Variations in Wave Energy and Amplitudes along the Energy Dispersion Paths of Nonstationary Barotropic Rossby Waves

The variations in the wave energy and the amplitude along the energy dispersion paths of the barotropic Rossby waves in zonally symmetric basic flow are studied by solving the wave energy equation,which expresses that the wave energy variability is determined by the divergence of the group velocity and the energy budget from the basic flow.The results suggest that both the wave energy and the amplitude of a leading wave increase significantly in the propagating region that is located south of the jet axis and enclosed by a southern critical line and a northern turning latitude.The leading wave gains the barotropic energy from the basic flow by eddy activities.The amplitude continuously climbs up a peak at the turning latitude due to increasing wave energy and enlarging horizontal scale(shrinking total wavenumber).Both the wave energy and the amplitude eventually decrease when the trailing wave continuously approaches southward to the critical line.The trailing wave decays and its energy is continuously absorbed by the basic flow.Furthermore,both the wave energy and the amplitude oscillate with a limited range in the propagating region that is located near the jet axis and enclosed by two turning latitudes.Both the leading and trailing waves neither develop nor decay significantly.The jet works as a waveguide to allow the waves to propagate a long distance.

Recent Progresses on Ionospheric Climatology Investigations

The ionosphere varies over multiple time scales,which are classified into two categories: the climatology and weather variations.In this national report,we give a brief summary of recent progresses in ionospheric climatology with focus on(1) the seasonal variations,(2) solar cycle effects, and(3) empirical modeling of the ionosphere.The seasonal variations of the ionosphere have been explored in many works to give a more detailed picture with regional and global features at various altitudes by analyzing the observation data from various sources and models.Moreover,a series of studies reported the response of the ionosphere to solar cycle variations,which revealed some novel and detailed features of solar activity dependence of ionospheric parameters at different altitudes. These investigations have improved our understanding on the states of the ionosphere and underlying fundamental processes,provided clues to future studies on ionospheric weather,and guided ionospheric modeling,forecasting and related applications.

Recent ionospheric investigations in China(2018–2019)

Since the release of the 2018 National Report of China on ionospheric research(Liu LB and Wan WX,2018)to the Committee on Space Research(COSPAR),scientists from China's Mainland have made many new fruitful investigations of various ionospheric-related issues.In this update report,we briefly introduce more than 130 recent reports(2018–2019).The current report covers the following topics:ionospheric space weather,ionospheric structures and climatology,ionospheric dynamics and couplings,ionospheric irregularity and scintillation,modeling and data assimilation,and radio wave propagation in the ionosphere and sounding techniques.

Assimilation of GMS-5 satellite winds using nudging method with MM5

With the aid of Meteorological Information Composite and Processing System (MICAPS), satellite wind vectors derived from the Geostationary Meteorological Statellite-5 (GMS-5) and retrieved by National Satellite Meteorology Center of China (NSMC) can be obtained. Based on the nudging method built in the fifth-generation Mesoscale Model (MM5) of Pennsylvania State University and Na- tional Center for Atmospheric Research, a data preprocessor is developed to convert these satellite wind vectors to those with specified format required in MM5. To examine the data preprocessor and evaluate the impact of satellite winds from GMS-5 on MM5 simulations, a series of numerical experimental fore- casts consisting of four typhoon cases in 2002 are designed and implemented. The results show that the preprocessor can process satellite winds smoothly and MM5 model runs successfully with a little extra computational load during ingesting these winds, and that assimilation of satellite winds by MM5 nudging method can obviously improve typhoon track forecast but contributes a little to typhoon intensity forecast. The impact of the satellite winds depends heavily upon whether the typhoon bogussing scheme in MM5 was turned on or not. The data preprocessor developed in this paper not only can treat GMS-5 satellite winds but also has capability with little modification to process derived winds from other geostationary satellites.

First results of optical meteor and meteor trail irregularity from simultaneous Sanya radar and video observations

Meteoroids entering the Earth's atmosphere can create meteor trail irregularity seriously disturbing the background ionosphere. Although numerous observations of meteor trail irregularities were performed with VHF/UHF coherent scatter radars in the past, no simultaneous radar and optical instruments were employed to investigate the characteristics of meteor trail irregularity and its corresponding meteoroid. By installing multiple video cameras near the Sanya VHF radar site, an observational campaign was conducted during the period from November 2016 to February 2017. A total of 242 optical meteors with simultaneous non-specular echoes backscattered from the plasma irregularities generated in the corresponding meteor trails were identified. A good agreement between the angular positions of non-specular echoes derived from the Sanya radar interferometer and those of optical meteors was found,validating that the radar system phase offsets have been properly calibrated. The results also verify the interferometry capability of Sanya radar for meteor trail irregularity observation. The non-specular echoes with simultaneous optical meteors were detected at magnetic aspect angles greater than ~78°. Based on the meteor visual magnitude estimated from the optical data, it was found that the radar nonspecular echoes corresponding to brighter meteors survived for longer duration. This could provide observational evidence for the significance of meteoroid mass on the duration of meteor trail irregularity. On the other hand, the simultaneous radar and video common-volume observations showed that there were some cases with optical meteors but without radar non-specular echoes. One possibility could be that some of the optical meteors appeared at extremely low altitudes where meteor trail irregularities rarely occur.

Electric Character of Strange Stars

Using the Thomas-Fermi model,we investigated the electric characteristics of a static non-magnetized strange star without crust.The exact solutions of electron number density and electric field above the quark surface are obtained.These results are useful if we are concerned about physical processes near the quark matter surfaces of strange stars.

Anomaly distribution of ionospheric total electron content responses to some solar flares

Previous studies have shown that the ionospheric responses to a solar flare are significantly dependent on the solar zenith angle(SZA):the ionospheric responses are negatively related to the SZAs.The largest enhancement in electron density always occurs around the subsolar point.However,from 2001 to 2014,the global distribution of total electron content(TEC)responses showed no obvious relationship between the increases in TEC and the SZA during some solar flares.During these solar flares,the greatest enhancements in TEC did not appear around the subsolar point,but rather far away from the subsolar point.The distribution of TEC enhancements showed larger TEC enhancements along the same latitude.The distribution of anomalous ionospheric responses to the solar flares was not structured the same as traveling ionospheric disturbances.This anomaly distribution was also unrelated to the distribution of background neutral density.It could not be explained by changes in the photochemical process induced by the solar flares.Thus,the transport process could be one of the main reasons for the anomaly distribution of ionospheric responses to the solar flares.This anomaly distribution also suggests that not only the photochemical process but also the transport process could significantly affect the variation in ionospheric electron density during some solar flares.

Preliminary experimental results by the prototype of Sanya Incoherent Scatter Radar

In the past decades,the Incoherent Scatter Radar(ISR)has been demonstrated to be one of the most powerful instruments for ionosphere monitoring.The Institute of Geology and Geophysics at the Chinese Academy of Sciences was founded to build a state-ofthe-art phased-array ISR at Sanya(18.3°N,109.6°E),a low-latitude station on Hainan Island,named the Sanya ISR(SYISR).As a first step,a prototype radar system consisting of eight subarrays(SYISR-8)was built to reduce the technical risk of producing the entire large array.In this work,we have summarized the preliminary experimental results based on the SYISR-8.The amplitude and phase among 256 channels were first calibrated through an embedded internal monitoring network.The mean oscillation of the amplitude and phase after calibration were about 1 dB and 5°,respectively,which met the basic requirements.The beam directivity was confirmed by crossing screen of the International Space Station.The SYISR-8 was further used to detect the tropospheric wind profile and meteors.The derived winds were evaluated by comparison with independent radiosonde and balloon-based GPS measurements.The SYISR-8 was able to observe several typical meteor echoes,such as the meteor head echo,range-spread trail echo,and specular trail echo.These results confirmed the validity and reliability of the SYISR-8 system,thereby reducing the technical risk of producing the entire large array of the SYISR to some extent.

A local Martian crustal field model: Targeting the candidate landing site of the 2020 Chinese Mars Rover

Unlike Earth,Mars lacks a global dipolar magnetic field but is dominated by patches of a remnant crustal magnetic field.In 2021,the Chinese Mars Rover will land on the surface of Mars and measure the surface magnetic field along a moving path within the possible landing region of 20°W-50°W,20°N-30°N.One scientific target of the Rover is to monitor the variation in surface remnant magnetic fields and reveal the source of the ionospheric current.An accurate local crustal field model is thus considered necessary as a field reference.Here we establish a local crust field model for the candidate landing site based on the joint magnetic field data set from Mars Global Explorer(MGS)and Mars Atmosphere and Volatile Evolution(MAVEN)data combined.The model is composed of 1,296 dipoles,which are set on three layers but at different buried depths.The application of the dipole model to the joint data set allowed us to calculate the optimal parameters of their dipoles.The calculated results demonstrate that our model has less fitting error than two other state-of-the art global crustal field models,which would indicate a more reasonable assessment of the surface crustal field from our model.

Response of atmospheric carbon dioxide to the secular variation of weakening geomagnetic field in whole atmosphere simulations

Responses of atmospheric carbon dioxide(CO_(2))density to geomagnetic secular variation are investigated using the Whole Atmosphere Community Climate Model-eXtended(WACCM-X).Our ensemble simulations show that CO_(2) volume mixing ratios(VMRs)increase at high latitudes and decrease at mid and low latitudes by several ppmv in response to a 50%weakening of the geomagnetic field.Statistically significant changes in CO_(2) are mainly found above~90 km altitude and primarily redetermine the energy budget at~100-110 km.Our analysis of transformed Eulerian mean(TEM)circulation found that CO_(2) change is caused by enhanced upwelling at high latitudes and downwelling at mid and low latitudes as a result of increased Joule heating.We further analyzed the atmospheric CO_(2) response to realistic geomagnetic weakening between 1978 and 2013,and found increasing(decreasing)CO_(2) VMRs at high latitudes(mid and low latitudes)accordingly.For the first time,our simulation results demonstrate that the impact of geomagnetic variation on atmospheric CO_(2) distribution is noticeable on a time scale of decades.

Observations of equatorial plasma bubbles during the geomagnetic storm of October 2016

We investigated the variations of equatorial plasma bubbles(EPBs)in the East-Asian sector during a strong geomagnetic storm in October 2016,based on observations from the Beidou geostationary(GEO)satellites,Swarm satellite and ground-based ionosonde.Significant nighttime depletions of F region in situ electron density from Swarm and obvious nighttime EPBs in the Beidou GEO observations were observed on 13 October 2016 during the main phase.Moreover,one interesting feature is that the rare and unique sunrise EPBs were triggered on 14 October 2016 in the main phase rather than during the recovery phase as reported by previous studies.In addition,the nighttime EPBs were suppressed during the whole recovery phase,and absent from 14 to 19 October 2016.Meanwhile,the minimum virtual height of F trace(h’F)at Sanya(18.3°N,109.6°E,MLAT 11.1°N)displayed obvious changes during these intervals.The h’F was enhanced in the main phase and declined during the recovery phase,compared with the values at pre-and post-storm.These results indicate that the enhanced nighttime EPBs and sunrise EPBs during the main phase and the absence nighttime EPBs for many days during the recovery phase could be associated with storm-time electric field changes.

Wavenumber-4 spectral component extracted from TIMED/SABER observations

The wavenumber spectral components WN4 at the mesosphere and low thermosphere(MLT)altitudes(70–10 km)and in the latitude range between±45°are obtained from temperature data(T)observed by the Sounding of the Atmosphere using Broadband Emission Radiometry(SABER)instruments on board the National Aeronautics and Space Administration(NASA)’s Thermosphere–Ionosphere–Mesosphere Energetics and Dynamics(TIMED)spacecraft during the 11-year solar period from 2002 to 2012.We analyze in detail these spectral components WNk and obtain the main properties of their vertical profiles and global structures.We report that all of the wavenumber spectral components WNk occur mainly around 100 km altitude,and that the most prominent component is the wavenumber spectral component WN4 structure.Comparing these long duration temperature data with results of previous investigations,we have found that the yearly variation of spectral component WN4 is similar to that of the eastward propagating non-migrating diurnal tide with zonal wavenumber 3(DE3)at the low latitudes,and to that of the semi-diurnal tide with zonal wavenumber 2(SE2)at the mid-latitudes:the amplitudes of the A4 are larger during boreal summer and autumn at the low-latitudes;at the mid-latitudes the amplitudes have a weak peak in March.In addition,the amplitudes of component WN4 undergo a remarkable short period variation:significant day-to-day variation of the spectral amplitudes A4 occurs primarily in July and September at the low-latitudes.In summary,we conclude that the non-migrating tides DE3 and SE2 are likely to be the origins,at the low-latitudes and the mid-latitudes in the MLT region,respectively,of the observed wavenumber spectral component WN4.

Preliminary Estimation of Moisture Exchange in Rongbuk Valley on the Northern Slope of Mt. Qomolangma

Using observed wind and water vapor data from June 2006,water vapor exchange between the Rongbuk Valley and its above atmosphere is estimated for the first time.The water vapor level shows a high value from 23-29 June and a low from 12-21 June,which co-incide with the South Asian summer monsoon (SASM) active and break stages,respectively.The water vapor can be strongly injected into the closed region of the Rongbuk Valley from the outside atmosphere,with an average strength of 0.4 g s-1 m-2 in June 2006,given that no evaporation occurred.The air moisture exchange proc-esses can be greatly affected by the SASM evolution through changes in local radiation forcing.

An Improved Method for Correction of Air Temperature Measured Using Different Radiation Shields

The variation of air temperature measurement errors using two different radiation shields （DTR502B Vaisala,Finland,and HYTFZ01,Huayun Tongda Satcom,China） was studied.Datasets were collected in the field at the Daxing weather station in Beijing from June 2011 to May 2012.Most air temperature values obtained with these two commonly used radiation shields were lower than the reference records obtained with the new Fiber Reinforced Polymers （FRP） Stevenson screen.In most cases,the air temperature errors when using the two devices were smaller on overcast and rainy days than on sunny days; and smaller when using the imported rather than the Chinese shield.The measured errors changed sharply at sunrise and sunset,and reached maxima at noon.Their diurnal variation characteristics were,naturally,related to changes in solar radiation.The relationships between the record errors,global radiation,and wind speed were nonlinear.An improved correction method was proposed based on the approach described by Nakamura and Mahrt （2005） （NM05）,in which the impact of the solar zenith angle （SZA） on the temperature error is considered and extreme errors due to changes in SZA can be corrected effectively.Measurement errors were reduced significantly after correction by either method for both shields.The error reduction rate using the improved correction method for the Chinese and imported shields were 3.3％ and 40.4％ higher than those using the NM05 method,respectively.

Statistical study on great geomagnetic storms during solar cycle 23

Characteristics of great geomagnetic storms during solar cycle 23 were statistically investigated. Firstly, we focused on the uniqueness of solar cycle 23 by analyzing both the great storm number and sunspot number from 1957 to 2008. It was found that the relationship between the sunspot number and great storm number weakened as the activity of the storms strengthened. There was no obvious relationship between the annual sunspot number and great storm number with Dst≤-300 nT. Secondly, we studied the relationship between the peak Dst and peak Bz in detail. It was found that the condition Bz〈-10 nT is not necessary for storms with Dst≤-100 nT, but seems necessary for storms with Dst≤-150 nT. The duration for Bz≤-10 nT has no direct relationship with the giant storm. The correlation coefficient between the Dst peak and Bz peak for the 89 storms studied is 0.81. After removing the effect of solar wind dynamic pressure on the Dst peak, we obtained a better correlation coefficient of 0.86. We also found the difference between the Dst peak and the corrected Dst peak was proportional to the Dst peak.

A Review of the Ionospheric Investigations in China:Progress During 2008-2010

In the ionospheric research,various progresses have been made during the last two years.This paper reviews the recent works of Chinese scientists.For convenience,the contents include:ionospheric storms and space weather;ionospheric irregularities and scintillation;ionospheric variability;ionospheric disturbances;ionospheric response to solar eclipses;ionospheric coupling with atmosphere and lithosphere;ionospheric climatology;ionospheric modeling;and ionospheric prediction and application.

GEOMETRICAL OPTICS IN AN INHOMOGENEOUS UNIVERSE

In comparison with a homogeneous universe,a clumpy universe possess two types of effects on geometrical optics:1.the convergence due to the gravititational-lens effects of the clumps;t.the divergence due to the less mass density outside the clumps.On the other hand,thermodynamics requires that the total effects are double offset.This give us an effective method to judge the rationality of various calculations of the lensing effect in a clumpy universe.

NEUTRINO MASS AND SUPERNOVA 1987A

If the rest mass of electron neutrinos is non-zero,the arrival times of neutrinos emitted from supernova 1987a will be dispersed due to the dependence of neutrino speed on their energy.By using this effect,an upper limit of the neutrino mass,5-10eV/c^(2),can be derived from the data of neutrinos recorded by Mont Blanc neutrino observatory.

Self-Microlensing in Compact Binary Systems

The signature of the self-microlensing in compact binaries(white dwarfs,neutron stars and black holes)is a flare with the characteristic time of typically a few minutes.The probability of detecting these microlensing events can be as high as 1/50 for a photometric accuracy of Δm=0.01 in magnitude.The discovery of the self-microlensing by binaries would furnish an additional way to find the masses of the lens and the companion,and will be promising for the searches of black holes.

On the solar activity dependence of midnight equatorial plasma bubbles during June solstice periods

The occurrence of midnight Equatorial Plasma Bubbles(EPBs)during the June solstice period of the ascending phase of solar cycle 24,from 2010 to 2014,was studied using data from the 47 MHz Equatorial Atmosphere Radar(EAR)at Kototabang,Indonesia.The analysis shows that the occurrence of midnight hour EPBs was at its maximum during the low solar activity year 2010 and monotonically decreased thereafter with increasing solar activity.Details of the dependence of midnight hour EPB occurrence on solar activity were investigated using SAMI2 model simulation with a realistic input of E×B drift velocity data obtained from the CINDI-IVM onboard the C/NOFS satellite.Results obtained from term-by-term analysis of the flux tube integrated linear growth rate of RT instability indicate that the formation of a high flux tube electron content height gradient(steep vertical gradient)region at higher altitudes,due to the elevated F layer,is the key factor enhancing the growth rate of RT instability during low solar activity June solstices.Other factors are discussed in light of the relatively weak westward zonal electric field in the presence of the equatorward neutral wind and north-to-south transequatorial wind around the midnight hours of low solar activity June solstices.Also discussed are the initial seeding of RT instability by MSTIDs and how the threshold height required for EPB development varies with solar activity.