of H in CAMS-CSM were all greater than those from the ERA-Interim reanalysis,but less than or comparable to those from *** spatial correlations for H in CAMS-CSM were the lowest in nearly all regions,except for North ***-CSM LE produced the lowest bias in Siberia,North America,and South America,but with the lowest spatial correlation ***,there are still scopes for improving H and LE simulations in CAMS-CSM,particularly for LE.

关键词： climate System Model of the Chinese Academy of Meteorological Sciences Atmospheric Model Intercomparison Project sensible heat flux latent heat flux

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Parameterizing sea surface temperature cooling induced by tropical cyclones using a multivariate linear regression model

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Acta Oceanologica Sinica 2018年第1期37卷 1-10页

作者： WEI Jun LIU Xin JIANG Guoqing Laboratory for climate and Ocean-Atmosphere Studies Department of Atmospheric and Oceanic Sciences Peking University State Key Laboratory of severe weather Chinese Academy of Meteorological Sciences

Combining a linear regression and a temperature budget formula, a multivariate regression model is proposed to parameterize and estimate sea surface temperature（SST） cooling induced by tropical cyclones（TCs）. Three major dynamic and thermodynamic processes governing the TC-induced SST cooling（SSTC）, vertical mixing, upwelling and heat flux, are parameterized empirically using a combination of multiple atmospheric and oceanic variables：sea surface height（SSH）, wind speed, wind curl, TC translation speed and surface net heat flux. The regression model fits reasonably well with 10-year statistical observations/reanalysis data obtained from 100 selected TCs in the northwestern Pacific during 2001–2010, with an averaged fitting error of 0.07 and a mean absolute error of 0.72°C between diagnostic and observed SST cooling. The results reveal that the vertical mixing is overall the pre dominant process producing ocean SST cooling, accounting for 55% of the total cooling. The upwelling accounts for 18% of the total cooling and its maximum occurs near the TC center, associated with TC-induced Ekman pumping. The surface heat flux accounts for 26% of the total cooling, and its contribution increases towards the tropics and the continental shelf. The ocean thermal structures, represented by the SSH in the regression model,plays an important role in modulating the SST cooling pattern. The concept of the regression model can be applicable in TC weather prediction models to improve SST parameterization schemes.

关键词： tropical cyclones SST cooling regression model parameterization

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Improvement of Radar Quantitative Precipitation Estimation Based on Real-Time Adjustments to Z-R Relationships and Inverse Distance Weighting Correction Schemes

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Advances in Atmospheric Sciences 2012年第3期29卷 575-584页

作者：王改利刘黎平丁媛媛 State Key Laboratory of severe weather Chinese Academy of Meteorological Science

The errors in radar quantitative precipitation estimations consist not only of systematic biases caused by random noises but also spatially nonuniform biases in radar rainfall at individual rain-gauge stations. In this study, a real-time adjustment to the radar reflectivity rainfall rates （Z R） relationship scheme and the gauge-corrected, radar-based, estimation scheme with inverse distance weighting interpolation was devel- oped. Based on the characteristics of the two schemes, the two-step correction technique of radar quantitative precipitation estimation is proposed. To minimize the errors between radar quantitative precipitation es- timations and rain gauge observations, a real-time adjustment to the Z R relationship scheme is used to remove systematic bias on the time-domain. The gauge-corrected, radar-based, estimation scheme is then used to eliminate non-uniform errors in space. Based on radar data and rain gauge observations near the Huaihe River, the two-step correction technique was evaluated using two heavy-precipitation events. The results show that the proposed scheme improved not only in the underestimation of rainfall but also reduced the root-mean-square error and the mean relative error of radar-rain gauge pairs.

关键词： precipitation estimation adjusted Z R relationship gauge correction

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A Possible Mechanism of the Impact of Atmosphere-Ocean Interaction on the Activity of Tropical Cyclones Affecting China

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Advances in Atmospheric Sciences 2012年第4期29卷 661-674页

作者：任福民白莉娜吴国雄王在志王元 Laboratory for climate Studies China Meteorological Administration Key Laboratory of Mesoscale severe weather of Ministry of Education Nanjing University Shanghai Typhoon institute China Meteorological Adminstration Atmospheric Physics Research institute of Chinese Academy of Sciences

In this study, tropical cyclone data from China Meteorological Administration （CMA） and the ECMWF reanalysis data for the period 1958-2001 was used to propose a possible mechanism for the impacts of air- sea interaction on the activity of tropical cyclones （TCs） affecting China. The frequency of TCs affecting China over past 40 years has trended downward, while during the same period, the air sea interaction in the two key areas of the Pacific region has significantly weakened. Our diagnoses and simulations suggest that air sea interactions in the central North Pacific tropics and subtropics （Area 1） have an important role in adjusting typhoon activities in the Northwest Pacific in general, and especially in TC activity affecting China. On the contrary, impacts of the air-sea interaction in the eastern part of the South Pacific tropics （Area 2） were found to be rather limited. As both observational analysis and modeling studies show that, in the past four decades and beyond, the weakening trend of the latent heat released from Area 1 matched well with the decreasing Northwest Pacific TC frequency derived from CMA datasets. Results also showed that the weakening trend of latent heat flux in the area was most likely due to the decreasing TC frequency over the Northwest Pacific, including those affecting China. Although our preliminary analysis revealed a possible mechanism through which the air sea interaction may adjust the genesis conditions for TCs, which eventually affect China, other relevant questions, such as how TC tracks and impacts are affected by these trends, remain unanswered. Further in-depth investigations are required.

关键词： air sea interaction latent heat affecting China tropical cyclones impact mechanism

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ASIAN-PACIFIC OSCILLATION IN AUTUMN AND ITS RELATIONSHIPS WITH THE SUBTROPICAL MONSOON IN EAST ASIA

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Journal of Tropical Meteorology 2015年第2期21卷 143-152页

作者：邹燕赵平林秋 Fujian climate Centre State Key Laboratory of severe weather Chinese Academy of Meteorological Sciences Fujian Meteorological Bureau

Based on the 1961-2010 NCEP/NCAR reanalysis, this work uses empirical orthogonal function(EOF) and composite analysis to study the distributions of zonal land-sea thermal contrast between Asia and the Pacific during transitions from the summer monsoon to the winter monsoon in East Asian subtropics, and investigates the interannual variations of the thermal contrast and their relationships with circulation systems over the East Asian subtropics. The findings are as follows. 1) In autumn, the interannual variations of the temperature deviation in the middle and upper troposphere show significant east-west out-of-phase teleconnection over Asia and the central and eastern Pacific, i.e. the Asian-Pacific Oscillation, or APO. 2) While not as significant as in summer with regard to coverage and intensity, the APO shows interannual variations in autumn that well depicts the change in the intensity of the subtropical monsoon. In the high(low) APO year, the current subtropical summer monsoon is strong(weak) and the winter monsoon is weak(strong) in East Asia as derived from the general circulation and wind field of the East Asian-Pacific region.

关键词： Asian-Pacific Oscillation autumn East Asia Monsoon

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A Modeling Study of Land Surface Process Impacts on Inland Behavior of Typhoon Rananim(2004)

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Advances in Atmospheric Sciences 2013年第2期30卷 367-381页

作者：魏娜李英 State Key Laboratory of severe weather Chinese Academy of Meteorological Sciences

On 12 August 2004, Typhoon Rananim （0414） moved inland over China and stagnated over the Poyang Lake area, resulting in torrential rainfall and severe geologic hazards. The Advanced weather Research and Forecasting （ARW-WRF） model and its different land surface models （LSMs） were employed to study the impacts of land surface process on the inland behavior of Typhoon Rananim. Results show that simulations, coupled with LSMs or not, have no significant differences in predicting typhoon track, intensity, and largescale circulation. However, the simulations of mesoscale structure, rainfall rate, and rainfall distribution of typhoon are more reasonable with LSMs than without LSMs. Although differences are slight among LSMs, NOAH is better than the others. Based on outputs using the NOAH scheme, the interaction between land surtace and typhoon was explored in this study. Notably, typhoon rainfall and cloud cover can cool land surface, but rainfall expands the underlying saturated wetland area, which exacerbates the asymmetric distribution of surface heat fluxes. Accordingly, an energy frontal zone may form in the lower troposphere that enhances ascending motion and local convection, resulting in heavier rainfall. Moreover, the expanded underlying saturated wetlands provide plentiful moisture and unstable energy for the maintenance of Typhoon Rananim and increased rainfall in return.

关键词： tropical cyclone land surface process surface heat flux mesoscale vortex

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Using the Inverse of Expected Error Variance to Determine Weights of Individual Ensemble Members： Application to Temperature Prediction

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Journal of Meteorological Research 2017年第3期31卷 502-513页

作者： Xiaogong SUN Jinfang YIN Yan ZHAO State Key Laboratory of severe weather Chinese Academy of Meteorological Sciences

The inverse of expected error variance is utilized to determine weights of individual ensemble members based on the THORPEX （The Observing System Research and Predictability Experiment） Interactive Grand Global Ensemble （TIGGE） forecast datasets. The weights of all ensemble members are thus calculated for summer 2012, with the NCEP final operational global analysis （FNL） data as the truth. Based on the weights of all ensemble members, the variable weighted ensemble mean （VWEM） of temperature of summer 2013 is derived and compared with that from the simple equally weighted ensemble mean. The results show that VWEM has lower root-mean-square error （RMSE） as well as absolute error, and has improved the temperature prediction accuracy. The improvements are quite notable over the Tibetan Plateau and its surrounding areas; specifically, a relative improvement rate of RMSE of more than 24% in 2-m temperature is demonstrated. Moreover, the improvement rates vary slightly with the pre- diction lead-time （24-96 h）. It is suggested that the VWEM approach be employed in operational ensemble predic- tion to provide guidance for weather forecasting and climate prediction.

关键词： ensemble forecast variable weighted ensemble mean simple equally weighted ensemble mean predic-tion accuracy

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The Impact of Deformation on Vortex Development in a Baroclinic Moist Atmosphere

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Advances in Atmospheric Sciences 2016年第2期33卷 233-246页

作者： Na LI Lingkun RAN Shouting GAO Key Laboratory of Cloud-Precipitation Physics and severe Storms Institute of Atmospheric PhysicsChinese Academy of Sciences State Key Laboratory of severe weather Chinese Academy of Meteorological Sciences

A mathematical relation between deformation and vertical vorticity tendency is built by introducing the frontogenesis function and the complete vertical vorticity equation, which is derived by virtue of moist potential vorticity. From the mathematical relation, it is shown that properly configured atmospheric conditions can make deformation exert a positive contribution to vortex development at rates comparable to other favorable factors. The effect of deformation on vortex development is not only related to the deformation itself, but also depends on the current thermodynamic and dynamic structures of the atmosphere, such as the convective stability, moist baroclinicity and vertical wind shear （or horizontal vorticity）. A diagnostic study of a heavy-rainfall case that occurred during 20-22 July 2012 shows that deformation has the most remarkable effect on the increase in vertical vorticity during the rapid development stage of the low vortex during its whole life cycle. This feature is mainly due to the existence of an approximate neutral layer （about 700 hPa） in the atmosphere where the convective stability tends to be zero. The neutral layer makes the effect of deformation on the vertical vorticity increase significantly during the vortex development stage, and thus drives the vertical vorticity to increase.

关键词： deformation low vortex vorticity frontogenesis function

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