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Propagation of gravity wave packet near critical level

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Science China(Technological Sciences) 2005年第5期48卷 538-555页

作者： YUE Xianchang YI Fan electronic information school of Wuhan University Key Laboratory of Geospace Environment and Geodesy Ministry of Education Wuhan 430079 China Electronic Information School of Wuhan University Key Laboratory of Geospace Environment and Geodesy Ministry of Education Wuhan 430079 China

A couple of two-dimensional linear and fully nonlinear numerical models for compressible atmosphere are used to numerically study the propagation of the gravity wave packet into a mean wind shear. For a linear propagation wave packet, the critical level interactions are in good agreement with the linear critical level theory. The dynamically and convectively unstable regions are formed due to the critical level interaction of a finite-amplitude wave packet, but they would not break. The free exchange of potential energy with kinetic energy in the background atmosphere at rest ceases after entering the mean wind shear. However, it still goes on in the nonlinear propagation. It is shown that the nonlinear effects modify the mean flow markedly, reduce the momentum and energy propagation velocity and drop the elevation of the critical level. The gravity wave packet becomes unstable and breaks down into smaller scales in some regions. It expends much more kinetic energy than potential energy in the early phase of the breakdown. This means that the wave breakdown sets up due to the action of the shear instability rather than a convective one.

关键词： gravity wave, nonlinear effect, critical level, instability, numerical simulation.

Climatology of global gravity wave activity and dissipation revealed by SABER/TIMED temperature observations

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Science China(Technological Sciences) 2014年第5期57卷 998-1009页

作者： SHUAI Jing ZHANG ShaoDong HUANG ChunMing YI Fan HUANG KaiMing GAN Quan GONG Yun electronic information school Wuhan University key laboratory of Geospace environment and geodesy Ministry of Education State Observatory for Atmospheric Remote Sensing

Gravity wave activity and dissipation in the height range from the low stratosphere to the low thermosphere(25–115 km)covering latitudes between 50°S and 50°N are statistically studied by using 9-year(January 22,2002–December 31,2010)SABER/TIMED temperature *** propose a method to extract realistic gravity wave fluctuations from the temperature profiles and treat square temperature fluctuations as GW ***,the gravity wave activity generally increases with *** the equator(0°–10°),the gravity wave activity shows a quasi-biennial variation in the stratosphere(below 40 km)while from 20°to 30°,it exhibits an annual variation below 40 km;in low latitudes(0°–30°)between the upper stratosphere and the low thermosphere(40–115 km),the gravity wave activity shows a semi-annual *** middle latitudes(40°–50°),the gravity wave activity has a clear annual variation below 85 *** addition,we observe a four-monthly variation with peaks occurring usually in April,August,December in the northern hemisphere and in February,June,October in the southern hemisphere,respectively,above 85 km in middle latitudes,which has been seldom reported in gravity wave *** order to study the dissipation of gravity wave propagation,we calculate the gravity wave dissipation ratio,which is defined as the ratio of the gravity wave growth scale height to the atmosphere density scale *** height variation of the dissipation ratio indicates that strong gravity wave dissipation mainly concentrates in the three height regions:the stratosphere(30–60 km),the mesopause(around 85 km)and the low thermosphere(above 100 km).Besides,gravity wave energy enhancement can be also observed in the background atmosphere.

关键词： gravity wave dissipation climatology middle and high atmosphere TIMED/SABER

Observations of gravity wave activity during stratospheric sudden warmings in the Northern Hemisphere

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Science China(Technological Sciences) 2015年第6期58卷 951-960页

作者： JIA Yue ZHANG ShaoDong YI Fan HUANG ChunMing HUANG KaiMing GAN Quan GONG Yun school of electronic information Wuhan University key laboratory of Geospace environment and geodesy Ministry of Education State Observatory for Atmospheric Remote Sensing State key laboratory of information Engineering in Surveying Mapping and Remote Sensing

Arctic stratospheric sudden warming(SSW) with polar vortex displacement and splitting occurred in 2008 and 2009, respectively. The temperature profiles derived from the Constellation Observing System for Meteorology, Ionosphere and Climate(COSMIC) along with NCEP/NCAR reanalysis are used to investigate the gravity wave(GW) variations during these SSW events. Some phenomena are characterized and possible mechanisms are discussed. The GW variations during both types of SSW events shared some similarities. During the warming events, enhanced zonal mean GW amplitudes are detected. The enhancements of GW amplitudes first appeared at higher altitudes and then progressed downward during the major warming events. The downward progressions correspond well with the height variations of the zonal wind reversal, and the enhancements seem to occur at the same time with the wind reversal. The spatial variations of GWs showed evident correlation to the polar vortex. Generally, GWs were enhanced at the edge of the polar vortex where the background wind was strong, whereas the areas with the largest GW amplitudes did not always correspond with those with the strongest background wind. The differences during the two types of SSW are also noticeable. In the 2008 major event, the magnitudes of the zonal mean GW enhancements during the downward progression were relatively stable, whereas in the 2009 major event, a clear reduction was detected as the GW enhancement was progressing downward. Also, the recovery time of the polar vortex was longer in 2009. These differences indicate that different types of SSWs may have different impacts on the GW.

关键词： stratospheric sudden warming gravity wave COSMIC

Numerical study of the auroral particle transport in the polar upper atmosphere

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Science China(Technological Sciences) 2008年第10期51卷 1759-1771页

作者： CAI HongTao1,2, MA ShuYing1,2 & PU ZuYin3 1 school of electronic information, Wuhan University, Wuhan 430079, China 2 key laboratory of Geospace environment and geodesy, ministry of education of PRC, Wuhan 430079, China 3 school of Earth and Space Sciences, Peking University, Beijing 100871, China school of electronic information Wuhan University key laboratory of Geospace environment and geodesy Ministry of Education of PRC school of Earth and Space Sciences Peking University

Starting from the Boltzmann equation and with some reasonable assumptions, a one-dimensional transport equation of charged energetic particles is derived by taking account of major interactions with neutral species in the upper atmosphere, including the processes of elastic scattering, the excitation, the ionization and the secondary electron production. The transport equation is numerically solved, for a simplified atmosphere consisting only of nitrogen molecules (N2), to obtain the variations of incident electron fluxes as a function of altitude, energy and pitch angle. The model results can describe fairly the transport characteristics of pre-cipitating auroral electron spectra in the polar upper atmosphere; meanwhile the N2 ionization rates calculated from the modeled differential flux spectra also exhibit good agreements with existing empirical models in terms of several key parameters. Taking the energy flux spectra of precipitating electrons observed by FAST satellite flying over EISCAT site on May 15, 1997 as model inputs, the model-calculated ionization rate profile of neutral atmosphere consists reasonably with that recon-structed from electron density measurements by the radar.

关键词： aurora particle precipitation polar upper atmosphere electron transport equation numerical simulation

A numerical study on nonlinear propagation and short-term variability of the migrating diurnal and semidiurnal tides

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Chinese Science Bulletin 2005年第17期50卷 1940-1948页

作者： HUANG Chunming1,2, ZHANG Shaodong1,2 & YI Fan1,2 1. school of electronic information, Wuhan Universiy, Wuhan 430079, China 2. key laboratory of Geospace environment and geodesy, ministry of education, Wuhan University, Wuhan 430079, China school of electronic information Wuhan Universiy Wuhan China key laboratory of Geospace environment and geodesy Ministry of Education Wuhan University Wuhan China

By using a three-dimensional fully nonlinear numerical model in spherical coordinates and taking the linear steady solutions of the migrating diurnal and semidi-urnal tides in January from the Global-Scale Wave Model (GSWM) as the initial values, we simulate the linear and nonlinear propagations of the migrating diurnal and semidi-urnal tides in the atmosphere from the ground to the lower thermosphere. A comparison of our simulations with the results of GSWM is also presented. The simulation results show that affected by the nonlinearity, the migrating diurnal and semidiurnal tides propagating in the middle and upper atmosphere exhibit evident short-term variability. The nonlinear interactions between the migrating tides and the background atmosphere can obviously alter the background wind and temperature fields, which suggests that the nonlin-ear propagations of the migrating diurnal and semidiurnal tides impact significantly on the transient dynamical and thermal structures of the background middle and upper at-mosphere and the nonlinear effect is an important cause of the difference between the results of GSWM and observa-tions.

关键词：大气非线性传播数学模型可变性温度场

Numerical Simulation of Ionization Enhancement in the Topside Ionosphere of Cusp Foot-Point Region Caused by Low Energy Particle Precipitation

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Wuhan University Journal of Natural Sciences 2008年第2期13卷 185-190页

作者： CAI Hongtao MA Shuying G Kirchengast school of electronic information/key laboratory ofgeospace environment and geodesy of ministry of education Wuhan University Wuhan 430072 China Institute for Geophysics Astrophysics and MeteorologyUniversity of Graz Graz A-8010 Austria

The Graz Ionospheric Flux Tube Simulations （GIFTS） has been improved. The improved GIFTS model was used to numerically investigate the energy particle precipitation on the distribution of electron density in the ionospheric cusp foot-point region under conditions of large plasma convection during magnetic storm. After including the effects of low energy incident particles, the ionospheric electron densities increase remarkably above altitude of -250 km, showing a peak at about 350 km. The percent enhancements of electron densities increase gradually with altitude, exceed- ing 60% near the upper boundary of the calculation. The calculated ionospheric F2-peak was remarkably enhanced and lifted up by the incident low energy electrons.

关键词： magnetic storms particle precipitation cusp ionization enhancement ionospheric physical model numerical simulation

Nonlinear Interactions between the Quasi 5-day Wave and Tides Based on Meteor Radar Observations at Maui

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空间科学学报 2015年第4期35卷 445-452页

作者： GU Jingxiao HUANG Chunming HUANG Kaiming school of electronic information Wuhan University key laboratory of Geospace environment and geodesy Ministry of Education State Observatory for Atmospheric Remote Sensing

Nonlinear interactions between the quasi 5-day wave and tides based on meteor radar observation in the Mesosphere and Lower Thermosphere(MLT) at Maui are studied in this *** sum interaction between quasi 5-day wave and diurnal tide,and evident difference interaction between quasi 5-day wave and semidiurnal tide are observed during the time of ***,their difference and sum counterparts are clearly *** secondary waves generated from those interactions beat with the tide and show intense modulation at the period of 5 days which confirms the existence of their ***,correlation coefficients among these waves are calculated to further explore their interactions and find that they can persist for several days although they are highly *** energy exchange among these waves can be reversible during the observational *** periods when the significant difference interaction between the quasi 5-day wave and semidiurnal tide occur are much shorter than those when the significant sum interaction between the quasi 5-day wave and diurnal tide ***,these two strong interactions can take place *** generally,this study provides the proof of nonlinear interactions between quasi 5-day wave and tides which were seldom reported before.

关键词： Quasi 5-day wave Tides Nonlinear interaction Mesos

High resolution full-spectrum water Raman lidar

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Science China(Technological Sciences) 2012年第5期55卷 1224-1229页

作者： LIU FuChao YI Fan JIA JingYu ZHANG YunPeng ZHANG ShaoDong YU ChangMing TAN Ying school of electronic information Wuhan UniversityWuhan 430079China key laboratory of Geospace environment and geodesy Ministry of EducationWuhan 430079China State Observatory for Atmospheric Remote Sensing Wuhan 430079China

Knowledge of the temporal-spatial distribution of water content in atmosphere and water phase change in cloud is important for atmospheric study. For this purpose, we have developed a high resolution full-spectrum water Raman lidar that can collect Raman signals from ice, water droplets and water vapor simultaneously. A double-grating polychromator and a 32-channel photomultiplier-tube detector are used to obtain a spectral resolution of-0.19 nm in the full Raman spectrum range of water, Preliminary observations present the water Raman spectrum characteristics of both the mixed-phase cloud and humid air under cloudless condition.

关键词： cloud water phase high spectral resolution Raman lidar

Anomalous changes of temperature and ozone QBOs in 2015−2017 from radiosonde observation and MERRA-2 reanalysis

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Earth and Planetary Physics 2021年第3期5卷 280-289页

作者： XiaoYan Bai KaiMing Huang ShaoDong Zhang ChunMing Huang Yun Gong school of electronic information Wuhan UniversityWuhan 430072China key laboratory of Geospace environment and geodesy Ministry of EducationWuhan 430072China State Observatory for Atmospheric Remote Sensing Wuhan 430072China

Anomalous changes of zonal wind quasi-biennial oscillation(QBO)in winter 2015−2016 have received close *** radiosonde and satellite observations and reanalysis data,we investigate anomalous changes in temperature and ozone QBOs from the lower to middle *** wind shear direction is reversed due to unexpected changes of zonal wind QBO at about 24−30 km,the shortest cold phase at 21−27 km appears in temperature *** is different from the completely interrupted westward phase in zonal wind QBO,while the longest cold phase above almost 27 km lasts for 2−3 years from 2015 to 2017,owing to the absence of corresponding warm *** scale reduction of temperature QBO causes a small temperature anomaly,thus the thermal wind relationship looks seemingly different from that in the other regular QBO *** in the ozone mixing ratio anomaly shows a double-peak with inverse phase,and its phase below(above)30 km is in agreement with(opposite to)the phase of temperature QBO because of different control mechanisms of *** temperature QBO variation,QBO in the ozone mixing ratio anomaly exhibits a less positive phase at 20−30 km in 2016−2017,and a very long positive phase above 30 km from 2015 to *** in total column ozone shows a small peak in winter 2016−2017 since ozone is mainly concentrated at 20 to 30 *** changes of temperature and ozone QBOs due to unexpected QBO zonal wind variation can be well-explained according to thermal wind balance and thermodynamic balance.

关键词： QBO temperature anomaly ozone anomaly thermal wind balance