資料9-G

Commission G Report
June 10, 2016
1. Meeting announcement/report•

JpGU Meeting 2016 was held at Makuhari, Chiba on May 22-26, 2016. There are Commission Grelated sessions in the meeting. http://www.jpgu.org/meeting_2016/•2016 Beacon Scintillation Symposium will be held at Trieste, Italy on June 27 – July 1, 2016. This
meeting is co-sponsored by URSI Commission G. http://t-ict4d.ictp.it/beacon2016•

41st COSPAR Scientific Assembly will be held at Istanbul, Turkey on July 30 – August 7, 2016.
http://cospar2016.tubitak.gov.tr•

AOGS 13th Annual Meeting will be held at Beijing, China on July 31 – August 5, 2016.
http://www.asiaoceania.org/aogs2016/•

International Symposium on the Whole Atmosphere (ISWA) will be held at Ito Hall, The
University of Tokyo on September 14-16, 2016. Observations and studies of all height of theatmosphere especially featuring PANSY radar will be discussed. http://pansy.eps.s.utokyo.ac.jp/iswa/•

MU radar /Equatorial Atmosphere Radar Symposium was held at RISH, Kyoto University on
September 8-9, 2016. This is the annual meeting for the cooperative use of the facilities.
Commission G of Japanese URSI co-sponsors this symposium.

2. Research Report
2.1. Report from National Institute for Polar Research (NIPR)(Yasunobu Ogawa, NIPR)=== Research activity of PANSY ===A 1-year continuous full system observation of the PANSY radar started from late September 2015. It
enables us to capture various temporal- and spatial-scale phenomena in the Antarctic troposphere,
stratosphere, mesosphere, and thermosphere/ionosphere with high temporal and vertical resolution
throughout the year and to contribute to improving global climate models for better understanding of
future climate change.
In addition, the first international campaign based on a combination of GCM (General Circulation
Model) simulations and simultaneous observations by several MST/IS radars over the world including
PANSY and some complementary instruments such as MF (Medium Frequency) and meteor radars,
lidars, imagers, and so on was successfully conducted from January 22 to February 17, 2016. This
campaign was named the Interhemispheric Coupling Study by Observations and Modeling (ICSOM:
see details at http://pansy.eps.s.u-tokyo.ac.jp/icsom/), and approved as a project for ROSMIC (Role Of
the Sun and the Middle atmosphere/thermosphere/ionosphere In Climate) of SCOSTEP (ScientificCommittee on Solar-Terrestrial Physics) under ICSU (International Council for Science). It is
expected that these international collaborations including the PANSY radar will promote a moreaccurate understanding of the Antarctic atmosphere and interhemispheric coupling processes.
=== Recent papers ===(PANSY related papers)
Minamihara, Y., K. Sato, M. Kohma, and M. Tsutsumi, Characteristics of vertical wind fluctuations in
the lower troposphere at Syowa Station in the Antarctic revealed by the PANSY radar, SOLA,
12, 116-120, doi:10.2151/sola.2016-026, 2016.
Using wind data over three years from July 2012 - June 2015 from the PANSY radar, an MST
radar, newly installed at Syowa Station (39.59°E, 69.0°S), statistical characteristics of verticalwinds and vertical momentum fluxes in the Antarctic lower troposphere are examined.
Frequency spectra covering a wide frequency range from (30 d)-1 to (8 min)-1 are divided into
three frequency regions obeying power laws with different scaling exponents. The transition1

資料9-G

frequencies are different between horizontal and vertical wind spectra. Vertical fluxes ofhorizontal momentum were estimated for two wave period ranges of 8 min - 2 h and 2 h - 1 dand having almost equal logarithmic scales. The momentum fluxes are larger for longer period
components. There are evidences showing that the vertical wind disturbances in the lower
troposphere are due to gravity waves forced by topography aligned in the north-south direction.
First, the strong disturbances are observed when horizontal winds are strong near the surface.
Second, zonal winds tend to almost zero around the top of the disturbances. Third, frequency
spectra are large at a wide range of frequency below a critical level, as is consistent with thephase modulation of mountain waves by unsteady mean flow.
Mihalikova, M., K. Sato, M. Tsutsumi, and T. Sato, Properties of inertia‐gravity waves in thelowermost stratosphere as observed by the PANSY radar over Syowa Station in the Antarctic,
Ann. Geo., 34, 543-555, doi:10.5194/angeo-34-543-2016, 2016.
Inertia-gravity waves (IGWs) are an important component for the dynamics of the middle
atmosphere. However, observational studies needed to constrain their forcing are stillinsufficient especially in the remote areas of the Antarctic region. One year of observational data
(January to December 2013) by the PANSY radar of the wind components (vertical resolution of
150m and temporal resolution of 30 min) are used to derive statistical analysis of the properties
of IGWs with short vertical wavelengths (≤ 4 km) and ground-based periods longer than 4 h in
the lowermost stratosphere (height range 10 to 12 km) with the help of the hodograph method.
The annual change of the IGWs parameters are inspected but no pronounced year cycle is found.
The year is divided into two seasons (summer and winter) based on the most prominent
difference in the ratio of Coriolis parameter f to intrinsic frequency ω distribution. Average off/ω for the winter season is 0.40 and for the summer season 0.45 and the average horizontal
wavelengths are 140 and 160 km respectively. Vertical wavelengths have an average of 1.85 km
through the year. For both seasons the properties of IGWs with upward and downward
propagation of the energy are also derived and compared. The percentage of downward
propagating waves is 10.7 and 18.4% in the summer and winter season respectively. Thisseasonal change is more than the one previously reported in the studies from mid-latitudes andmodel-based studies. It is in agreement with the findings of past radiosonde data-based studies
from the Antarctic region. In addition, using the so-called dualbeam technique, vertical
momentum flux and the variance of the horizontal perturbation velocities of IGWs are examined.
Tropospheric disturbances of synoptic-scale are suggested as a source of episodes of IGWs withlarge variance of horizontal perturbation velocities, and this is shown in a number of cases.
2.2. Report from Institute for Space-Earth Environmental Research (ISEE), Nagoya University(Satonori Nozawa, Nagoya University)== Recent papers ===Dao, T., Y. Otsuka, K. Shiokawa, S. Tulasi Ram, and M. Yamamoto, Altitude development of
postmidnight F region field-aligned irregularities observed using Equatorial Atmosphere
Radar in Indonesia, Geophys. Res. Lett., 43, 1015-1022, doi:10.1002/2015GL067432, 2016.
Vertical rise velocities of post-midnight field-aligned irregularities (FAIs) at low
geomagnetic latitudes have been examined near the June solstice by using two-dimensional
maps of F-region FAI echoes observed with the Equatorial Atmosphere Radar in Indonesia
for 3 years. A lower limit for the generation time of the post-midnight FAIs is estimated tobe between 21:30 LT and 02:00 LT for 14 of the 15 events, indicating that this class of FAIs
is distinct from the post-sunset FAIs.
Li, G., Y. Otsuka, B. Ning, M. A. Abdu, M. Yamamoto, W. Wan, L. Liu, and P. Abadi, Enhanced
ionospheric plasma bubble generation in more active ITCZ, Geophys. Res. Lett., 43(6),2389-2395, doi:10.1002/2016GL068145, 2016.
From simultaneous radar measurements with multi-beams at Kototabang, Indonesia andSanya, China, we find that occurrence rate of the plasma bubble generated locally over
Kototabang is clearly more than that over Sanya. More active intertropical convergence2

資料9-G

zone (ITCZ) is situated around the longitude of Kototabang. We surmise that the enhanced
ionospheric bubble generation at Kototabang longitude could be caused by a higher gravity
wave activity associated with the more active ITCZ.
Jun C.-W, K. Shiokawa, M. Connors, I. Schofield, I. Poddelsky, and B. Shevtsov, Possible
generation mechanisms for Pc1 pearl structures in the ionosphere, based on 6 years ofground observations in Canada, Russia, and Japan, J. Geophys. Res. Space Phys., 121, doi:
10.1002/2015JA022123, 2016.
We investigate pearl structures (amplitude modulations) of Pc1 pulsations simultaneously
observed at Canada, Russia, and Japan. From 6 years of ground observations, we conclude
that ionospheric beating effect could be a dominant process for the generation of Pc1 pearl
structures. Through ionospheric duct propagation.
Sakaguchi, K., K. Shiokawa, Y. Miyoshi, and M. Connors, Isolated proton auroras and Pc1/EMIC
waves at subauroral latitudes, in Auroral Dynamics and Space Weather, Geophysical
Monograph 215, Edited by Yongliang Zhang and Larry J. Paxton, American GeophysicalUnion. Published by John Wiley & Sons, Inc., 2016.
In this study, spatial distribution and occurrence probability of isolated proton auroras(IPAs) were statistically investigated, as a proxy for regions of EMIC wave occurrence,using ground ‐ based imaging data during 2006-2012 at Athabasca, Canada. The IPA
occurrence probability are shown as function of local time, magnetic activity, solar cycle
variation. Quantitative estimation is given for the IPA size, providing quantitative estimate
the loss rate of energetic particles, contributing to space weather studies.
Nomura, R., K. Shiokawa, Y. Omura, Y. Ebihara, Y. Miyoshi, K. Sakaguchi, Y. Otsuka, and M.
Connors, Pulsating proton aurora caused by rising tone Pc1 waves, J. Geophys. Res. Space
Phys., 121, 1608-1618, doi:10.1002/2015JA021681, 2016.
We found rising tone emissions with a dispersion of ~1 Hz per several tens of seconds in the
dynamic spectrum of a Pc1 geomagnetic pulsation (Pc1) observed on the ground.
Simultaneously, a THEMIS panchromatic all-sky camera detected pulsations of an isolated
proton aurora. The pulsations of the proton aurora close to the zenith of ATH have one-toone correspondences with the Pc1 rising tones. This suggests that these rising tones scattermagnetospheric protons intermittently at the equatorial region.
Lin, F. F., C. Y. Wang, C. L. Su, K. Shiokawa, S. Saito, and Y. H. Chu, Coordinated observationsof F region 3-m field-aligned plasma irregularities associated with medium-scale travelling
ionospheric disturbances, J. Geophys. Res. Space Phys., 121, 3750-3766,
doi:10.1002/2016JA022511, 2016.
Three ‐ meter field ‐ aligned irregularities (3 ‐ m FAIs) associated with medium scale
travelling ionospheric disturbances (MSTIDs) occurred on 5 February 2008 were observedby using the Chung‐Li 52 MHz coherent scatter radar. The VHF radar echo structuresfrom the 3‐m FAIs combined with the 630 nm airglow images provided by the Yonaguni
all‐sky imager are compared and analyzed. The results suggest that, through the nonlinear
turbulence cascade process, the MSTID‐associated 3‐m FAIs are very likely generated
from the kilometer‐scale plasma irregularities with large amplitude excited by the gradientdrift instability.
2.3. Report from National Institute for Information and Communications Technology (NICT)(Minoru Kubota, NICT)=== Recent papers===

Maruyama, T., K. Yusupov, and A. Akchurin, Ionosonde tracking of infrasound wavefronts in thethermosphere launched by seismic waves after the 2010 M8.8 Chile earthquake, J. Geophys.
Res. Space Phys., 121, 2683–2692, 2016, doi:10.1002/2015JA022260.
3

資料9-G

Maruyama, T., K. Yusupov, and A. Akchurin, Interpretation of deformed ionograms induced byvertical ground motion of seismic Rayleigh waves and infrasound in the thermosphere, Ann.
Geophys., 34, 271–278, doi:10.5194/angeo-34-271-2016, 2016.
Ionospheric disturbances associated with the M8.8 Chile earthquake (35.91S, 72.73W) on 27
February 2010 were observed at Kazan, Russia (55.85N, 48.81E). Rapid-run ionograms at 1-min
intervals exhibited multiple cusp signatures (MCSs) for more than 30 min, which have been
observed several times after large earthquakes. The ionospheric disturbances were caused byinfrasound propagating upward in the atmosphere launched by seismic Rayleigh waves, which
modified the vertical electron density distribution through ion-neutral collisions. The density
profiles at 1-min intervals allowed the tracking of the propagation of infrasound and provided
information on parameters of acoustic waves, which was not possible from the previous radio
measurements. The speed of acoustic waves in the thermosphere, and corresponding
thermospheric temperature, was slightly higher than that calculated using the Mass Spectrometerand Incoherent Scatter Radar empirical model (NRLMSISE-00). One extreme case of MCS
ionogram was characterized by steep satellite traces for which the virtual heights increased
rapidly with frequency starting near the top of cusps and continuing for 0.1–0.2 MHz. Ray
tracing model calculations revealed that the inclined periodic perturbation yielded obliquereturns of sounding radio waves in addition to the nearly vertical returns of the main trace.
Jiang, C., G. Yang, C. Deng, C. Zhou, P. Zhu, T. Yokoyama, H. Song, T. Lan, B. Ni, Z. Zhao, and Y.
Zhang, Simultaneous observations of F2 layer stratification and spread F at post-midnight overa northern equatorial anomaly region, J. Geophys. Res. Space Phys., 120, 10,979-10,991,
doi:10.1002/2015JA021861, 2015.
Simultaneous observations of F2 layer stratification and spread F at postmidnight (00:00 LT to
05:00 LT) were carried out on 22, 23, and 28 November 2013, using ionosondes distributed overa northern equatorial anomaly region at three specific locations, i.e., Puer (PUR, 22.7°N,
101.05°E, dip latitude 12.9°N), Chiang Mai (CMU, 18.8°N, 98.9°E, dip latitude 9.04°N), andChumphon (CPN, 10.7°N, 99.4°E, dip latitude 0.93°N). The results show that both the PUR andCMU stations observed the F2 layer stratification at postmidnight in the Northern Hemisphere,
frequently accompanied with gravity waves (the periods~30–100min). It is reported that F2 layer
stratification at postmidnight can be observed in the Northern Hemisphere for the first time. It issuggested that the thermospheric neutral wind triggered by gravity waves strongly contribute to
the altitude dependence of the combined vertical plasma velocity, which consequently posessignificant impacts on the occurrence of the low-latitude F2 layer stratification at postmidnight.
Tulasi Ram, S., T. Yokoyama, Y. Otsuka, K. Shiokawa, S. Sripathi, B. Veenadhari, R. Heelis, K. K.
Ajith, V. S. Gowtam, S. Gurubaran, P. Supnithi, and M. Le Huy, Dusk side enhancement ofequatorial zonal electric field response to convection electric fields during the intense
geomagnetic storm of March 17, 2015, J. Geophys. Res. Space Phys., 121, 538-548,
doi:10.1002/2015JA021932, 2016.
The equatorial zonal electric field responses to prompt penetration of eastward convection
electric fields (PPEF) were compared at closely spaced longitudinal intervals at dusk topremidnight sectors during the intense geomagnetic storm of 17 March 2015. At dusk sector(Indian longitudes), a rapid uplift of equatorial F layer to >550 km and development of intense
equatorial plasma bubbles (EPBs) were observed. These EPBs were found to extend up to
27.13°N and 25.98°S magnetic dip latitudes indicating their altitude development to ~1670 km at
apex. In contrast, at few degrees east in the premidnight sector (Thailand-Indonesian longitudes),no significant height rise and/or EPB activity has been observed. The eastward electric field
perturbations due to PPEF are greatly dominated at dusk sector despite the existence of
background westward ionospheric disturbance dynamo (IDD) fields, whereas they were mostly
counter balanced by the IDD fields in the premidnight sector.
Jiang, C., G. Yang, P. Zhu, M. Nishioka, T. Yokoyama, C. Zhou, H. Song, T. Lan, Z. Zhao, Y. Zhang,
Reconstruction of the vertical electron density profile based on vertical TEC using the simulated
annealing algorithm, Adv. Space Res., 57, 2167-2176, doi:10.1016/j.asr.2016.02.020, 2016.

4資料9-G

This paper presents a new method to reconstruct the vertical electron density profile based onvertical Total Electron Content (TEC) using the simulated annealing algorithm. The present
technique used the Quasi-parabolic segments (QPS) to model the bottomside ionosphere. The
initial parameters of the ionosphere model were determined from both International Reference
Ionosphere (IRI) (Bilitza et al., 2014) and vertical TEC (vTEC). Then, the simulated annealing
algorithm was used to search the best-fit parameters of the ionosphere model by comparing with
the GPS-TEC. The performance and robust of this technique were verified by ionosonde data.
The critical frequency (foF2) and peak height (hmF2) of the F2 layer obtained from ionograms
recorded at different locations and on different days were compared with those calculated by the
proposed method. The analysis of results shows that the present method is inspiring for obtaining
foF2 from vTEC. However, the accuracy of hmF2 needs to be improved in the future work.
2.4. Report from Chiba University(Hiroyuki Nakata, Chiba University)=== Recent papers===
K. Yoshikawa, K. Takaboshi, H. Nakata, T. Takano, M. Matsumura, H. Shinagawa, and I. Tomizawa,
Quantitative Estimation of the Ionospheric Disturbances Associated with Earthquakes observedwith HF Doppler by a Numerical Simulation of Neutral Atmospheric Waves, IEEJ Transactions
on Fundamentals and Materials, 136(5), 259-264, doi:10.1541/ieejfms.136.259, 2016.
In order to evaluate the relationship between the coseismic ionospheric perturbations and theground perturbations, we compare the coseismic disturbances determined by a numericalsimulation with those observed by HF Doppler. HF Doppler observation determines theionospheric vertical drift speed of the reflection point. The numerical simulation calculates the
temporal evolution of the neutral acoustic wave, In this numerical simulation, the ground
perturbations observed by seismometers closest to the reflection points are used as sources of theperturbations. The speed estimated from HF Doppler is about an order larger than that calculated
from numerical simulation. The difference is because the speed of the ionospheric vertical drift
is not same as the neutral atmospheric wave. In order to fix this difference, the ionospheric
neutral drift speed is modified considering the effects of the inclination of the magnetic field andthe compression of ionospheric plasma. As a result, the both speed are comparable each other.
H. Nakata, K. Abe, A. Tokunaga, T. Takano, T. Tsugawa, and M. Nishioka, Spectral density analysisof total electron content perturbations associated with earthquakes, IEEJ Transactions on
Fundamentals and Materials, 136(5), 272-277, doi:10.1541/ieejfms.136.272, 2016.
We performed the frequency analysis of time-series data of TEC, and examined the variations of
TEC associated with earthquakes. Using Fast Fourier Transform processing, the spectral
densities of coseismic TEC variations were calculated. The coseismic variations of TEC weredetected in 16 events out of 26 events where the earthquakes larger than M6.4 occurred around
Japan since 2000. In most events, the variations at the frequencies of 4.17, 5.21 mHz wereobserved. The spectral densities reached their maximums about 11 minutes after the earthquake.
Since this delay corresponds to the propagation time of acoustic wave from the ground to theionosphere, it is confirmed that the coseismic variations are due to the acoustic wave generated
by the ground/sea surface perturbations. The enhancement of the signal density increases withthe magnitude of earthquake and the height of tsunami. Using the enhancement of the TEC
variation, the magnitude of wave source can be estimated.
H. Nakata, K. Kawai, S. Akiyama, T. Chida, R. Tanaka, Y. Kawamura, T. Takano, and S. Shimakura,
Estimation of direction of arrival of VHF radio wave by interferometers, IEEJ Transactions on
Fundamentals and Materials, 136(5), 278-285, doi:10.1541/ieejfms.136.278, 2016.
In order to examine the direction of arrival of VHF radio waves dependent on the natural
phenomena, the interferometers have been installed at Katsuyama, Chiba Prefecture and Numata,Gunma Prefecture. In this study, the radio wave at the frequency of 77.1 MHz transmitted from
Tokyo Tower (assigned to FM broadcasting of the Open University of Japan) is observed. Theinterferometers consist of four Yagi antennas and estimate the directions of arrivals of the radio
wave. The observational results show that the directions of the wave are affected by the5

資料9-G

disturbances in the ionosphere and the atmosphere. In this paper, the system of theinterferometers is described and the examples of the observation results are presented.
2.5. Report from Electronic Navigation Research Institute (ENRI)(Susumu Saito, ENRI)=== Recent papers===
S. Saito, T. Yoshihara, and H. Nakahara, Performance of GAST-D ionospheric gradient monitor
studied with low latitude ionospheric disturbance data obtained in a real airport environment,
Proceedings of ION 2015 Pacific PNT meeting, 815-820, 2015.
In this paper, performance of ionospheric spatial gradient monitor (ISGM) for GNSS Groundbased augmentation system (GBAS) to support category-II/III approach and landing is evaluatedin a real airport environment located at Ishigaki (24.4N, 124.2E), Japan. The performance of the
ISGM in the nominal ionospheric conditions are shown to be satisfactory. It was also found that
there were some events of enhanced ISGM outputs, which may potentially cause false alarm of
ISGM. It was shown that they are likely to be tropospheric origin as speculated by previous
studies. This study is the first to support the existence of sharp tropospheric delay gradient withdual-frequency measurements.
S. Saito, T. Yoshihara, A. Kezuka, S. Saitoh, and S. Fukushima, GAST-D flight experiment resultswith disturbed and quiet ionospheric conditions, Proceedings of the 28th International Technical
Meeting of The Satellite Division of the Institute of Navigation (ION GNSS+ 2015), Tampa,
Florida, September 14-18, 2015, pp.1494-1499, 2015.
This paper reports on the results of flight experiments with a prototype of GNSS Ground-based
augmentation system (GBAS) to support category-II/III approach and landing. The prototype islocated at Ishigaki (24.4N, 124.2E), Japan. The main target of the flight experiment was toevaluate the performance with presence of plasma bubbles. Plasma bubble occurrences weremonitored by an all-sky airglow imager and GNSS scintillation receivers located near the
prototype. It was shown that the safety was maintained even with presence of well-developed
plasma bubbles. One of the integrity monitors onboard aircraft was shown to respond to theionospheric disturbances by using real data for the first time. Scintillation effects on GNSS
signals by plasma bubbles are shown to be severe to degrade availability of the system, andmulti-constellation and multi-frequency GNSS would be desired for the future development.
2.6. Report from Research Institute for Sustainable Humanosphere (RISH), Kyoto University(Mamoru Yamamoto, RISH)=== Masterplan 2017 ===Research Institute for Sustainable Humanosphere (RISH), Kyoto University, National Instituteof Polar Research (NIPR), Institute for Space-Earth Environmental Research (ISEE), Nagoya
University, and International Center for Space Weather Science and Education (ICSWSE),
Kyushu University proposed the research project “Coupling process in the solar-terrestrial
system” (PI: Prof. Toshitaka Tsuda at RISH) to Masterplan 2017 of Science Council of Japan.
This is a project to study the solar energy inputs into the Earth, and the response of Geospace(magnetosphere, ionosphere and atmosphere) to the energy input, which follows success of thesame project in Masterplan 2014. We plan to install large atmospheric radars with active phasedarray antenna at the equator and the Arctic regions. One is Equatorial MU (EMU) radar by RISH
in Sumatera Island, Indonesia, and the other is EISCAT_3D by NIPR in northern Scandinavia
under international collaborations. We develop the global observation network is planned (ISEE,ICSWSE with other institutions). The joining institutions have already started budget request of
their facilities.
=== Lecture “Introduction to Radio Science” ===Kyoto University holds the Institute for Liberal Arts and Sciences (ILAS) to integrate the efforts
of various schools and departments for planning, coordination, and implementation of liberal artsand sciences programs. From April 2016 a class named “Introduction to radio science” has been
started as a part of ILAS seminar course. The class teachs fundamental knowledge for the radio6資料9-Gand its propagation, and introduce variety aspects of radio science studies. Visits to several
sites/labs of the research field are also planned.
=== Recent papers===
C. H. Chen, A. Saito, C. H. Lin, M. Yamamoto, S. Suzuki and G. K. Seemala, Medium-scale travelingionospheric disturbances by three-dimensional ionospheric GPS tomography, Earth Planet
Space, 68:32, DOI 10.1186/s40623-016-0412-6, 2016.
In this study, we develop a three-dimensional ionospheric tomography with the ground-based
global position system (GPS) total electron content observations. Because of the geometriclimitation of GPS observation path, it is difficult to solve the ill-posed inverse problem for theionospheric electron density. Different from methods given by pervious studies, we consider analgorithm combining the least-square method with a constraint condition, in which the gradientof electron density tends to be smooth in the horizontal direction and steep in the vicinity of theionospheric F2 peak. This algorithm is designed to be independent of any ionospheric orplasmaspheric electron density models as the initial condition. An observation system simulation
experiment method is applied to evaluate the performance of the GPS ionospheric tomography indetecting ionospheric electron density perturbation at the scale size of around 200 km inwavelength, such as the medium-scale traveling ionospheric disturbances.
Marzuki, H. Hashiguchi, T. Kozu, T. Shimomai, Y. Shibagaki, and Y. Takahashi, Precipitation
microstructure in different Madden-Julian Oscillation phases over Sumatra, AtmosphericResearch, 168, 121-138, DOI:10.1016/j.atmosres.2015.08.022, 2016.
Intraseasonal variations of precipitation and its microstructure are investigated using
measurements of the Equatorial Atmospheric Radar (EAR) facilities at Kototabang, west
Sumatra, Indonesia (0.20°S, 100.32°E, 864 m above sea level). Raindrop size distribution (DSD)
observations are obtained from a 2D-Video Disdrometer (2DVD) with a near continuous recordof operation over eight consecutive years (2003-2010). Precipitation types are classified using
1.3-GHz wind profiler observation, and are partitioned according to active and inactive
convective phases of Madden-Julian Oscillation (MJO). It is found that precipitation systems
during the inactive phase are more continental in nature than those during the active phase.
Cloud propagation from brightness temperature data indicates that Sumatra receives the rainfall
mainly from maritime clouds during the active phase, while it is mainly from the continental
clouds (land-based convection) during the inactive phase. Other remarkable differences between
active and inactive phase precipitation systems are also observed from the vertical structure of
precipitation. The precipitation during the inactive phase has deeper storms, a higher reflectivity
aloft, more lightning activity and less stratiform characteristics, as compared to the active phase.
Assessment of cloud effective radius of the Moderate Resolution Imaging Spectroradiometer(MODIS) data also shows a slight difference in the cloud droplet between the active and theinactive MJO phases. Different convective storms in different MJO phases lead to different DSD
characteristics and Z-R relationships. The DSD during the inactive phase tends to have a higher
concentration of medium and large-size drops than the active counterpart, consistent with theprevious study during the first campaign of Coupling Processes in the Equatorial Atmosphere
project. Although the DSD parameters and coefficient of Z-R relationships fall within the rangeof tropical maritime precipitation, mass-weighted mean diameter (Dm) for the deep convective
rains during the inactive phase are somewhat larger than that for maritime and closer to thecontinental cluster. Therefore, continental-like DSDs are somewhat dominant during the inactive
phase, consistent with the intraseasonal variation of precipitation structure. The causative
processes of the observed difference in the DSD for the two phases have also been discussedwith the help of satellite and radar data. Evaporation and updraft associated with the intense
convection during the inactive phase seem to eliminate the small-sized drops from the spectra.
Finally, radar reflectivity during the inactive phase is larger than that during the active MJO
phase, at the same rainfall rate. This condition can limit the accuracy of radar-derived rainfall
estimates for the tropics when applying a single Z-R relation to the two MJO phases, particularly
for deep convective rains.

7資料9-G

Jenn-Shyong Chen, Yen-Hsyang Chu, Ching-Lun Su, Hiroyuki Hashiguchi, and Ying Li, Range
Imaging of E-region Field-Aligned Irregularities by Using a Multifrequency Technique:
Validation and Initial Results, IEEE Transactions on Geoscience and Remote Sensing, 54(7),3739-3749, DOI:10.1109/TGRS.2016.2521702, 2016.
This paper reports the first use of a multifrequency range imaging (RIM) technique for observing
E-region field-aligned irregularities (FAIs) in the midlatitude ionosphere. The Middle and Upper
atmosphere Radar (MUR; 34.85°N, 136.10°E) was used to conduct experiments with fiveequally spaced frequencies between 46.25 and 46.75 MHz. Three types of RIM data were
examined: data with 13-element binary Barker codes, with 16-element binary complementary
codes, and without phase codes. Moreover, two calibration approaches were adopted to validate
the applicability of the RIM technique, which functioned as intended. Excellent RIM
performance such as the ability to resolve several striations in an echo region of FAIs wasdemonstrated. However, sidelobe echoes caused by pulse coding mechanisms were occasionallyobserved at altitudes above and below the source regions in the coded data. Therefore, aprocedure was developed according to one of the calibration approaches to identify and remove
such kind of sidelobe echoes, which was shown to be applicable for the complementary-coded
data. In addition to FAIs, a thin plasma layer with a thickness of approximately 1 km was
identified as being structured with some tilted finer structures, which could not be observed in
the original intensity images with a range resolution of 600 m. Preliminary estimates of the
Doppler velocities indicated that a wind shear effect could be the cause of such tilted finer
structures.
Oigawa, M., E. Realini, and T. Tsuda, Study of Water Vapor Variations Associated with Meso-γ Scale
Convection: Comparison between GNSS and Non-Hydrostatic Model Data, SOLA, 11, 27-30,
March 11, 2015.
Water vapor variations associated with a meso-γ scale convection were investigated using GNSS
(Global Navigation Satellite System) derived PWV (precipitable water vapor) and highresolution numerical model data with a 250 m horizontal grid interval. A rapid increase of
GNSS-derived PWV that occurred prior to the initiation of surface rainfall was well simulatedby the numerical model. In the model, PWV values began to increase 16 min before the rainfall
occurred at the surface. A local maximum of PWV was formed because of the generation ofshallow free convection and surface water vapor flux convergence due to a lifting of an air parcel
at approximately 1 km elevation by a preceding surface wind convergence. Due to the existenceof a stable inversion layer between 2.2 and 3.5 km elevation, the shallow free convection took 11
min to rise above the inversion layer to form a deep convection. These results suggest thatobservation of local distributions of GNSS-derived PWV is useful for monitoring the generationof deep moist convection.
Ando, H., T. Imamura, T. Tsuda, S. Tellm ann, M. Pätzold, and B. Häusler, Vertical Wavenumber
Spectra of Gravity Waves in the Venus Atmosphere Obtained from Venus Express Radio
Occultation Data: Evidence for Saturation, Journal of the Atmospheric Sciences, 72, 2318-2329,
doi:10.1175/JAS-D-14-0315.1, 2015.
By using the vertical temperature profiles obtained by the radio occultation measurements on theEuropean Space Agency (ESA)’s Venus Express, the vertical wavenumber spectra of small-scaletemperature fluctuations that are thought to be manifestations of gravity waves are studied.
Wavenumber spectra covering wavelengths of 1.4–7.5 km were obtained for two altitude regions(65–80 and 75–90 km) and seven latitude bands. The spectra show a power-law dependence on
the high-wavenumber side with the logarithmic spectral slope ranging from −3 to −4, which issimilar to the features seen in Earth’s and Martian atmospheres. The power-law portion of thespectrum tends to follow the semiempirical spectrum of saturated gravity waves, suggesting thatthe gravity waves are dissipated by saturation as well as radiative damping. The spectral power islarger at 75–90 km than at 65–80 km at low wavenumbers, suggesting amplitude growth withheight of unsaturated waves. It was also found that the wave amplitude is larger at higher
latitudes and that the amplitude is maximized in the northern high latitudes. On the assumptionthat gravity waves are saturated in the Venusian atmosphere, the turbulent diffusion coefficient
was estimated. The diffusion coefficient in the Venusian atmosphere is larger than those in8

資料9-G

Earth’s atmosphere because of the longer characteristic vertical wavelength of the saturated
waves.
Mehta, S. K., M. Fujiwara, T. Tsuda, and J.-P. Vernier, Effect of recent minor volcanic eruptions on
temperatures in the upper troposphere and lower stratosphere, Journal of Atmospheric andSolar-Terrestrial Physics, vol.129, 99-110, doi:10.1016/j.jastp.2015.04.009, 2015.
The impact of the recent minor volcanic eruptions during 2001-2010 in the temperature of theupper troposphere and lower stratosphere (UTLS) is investigated using data from the Global
Positioning System Radio Occultation (GPS RO), three radiosonde compilations and two
reanalyses (ERA-Interim and MERRA). The volcanic signals are identified in the residual
temperature time series after removal of the linear trend, the quasi-biennial oscillation and El
Nino Southern Oscillation components. Eight minor volcanic eruptions (six from the tropics andtwo from midlatitude) over the last decade (2001-2010) are analyzed in this study. We foundsignificant volcanic signals in the UTLS temperature only in association with the tropicalSoufrière Hills and Tavurvur eruptions (in May 2006 and in October 2006, respectively). Other
four tropical eruptions had very small aerosol perturbations and did not show any significant
UTLS temperature change. Out of the two midlatitude eruptions, Sarychev peak had similar
stratospheric aerosol perturbations as Soufrière Hills and Tavurvur eruptions, but did not show
any significant UTLS temperature change. The volcanic signals in the UTLS temperature fromthe tropical Soufrière Hills and Tavurvur eruptions were observed for the period of 7 months
after August 2006. A warming of 0.5-0.8 K in the tropical 16-18.5 km (100-70 hPa) layer wasobserved in association with these two tropical eruptions.
Realini E., Sato K., Tsuda T., Oigawa M., Iwaki Y., Shoji, Y., Seko, H., Local-scale precipitable water
vapor retrieval from high-elevation slant tropospheric delays using a dense network of GNSS
receivers, International Association of Geodesy (IAG) Symposia, PP1-6, 07 July 2015,
DOI:10.1007/1345_2015_167, 2015.
Local-scale monitoring of the temporal and spatial variability of precipitable water vapor (PWV)
is crucial to improve the nowcasting and forecasting of localized meteorological hazards. While
GPS is now routinely employed to retrieve PWV from estimated tropospheric delays (GPSmeteorology), even the densest GPS networks available have a spatial resolution of the order oftens of kilometers, which is too coarse for detecting local fluctuations of water vapor. A
densification of existing networks, at least in urban areas, is necessary to provide reliable andcontinuous water vapor monitoring with sufficiently high horizontal resolution. Densifying
existing networks down to few kilometers of inter-station distances, however, introduces at least
two issues: first, a horizontal smoothing effect occurs, induced by the significant overlapping of
the inverse cones above low elevation angles typically used for GPS observation processing;second, an issue of economic nature might arise if geodetic receivers are used for large-scaledensifications (e.g. for early warning systems serving large cities). We tackle the first issue by
using only high-elevation slant delays for PWV retrieval, and in particular by exploiting theJapanese Quasi-Zenith Satellite System (QZSS), and the second issue by investigating the use of
low-cost single-frequency receivers with local ionosphere delay models. In this work we
describe the results obtained in PWV retrieval from high-elevation GPS and QZSS slant delays,estimated using a dense network of receivers installed near Kyoto, Japan.
Noersomadi and T. Tsuda, Global distribution of vertical wavenumber spectra in the lower
stratosphere observed using high-vertical-resolution temperature profiles from COSMIC GPS
radio occultation, Ann. Geophys., 34, 203-213, doi:10.5194/angeo-34-203-2016, 2016.
We retrieved temperature (T) profiles with a high vertical resolution using the full spectrum
inversion (FSI) method from the Constellation Observing System for Meteorology, Ionosphere
and Climate (COSMIC) GPS radio occultation (GPS-RO) data from January 2007 to December
2009. We studied the characteristics of temperature perturbations in the stratosphere at 20–27 km
altitude. This height range does not include a sharp jump in the background Brunt–Väisälä
frequency squared (N2) near the tropopause, and it was reasonably stable regardless of season
and latitude. We analyzed the vertical wavenumber spectra of gravity waves (GWs) with vertical
wavelengths ranging from 0.5 to 3.5 km, and we integrated the (total) potential energy EpT.

9

資料9-G

Another integration of the spectra from 0.5 to 1.75 km was defined as EpS for short vertical
wavelength GWs, which was not studied with the conventional geometrical optics (GO)retrievals. We also estimated the logarithmic spectral slope (p) for the saturated portion ofspectra with a linear regression fitting from 0.5 to 1.75 km.
Riggin D.M., T. Tsuda, A. Shinbori, Evaluation of momentum flux with radar, Journal of Atmosphericand Solar-Terrestrial Physics, 142, 98-107, doi:10.1016/j.jastp.2016.01.013, 2016.
The statistics of gravity wave momentum flux estimation are investigated using data from the
MU radar at Shigariki, Japan (136°E, 35°N). The radar has been operating during campaign
periods since 1986. The first part of the paper focuses on a multi-day campaign during October
13–31, 1986. The second part of the paper investigates data after 2006 when the radar was
operated in a meteor scatter mode. Momentum fluxes are derived from both the turbulent scatterand the meteor scatter measurements, but the techniques are quite different. Probability
Distribution Functions are formed using turbulent scatter data. These show that wave packets
sometimes have momentum flux magnitudes in excess of 100 m2 s−2. The technique for meteor
radars, introduced by Hocking (2005), has been widely adopted by the radar community inrecent years. The momentum flux estimated using this technique is found to be anti-correlatedwith the background tidal winds. A validation investigation is carried out for periods with a highmeteor echo data rate. The conclusion was that the method can be used to calculate the sign ofmomentum flux, but does not accurately specify the magnitude.
Matsumoto, N., A. Shinbori, D. M. Riggin, and T. Tsuda, Measurement of momentum flux using two
meteor radars in Indonesia, Ann. Geophys., 34, 369–377, doi:10.5194/angeo-34-369-2016, 2016.
Two nearly identical meteor radars were operated at Koto Tabang (0.20° S, 100.32° E), West
Sumatra, and Biak (1.17° S, 136.10° E), West Papua, in Indonesia, separated by approximately
4000 km in longitude on the Equator. The zonal and meridional momentum flux, u’w’ and v’w’,
where u, v, and w are the eastward, northward, and vertical wind velocity components,
respectively, were estimated at 86 to 94 km altitudes using the meteor radar data by applying amethod proposed by Hocking (2005). The observed u’w’ at the two sites agreed reasonably wellat 86, 90, and 94 km during the observation periods when the data acquisition rate wassufficiently large enough. Variations in v’w’ were consistent between 86, 90, and 94 km altitudes
at both sites. The climatological variation in the monthly averaged u’w’ and v’w’ wasinvestigated using the long-term radar data at Koto Tabang from November 2002 to November
2013. The seasonal variations in u’w’ and v’w’ showed a repeatable semiannual and annual
cycles, respectively. u’w’ showed eastward values in February–April and July–September andv’w’ was northward in June to August at 90–94 km, both of which were generally anti-phasewith the mean zonal and meridional winds, having the same periodicity. Our results suggest theusefulness of the Hocking method.

10