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Sensitivity of Snowfall Characteristics to Meteorological Conditions in the Yeongdong Region of Korea

Advances in Atmospheric Sciences 2021年第3期38卷 413-429页

作者： Yoo-Jun KIM So-Ra IN Hae-Min KIM Jin-Hwa LEE Kyu Rang KIM Seungbum KIM Byung-Gon KIM high impact weather research department National Institute of Meteorological SciencesGangneung 25457Korea Operational Systems Development department National Institute of Meteorological SciencesSeogwipo 63568Korea department of Atmospheric Environmental Sciences Gangneung-Wonju National UniversityGangneung 25457Korea

This study investigates the characteristics of cold clouds and snowfall in both the Yeongdong coastal and mountainous regions under different meteorological conditions based on the integration of numerical modeling and three-hourly rawinsonde observations with snow crystal photographs for a snowfall event that occurred on 29−30 January *** found that rimed particles predominantly observed turned into dendrite particles in the latter period of the episode when the 850 hPa temperature decreased at the coastal site,whereas the snow crystal habits at the mountainous site were largely needle or rimed *** soundings showed a well-defined,two-layered cloud structure along with distinctive wind-directional shear,and an inversion in the equivalent potential temperature above the low-level cloud *** first experiment with a decrease in lower-layer temperature showed that the low-level cloud thickness was reduced to less than 1.5 km,and the accumulated precipitation was decreased by 87%compared with the control *** difference in precipitation amount between the single-layered experiment and control experiment(two-layered)was not so significant to attribute it to the effect of the seeder−feeder *** precipitation in the last experiment by weakening winddirectional shear was increased by 1.4 times greater than the control experiment specifically at the coastal site,with graupel particles accounting for the highest proportion(~62%).The current results would improve snowfall forecasts in complicated geographical environments such as Yeongdong in terms of snow crystal habit as well as snowfall amount in both time and space domains.

关键词： Yeongdong snow crystal rawinsonde cloud-resolving model

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Predictability of the 7·20 extreme rainstorm in Zhengzhou in stochastic kinetic-energy backscatter ensembles

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Science China Earth Sciences 2024年第7期67卷 2226-2241页

作者： Min YANG Peilong YU Lifeng ZHANG Xiaobing PAN Quanjia ZHONG Yunying LI College of Meteorology and Oceanography National University of Defense TechnologyChangsha 410073China Key Laboratory of high impact weather(Special) China Meteorological AdministrationChangsha 410073China Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters/Key Laboratory of Meteorological Disaster Ministry of Education/Joint International Research Laboratory of Climate and Environment ChangeNanjing University of Information Science and TechnologyNanjing 210044China department of Ocean Science Hong Kong University of Science and TechnologyHong Kong 999077China

The scale-dependent predictability of the devastating 7·20 extreme rainstorm in Zhengzhou,China in 2021 was investigated via ensemble experiments,which were perturbed on different scales using the stochastic kinetic-energy backscatter(SKEB)scheme in the WRF model,with the innermost domain having a 3-km grid *** daily rainfall(RAIN24h)and the cloudburst during 1600-1700 LST(RAIN1h)were *** demonstrated that with larger perturbation scales,the ensemble spread for the rainfall maximum widens and rainfall forecasts become closer to the *** ensembles with mesoscale or convective-scale perturbations,RAIN1h loses predictability at scales smaller than 20 km and RAIN24h is predictable for all *** in ensembles with synoptic-scale perturbations,the largest scale of predictability loss extends to 60 km for both RAIN1h and ***,the average positional error in forecasting the heaviest rainfall for RAIN24h(RAIN1h)was 400 km(50-60)*** southerly low-level jet near Zhengzhou was assumed to be directly responsible for the forecast uncertainty of *** rapid intensification in low-level cyclonic vorticity,mid-level divergence,and upward motion concomitant with the jet dynamically facilitated the *** analysis of the divergent,rotational and vertical kinetic spectra and the corresponding error spectra showed that the error kinetic energy at smaller scales grows faster than that at larger scales and saturates more quickly in all ***-scale perturbations not only boost larger-scale error growth but are also conducive to error growth at all scales through a downscale cascade,which indicates that improving the accuracy of larger-scale flow forecast may discernibly contributes to the forecast of cloudburst intensity and position.

关键词： Stochastic kinetic-energy backscatter(SKEB) Extreme rainfall Ensemble forecast Predictability

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ANALYSIS OF A CASE OF EAST ASIA COASTAL CYCLOGENESIS

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Acta meteorologica Sinica 1993年第4期7卷 385-411页

作者：陈受钧郭英华白乐生 department of Geophysics Peking University National Center for Atmospheric research Liaoning weather Bureau

The evolution of an explosive cyclone off the East Asia coast in March 1979 is described.A shortwave trough in the southern branch of upper-level westerlies initiated the incipient ***,a polar trough in the north amplified and became in phase with the southern shortwave to form a major *** major trough was responsible for the rapid intensification of the surface *** the early development stage,warm and moist air was transported northward to the developing area by a strong low-level *** ageostrophic wind associated with the low-level jet contributed to the frontogenesis,creating a favorable low-level environment for the rapid deepening.A low-level positive potential vorticity anomaly was created prior to the onset of rapid *** was a result of frontal cloud *** cyclone intensified rapidly when stratospheric air with high potential vorticity penetrated to the *** rapid deepening took place at a location under the left-exit region of an amplifying jet streak behind the major trough and the right-entrance region of another anticyclonically-curved subtropical jet streak in a quasi-stationary ridge over Japan. Due to the blocking effect of the Tibetan Plateau,two shortwave disturbances were observed in the upper-level westerlies on the north and south sides of the *** southern disturbance initiated the incipient surface cyclone, while the amplifying northern disturbance was responsible for the rapid ***,the evolution of the explosive cyclone in this case can be regarded as consecutive Petterssen's 'type-B' cyclogenesis in two separate stages.

关键词： cyclone explosive deeping coastal meteorology

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A comparison study of a solar active-region eruptive filament and a neighboring non-eruptive filament

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research in Astronomy and Astrophysics 2016年第1期16卷 151-158页

作者： Chao-Wei Jiang Shi-Tsan Wu Xue-Shang Feng Qiang Hu SIGMA weather Group State Key Laboratory for Space WeatherNational Space Science CenterChinese Academy of Sciences Center for Space Plasma & Aeronomic research The University of Alabama in Huntsville department of Mechanical & Aerospace Engineering The University of Alabama in Huntsville department of Space Sciences The University of Alabama in Huntsville

Solar active region （AR） 11283 is a very magnetically complex region and it has produced many eruptions. However, there exists a non-eruptive filament in the plage region just next to an eruptive one in the AR, which gives us an opportunity to perform a comparison analysis of these two filaments. The coronal magnetic field extrapolated using our CESE-MHD-NLFFF code reveals that two magnetic flux ropes （MFRs） exist in the same extrapolation box supporting these two filaments, respectively. Analysis of the magnetic field shows that the eruptive MFR contains a bald-patch separatrix surface （BPSS） co- spatial very well with a pre-eruptive EUV sigmoid, which is consistent with the BPSS model for coronal sigmoids. The magnetic dips of the non-eruptive MFRs match Hα observation of the non-eruptive filament strikingly well, which strongly supports the MFR-dip model for filaments. Compared with the non-eruptive MFR/filament （with a length of about 200 Mm）, the eruptive MFR/filament is much smaller （with a length of about 20 Mm）, but it contains most of the magnetic free energy in the extrapolation box and holds a much higher free energy density than the non-eruptive one. Both the MFRs are weakly twisted and cannot trigger kink instability. The AR eruptive MFR is unstable because its axis reaches above a critical height for torus instability, at which the overlying closed arcades can no longer confine the MFR stably. On the contrary, the quiescent MFR is very firmly held by its overlying field, as its axis apex is far below the torus-instability threshold height. Overall, this comparison investigation supports that an MFR can exist prior to eruption and the ideal MHD instability can trigger an MFR eruption.

关键词： magnetic fields -- Sun: corona -- Sun: filaments -- Sun: eruptions

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Modeling Density and Anisotropy of Energetic Electrons Along Magnetic Field Lines

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Plasma Science and Technology 2006年第3期8卷 279-284页

作者：肖伏良冯学尚 department of Physics and Electronic Sciences Changsha University of Science and Technology Changsha 410076 China State Key Laboratory of Space Weather Center for Space Science and Applied Research Chinese Academy of Sciences Beijing 100080 China State Key Laboratory of Space weather Center for Space Science and Applied Research Chinese Academy of Sciences Beijing 100080 China

The electromagnetic wave growth or damping depends basically on the number density and anisotropy of energetic particles as the resonant interaction takes place between the particles and waves in the magnetosphere. The variance of both the number density and anisotropy along the magnetic field line is evaluated systematically by modeling four typically prescribed distribution functions. It is shown that in the case of ＂the positive anisotropy＂（namely, the perpendicular temperature T⊥ exceeds the parallel temperature T｜｜）, the number density of energetic electrons always decreases with the magnetic latitude for a regular increasing magnetic field and the maximum wave growth is therefore generally confined to the equator where the resonant energy is minimum, and the number density is the largest. However, the ＂loss-cone＂ anisotropy of the electrons with a ＂pancake＂ distribution or kappa distribution keeps invariant or nearly invariant, whereas the ＂temperature＂ anisotropy with a pure bi-Maxwellian distribution or Ashour-Abdalla and Kennel＇s distributions decreases with the magnetic latitude. The results may provide a useful approach to evaluating the number density and anisotropy of the energetic electrons at latitudes where the observation information is not available.

关键词： number density anisotropy distribution function magnetic field line

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Responses of the Ionosphere to the Great Sumatra Earthquake and Volcanic Eruption of Pinatubo

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Chinese Physics Letters 2006年第7期23卷 1955-1957页

作者：郝永强肖佐张东和 department of Geophysics Peking University Beijing 100871 Key Laboratory of Space weather Center for Space Science and Applied Research Chinese Academy of Sciences Beijing 100080

A sudden ionospheric disturbance was detected by the Doppler shift sounding equipment at Beijing, about 25 min later after the outbreak of the Sumatra earthquake on 26 December 2004. This ionospheric disturbance appeared less than lOmin after the earthquake was first recorded at Beijing seismological station by the arrival of the seismic Rayleigh wave. The analysis shows that about 18rain is the time necessary for the seismic Rayleigh wave to propagate from the epicentre to Beijing and then about 5-10min for acoustic waves to propagate from the surface of the Beijing area to the altitude of the ionosphere. Also, a report was made as another example to show the ionospheric response of Doppler shift observation at Beijing area during the Mount Pinatubo eruption of 1991. These two examples show clear evidence of the lithosphere-atmosphere-ionosphere coupling. The former case is in the frequency domain of infrasonic waves of the Earth surface oscillation due to the Rayleigh waves caused by the earthquake, while the latter is in the acoustic-gravity wave category directly excited in the atmosphere by the mass and energy eruptions of Mount Pinatubo.

关键词： MOUNT-PINATUBO ATMOSPHERIC OSCILLATIONS WAVES EXCITATION PERIOD RAYLEIGH

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Application of Variational Algorithms in Semi-Lagrangian Framework

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Advances in Atmospheric Sciences 1999年第3期16卷 419-430页

作者：王云峰伍荣生王元潘益农 Laboratory of Mesoscale Severe weather Department of Atmospheric Sciences Nanjing University Nanjing

The variational data assimilation scheme (VAR) is applied to investigating the advective effect and the evolution of the control variables in time splitting semi-Lagrangian framework. Two variational algorithms are used. One is the conjugate code method-direct approach, and another is the numerical backward integration of analytical adjoint equation—indirect approach. Theoretical derivation and sensitivity tests are conducted in order to verify the consistency and inconsistency of the two algorithms under the semi-Lagrangian framework. On the other hand, the sensitivity of the perfect and imperfect initial condition is also tested in both direct and indirect approaches. Our research has shown that the two algorithms are not only identical in theory, but also identical in numerical calculation. Furthermore, the algorithms of the indirect approach are much more feasible and efficient than that of the direct one when both are employed in the semi-Lagrangian framework. Taking advantage of semi-Lagrangian framework, one purpose of this paper is to illustrate when the variational assimilation algorithm is concerned in the computational method of the backward integration, the algorithm is extremely facilitated. Such simplicity in indirect approach should be meaningful for the VAR design in passive model. Indeed, if one can successfully split the diabatic and adiabatic process, the algorithms represented in this paper might be easily used in a more general vision of atmospheric model.

关键词： Variational algorithms Semi-Lagrangian framework Indirect approach Direct approach

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Analytical investigation on 3D non-Boussinesq mountain wave drag for wind profiles with vertical variations

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Applied Mathematics and Mechanics(English Edition) 2007年第3期28卷 317-325页

作者：唐锦赟汤杰王元 department of Atmospheric Science Key Laboratory of Mesoscale Severe Weather of Ministry of EducationNanjing University

A new analytical model was developed to predict the gravity wave drag （GWD） induced by an isolated 3-dimensional mountain, over which a stratified, nonrotating non-Boussinesq sheared flow is impinged. The model is confined to small amplitude motion and assumes the ambient velocity varying slowly with height. The modified Taylor-Goldstein equation with variable coefficients is solved with a Wentzel-Kramers-Brillouin （WKB） approximation, formally valid at high Richardson numbers. With this WKB solution, generic formulae of second order accuracy, for the GWD and surface pressure perturbation （both for hydrostatic and non-hydrostatic flow） are presented, enabling a rigorous treatment on the effects by vertical variations in wind profiles. In an ideal test to the circular bell-shaped mountain, itwas found that when the wind is linearly sheared, that the GWD decreases as the Richardson number decreases. However, the GWD for a forward sheared wind （wind increases with height） decreases always faster than that for the backward sheared wind （wind deceases with height）. This difference is evident whenever the model is hydrostatic or not.

关键词： gravity wave drag (GWD) wind shear Wentzel-Kramers-BriUouin (WKB) approximation circular bell-shaped mountain

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A Three-Dimensional Model of Transport and Diffusion of Seeding Agents within Stratus

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Advances in Atmospheric Sciences 2000年第4期17卷 617-635页

作者：余兴戴进蒋维楣樊鹏 Center of weather Modification of Shaanxi Province Xi’an department of Atmospheric Sciences Nanjing University Nanjing

It is essential to learn the temporal and spatial concentration distributions and variations of seeding agents in cloud seeding of precipitation enhancement. A three-dimensional puff trajectory model incorporating a mesoscale nonhydrostatic model has been formulated, and is applied to simulating the transporting and diffusive characteristics of multiple line sources of seeding agents within super-cooled stratus. Several important factors are taken into consideration that affect the diffusion of seeding materials such as effects of topography and vertical wind shear, temporal and spatial variation of seeding parameters and wet deposition. The particles of seeding agents are assumed to be almost inert, they have no interaction with the particles of the cloud or precipitation except that they are washed out by precipitation. The model validity is demonstrated by the analyses and comparisons of model results, and checked by the sensitivity experiments of diffusive coefficients and atmospheric stratification. The advantage of this model includes not only its exact reflection of heterogeneity and unsteadiness of background fields, but also its good simulation of transport and diffusion of multiple line sources. The horizontal diffusion rate and the horizontal transport distance have been proposed that they usually were difficult to obtain in other models. In this simulation the horizontal diffusion rate is 0.82 m s(-1) for average of one hour, and the horizontal average transport distance reaches 65 km after 1 4 which are closely related to the background Fields.

关键词： puff trajectory model transport and diffusion multiple line sources of seeding agents heterogeneity and unsteadiness diffusion rate and transport distance super-cooled stratus

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A Modeling Analysis of Rainfall and Water Cycle by the Cloud-resolving WRF Model over the Western North Pacific

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Advances in Atmospheric Sciences 2013年第6期30卷 1695-1711页

作者：高文华隋中兴 State Key Laboratory of Severe weather Chinese Academy of Meteorological Sciences department of Atmospheric Sciences

Simulated regional precipitation, especially extreme precipitation events, and the regional hydrologic budgets over the western North Pacific region during the period from May to June 2008 were investigated with the high-resolution （4-km grid spacing） weather research and Forecast （WRF v3.2.1） model with explicit cloud microphysics. The model initial and boundary conditions were derived from the National Centers for Environmental Prediction/department of Energy （NCEP/DOE） Reanalysis 2 data. The model precipitation results were evaluated against the Tropical Rainfall Measuring Mission （TRMM） Multisatellite Precipitation Analysis 3B42 product. The results show that the WRF simulations can reason- ably reproduce the spatial distributions of daily mean precipitation and rainy days. However, the simulated frequency distributions of rainy days showed an overestimation of light precipitation, an underestimation of moderate to heavy precipitation, but a good representation of extreme precipitation. The downscaling approach was able to add value to the very heavy precipitation over the ocean since the convective processes are resolved by the high-resolution cloud-resolving model. Moreover, the water vapor budget analysis indi- cates that heavy precipitation is contributed mostly by the stronger moisture convergence; whereas, in less convective periods, the precipitation is more influenced by the surface evaporation. The simulated water vapor budgets imply the importance in the tropical monsoon region of cloud microphysics that affects the precipitation, atmospheric latent heating and, subsequently, the large-scale circulation.

关键词： cloud-resolving WRF precipitation western North Pacific

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