AAS11-01

Japan Geoscience Union Meeting 2016

An International Observation Campaign for a Study of Interhemispheric Coupling Initiatedby Sudden Stratospheric Warmings in the Arctic*Kaoru Sato1, Yoshihiro Tomikawa2,3, Masaki Tsutsumi2,3, Masashi Kohma1, Koji Nishimura2,3
1.Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo,
2.National Institue of Polar Research, 3.The Graduate University for Advanced Studies
Recent observational and modelling studies suggest that the Northern and Southern Hemispheres ofthe earth atmosphere are potentially coupled by the Lagrangian mean flow in the mesospheremodulated by waves interacting with the mean flow. However, observations of modulated wave and flow
fields which are needed for quantitative understanding of the interhemispheric coupling are notsufficient. Simultaneous observations of gravity waves at various locations are most importantbecause they are a main driver of the Lagrangian mean flow in the mesosphere.
With the start of full system observation by the PANSY radar in the Antarctic in March 2015, a
global mesosphere-stratosphere-troposphere (MST) radar network extending from the Arctic to the
Antarctic has been realized. The MST radars are able to observe wind vectors with fine temporal andvertical resolutions including vertical wind components in the troposphere, stratosphere andmesosphere, although an observational gap of the middle and upper stratosphere remains. Thus, thecharacteristics of small-scale or short-period wave motions including gravity waves and themomentum fluxes associated with these waves can be estimated with a good accuracy.
In addition, recent high-resolution general circulation models enable an explicit simulation ofgravity waves under ideal and/or climatological boundary conditions and allow us to examine themomentum budget in the MST region including gravity waves, although their resolution is currently
not sufficient to resolve the entire gravity wave spectrum. Real atmosphere simulations utilizing
such high-resolution models are still a challenge for the MST region. However, if such real
atmosphere simulations are successful, they will help quantitative interpretation of the dynamical
fields observed by the MST radar network, and the observations will provide invaluable validation
data for the model improvement.
Therefore we will examine the interhemispheric coupling of the earth atmosphere through a
combination of simultaneous observations by networking the MST radars over the world andhigh-resolution model simulations of the observed atmosphere. This is an official project, ICSOM,
for SCOSTEP, but it is closely related to SPARC. The first international observation campaign was
successfully performed during a time period from 22 January-17 February, 2016 when two minor
warming occurred in the Arctic stratosphere. Seven MST radars and many other radars and optical
instruments providing complementary observational data were operated. More than 30 scientists ineight countries are participated in this project. A preliminary result from this observation
campaign will be presented.
Keywords: interhemispheric coupling, middle atmospehre, sudden stratospheric warming, gravity
waves, mesosphere-stratospehre-troposphere radars, general circulation©2016. Japan Geoscience Union. All Right Reserved.

- AAS11-01 -AAS11-02

Japan Geoscience Union Meeting 2016

Characteristic of Vertical Winds Fluctuations in the Lower Troposphere at Syowa Station in
the Antarctic Revealed by the PANSY Radar*Yuichi Minamihara1, Kaoru Sato1, Masaki Tsutsumi2, Masashi Kohma1
1.Department of Earth and Planetary Science Graduate School of Science The University of Tokyo,
2.National Institute of Polar Research and The Graduate University for Advanced Studies
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 vertical winds andvertical 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 transition frequencies are different
between horizontal and vertical wind spectra. Vertical fluxes of horizontal momentum and variancesof vertical wind were estimated for two wave period ranges of 1 d-2 h and 2 h-8 min having almost
equal logarithmic scales. The momentum fluxes are larger for longer period components, and thevariances of vertical wind disturbances are larger for shorter period component than longer period
component. There are a few evidences showing that the vertical wind disturbances in the lower
troposphere are due to gravity waves forced by topography aligned 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 arelarge at a wide range of frequency below a critical level, as is consistent with the phasemodulation of mountain waves by unsteady mean flow.
Keywords: MST Radar, Polar Atmosphere©2016. Japan Geoscience Union. All Right Reserved.

- AAS11-02 -AAS11-02©2016. Japan Geoscience Union. All Right Reserved.

Japan Geoscience Union Meeting 2016

- AAS11-02 -AAS11-03

Japan Geoscience Union Meeting 2016

Inertia-gravity waves in the mesosphere observed by the PANSY radar*Ryosuke Shibuya1, Kaoru Sato1, Masaki Tsutsumi2,3, Yoshihiro Tomikawa2,3, Toru Sato4, Koji Nishimura2, Takuji Nakamura2, Masashi Kohma1
1.Graduate School of Science, The University of Tokyo, 2.National Institute of Polar Reserch,
3.University for Advanced Studies (SOKENDAI), 4.Department of Communications and Computer
Engineering, Kyoto University
The PANSY (Program of the Antarctic Syowa MST/IS radar) radar installed at Syowa Station (39oE, 69oS), the first MST/IS radar in the Antarctic, provides vertical profiles of three-dimensional windvectors with fine height and time resolutions in the troposphere, stratosphere and mesosphere. We
performed the first successful observation with a complete system of the PANSY radar in 16–24 March2015. During this observation period, strong wave-like wind disturbances propagating phases
downward were observed in the mesosphere. Their zonal wind amplitudes, vertical wavelengths andvertical phase velocities were estimated at about 30 m/s, 13 km and −0.3 m/s, respectively. Thismeans that wave periods are about 11 h. We newly developed a grid configuration which were fine andequally-spaced only for high latitudes of the Southern Hemisphere, and performed a simulation using
NICAM (a Nonhydrostatic ICosahedral Atmospheric Model) with the newly-developed grids. We
successfully simulated strong wind disturbances similar to the PANSY radar observations with wave
periods from 10–13 h in the mesosphere. First we examined amplitudes of the diurnal andsemi-diurnal migrating tidal components and those of gravity wave components with horizontal
wavelengths smaller than 1000 km as frequently examined by previous studies in the model-simulated
wind field. Their amplitudes were much smaller than the observation, suggesting that dominant wavestructures in the mesosphere were not due to migrating tides nor small-scale gravity waves. The
remaining components have quite similar structure and amplitudes to the observations. We estimatedwave parameters of five dominant wave packets simulated near Syowa Station. Wave parameters of eachwave packet were estimated as was consistent with the linear theory of hydrostatic inertia-gravity
waves. Horizontal wavelengths are about 2000 km, which is also consistent with those estimated forthe wavelike disturbances observed by the PANSY radar assuming that they are due to inertia-gravity
waves. We examined propagation and sources of these wave packets using backward ray tracing method.
It was suggested that a wave packet simulated at 00 UTC 19 March at 40o E in the mesosphere was
generated by spontaneous radiation from the imbalance of polar night jet at the height of 50 km,
while a wave packet simulated at 09 UTC 21 March at 120o W in the mesosphere was generated byspontaneous radiation from the imbalance of polar front jet at the tropopause.
Keywords: Atmospheric gravity waves, mesosphere©2016. Japan Geoscience Union. All Right Reserved.

- AAS11-03 -AAS11-04

Japan Geoscience Union Meeting 2016

A study on data assimilation using the ensemble Kalman filter and simulation of a sudden
stratospheric warming*Dai Koshin1, Kaoru Sato2, Kazuyuki Miyazaki3
1.Department of Earth and Planetary Science, School of Science, The University of Tokyo,
2.Department of Earth and Planetary Science, The University of Tokyo, 3.Japan Agency for
Marine-Earth Science and Technology
There are many important phenomena in the middle atmosphere, such as sudden stratospheric warmings(SSW), and the quasi-biennial oscillation (QBO). It is suggested that these phenomena affect global
atmosphere through stratospheric and mesospheric circulations respectively from the equator to thepole and from the summer pole to the winter pole. With the aid of technology development,
resolutions of observations and numerical models have become higher. Most analysis data are mainly
made by meteorological centers by assimilating observation data up to the stratosphere. Dataassimilation for the mesosphere is not yet very common. Thus, we performed a preliminary study forthe data assimilation from the ground to the mesosphere, so as to make realistic grid data andsimulation of the middle atmosphere.
First, using a global model called MIROC, whose top is in the upper stratosphere (~40km), we
examined impacts of assimilation of satellite observations in the stratosphere. The PREPBUFR data
(ground-based observations including these by aircrafts, balloons, and wind profilers) data from
NCEP, and temperature retrieval data in the stratosphere by Aura MLS from NASA were used asconventional and satellite observations, respectively. The model has horizontal resolution of T42
and 32 vertical levels. We used the method of ensemble Kalman filter (EnKF) for data assimilation,and made analysis data for January and February 2014, when an SSW occurred in the northernhemisphere. As SSWs are highly non-linear phenomena, their simulation is generally difficult.
We made two kinds of analysis data. One is the data in which only PREPBUFR data are assimilated,
and the other in which both PREPBUFR and MLS data are assimilated. In both analysis data, timing of
the SSW onset was realistic. However, the data with MLS observation have higher accuracy in the
middle atmosphere than that only with PREPBUFR data. It is seen from standard deviation of ensemble
members that assimilation of satellite data is more effective (i.e. small standard deviation) in
the stratosphere.
Second, we made ensemble forecast experiments using analysis data on February 1, several days
before the SSW onset. The prediction using analysis data assimilated with both MLS and PREPBUFR was
more accurate than that assimilated only with PREPBUFR. It is seen that there is significant
difference in the stratospheric wave activity between the two prediction experiments, although thetropospheric wave activity is not so different. This fact suggests that accurate background fields
around the tropopause are important so as to simulate realistic propagation of planetary waves fromthe tropopause to the stratosphere. For future studies, we will optimize each parameter at data
assimilation, and use a hi-top model so that highly accurate data assimilation can be made in the
middle atmosphere.
Keywords: data assimilation, sudden stratospheric warming, ensemble Kalman filter©2016. Japan Geoscience Union. All Right Reserved.

- AAS11-04 -AAS11-05

Japan Geoscience Union Meeting 2016

Comparison of large-scale dynamical variations in the extratropical stratosphere among theJRA-55 family datasets*Masakazu Taguchi1
1.Aichi University of Education
This study seeks to compare the “JRA-55 family” datasets in terms of the extratropicalstratospheric and tropospheric circulation in both hemispheres. In particular, we explore
large-scale dynamical variations such as stratospheric sudden warmings (SSWs) during NH winter andSH spring when the extratropical stratosphere is dynamically active.
The JRA-55 family consists of three datasets: a main product of the JRA-55 reanalysis data
(referred to as STDD below), and two sub-products of JRA-55C and JRA-55AMIP (referred to as CONV
and AMIP, respectively). CONV assimilates only conventional observations, whereas AMIP runs thesame numerical weather prediction (NWP) model without assimilation of observational data. Kobayashi
et al. (2014) reported preliminary results from these data, such as cold bias in the SH winterupper stratosphere (i.e., strong polar night jet bias) for CONV and AMIP compared to STDD.
Our comparison of AMIP to STDD reveals characteristic features of AMIP in frequency and vortex
morphology of major SSWs during NH winter: AMIP shows a much smaller frequency, and has only vortex
displacement events. These differences are contributed by two factors. First, the fixed threshold,or zonal wind reversal, for the major SSWs is disadvantageous to AMIP where the polar night jet isstrong more often. Furthermore, the zonal wind response to planetary wave activity bursts in thelower stratosphere of a similar strength is weaker in AMIP than in STDD. This is particularly thecase when wave 2 plays an important role. As for SH spring, large variability occurs later in AMIP
than in STDD; e.g., AMIP exhibits no zonal wind reversal before late October
It is also found that CONV reproduces most of the DJF major SSWs identified in STDD, although somecases are identified a few days later or missed. In SH spring, CONV misses the major SSW in
September 2002, as it, albeit slightly, underestimates the zonal wind deceleration. These
differences of CONV would be understood by the bias of the NWP model (as seen in AMIP) and thepaucity of data assimilation as hypothesized by Kobayashi et al. (2014).
Keywords: JRA-55 family datasets, Stratospheric sudden warmings©2016. Japan Geoscience Union. All Right Reserved.

- AAS11-05 -AAS11-06

Japan Geoscience Union Meeting 2016

Formation of two dimensional and three dimensional circulation responding to unsteady wave
forcing in the middle atmosphere*Yuuki Hayashi1, Kaoru Sato1, Yuki Yasuda1
1.School of science, The Univercity of Tokyo
Lagrangian-mean meridional circulation in the middle atmosphere is important for the earth climate
because it globally transports minor species such as ozone and changes the temperature structure
through adiabatic heating/cooling associated with its vertical branches. This meridional
circulation is mainly driven by remote redistribution of the momentum by atmospheric waves. In many
previous studies such as Haynes et al. (1991), a steady-state assumption is frequently used for the
analysis of the meridional circulation. In general, however, the wave forcing is not steady. Thus,
dynamical understanding under the steady-state assumption is limited. When a stratospheric sudden
warming occurs, for example, time scales of wave forcing is so short that behavior of the resultant
circulation may differ from that expected under the steady-state assumption. So as to understandsuch transient behavior and formation of the circulation, we must investigate the time evolution of
not only “slow” variable (linearized potential vorticity) but also “fast” variables such as
horizontal divergence and ageostrophic vorticity. The purpose of this study is to theoreticallyexamine the response of meridional circulation to unsteady wave forcing. In the first part of thisstudy, we examine a two-dimensional problem using a Boussinesq equation system in which azonally-uniform unsteady forcing is given. In the second part, the three-dimensional response to azonally-nonuniform and unsteady forcing is examined using a balance equation which is derived inthis study.
As large-scale atmospheric response to the forcing can be described as a linear response, themethod of Green’s function, which is a response to the delta function, is one of useful approaches
for analysis of the linear response to forcing. By using the Green's function method, we mainly
examine the response to a wave forcing in the zonal momentum equation.
First, we investigate the response to the zonally-uniform forcing. The steady solution of themeridional circulation responding to a constant forcing is composed of two cells in the vertical.
For a forcing with a shaped of the step function in time, gravity waves are radiated as a transient
response, and a meridional circulation with an inertial oscillation finally remains. The
quasi-steady meridional circulation accords well with the steady state solution for a constantforcing. The time scale needed for the formation of the meridional circulation depends on the
aspect ratio of the wave forcing structure, as is consistent with a theoretical expectation. In
addition, it is shown that the group velocity of gravity waves and the spatial scale of the forcing
determine the time scale of the circulation formation. We also investigate the case for the forcing
which changes gradually in time. When the forcing time change is slower than the inertial period,
the meridional circulation always accords with that estimated using the “steady-state assumption”.
The distribution ratio of the wave forcing to the zonal-wind acceleration and the Coriolis torqueis also investigated. The distribution ratio is determined by the shape of the wave forcing andexplained by the dimensional analysis.
Second, we investigate the response to zonally-nonuniform forcing. In this case, it is expectedthat Rossby waves are radiated as transient response because of beta effect. So as to focus only on
the Rossby wave response, governing equations are derived following the method of balance equations
used by Leith (1980). For the steady forcing case with beta effect, the geostrophic flow becomes
zonally asymmetric and has large magnitudes to the west of the forcing. For the step-function
forcing, Rossby waves are radiated as a transient response. Rossby waves having smaller zonal wave

©2016. Japan Geoscience Union. All Right Reserved.

- AAS11-06 -AAS11-06

Japan Geoscience Union Meeting 2016

numbers radiated faster from the forcing region. Time period needed to reach the steady state
depends strongly on the strength of the linear relaxation.
Keywords: middle atmosphere, circulation, wave forcing©2016. Japan Geoscience Union. All Right Reserved.

- AAS11-06 -AAS11-07

Japan Geoscience Union Meeting 2016

A study of three dimensional structure of stratospheric material transport and ozone*Takenari Kinoshita1, Kaoru Sato2
1.National Institude of Information and Communications Technology, 2.Department of Earth andPlanetary Science, Graduate School of Science, The University of Tokyo
The Transformed Eulerian-Mean (TEM) equations have been widely used to examine wave-mean flowinteraction in the meridional cross section. According to previous studies, the Brewer-Dobson
circulation in the stratosphere is driven by planetary waves, baroclinic waves, and inertia-gravity
waves, and that the meridional circulation from the summer hemisphere to the winter hemisphere in
the mesosphere is mainly driven by gravity waves. However, the TEM equations do not provide thethree-dimensional view of the transport, so that the three dimensional TEM equations have beenformulated. On the other hand, the TEM equations cannot properly treat the lower boundary andunstable waves. The Mass-weighted Isentropic Mean (MIM) equations are the equations that overcome
those problems and the formulation of three-dimensional MIM equations have been studied. The
present study applies the three-dimensional TEM and MIM equations to the ERA-Interim reanalysis
data and examines the three-dimensional structure of Stratospheric Brewer-Dobson circulation. Next,
we will discuss material transport due to disturbances on the distribution of stratospheric ozone.
Keywords: residual mean flow, ozone, meridional circulation©2016. Japan Geoscience Union. All Right Reserved.

- AAS11-07 -AAS11-08

Japan Geoscience Union Meeting 2016

Three dimensional structure of mean meridional circulations and their forcing*Yuki Kanno1, Toshiki Iwasaki1
1.Tohoku University
The zonal mean meridional circulation in the stratosphere is called Brewer-Dobson circulation(BDC). It transports air masses upward in the tropics, poleward in mid-latitudes, and downward in
the extratropics. In the winter troposphere, direct circulation is depicted in the extratropics byisentropic zonal means. However, longitudinal variation of these circulations is not fully
understood. This study examines the three dimensional structure of BDC and extratropical direct(ETD) circulation based on mass-weighted isentropic time mean method.
The mass-weighted isentropic time mean method expands Mass-weighted isentropic zonal means(Iwasaki, 1989) longitudinally by substituting the time means for the zonal means. The longitudinalvariation of the BDC and ETD circulation are depicted by mass-weighted isentropic time mean
meridional winds and temporal change of potential temperature. The zonal momentum equation of the
mass-weighted isentropic time mean is composed of Coriolis term, advection term, Eliassen-Palm flux
(EP flux) divergence term, and residual term. The EP flux divergence term can be divided into form
drag terms by stationary and transient waves and reynolds stress term. A momentum budget analysis
shows the forcing term of mean meridional circulations.
Mass-weighted time mean meridional winds at 45N take a wave-number three pattern in the troposphereand a wave-number two pattern in the stratosphere. Compared with time mean meridional wind inpressure coordinates, it has strong northerly wind in the lower troposphere, which indicates timemean cold air outbreak from the northern high latitudes. The geographical patterns of themeridional winds are similar in the stratosphere. The momentum budget analysis shows that the form
drag term induced by the stationary waves is almost balanced with the Coriolis term.
Keywords: Meridional circulation, Isentropic coordinate©2016. Japan Geoscience Union. All Right Reserved.

- AAS11-08 -AAS11-09

Japan Geoscience Union Meeting 2016

Dynamical characteristics of mesoscale disturbances around Asian monsoon anticyclone andits influence on Stratosphere-Troposphere exchange*Arata Amemiya1, Kaoru Sato1
1.Graduate School of Earth and Planetary Science, Tokyo University
Recent studies on the stratosphere-troposphere exchange of tracers have focused on the importanceof the Asian monsoon anticyclone (hereafter ‘AMA’), which is planetary-scale, thermally driven
circulation dominating the upper troposphere and lower stratosphere (UTLS) over South and Southeast
Asia (Randel et al., 2010). On 360-380K isentropic surfaces, in most cases, the AMA is surrounded
by a boundary between the tropospheric air inside and the stratospheric air outside. Isentropic
mixing between inside and outside the AMA is suppressed by the strong anticyclonic circulation,
which corresponds to the maximum in PV gradient acting as a mixing barrier (Ploeger et al., 2015).
On the other hand, the AMA itself has a large intra-seasonal variability including synoptic-scaledisturbances and vortex-shedding due to instability (Popovic and Plumb, 2001), which are probably
essential processes that lead to irreversible mixing. In this study, we explore dynamical
characteristics of synoptic-scale disturbances around the AMA, focusing on a vertical flow.
We used ERA-Interim reanalysis data for June-September, 2011-2015 with the horizontal resolution
1.5ox1.5o. Because of possible large differences in the UTLS region among reanalysis data sets, we
also performed the same analyses using JRA55 and MERRA to confirm the results.
First, the intermittent nature of the occurrence of a large PV air in 5-20oN on the southern flankof the AMA is confirmed. The air with large stratospheric PV is formed as an occasional cutoff of
mid-latitude stratospheric air and is advected from the northeastern part of the AMA (‘in-mixing’).
The positive anomalies of PV averaged over 0-20oN on 370K decay gradually during westward
migration, suggesting that in-mixing is essentially irreversible. Thus, we next focus on individual
events of PV disturbances and associated meridional circulation, which is likely important for theirreversible diabatic mixing.
On 150 hPa level, it seems that most high PV anomalies appear with a downward flow. This feature
can be understood as a low-latitude version of a well-known tropopause descent around a westerly
jet, which is seen also on the northern flank of the AMA. Similar results are obtained fromdifferent reanalysis data.
Next, this characteristic vertical flow pattern is examined from a perspective of the balanced jet
dynamics. Even in the low latitude UTLS region, the horizontal flow roughly satisfies thegeostrophic balance because it is dominated by easterly jet. This means that the meridional
circulation on a plane perpendicular to the geostrophic wind can be diagnosed using the
Sawyer-Eliassen equation, which is based on a balanced-jet approximation (Hoskins, 1975).
N2∂2ψ/∂y2+2S2∂2ψ/∂y∂z+Fs2(∂2ψ/∂z2-ψ/4H2)=Qy
Note that Qy is regarded as the forcing by the balanced flow. A previous study on the tropopause
folding around the cold-front jet (Uccelini et al., 1985) successfully reproduced a spatial patternof the meridional flow using this equation. On the northern flank of the AMA, a similar pattern of
Qy is observed around the meandering jet, which is characterized as a vertical dipole across thejet exit region. However, on the southern flank, Qy is not always consistent with the vertical flow
pattern. Instead, we found that it can be explained as moist symmetric instability. Figure 1 shows
snapshots of PV, vertical flow, equivalent potential temperature and absolute angular momentum.
Isopleths of the latter two quantities are inclined southward closely each other around 15o-25oN,
125-250hPa. This implies the existence of oblique instability forming a vertical flow patternobserved near the tropopause.

©2016. Japan Geoscience Union. All Right Reserved.

- AAS11-09 -AAS11-09

Japan Geoscience Union Meeting 2016

Keywords: Atmospheric dynamics, Stratosphere-Troposphere coupling, Tracer transport and mixing©2016. Japan Geoscience Union. All Right Reserved.

- AAS11-09 -AAS11-10

Japan Geoscience Union Meeting 2016

Spatial and temporal variations of atmospheric methane concentration and its carbon andhydrogen isotopic ratios in the upper troposphere/lower stratosphere over the Eurasiancontinent observed by commercial airliner*Ryo Fujita1, Shinji Morimoto1, Shuji Aoki1, Toshinobu Machida2, Yousuke Sawa3, Hidekazu Matsueda3,
Yosuke Niwa3, Kazuhiro Tsuboi3, Keiich Katsumata2, Takakiyo Nakazawa1
1.Center for Atmospheric and Oceanic Studies, Graduate School of Science, Tohoku University,
2.National Institute for Environmental Studies, 3.Meterological Research InstituteAircraft observation campaigns over the northern high latitudes have been conducted to clarify thespatial and temporal variations of GHGs concentrations and their sources in the surfaces (Sugawara
et al., 1996; Tohjima et al., 1997; Nakazawa et al., 1997; Paris et al., 2008); however, systematictime-series observations using aircrafts are still limited (Matsueda et al., 2002; Haszpra et al.,2012; Umezawa et al., 2012). In addition, there is no systematic and simultaneous observation for
the atmospheric CH4 concentrations and their isotopic ratios (δ13C, δD) in the upper
troposphere/lower stratosphere over the northern high latitudes; except for a few studies using
balloon flights and aircraft observation campaigns (Sugawara et al., 1997; Rice et al., 2003; Röckmann et al., 2011). In this study, we have conducted monthly air sampling on-board a commercial
airliner between Europe and Japan from April 2012, and clarified the spatiotemporal variations ofCH4, δ13C and δD in the upper troposphere/lower stratosphere over the Eurasian continent.
In the upper troposphere, CH4 concentrations, δ13C and δD showed no clear seasonal variations. In
the lower stratosphere, on the other hand, CH4 and δ13C, δD showed clear aniti-phase seasonalvariations; seasonal maximum (minimum) of the CH4 concentration (δ13C, δD) was found in November toJanuary and seasonal minimum (maximum) was in spring. They can be explained by effective flushingof the lowermost stratospheric air with the tropospheric air in autumn and subsidence of the middle
stratospheric air in spring (Sawa et al., 2015). Moreover, compact correlations of CH4 with respectto δ13C and δD were found in the lower stratosphere, suggesting the occurrence of reactions of CH4
not only with OH, but also with Cl and O(1D).
Keywords: Methane, carbon and hydrogen isotopic ratios, upper troposphere/lower stratosphere,
Eurasian continent©2016. Japan Geoscience Union. All Right Reserved.

- AAS11-10 -AAS11-11

Japan Geoscience Union Meeting 2016

CO2 and SF6 concentrations in the stratosphere over Indonesia*Satoshi Sugawara1, Shuji Aoki2, Shinji Morimoto2, Shigeyuki Ishidoya3, Takakiyo Nakazawa2, Sakae
Toyoda4, Chusaku Ikeda5, Hideyuki Honda5, Yoichi Inai6, Fumio Hasebe6, Fanny Aditya Putri7, Daisuke
Goto8
1.Miyagi University of Education, 2.Tohoku University, 3.AIST, 4.TITECH, 5.JAXA/ISAS, 6.Hokkaido
University, 7.LAPAN, 8.NIPR
Stratospheric air collections were carried out at Biak, Indonesia in February 2015, by using thecompact cryogenic air sampler (J-T sampler). Eight sets of air sampler were launched from theexperiment field in LAPAN observatory (001°10'32" S, 136° 06'02" E) using 4 large plastic balloons.
The data obtained at 8 different altitudes will be used for elucidating the vertical structures of
GHGs and their chemical processes in the TTL and the tropical stratosphere, with an average
vertical resolution better than 2km. Air samples were analyzed for concentrations of CO2, CH4, N2O,
and SF6 at Tohoku University and Miyagi University of Education. The concentrations of CO2 and SF6
at 29 km altitude were 392.9 ppmv and 7.5 pptv, respectively. Stratospheric CO2 and SF6 are known
as the ‘clock tracer’. In this study, we estimated the mean age of air in the tropical stratosphere
over Biak, and compared them with the results obtained from the previous experiments at Japan,
Kiruna, and Syowa station. The CO2 concentration data was corrected for the airborne production bymethane oxidation. CO2- and SF6-age were estimated by comparing the observed concentrations with
the CONTRAIL data records in the tropical upper troposphere. As a result, the mean age of air was
estimated to be about 3 years at 29km altitude. This value was significantly lower than thoseobtained from the satellite SF6 measurements.
Keywords: CO2, SF6, Age of air©2016. Japan Geoscience Union. All Right Reserved.

- AAS11-11 -AAS11-12

Japan Geoscience Union Meeting 2016

Diffusive separation of major atmospheric components in the stratosphere over Indonesia*Shigeyuki Ishidoya1, Satoshi Sugawara2, Shuji Aoki3, Shinji Morimoto3, Takakiyo Nakazawa3, Sakae
Toyoda4, Chusaku Ikeda5, Hideyuki Honda5, Yoichi Inai6, Fumio Hasebe6, Fanny A. Putri7, Daisuke Goto8, Shohei Murayama1
1.National Institute of Advanced Industrial Science and Technology (AIST), 2.Miyagi University of
Education, 3.Tohoku University, 4.Tokyo Institute of Technology, 5.Japan Aerospace Exploration
Agency (JAXA), 6.Hokkaido University, 7.Lembaga Penerbangan dan Antariksa Nasional (LAPAN),
8.National Institute of Polar Research
In the atmosphere over the turbopause (about 100 km), the mole fraction of heavier molecules
decreases with increasing altitude due to diffusive separation in Earth’s gravitational field.
Recently, Ishidoya et al. (2013) reported such gravitational separation of the atmosphere is also
found in the middle to lower stratosphere (about 15-35 km) over Japan from high precision
measurements of the composition of the atmospheric major components. To investigate whether
gravitational separation is also detectable over the equatorial region or not, we carried out
collection of the stratospheric air using a balloon-borne cryogenic air sampler over Biak,Indonesia during February 22-28, 2015. For the observation, we used a Joule-Thomson minicooler,developed by Morimoto et al. (2009), as the cryogenic air sampler, and succeeded to collect 8 airsamples at heights of 17-29 km. The collected air samples were analyzed for delta(Ar/N2), delta(O2/N
2),

delta15N of N2, delta18O of O2 and delta40Ar by using a mass spectrometer (Ishidoya and Murayama,2014), and the measured values showed small but significant decrease with altitude probably due togravitational separation. The amount of gravitational separation, evaluated as delta values for themass number difference of 1 (e.g. delta for 15N14N/14N14N), is found to be 11 per meg at the heightof 29 km. Based on the observed gravitational separation and a 1-dimensional steady state eddy
diffusion/molecular diffusion model, we estimated 1-dimensional vertical eddy diffusion
coefficients (Kz) over the equatorial region. By using the average Kz from the surface to the
middle stratosphere, we calculated a timescale of the vertical diffusion for a length scale fromthe surface to the middle stratosphere assuming simple Fickian diffusion. We found that thecalculated timescale agrees with the elapsed time since the stratospheric air passed an upperboundary of the tropical tropopause layer (TTL), estimated from tape recorder signals ofstratospheric water vapor (Mote et al., 1996), which is significantly smaller than the mean age of
air estimated from CO2 concentration (CO2 age). This discrepancy may be due to insensitivity ofgravitational separation to mixing processes in Brewer-Dobson circulation, of which variations
change the mean age of air significantly.
References
Ishidoya, S. et al. (2013) Gravitational separation in the stratosphere –a new indicator ofatmospheric circulation. Atmos. Chem. Phys., 13, 8787–8796, www.atmos-chem-phys.net/13/8787/2013/,
doi:10.5194/acp-13-8787-2013.
Ishidoya, S. & Murayama, S. (2014) Development of high precision continuous measuring system of theatmospheric O2/N2 and Ar/N2 ratios and its application to the observation in Tsukuba, Japan. Tellus

B, 66, 22574, http://dx.doi.org/ 10.3402/tellusb.v66.22574.
Morimoto et al. (2009) A new compact air sampler and its application in stratospheric greenhousegas observation at Syowa station, Antarctia. J. Atmos. Oceanic and Technol., 26
10.1175/2009JTECHA1283.1.
Mote, P. W. et al. (1996) An atmospheric tape recorder: The imprint of tropical tropopause
temperatures on stratospheric water vapor. J. Geophys. Res., 101, 3989-4006.

©2016. Japan Geoscience Union. All Right Reserved.

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Japan Geoscience Union Meeting 2016

Keywords: gravitational separation of atmospheric components, cryogenic air sampler, stratosphere
over Indonesia©2016. Japan Geoscience Union. All Right Reserved.

- AAS11-12 -AAS11-13

Japan Geoscience Union Meeting 2016

Observational study of the short-lived ozone depleting substances, bromoform anddibromomethane*Yoko Yokouchi1, Takuya Saito1, Jiye Zeng1, Hitoshi Mukai1, Stephen Montzka2
1.National Institute for Environmental Studies, 2.National Oceanic and Atmospheric Administration
Bromoform (CHBr3) and dibromomethane (CH2Br2), which undergo photolytic degradation and react with
OH to produce inorganic bromine, are the large contributors of organic bromine from the ocean tothe atmosphere, where it can affect stratospheric and tropospheric ozone chemistry (Carpenter andLiss 2000; Montzka and Reimann 2011). These naturally produced ozone-depleting substances (ODS) are
attracting more interest as concentrations of anthropogenic ODS decrease under the provisions of
the Montreal Protocol. The major sources of these bromocarbons are believed to be seaweed ormacroalgae, followed by phytoplankton and other biological sources, but many uncertainties remain
with regard to their production amount and mechanism. In this study, we conducted high-frequency
long-term measurements of CH2Br2 and CHBr3 at Hateruma Island, and found that the relationshipbetween [CH2Br2]/[CHBr3] and [CHBr3] could be explained by their chemical decay in the atmospherewith a fairly consistent CH2Br2/CHBr3 initial emission ratio, and some additional coastal effects.
By combining these data with NOAA global observation data (14-yr monthly data from 14 groundstations), we obtained new insight into the global sources of these bromocarbons and their chemicaldegradation.
Keywords: bromocarbons, sources, long-term observation©2016. Japan Geoscience Union. All Right Reserved.

- AAS11-13 -AAS11-14

Japan Geoscience Union Meeting 2016

Box-model simulation for atmospheric effect of solar energetic particles: variation of
trace chemical species in the middle atmosphere*Yoichi Nakai1, Yuko MOTIZUKI1, Manami MARUYAMA1, Hideharu Akiyoshi2, Takashi Imamura2
1.RIKEN Nishina Center, 2.National Institute for Environmental Studies
Recently, the atmospheric effect of solar energetic particles (SEPs) has attracted interests.
High-energy protons in SEPs are able to come down to the stratosphere in the polar region and they
are considered to induce increase of reactive odd nitrogen species (NOy) due to dissociation of
nitrogen molecules. Furthermore, they cause depletion of ozone through the catalytic reaction cycle
involving NOy over a period longer than SEP events. The concentration variations of several
chemical species have been observed and their simulations have been attempted [1].
We have studied concentration variation of trace chemical species induced by SEP protons throughthe Box-model simulation. It involves multitudinous reactions of various ionic and neutral chemical
species but no transport processes. We simulated the concentration variations for the middle
atmosphere in polar region during the SEP event in October-November 2003. In this simulation, we
adopt 77 chemical species and 522 gas-phase ionic and neutral reactions. We assume that the prompt
products are charged and neutral species generated from nitrogen and oxygen molecules and that theyields of the prompt products are determined only with the energy deposit in the air. These prompt
products generated by the SEP protons induce subsequent ionic and neutral chemical reactions(SEP-induced reactions). The production rates of the prompt products were estimated using theG-value [2,3]. The daily energy deposits were estimated from the calculated daily ion-pair creation
rate due to the SEP protons [4]. The concentration variation of each species due to SEP protons wasestimated as the difference between the result by considering both SEP-induced and photochemical
reactions and that only for photochemical reactions under the same initial condition.
In this talk, we will mainly report the results of our simulation for the variations of ozone andreactive odd nitrogen species for the SEP event in October-November 2003.
References[1] For example, B. Funke et al., Atmos. Chem. Phys. 11, 9089 (2011).
[2] C. Willis and A. W. Boyd, Int. J. Radiat. Phys. Chem. 8, 71 (1976).
[3] H. Mätzing, Adv. Chem. Phys. LXXX, 315 (1991).
[4] C.H. Jackman et al., Atmos. Chem. Phys. 8, 765 (2008).

©2016. Japan Geoscience Union. All Right Reserved.

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Japan Geoscience Union Meeting 2016

Characteristics of dynamical and chemical fields in Chemistry Climate Models
Takuya Sasaki1, *Masato Shiotani1, Hideharu Akiyoshi2, Makoto Deushi3, Douglas Kinnison4
1.Research Institute for Sustainable Humanosphere, Kyoto University, 2.National Institute forEnvironmental Studies, 3.Meteorological Research Institute, 4.National Center for AtmosphericResearch
We analyzed results from three coupled chemistry-climate models (CCM) to investigate
characteristics of climatological differences between free-running (FR) and specified dynamics (SD)modes, by paying attention to interactions between dynamical and chemical fields. The three models
used in this study are the NCAR Whole Atmosphere Community Climate Model, version 4 (WACCM4) (Marshet al., 2013), the Model for Interdisciplinary Research on Climate 3.2-Chemistry-Climate Model(MIROC3.2-CCM) (Imai et al., 2013; Sakazaki et al., 2013), and the Meteorological ResearchInstitute-Earth System Model Version 1 Revision 1 (MRI-ESM1r1) (Deushi and Shibata, 2011; Adachi etal., 2013). Outputs from the three models are based on simulations proposed by IGAC/SPARC
Chemistry-Climate Model Initiative (CCMI) to improve our understanding in modelling of thechemistry and dynamics of the troposphere and stratosphere. REF-C1 and REF-C2 simulations for FR
mode CCM (FR-CCM) and REF-C1SD simulation for SD mode CCM (SD-CCM) are used for the period of
1980-2010 as monthly means.
We carefully analyzed differences found at mid-high latitudes in the stratosphere of the winterhemisphere, the extratropical upper troposphere and lower stratosphere (Ex-UTLS) and the tropical
tropopause layer (TTL). Comparisons of stratospheric temperatures at mid-high latitudes show thatfor all FR-CCM results the seasonal change is delayed in both hemispheres during the winter andspring; especially in the southern hemisphere all FR-CCM results show cold biases in early spring.
Results for ozone are similar to those for temperature, and the biases in the southern hemisphereare clearer than in the northern hemisphere. We also investigated the Eliassen-Palm fluxes (EPflux) and resulting residual mean meridional circulations, because the seasonal changes intemperature and ozone during these seasons and in those regions are affected by the meridional
circulation. EP flux convergences and downward velocities in winter are smaller for all FR-CCM
results than SD-CCM ones, indicating that the time of maximum wave activities seen in EP fluxes aredelayed about 1-2 months for all FR-CCM results. These suggest that the temperature and ozone
biases are due to some problems with model reproducibility of planetary waves propagating into thestratosphere from the troposphere.
In the Ex-UTLS, all FR-CCM results show cold biases especially in summer, and all SD-CCM results
overestimate radiative cooling effects. Comparisons of water vapor with satellite observations(Aura-MLS) and models show that all model results overestimate water vapor in the upper troposphereat mid- and high latitudes. Because water vapor has an important role in the radiation budget
during the summer in this region, the FR-CCM cold biases and the SD-CCM overestimations ofradiative effects are from water vapor overestimations. The dynamical fields are specified in
SD-CCM, therefore these overestimations are due to the model reproducibility of chemical, transportand microphysics processes associated with water.
In the TTL, we compared ozone distributions in SD-CCM and FR-CCM results. We found that FR-CCM of
MIROC3.2-CCM and WACCM4 cannot reproduce the increase of ozone in boreal summer. This is due to theannual cycle of upwelling and the horizontal transport from mid latitude; this mechanism is called
in-mixing and is understood as the nearly isentropic transport owing to the Asian and North
American monsoon anticyclones. WACCM4 FR-CCM can reproduce this increase in isentropic coordinate,
and the Asian monsoon anticyclone is weak in the FR-CCM of MIROC3.2-CCM. These indicate that

©2016. Japan Geoscience Union. All Right Reserved.

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Japan Geoscience Union Meeting 2016

temperature and monsoon anticyclone reproducibility is strongly related to the improvement of ozone
results in the TTL.
Keywords: Chemistry Climate Model, stratospheric dynamics and chemistry, extratropical upper
troposphere and lower stratosphere, tropical tropopause layer©2016. Japan Geoscience Union. All Right Reserved.

- AAS11-15 -AAS11-16

Japan Geoscience Union Meeting 2016

Future changes in quasi-biennial oscillation of ozone with increasing GHS and ozone
recovery in CCMI simulation*Hiroaki Naoe1, Makoto Deushi1, Kohei Yoshida1, Kiyotaka Shibata2
1.Meteorological Research Institute, 2.Kochi University of Technology
The future quasi-biennial oscillation (QBO) in ozone in the equatorial stratosphere is examined byanalyzing future transient reference simulation (REF-C2) for the period from 1960 to 2100 in a
climate change due to increasing GHGs and decreasing ODSs under the Chemistry-Climate Model
Initiative (CCMI) activities. The REF-C2 simulation is conducted using the Meteorological ResearchInstitute Earth System Model (MRI-ESM), which constitutes a core component of the atmosphere-ocean
coupled global climate model and components of sea-ice, aerosol, and ozone models. We haveconducted the wavelet analysis to provide inter-annual variability of amplitude and phase of theozone QBO in the vertical structure of tropical stratosphere.
In the simulation the power spectra of the equatorial zonal-mean ozone mixing ratio shows a double
peak structure with maximum amplitude at two pressure levels of around 30 hPa and 10 hPa and a nodeat 15 hPa. The vertical residual-velocity anomalies are in phase with the ozone anomalies in theupper stratosphere with the abrupt phase change at around 15 hPa. Below this level, the phase isalmost reversed from what it is above. Quantitatively, the amplitude of the ozone QBO in themodel-free simulation (REF-C2) is reduced to 0.25 ppmv at 10 hPa, which is about half of that in
the simulation forced by the meteorological reanalysis data (REF-C1sd).
Compared with the past climatology of 1960-1980 at the time before the severe ozone destruction,
the amplitude of the future equatorial ozone QBO during the period of 2040-2070 at the time of theozone recovery is characterized by the decrease by 20-30% at 30 hPa and the increase by around 20%
at 5-10 hPa. This can be explained by the fact that the dominant role of future ozone decrease in
the lower stratosphere is due to the changes in tropical upwelling. In addition, it is found thatchemical ozone production and destruction do contribute to the ozone changes in the tropical upper
stratosphere.
Keywords: ozone QBO, quasi-biennial oscillation, ozone depletion and recovery©2016. Japan Geoscience Union. All Right Reserved.

- AAS11-16 -AAS11-17

Japan Geoscience Union Meeting 2016

Forcing and feedbacks of geoengineering by SO2 injection into the stratosphere: Analysisof GeoMIP G4 experiment*Hiroki Kashimura1, Takashi Sekiya2, Manabu Abe1, Shingo Watanabe1
1.Japan Agency for Marine-Earth Science and Technology, 2.Graduate School of Environment Studies,
Nagoya University
Geoengineering is a deliberate large-scale manipulation of the planetary environment to counteract
anthropogenic climate change. Manners of geoengineering for lessening the effects of global warming
can be classified into two groups. One is Solar Radiation Management (SRM), which aims to reduce
the amount of solar radiation at the surface by increasing the reflection rate. The other is Carbon
Dioxide Removal, which aims to reduce the amount of CO2 in the atmosphere. One of the most probableapproaches for SRM is to mimic a large volcanic eruption by injecting sulfate aerosol precursors,
such as SO2, into the stratosphere. The sulfate aerosols increase the solar reflectance of theatmosphere, decrease the shortwave radiation (SW) reaching the surface, and cause cooling of
surface air temperature. The Geoengineering Model Intercomparison Project (GeoMIP) was established
to coordinate simulations with a common framework and to determine the robust effects and responses
to geoengineering processes.
In this study, we analyze GeoMIP's G4 experiment, which is designed to inject SO2 into the lower
stratosphere at the equator by 5 Tg/year from 2020 to 2070 with adopting the RCP4.5 scenario as thebaseline. This injection rate is about 1/4 of the 1991 eruption of Mount Pinatubo. Some participant
models have explicitly calculated the formation of sulfate aerosols from SO2 and theirdistribution; whereas some models have just used prescribed aerosol optical depth (AOD) based on
the observed AOD after 1991 eruption of Mount Pinatubo. Therefore, a careful comparison isrequired. In addition, at least cloud amounts, water vapor amounts, and surface albedo can change
because of the cooling of the air temperature by SRM. Changes of these amounts affect thereflection and absorption of SW and give some feedbacks to the effect of SRM.
To separately estimate the direct SRM forcing and the feedbacks on each model, we use a single
layer atmospheric model for SW transfer. By using this model, we can derive the SW reflection andabsorption rates of the atmosphere and surface albedo from the following model outputs: upwellingand downwelling SW at the surface and at the top of the atmosphere. In addition, these calculation
can be done with whole-sky amounts and clear-sky amounts, and we can estimate the cloud effects by
the their differences. Then, we calculate the contribution of each term described above to thechange of net SW at the surface from RCP4.5 to G4, and estimate the direct SRM forcing and thefeedbacks. Here, we assume that the change of clear-sky reflection rate is due to the injectedsulfate aerosols and that of clear-sky absorption rate is due to the change of water vapor amounts.
Our analysis shows that the globally and temporally averaged SRM forcing ranges widely from -3.6 to-1.6 W/m2 depending on the models. The SRM forcing on the models with sulfate aerosol calculation
is significantly higher than that using the prescribed AOD. This means that the prescribed AOD
might underestimate the SRM forcing by 5 Tg/year SO2 injection. The feedback from cloud amounts andthat from water vapor amounts are comparable and range from +0.5 to +1.5 W/m2 (heating effects).
The feedback from water vapor amounts is almost proportional to the cooling of the near-surface airtemperature. On the other hand, the cloud feedback shows strong model dependency. The surface
albedo feedback works for cooling but it is small (for averaged value).
Our results show the fact that, in the simulation of the geoengineering with SO2 injection, theuncertainty of the SRM forcing itself is considerably large and that SRM forcing could be decreased
by about 50% by the feedbacks from changes in cloud amounts, water vapor amounts, and surface©2016. Japan Geoscience Union. All Right Reserved.

- AAS11-17 -AAS11-17

Japan Geoscience Union Meeting 2016

albedo.
Keywords: Geoengineering, Stratospheric aerosols, Shortwave radiation, GeoMIP©2016. Japan Geoscience Union. All Right Reserved.

- AAS11-17 -AAS11-18

Japan Geoscience Union Meeting 2016

Effects of geoengineering by stratospheric SO2 injection on stratospheric sulfate aerosols
and circulation*Takashi Sekiya1, Hiroki Kashimura2, Shingo Watanabe2, Kengo Sudo1,2
1.Graduate School of Environmental Studies, Nagoya University, 2.Japan Agency for Marine-Earth
Science and Technology
Geoengineering is deliberate manipulation of climate system to counteract anthropogenic climatechange due to greenhouse gases. In the geoengineering techniques, stratospheric SO2 injection is
analogically based on SO2 injection by explosive volcanic eruption and subsequent surface cooling.
However, climate models participating in the Geoengineering Model Intercomparison Project (GeoMIP)
demonstrate diverse results. Some of uncertainties of the results are aerosol microphysicalproperties and stratospheric circulation. This study introduces an aerosol microphysics module ofstratospheric sulfate aerosols into the MIROC-ESM-CHEM earth system model (hereinafter,
MIROC-ESM-CHEM-AMP). The model can represent aerosol microphysical properties and aerosol transport
explicitly. We conducted the geoengineering simulation using MIROC-ESM-CHEM-AMP in the same manneras the GeoMIP’s G4 experiment. G4 experiment assumes stratospheric SO2 injection of 5 Tg/year into
the lower stratosphere at the equator during 2020—2070 under RCP4.5 scenario. We also compare theresults of MIROC-ESM-CHEM-AMP with the results of MIROC-ESM-CHEM. G4 experiment with MIROC-ESM-CHEMprescribes stratospheric aerosol optical depth (SAOD) based on the observed SAOD after the 1991
eruption of Mt. Pinatubo. The results show that SAOD in MIROC-ESM-CHEM-AMP is twice as large as
SAOD in MIROC-ESM-CHEM. In MIROC-ESM-CHEM-AMP, the effective radius of stratospheric sulfate
aerosols grew by 0.51 μm in the tropical lower stratosphere because of the stratospheric SO2
injection. Mean residence time of stratospheric sulfate aerosols is 1.13 year. The stratosphericburden is 2.85 TgS that is larger than the yearly injected SO2 amount (2.5 TgS).
This study also investigates effects of the stratospheric SO2 injection on mean age ofstratospheric air. In the both models, the stratospheric SO2 injection increases the mean age by
0.15 year at maximum and decreases the mean age by 0.25 year at maximum. The changes in the mean
age in MIROC-ESM-CHEM-AMP are more than three times as large as the changes in MIROC-ESM-CHEM. We
furthermore assess the effects of the stratospheric SO2 injection on the mean age of stratospheric
air using the G4 experiment with sea surface temperature (SST) of the RCP4.5 experiment (without
geoengineering). The results suggest that the increase in the mean age is caused by slow response(e.g., SST changes) and that the decrease is caused by fast response (e.g., longwave radiation
absorption of sulfate aerosols). The model results also demonstrate that the slow response leads toweakened circulation in the lower stratosphere, resulting in a slight increase in SAOD (about 5%).
Keywords: Geoengineering, Stratospheric aerosols, Stratospheric circulation, Aerosol microphysics©2016. Japan Geoscience Union. All Right Reserved.

- AAS11-18 -