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Gravitational Separation in the Stratosphere EGU Journal Logos (RGB) Open Access Open Access Open Access Advances in Annales Nonlinear Processes Geosciences Geophysicae in Geophysics Open Access Open Access Natural Hazards Natural Hazards and Earth System and Earth System Sciences Sciences Discussions Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Open Access Open Access Atmos. Chem. Phys. Discuss., 13, 4839–4861,Atmospheric 2013 Atmospheric www.atmos-chem-phys-discuss.net/13/4839/2013/Chemistry Chemistry doi:10.5194/acpd-13-4839-2013 ACPD and Physics and Physics © Author(s) 2013. CC Attribution 3.0 License. 13, 4839–4861, 2013 Discussions Open Access Open Access Atmospheric Atmospheric This discussion paper is/hasMeasurement been under review for the journal AtmosphericMeasurement Chemistry Gravitational and Physics (ACP). Please referTechniques to the corresponding final paper in ACP ifTechniques available. separation in the Discussions stratosphere Open Access Open Access S. Ishidoya et al. GravitationalBiogeosciences separation in theBiogeosciences stratosphere – a new indicator of Discussions Open Access Open Access Title Page atmospheric circulationClimate Climate Abstract Introduction of the Past of the Past 1 2 3 4 4 Discussions 5 S. Ishidoya , S. Sugawara , S. Morimoto , S. Aoki , T. Nakazawa , H. Honda , Conclusions References 1 Open Access and S. Murayama Open Access Earth System Tables Figures 1 Earth System National Institute of Advanced Industrial Science and Technology (AIST),Dynamics Tsukuba 305–8569, Japan Dynamics Discussions J I 2Miyagi University of Education, Sendai 980–0845, Japan 3 Open Access National Institute of Polar Research,Geoscientific Tokyo 190-8518, Japan Geoscientific Open Access J I 4Center for Atmospheric andInstrumentation Oceanic Studies, Tohoku University, SendaiInstrumentation 980–8578, Japan Back Close 5Institute of Space and AstronauticalMethods Science and (ISAS), Japan AerospaceMethods Exploration and Agency (JAXA), Sagamihara 252-5210,Data Japan Systems Data Systems Full Screen / Esc Discussions Open Access Received: 30 December 2012 – Accepted: 12Open Access February 2013 – Published: 20 February 2013 Geoscientific Geoscientific Printer-friendly Version Correspondence to: S. Ishidoya ([email protected]) Model Development Model Development Published by Copernicus Publications on behalf of the European GeosciencesDiscussions Union. Interactive Discussion Open Access Open Access Hydrology and Hydrology and Earth System 4839 Earth System Sciences Sciences Discussions Open Access Open Access Ocean Science Ocean Science Discussions Open Access Open Access Solid Earth Solid Earth Discussions Open Access Open Access The Cryosphere The Cryosphere Discussions Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Abstract ACPD As a basic understanding of the dynamics of the atmospheric circulation, it has been believed that the gravitational separation of atmospheric components is observable 13, 4839–4861, 2013 only in the atmosphere above the turbopause. However, we found, from our high- 5 precision measurements of not only the isotopic ratios of N2,O2 and Ar but also the Gravitational concentration of Ar, that the gravitational separation occurs even in the stratosphere separation in the below the turbopause; their observed vertical profiles are in good agreement with stratosphere those expected theoretically from molecular mass differences. The O2/N2 ratio ob- served in the middle stratosphere, corrected for the gravitational separation, showed S. Ishidoya et al. 10 the same mean air age as estimated from the CO2 concentration. Simulations with a 2- dimensional model of the middle atmosphere indicated that a relationship between the gravitational separation and the air age in the stratosphere would be significantly af- Title Page fected if the Brewer-Dobson circulation is enhanced due to global warming. Therefore, Abstract Introduction the gravitational separation is usable as a new indicator of changes in the atmospheric 15 circulation in the stratosphere. Conclusions References Tables Figures 1 Introduction J I The gravity of the earth prevents the atmosphere from dissipating into space. It is also known that the gravity causes atmospheric molecules to separate depending on their J I molar masses, which is called “gravitational separation”. It is widely recognized that the Back Close 20 gravitational separation of atmospheric components occurs in the atmosphere above the turbopause (Lewis and Prinn, 1984; Jacobs, 1999). On the other hand, we have Full Screen / Esc suggested from our measurements of the stable isotopic ratios of major atmospheric 15 18 components (δ( N) of N2 and δ( O) of O2) (Ishidoya et al., 2006; Ishidoya et al., Printer-friendly Version 2008a, b) that the gravitational separation exists even in the stratosphere. However, in Interactive Discussion 25 our earlier studies, we were not able to exclude the possibility that some other factors affect our measurement results. 4840 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | In this paper, we present a new concrete evidence for the existence of the gravi- tational separation in the stratosphere. We also show a significant effect of the gravi- ACPD tational separation on the O concentration (δ(O /N )) value measured in the strato- 2 2 2 13, 4839–4861, 2013 sphere. Furthermore, we propose to use the gravitational separation as a new indica- 5 tor to detect a change in the Brewer-Dobson Circulation (BDC) (Brewer, 1949) in the stratosphere. Atmospheric general circulation models have shown that the mean age Gravitational of stratospheric air decreases as the BDC is enhanced under global warming (Austin separation in the and Li, 2006; Li et al., 2008), but a significant change of the air age has not been ob- stratosphere served so far (Engel et al., 2009). Since the gravitational separation occurs physically S. Ishidoya et al. 10 due to gravity, its effect is expected to become more pronounced as the stratospheric air is slowly transported poleward after its intrusion from the troposphere in the trop- ics. Therefore, in this conceptual framework, by measuring the gravitational separation, Title Page it would be possible to obtain information about changes in the stratospheric circula- tion. To confirm this supposition, we simulate the stratospheric gravitational separation Abstract Introduction 15 using a 2-dimensional model of the middle atmosphere (SOCRATES) (Huang et al., 1998), and then examine the relationship between the gravitational separation and the Conclusions References stratospheric circulation. Tables Figures 2 Stratospheric air collection and sample analyses J I The collection of stratospheric air has been carried out using a balloon-borne cryo- J I ◦ ◦ ◦ ◦ 20 genic air sampler over Sanriku (39 N, 142 E) and Taiki (43 N, 143 E), Japan since Back Close 1985 (e.g. Nakazawa et al., 1995; Aoki et al., 2003). Our air sampler consists mainly of 12 stainless-steel sample containers, a liquid helium dewar, a receiver, a transmitter, Full Screen / Esc a control unit and batteries; all these components are housed in a water- and pressure- proof aluminum chamber (Honda, 1990; Honda et al., 1996). The volume of each sam- Printer-friendly Version 25 ple container is about 760 mL, and its inner wall is electrically polished. A motor-driven Interactive Discussion metal-to-metal seal valve is attached to each sample container. The other end of the motor-driven valve is connected to a sample intake, located 3.5 m below the bottom of 4841 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | the aluminum chamber, through a manifold and a stainless-steel bellows tube with an inner diameter of 15 mm reinforced with mesh. Before sampling, all the sample con- ACPD tainers were evacuated with heating and then cooled by filling the dewar with liquid 13, 4839–4861, 2013 He. Then, the cryogenic air sampler was connected to a large balloon, launched from 5 the balloon center at Sanriku or Taiki early in the morning and recovered from the Pacific Ocean around noon. Air samples were collected in the containers at assigned Gravitational altitudes by opening and closing the motor-driven valves using a telecommand system. separation in the The flow rates of sample air at the respective altitudes were 50–100 Lmin−1 at ambient stratosphere pressures, and typical amounts of air samples collected were about 25 L at standard ◦ S. Ishidoya et al. 10 temperature (0 C) and pressure (1013.25 hPa). 15 To detect the gravitational separation in the stratosphere, we measured δ( N) of N2, δ(18O) of O and δ(O /N ) of the air samples collected over Sanriku on 31 May 1999, 2 2 2 Title Page 28 August 2000, 30 May 2001, 4 September 2002, 6 September 2004, 3 June 2006 and 4 June 2007, as well as of those over Taiki on 22 August 2010, using a mass spec- Abstract Introduction 15 18 15 trometer (Finnigan MAT-252) (Ishidoya et al., 2003). δ( N) of N2 and δ( O) of O2 were also measured for the samples collected over Sanriku on 8 June 1995. Furthermore, Conclusions References 15 18 the air samples over Sanriku on 4 June 2007 were analyzed for δ( N) of N2, δ( O) Tables Figures 40 of O2, δ(O2/N2), δ(Ar/N2) and δ( Ar) using a new mass spectrometer (Thermo Sci- 15 18 entific DELTA-V). In this study, δ( N) of N2, δ( O) of O2, δ(O2/N2), δ(Ar/N2) and J I 40 −6 20 δ( Ar) are reported in per meg (one per meg is equal to 1 × 10 ), J I h 15 14 14 14 i n( N N)/n( N N) Back Close sample δ 15 − ( N) = h i 1, (1a) n(15N14N)/n(14N14N) Full Screen / Esc reference h 18 16 16 16 i n( O O)/n( O O) Printer-friendly Version sample δ(18O) = − 1, (1b) h i Interactive Discussion n(18O16O)/n(16O16O) reference 4842 h i Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | n(16O16O)/n(15N14N) sample δ / − ACPD (O2 N2) = h i 1, (1c) n(16O16O)/n(15N14N) 13, 4839–4861, 2013 reference h i n(40Ar)/n(14N14N) sample δ / − Gravitational (Ar N2) = h i 1, (1d) n(40Ar)/n(14N14N) separation in the reference stratosphere and S.
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