Advanced Search
Article Contents

Intraseasonal Oscillation of Tropospheric Ozone over the Indian Summer Monsoon Region


doi: 10.1007/s00376-018-8113-7

  • Boreal summer intraseasonal oscillation (BSISO) of lower tropospheric ozone is observed in the Indian summer monsoon (ISM) region on the basis of ERA-Interim reanalysis data and ozonesonde data from the World Ozone and Ultraviolet Radiation Data Centre. The 30-60-day intraseasonal variation of lower-tropospheric ozone shows a northwest-southeast pattern with northeastward propagation in the ISM region. The most significant ozone variations are observed in the Maritime Continent and western North Pacific. In the tropics, ozone anomalies extend from the surface to 300 hPa; however, in extratropical areas, it is mainly observed under 500 hPa. Precipitation caused by BSISO plays a dominant role in modulating the BSISO of lower-tropospheric ozone in the tropics, causing negative/positive ozone anomalies in phases 1-3/5-6. As the BSISO propagates northeastward to the western North Pacific, horizontal transport becomes relatively more important, increasing/reducing tropospheric ozone via anticyclonic/cyclonic anomalies over the western North Pacific in phases 3-4/7-8. As two extreme conditions of the ISM, most of its active/break events occur in BSISO phases 4-7/1-8 when suppressed/enhanced convection appears over the equatorial eastern Indian Ocean and enhanced/suppressed convection appears over India, the Bay of Bengal, and the South China Sea. As a result, the BSISO of tropospheric ozone shows significant positive/negative anomalies over the Maritime Continent, as well as negative/positive anomalies over India, the Bay of Bengal, and the South China Sea in active/break spells of the ISM. This BSISO of tropospheric ozone is more remarkable in break spells than in active spells of the ISM, due to the stronger amplitude of BSISO in the former.
    摘要: 本文利用ERA再分析资料和WOUDC臭氧探空资料, 分析了印度季风区夏季对流层臭氧的季节内振荡(BSISO)特征. 结果表明对流层低层臭氧存在着30-60天的季节内振荡, 臭氧异常呈西北-东南向分布, 在季风区向东北方向传播. 最显著的臭氧异常在海洋大陆和西北太平洋区域. 臭氧异常在热带从地面延伸到300hPa, 而在热带外地区臭氧异常主要在500hPa以下. 在热带, BSISO引起的降水是导致臭氧异常的主要原因, 使得在1-3/5-6位相出现了臭氧负/正异常. 然而当BSISO传播到西北太平洋区域时, BSISO引起的大气环流异常对臭氧异常的形成更为重要, 通过反气旋性/气旋性环流异常导致了臭氧在3-4/7-8出现正/负异常. 大多数印度季风的活跃/中断发生在BSISO的4-7/1-8位相, 此时减弱/加强的对流出现在赤道东印度洋, 加强/减弱的对流出现在印度, 孟加拉湾和中国南海. 海洋大陆对流层臭氧出现显著的负/正异常, 印度, 孟加拉湾和中国南海对流层臭氧出现显著的正/负异常. 由于季风中断期BSISO的振幅比季风活跃期更大, 对流层臭氧的季节内振荡也更加显著.
  • 加载中
  • Annamalai H.,J. M. Slingo, 2001: Active/break cycles: Diagnosis of the intraseasonal variability of the Asian summer monsoon. Climate Dyn., 18, 85-102, https://doi.org/10.1007/s003820100161
    Annamalai H.,K. R. Sperber, 2005: Regional heat sources and the active and break phases of boreal summer intraseasonal (30-50 day) variability. J. Atmos. Sci., 62, 2726-2748, https://doi.org/10.1175/JAS3504.1
    Bessafi M.,M. C. Wheeler, 2006: Modulation of South Indian Ocean tropical cyclones by the Madden-Julian oscillation and convectively coupled equatorial waves. Mon. Wea. Rev., 134, 638-656, https://doi.org/10.1175/MWR3087.1
    Chan J. C. L.,W. Ai, and J. J. Xu, 2002: Mechanisms responsible for the maintenance of the 1998 South China Sea summer monsoon. J. Meteor. Soc. Japan, 80, 1103- 1113.10.2151/jmsj.80.1103http://joi.jlc.jst.go.jp/JST.JSTAGE/jmsj/80.1103?from=CrossRef
    Dee, D. P.,Coauthors, 2011: The ERA-Interim reanalysis: Configuration and performance of the data assimilation system. Quart. J. Roy. Meteor. Soc., 137, 553-597, https://doi.org/10.1002/qj.828
    Ding A. J.,T. Wang, V. Thouret, J.-P. Cammas, and P. Nédélec, 2008: Tropospheric ozone climatology over Beijing: Analysis of aircraft data from the MOZAIC program. Atmos. Chem. Phys., 8(1), 1-13, https://doi.org/10.5194/acp-8-1-2008
    Donald A.,H. Meinke, B. Power, A. de H. N. Maia, M. C. Wheeler, N. White, R. C. Stone, and J. Ribbe, 2006: Near-global impact of the Madden-Julian Oscillation on rainfall. Geophys. Res. Lett., 33, L09704, https://doi.org/10.1029/2005GL025155
    Dufour G.,M. Eremenko, J. Orphal, and J.-M. Flaud, 2010: IASI observations of seasonal and day-to-day variations of tropospheric ozone over three highly populated areas of China: Beijing, Shanghai, and Hong Kong. Atmos. Chem. Phys., 10(8),3787-3801,https://doi.org/10.5194/acp-10-3787-2010
    Fadnavis S.,R. Chattopadhyay, 2017: Linkages of subtropical stratospheric intraseasonal intrusions with Indian summer monsoon deficit rainfall. J. Climate, 30, 5083-5095, https://doi.org/10.1175/JCLI-D-16-0463.1
    Gao X. H.,J. L. Stanford, 1990: Low-frequency oscillations in total ozone measurements. J. Geophys. Res., 95, 13 797-13 806, https://doi.org/10.1029/JD095iD09p13797
    Garfinkel C. I.,S. B. Feldstein, D. W. Waugh, C. Yoo, and S. Lee, 2012: Observed connection between stratospheric sudden warmings and the Madden-Julian Oscillation. Geophys. Res. Lett., 39, L18807, https://doi.org/10.1029/2012GL053144
    Han R. Q.,W. J. Li, and M. Dong, 2006: The impact of 30-60day oscillations over the subtropical Pacific on the East Asian summer rainfall. Acta Meteorologica Sinica, 20, 459- 474.10.1016/S1872-2032(06)60022-Xe891d2e1da1075ad11394f1337fc0513http%3A%2F%2Fwww.cnki.com.cn%2FArticle%2FCJFDTotal-QXXW200604008.htmhttp://www.cnki.com.cn/Article/CJFDTotal-QXXW200604008.htmThe relationships between the precipitation over East Asia (20 -45 N, 110 -135 E) and the 30-60-day intraseasonal oscillation (ISO) over the Pacific during the boreal summer are studied in the paper. The daily wind and height fields of NCEP/NCAR reanalysis data, the 24-h precipitation data of 687 stations in China during 1958-2000, and the pentad precipitation of CMAP/NOAA from 1979 to 2002 are all analyzed by the space-time filter method. The analysis results, from every drought and flood summer in four different regions of East Asia respectively during 1958-2000, have shown that theflood (drought) in the East Asian summer monsoon region is absolutely companied with the strongly (weakly) westward propagations of ISO from the central-east Pacific, and depends little on the intensity changes of the East Asian summer monsoon.And the westward ISO is usually the low-frequency cyclones and anticyclones from the Bay of Alaska in northeastern Pacific and the Okhotsk in the northwestern Pacific of mid-high latitudes, and the ISO evolving in subtropical easterlies. In mid-high latitudes the phenomena are related to the westward propagating mid-ocean trough and the retreat of blocking high. Therefore the westward propagating ISO from the central-east Pacific to East Asia is indispensable for more rainfall occurring in East Asia in summer, which results from the long-wave adjustment process in the mid-high latitudes and ISO evolving in tropical easterlies.
    Kang I. S.,C. H. Ho, Y. K. Lim, and K. M. Lau, 1999: Principal modes of climatological seasonal and intraseasonal variations of the Asian summer monsoon. Mon. Wea. Rev., 127, 322-340,https://doi.org/10.1175/1520-0493(1999)127<0322:PMOCSA>2.0.CO;2
    Kikuchi K.,B. Wang, 2010: Formation of tropical cyclones in the northern Indian Ocean associated with two types of tropical intraseasonal oscillation modes. J. Meteor. Soc. Japan, 88(3), 475-496, https://doi.org/10.2151/jmsj.2010-313
    Kikuchi K.,B. Wang, and Y. Kajikawa, 2012: Bimodal representation of the tropical intraseasonal oscillation. Climate Dyn., 38, 1989-2000, https://doi.org/10.1007/s00382-011-1159-1
    Knutson T. R.,K. M. Weickmann, 1987: 30-60 day atmospheric oscillations: Composite life cycles of convection and circulation anomalies. Mon. Wea. Rev., 115, 1407-1436, https://doi.org/10.1175/1520-0493(1987)115<1407:DAOCLC>2.0.CO;2
    Kummerow, C., Coauthors, 2000: The status of the Tropical Rainfall Measuring Mission (TRMM) after two years in orbit. Journal of Applied Meteorology and Climatology, 39, 1965-1982, https://doi.org/10.1175/1520-0450(2001)040<1965:TSOTTR>2.0.CO;2
    Lau K. M.,P. H. Chan, 1985: Aspects of the 40-50 day oscillation during the northern winter as inferred from outgoing Longwave radiation. Mon. Wea. Rev., 113, 1889-1909, https://doi.org/10.1175/1520-0493(1985)113<1889:AOTDOD>2.0.CO;2
    Lau K. M.,P. H. Chan, 1986: Aspects of the 40-50 day oscillation during the northern summer as inferred from outgoing longwave radiation. Mon. Wea. Rev., 114, 1354-1367, https://doi.org/10.1175/1520-0493(1986)114<1354:AOTDOD>2.0.CO;2
    Lau K. M.,T. J. Phillips, 1986: Coherent fluctuations of fxtratropical geopotential height and tropical convection in intraseasonal time scales. J. Atmos. Sci., 43, 1164-1181, https://doi.org/10.1175/1520-0469(1986)043<1164:CFOFGH>2.0.CO;2
    Lau W. K. M.,D. E. Waliser, 2012: Intraseasonal Variability in the Atmosphere-ocean Climate System. 2nd ed. Springer, 581 pp.10.1007/b1388178e72ee2bed312cfd82ecc20caba2cb1bhttp%3A%2F%2Flink.springer.com%2F10.1007%2Fb138817http://link.springer.com/10.1007/b138817This is the first comprehensive review of intra-seasonal variability (ISV); the contents are balanced between observation, theory and modeling. Starting with an overview of ISV and historical observations, the book addresses the coupling between ocean and atmosphere, and the worldwide role of ISV in monsoon variability. Also considered are the connections between oscillations like the Madden, Julian and El Nino/Southern and short-term climate.
    Lau W. K. M.,D. E. Waliser, and B. J. Tian, 2012: Chemical and biological impacts. Intraseasonal Variability in the Atmosphere-Ocean Climate System, W. K. M. Lau and D. E. Waliser, Eds., Springer-Verlag, 569, https://doi.org/10.1007/978-3-642-13914-7
    Lawrence D. M.,P. J. Webster, 2002: The boreal summer intraseasonal oscillation: Relationship between northward and eastward movement of convection. J. Atmos. Sci., 59, 1593, https://doi.org/10.1175/1520-0469(2002)059<1593:TBSIOR>2.0.CO;2
    Lee J.,B. Wang, M. C. Wheeler, X. H. Fu, D. E. Waliser, and I. S. Kang, 2013: Real-time multivariate indices for the boreal summer intraseasonal oscillation over the Asian summer monsoon region. Climate Dyn., 40, 493-509, https://doi.org/10.1007/s00382-012-1544-4
    Li C. Y.,J. B. Wu, 2000: On the onset of the South China Sea summer monsoon in 1998. Adv. Atmos. Sci., 17, 193-204, https://doi.org/10.1007/s00376-000-0003-z
    Li K. F.,B. Tian, D. E. Waliser, M. J. Schwartz, J. L. Neu, J. R. Worden, and Y. L. Yung, 2012: Vertical structure of MJO-related subtropical ozone variations from MLS, TES, and SHADOZ data. Atmos Chem Phys, 12, 425-436, https://doi.org/10.5194/acp-12-425-2012
    Liebmann B.,C. A. Smith, 1996: Description of a complete (interpolated) outgoing longwave radiation dataset. Bull. Amer. Meteor. Soc., 77, 1275- 1277.
    Lin M.,T. Holloway, T. Oki, D. G. Streets, and A. Richter, 2009: Multi-scale model analysis of boundary layer ozone over East Asia. Atmos Chem Phys, 9, 3277-3301, https://doi.org/10.5194/acp-9-3277-2009
    Liu C. X.,Y. Liu, Z. N. Cai, S. T. Gao, D. R. Lü, and E. Kyrölä, 2009: A Madden-Julian Oscillation-triggered record ozone minimum over the Tibetan Plateau in December 2003 and its association with stratospheric "low-ozone pockets". Geophys. Res. Lett., 36, L15830, https://doi.org/10.1029/2009GL039025
    Liu C. X.,Y. Liu, Z. N. Cai, S. T. Gao, J. C. Bian, and X. Liu, and K. Chance, 2010a: Dynamic formation of extreme ozone minimum events over the Tibetan Plateau during northern winters 1987-2001. J. Geophys. Res., 115, D18311, https://doi.org/10.1029/2009JD013130
    Liu C. X.,B. J. Tian, K. F. Li, G. L. Manney, N. J. Liversey, Y. L. Yung, and D. E. Waliser, 2014: Northern Hemisphere mid-winter vortex-displacement and vortex-split stratospheric sudden warmings: Influence of the Madden-Julian Oscillation and Quasi-Biennial Oscillation. J. Geophys. Res., 119, 12 599-12 620, https://doi.org/10.1002/2014JD021876
    Liu C. X.,Y. Liu, and Y. L. Zhang, 2015a: Simulation of the Madden-Julian Oscillation in wintertime stratospheric ozone over the Tibetan Plateau and East Asia: Results from the specified dynamics version of the Whole Atmosphere Community Climate Model. Atmospheric and Oceanic Science Letters, 8, 264-270, https://doi.org/10.3878/AOSL20150020
    Liu, H. Y.,Coauthors, 2002: Sources of tropospheric ozone along the Asian Pacific Rim: An analysis of ozonesonde observations. J. Geophys. Res., 107, ACH 3-1-ACH 3-19, https://doi.org/10.1029/2001JD002005
    Liu X.,P. K. Bhartia, K. Chance, R. J. D. Spurr, and T. P. Kurosu, 2010b: Ozone profile retrievals from the Ozone Monitoring Instrument. Atmos. Chem. Phys., 10, 2521-2537, https://doi.org/10.5194/acp-10-2521-2010
    Liu Y.,Y. L. Zhang, Y. Wang, C. X. Liu, Z. N. Cai, P. Konopka, and R. Müller, 2015b: Dominant modes of tropospheric ozone variation over East Asia from GOME observations. Advances in Meteorology, 2015, Article ID 879578, https://doi.org/10.1155/2015/879578
    Lu X.,L. Zhang, X. Liu, M. Gao, Y. H. Zhao, and J. Y. Shao, 2018: Lower tropospheric ozone over India and its linkage to the South Asian monsoon. Atmos. Chem. Phys., 18, 3101-3188, https://doi.org/10.5194/acp-18-3101-2018
    Madden R. A.,1986: Seasonal variations of the 40-50 day oscillation in the tropics. J. Atmos. Sci., 43, 3138-3158, https://doi.org/10.1175/1520-0469(1986)043<3138:SVOTDO>2.0.CO;2
    Madden R. D.,P. R. Julian, 1971: Detection of a 40-50 day oscillation in the zonal wind in the tropical Pacific. J. Atmos. Sci., 28, 702, https://doi.org/10.1175/1520-0469(1971)028<0702:DOADOI>2.0.CO;2
    Madden R. D.,P. R. Julian, 1972: Description of global-Scale circulation cells in the tropics with a 40-50 day period. J. Atmos. Sci., 29, 1109, https://doi.org/10.1175/1520-0469(1972)029<1109:DOGSCC>2.0.CO;2
    Madden R. D.,P. R. Julian, 1994: Observations of the 40-50-day tropical oscillation——A review. Mon. Wea. Rev., 122, 814, https://doi.org/10.1175/1520-0493(1994)122<0814:OOTDTO>2.0.CO;2
    Matthews A. J.,B. J. Hoskins, and M. Masutani, 2004: The global response to tropical heating in the Madden-Julian oscillation during the northern winter. Quart. J. Roy. Meteor. Soc., 130, 1991-2011, https://doi.org/10.1256/qj.02.123
    Monks, P. S.,Coauthors, 2009: Atmospheric composition change - global and regional air quality. Atmos. Environ., 43, 5268-5350, https://doi.org/10.1016/j.atmosenv.2009.08.021
    Pohl B.,Y. Richard, and N. Fauchereau, 2007: Influence of the Madden-Julian oscillation on southern African summer rainfall. J. Climate, 20, 4227-4242, https://doi.org/10.1175/JCLI4231.1
    Pohl B.,N. Fauchereau, C. J. C. Reason, and M. Rouault, 2010: Relationships between the Antarctic oscillation, the Madden-Julian oscillation, and ENSO, and consequences for rainfall analysis. J. Climate, 23, 238-254, https://doi.org/10.1175/2009JCLI2443.1
    Raghavan K.,1973: Break-monsoon over India. Mon. Wea. Rev., 101, 33, https://doi.org/10.1175/1520-0493(1973)101<0033:BOI>2.3.CO;2
    Rajeevan M.,S. Gadgil, and J. Bhate, 2010: Active and break spells of the Indian summer monsoon. Journal of Earth System Science, 119(3), 229-247, https://doi.org/10.1007/s12040-010-0019-4
    Sabutis J. L.,J. L. Stanford, and K. P. Bowman, 1987: Evidence for 35-50 day low frequency oscillations in total ozone mapping spectrometer data. Geophys. Res. Lett., 14, 945-947, https://doi.org/10.1029/GL014i009p00945
    Samanta D.,M. K. Dash, B. N. Goswami, and P. C. Pandey, 2016: Extratropical anticyclonic Rossby wave breaking and Indian summer monsoon failure. Climate Dyn., 46, 1547-1562, https://doi.org/10.1007/s00382-015-2661-7
    Tian B.,Y. L. Yung, D. E. Waliser, T. Tyranowski, L. Kuai, E. J. Fetzer, and F. W. Irion, 2007: Intraseasonal variations of the tropical total ozone and their connection to the Madden-Julian Oscillation. Geophys. Res. Lett., 34, L08704, https://doi.org/10.1029/2007GL029451
    Tian B. J.,D. E. Waliser, R. A. Kahn, and S. Wong, 2011: Modulation of Atlantic aerosols by the Madden-Julian Oscillation. J. Geophys. Res., 116, D15108, https://doi.org/10.1029/2010JD015201
    Waliser D. E.,2006: Intraseasonal variability. The Asian Monsoon, B. Wang, Ed., Springer, 203, https://doi.org/10.1007/3-540-37722-0
    Wang B.,H. Rui, 1990: Synoptic climatology of transient tropical intraseasonal convection anomalies: 1975-1985. Meteor. Atmos. Phys., 44, 43-61, https://doi.org/10.1007/BF01026810
    Wang B.,P. J. Webster, and H. Y. Teng, 2005: Antecedents and self-induction of active-break south Asian monsoon unraveled by satellites. Geophys. Res. Lett., 32, L04704, https://doi.org/10.1029/2004GL020996
    Wang T.,X. L. Wei, A. J. Ding, C. N. Poon, K. S. Lam, Y. S. Li, L. Y. Chan, and M. Anson, 2009: Increasing surface ozone concentrations in the background atmosphere of Southern China, 1994-2007. Atmospheric Chemistry and Physics, 9(16), 6217-6227, https://doi.org/10.5194/acp-9-6217-2009
    Waugh D. W.,B. M. Funatsu, 2003: Intrusions into the tropical upper troposphere: Three-dimensional structure and accompanying ozone and OLR distributions. J. Atmos. Sci., 60, 637, https://doi.org/10.1175/1520-0469(2003)060<0637:IITTUT>2.0.CO;2
    Wen M.,R. H. Zhang, 2008: Quasi-biweekly oscillation of the convection around Sumatra and low-level tropical circulation in boreal spring. Mon. Wea. Rev., 136, 189-205, https://doi.org/10.1175/2007MWR1991.1
    Wespes C.,D. Hurtmans, C. Clerbaux, and P.-F. Coheur, 2017: O3 variability in the troposphere as observed by IASI over 2008-2016: Contribution of atmospheric chemistry and dynamics. J. Geophys. Res. Atmos., 122(4), 2429-2451, https://doi.org/10.1002/2016JD025875
    Wheeler M. C.,H. H. Hendon, 2004: An all-season real-time multivariate MJO index: Development of an index for monitoring and prediction. Mon. Wea. Rev., 132, 1917-1932, https://doi.org/10.1175/1520-0493(2004)132<1917:AARMMI>2.0.CO;2
    Xu J. L.,Y. X. Zhu, and J. L. Li, 1997: Seasonal cycles of surface ozone and NOx in Shanghai. J. Appl. Meteor., 36, 1424-1429, https://doi.org/10.1175/1520-0450(1997)036<1424:SCOSOA>2.0.CO;2
    Xu X. B.,W. L. Lin, 2011: Trends of tropospheric ozone over China based on satellite data (1979-2005). Advances in Climate Change Research, 2(1), 43-48, https://doi.org/10.3724/SP.J.1248.2011.00043
    Yasunari T.,1979: Cloudiness fluctuations associated with the northern hemisphere summer monsoon. J. Meteor. Soc. Japan, 57, 227-242, https://doi.org/10.2151/jmsj1965.57.3_227
    Zhang C. D.,2005: Madden-Julian oscillation. Rev. Geophys., 43, RG2003, https://doi.org/10.1029/2004RG000158
    Zhang C. D.,M. Dong, 2004: Seasonality in the Madden-Julian oscillation. J. Climate, 17, 3169-3180, https://doi.org/10.1175/1520-0442(2004)017<3169:SITMO>2.0.CO;2
    Zhang L.,W. Q. Han, Y. L. Li, and E. D. Maloney, 2018: Role of North Indian Ocean air-sea interaction in summer monsoon intraseasonal oscillation. J. Climate, 31, 7885-7908, https://doi.org/10.1175/JCLI-D-17-0691.1
    Zhang Y. L.,Y. Liu, C. X. Liu, and V. F. Sofieva, 2015: Satellite measurements of the Madden-Julian Oscillation in wintertime stratospheric ozone over the Tibetan Plateau and East Asia. Adv. Atmos. Sci., 32(11), 1481-1492, https://doi.org/10.1007/s00376-015-5005-y
  • [1] ZHAO Chongbo, ZHOU Tianjun, SONG Lianchun, REN Hongli, 2014: The Boreal Summer Intraseasonal Oscillation Simulated by Four Chinese AGCMs Participating in the CMIP5 Project, ADVANCES IN ATMOSPHERIC SCIENCES, 31, 1167-1180.  doi: 10.1007/s00376-014-3211-7
    [2] LIU Xiangwen, WU Tongwen, YANG Song, LI Qiaoping, CHENG Yanjie, LIANG Xiaoyun, FANG Yongjie, JIE Weihua, NIE Suping, 2014: Relationships between Interannual and Intraseasonal Variations of the Asian-Western Pacific Summer Monsoon Hindcasted by BCC_CSM1.1(m), ADVANCES IN ATMOSPHERIC SCIENCES, 31, 1051-1064.  doi: 10.1007/s00376-014-3192-6
    [3] Zheng HE, Pangchi HSU, Xiangwen LIU, Tongwen WU, Yingxia GAO, 2019: Factors Limiting the Forecast Skill of the Boreal Summer Intraseasonal Oscillation in a Subseasonal-to-Seasonal Model, ADVANCES IN ATMOSPHERIC SCIENCES, 36, 104-118.  doi: 10.1007/s00376-018-7242-3
    [4] WU Bingyi, 2005: Weakening of Indian Summer Monsoon in Recent Decades, ADVANCES IN ATMOSPHERIC SCIENCES, 22, 21-29.  doi: 10.1007/BF02930866
    [5] E. K. KRISHNA KUMAR, S. ABHILASH, SANKAR SYAM, P. VIJAYKUMAR, K. R. SANTOSH, A.V. SREENATH, 2023: Contrasting Regional Responses of Indian Summer Monsoon Rainfall to Exhausted Spring and Concurrently Emerging Summer El Niño Events, ADVANCES IN ATMOSPHERIC SCIENCES, 40, 697-710.  doi: 10.1007/s00376-022-2114-2
    [6] XIE Fei, LI Jianping, TIAN Wenshou, ZHANG Jiankai, SHU Jianchuan, 2014: The Impacts of Two Types of El Nio on Global Ozone Variations in the Last Three Decades, ADVANCES IN ATMOSPHERIC SCIENCES, 31, 1113-1126.  doi: 10.1007/s00376-013-3166-0
    [7] ZHANG Meigen, XU Yongfu, Itsushi UNO, Hajime AKIMOTO, 2004: A Numerical Study of Tropospheric Ozone in the Springtime in East Asia, ADVANCES IN ATMOSPHERIC SCIENCES, 21, 163-170.  doi: 10.1007/BF02915702
    [8] Bing XIE, Hua ZHANG, Zhili WANG, Shuyun ZHAO, Qiang FU, 2016: A Modeling Study of Effective Radiative Forcing and Climate Response Due to Tropospheric Ozone, ADVANCES IN ATMOSPHERIC SCIENCES, 33, 819-828.  doi: 10.1007/s00376-016-5193-0
    [9] Jae H. KIM, Hyunjin LEE, 2010: What Causes the Springtime Tropospheric Ozone Maximum over Northeast Asia?, ADVANCES IN ATMOSPHERIC SCIENCES, 27, 543-551.  doi: 10.1007/s00376-009-9098-z
    [10] Yu FU, Hong LIAO, Yang YANG, 2019: Interannual and Decadal Changes in Tropospheric Ozone in China and the Associated Chemistry-Climate Interactions: A Review, ADVANCES IN ATMOSPHERIC SCIENCES, 36, 975-993.  doi: 10.1007/s00376-019-8216-9
    [11] LIU Qianxia, ZHANG Meigen, WANG Bin, 2005: Simulation of Tropospheric Ozone with MOZART-2:An Evaluation Study over East Asia, ADVANCES IN ATMOSPHERIC SCIENCES, 22, 585-594.  doi: 10.1007/BF02918490
    [12] GAO Lijie, ZHANG Meigen, HAN Zhiwei, 2009: Model Analysis of Seasonal Variations in Tropospheric Ozone and Carbon Monoxide over East Asia, ADVANCES IN ATMOSPHERIC SCIENCES, 26, 312-318.  doi: 10.1007/s00376-009-0312-9
    [13] CHANG Wenyuan, LIAO Hong, WANG Huijun, 2009: Climate responses to direct radiative forcing of anthropogenic aerosols, tropospheric ozone, and long-lived greenhouse gases in eastern China over 1951-2000, ADVANCES IN ATMOSPHERIC SCIENCES, 26, 748-762.  doi: 10.1007/s00376-009-9032-4
    [14] Wen CHEN, Renhe ZHANG, Renguang WU, Zhiping WEN, Liantong ZHOU, Lin WANG, Peng HU, Tianjiao MA, Jinling PIAO, Lei SONG, Zhibiao WANG, Juncong LI, Hainan GONG, Jingliang HUANGFU, Yong LIU, 2023: Recent Advances in Understanding Multi-scale Climate Variability of the Asian Monsoon, ADVANCES IN ATMOSPHERIC SCIENCES, 40, 1429-1456.  doi: 10.1007/s00376-023-2266-8
    [15] Kai Chi WONG, Senfeng LIU, Andrew G. TURNER, Reinhard K. SCHIEMANN, 2018: Different Asian Monsoon Rainfall Responses to Idealized Orography Sensitivity Experiments in the HadGEM3-GA6 and FGOALS-FAMIL Global Climate Models, ADVANCES IN ATMOSPHERIC SCIENCES, 35, 1049-1062.  doi: 10.1007/s00376-018-7269-5
    [16] Shuang LIU, Kaiheng HU, Weiming LIU, Paul A. CARLING, 2022: Hydro-climatic Characteristics of Yarlung Zangbo River Basin since the Last Glacial Maximum, ADVANCES IN ATMOSPHERIC SCIENCES, 39, 415-426.  doi: 10.1007/s00376-021-1150-7
    [17] Liang Pingde, Liu Aixia, 1994: Winter Asia Jetstream and Seasonal Precipitation in East China, ADVANCES IN ATMOSPHERIC SCIENCES, 11, 311-318.  doi: 10.1007/BF02658150
    [18] LIAO Hong, CHANG Wenyuan, YANG Yang, 2015: Climatic Effects of Air Pollutants over China: A Review, ADVANCES IN ATMOSPHERIC SCIENCES, 32, 115-139.  doi: 10.1007/s00376-014-0013-x
    [19] YANG Jing, Bin WANG, WANG Bin, LI Lijuan, 2009: The East Asia-Western North Pacific Boreal Summer Intraseasonal Oscillation Simulated in GAMIL 1.1.1, ADVANCES IN ATMOSPHERIC SCIENCES, 26, 480-492.  doi: 10.1007/s00376-009-0480-7
    [20] SUN Ying, DING Yihui, 2008: Effects of Intraseasonal Oscillation on the Anomalous East Asian Summer Monsoon During 1999, ADVANCES IN ATMOSPHERIC SCIENCES, 25, 279-296.  doi: 10.1007/s00376-008-0279-y

Get Citation+

Export:  

Share Article

Manuscript History

Manuscript received: 01 June 2018
Manuscript revised: 25 October 2018
Manuscript accepted: 20 November 2018
通讯作者: 陈斌, bchen63@163.com
  • 1. 

    沈阳化工大学材料科学与工程学院 沈阳 110142

  1. 本站搜索
  2. 百度学术搜索
  3. 万方数据库搜索
  4. CNKI搜索

Intraseasonal Oscillation of Tropospheric Ozone over the Indian Summer Monsoon Region

    Corresponding author: Chuanxi LIU, lcx@mail.iap.ac.cn
  • 1. Key Laboratory of Middle Atmosphere and Global Environment Observation, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China

Abstract: Boreal summer intraseasonal oscillation (BSISO) of lower tropospheric ozone is observed in the Indian summer monsoon (ISM) region on the basis of ERA-Interim reanalysis data and ozonesonde data from the World Ozone and Ultraviolet Radiation Data Centre. The 30-60-day intraseasonal variation of lower-tropospheric ozone shows a northwest-southeast pattern with northeastward propagation in the ISM region. The most significant ozone variations are observed in the Maritime Continent and western North Pacific. In the tropics, ozone anomalies extend from the surface to 300 hPa; however, in extratropical areas, it is mainly observed under 500 hPa. Precipitation caused by BSISO plays a dominant role in modulating the BSISO of lower-tropospheric ozone in the tropics, causing negative/positive ozone anomalies in phases 1-3/5-6. As the BSISO propagates northeastward to the western North Pacific, horizontal transport becomes relatively more important, increasing/reducing tropospheric ozone via anticyclonic/cyclonic anomalies over the western North Pacific in phases 3-4/7-8. As two extreme conditions of the ISM, most of its active/break events occur in BSISO phases 4-7/1-8 when suppressed/enhanced convection appears over the equatorial eastern Indian Ocean and enhanced/suppressed convection appears over India, the Bay of Bengal, and the South China Sea. As a result, the BSISO of tropospheric ozone shows significant positive/negative anomalies over the Maritime Continent, as well as negative/positive anomalies over India, the Bay of Bengal, and the South China Sea in active/break spells of the ISM. This BSISO of tropospheric ozone is more remarkable in break spells than in active spells of the ISM, due to the stronger amplitude of BSISO in the former.

摘要: 本文利用ERA再分析资料和WOUDC臭氧探空资料, 分析了印度季风区夏季对流层臭氧的季节内振荡(BSISO)特征. 结果表明对流层低层臭氧存在着30-60天的季节内振荡, 臭氧异常呈西北-东南向分布, 在季风区向东北方向传播. 最显著的臭氧异常在海洋大陆和西北太平洋区域. 臭氧异常在热带从地面延伸到300hPa, 而在热带外地区臭氧异常主要在500hPa以下. 在热带, BSISO引起的降水是导致臭氧异常的主要原因, 使得在1-3/5-6位相出现了臭氧负/正异常. 然而当BSISO传播到西北太平洋区域时, BSISO引起的大气环流异常对臭氧异常的形成更为重要, 通过反气旋性/气旋性环流异常导致了臭氧在3-4/7-8出现正/负异常. 大多数印度季风的活跃/中断发生在BSISO的4-7/1-8位相, 此时减弱/加强的对流出现在赤道东印度洋, 加强/减弱的对流出现在印度, 孟加拉湾和中国南海. 海洋大陆对流层臭氧出现显著的负/正异常, 印度, 孟加拉湾和中国南海对流层臭氧出现显著的正/负异常. 由于季风中断期BSISO的振幅比季风活跃期更大, 对流层臭氧的季节内振荡也更加显著.

1. Introduction
2. Data and method
  • The daily mean ozone, zonal wind and meridional wind are from the ERA-Interim dataset (e.g., Dee et al., 2011). The climatology of the lower-tropospheric ozone column is from Ozone Monitoring Instrument (OMI) data. OMI ozone profiles in the troposphere have been validated (Liu et al., 2010b) and used in studying lower-tropospheric ozone (Lu et al., 2018). The precipitation related to BSISO is based on TRMM observations (Kummerow et al., 2000). The daily mean outgoing longwave radiation (OLR) data are from the AVHRR instrument onboard NOAA's polar-orbiting spacecraft (Liebmann and Smith, 1996). The time period of these datasets considered in this study is summer (June-August) 2000-2012.

    It has been proven that BSISO has quasi-oscillating periods of 30-60 days (Lee et al., 2013). As a result, a 30-60-day bandpass filter is applied to the daily anomalies (to remove the climatology from the daily mean) of variables like OLR, horizontal wind and ozone to derive their BSISO characteristics (i.e., BSISO-related OLR, horizontal wind and ozone anomalies). However, as bandpass filtering will reduce the effective sample size, the regular Student's t-test is no longer capable of testing the significance of anomalies related to BSISO (e.g., Tian et al., 2011; Liu et al., 2014). Instead, we use a two-tailed Student's t-test with reduced degrees of freedom (Tian et al., 2011; Liu et al., 2014; Zhang et al., 2015) to examine the BSISO-related composite results in this work.

    We use ozonesonde profiles at three stations (Fig. 1) from the World Ozone and Ultraviolet Radiation Data Centre (WOUDC). Hanoi (AAR) station (21.01°N, 105.8°E) is located in northern Vietnam, nearly 90 km away from the coast. Ozonesonde observations have been made every two or three weeks since 2004, with a gap in 2011 and 2012. Sepang Airport (SEP) station (2.73°N, 101.7°E) in Singapore has a long history of ozonesonde observations, every week or every two weeks, since 1998. Naha (NAH) station (26.21°N, 127.69°E) is located in southernmost Japan, observing ozone profiles since 1989.

    Figure 1.  (a) Climatology of the lower-tropospheric ozone column (700 hPa to the surface) in June-July-August, based on OMI observations. The red dots are the three ozonesonde locations. The solid blue line is the northeastward transect, and the blue dashed line is the northward transect. (b) Variance of the BSISO-related lower-tropospheric ozone column (700 hPa to the surface) in June-July-August, based on ERA-Interim data.

  • BSISO is more complicated than wintertime MJO, as it involves the northward propagation of deep convection extending further from the equator to the extratropical Northern Hemisphere. The widely-used real-time multivariate MJO index (Wheeler and Hendon, 2004) is unable to show this northward propagation. Therefore, we use another BSISO index, suggested by (Lee et al., 2013), which is based on multivariate empirical orthogonal function (MV-EOF) analysis of OLR and zonal wind at 850 hPa in the region of (10°S-40°N, 40°-160°E). The BSISO index is defined by the first two principal components (PCs) of the MV-EOF analysis, representing the northward and eastward propagation of the 30-60-day BSISO. The lifecycle of BSISO is divided into eight phases according to this BSISO index, indicating the location of deep convection along its northeast propagation pathway. We select BSISO events with amplitudes greater than 1.0 [(PC12 + PC22)1/2>1.0] in this study.

  • There are intraseasonal variabilities of convection and rainfall over the ISM region. ISM rainfall fluctuates between being copious and scant, referred to as active and break spells of the ISM, respectively. These two spell types are usually defined during the peak monsoon months (July and August) by the average daily rainfall over the core ISM area (18.0°-28.0°N, 65.0°-88.0°E). According to the definition, an active (break) spell of the ISM is a period of three consecutive days or more during which the rainfall anomaly over the core ISM region is more (less) than +1.0 (-1.0) the standard deviation (Rajeevan et al., 2010).

3. ISO of tropospheric ozone
  • Figure 1a shows the climatology of the lower-tropospheric ozone column (700 hPa to the surface) in summer (June-July-August) based on OMI data. The ozone in the midlatitudes is higher than in the tropics, with the most significant gradients at 25°-30°N. In the tropics, the ozone over the western Pacific is lower than over the Indian Ocean.

    After applying a 30-60-day bandpass filter to the lower-tropospheric ozone column, we obtain the variance of BSISO-related ozone in the lower troposphere (Fig. 1b). There are two areas in which the most significant variance is observed: one is the Maritime Continent, especially Malaysia and the Celebes Sea; and the other is the western North Pacific. The lower-tropospheric ozone in these two areas has the most prominent variability on the intraseasonal time scale. The power spectra of the lower-tropospheric ozone (Fig. 2) in the Maritime Continent (5°S-10°N, 100°-140°E) and western North Pacific (15°-30°N, 120°-140°E) confirm that the ozone variance is concentrated in intraseasonal periods of 30-60 days, especially in the Maritime Continent (Fig. 2a).

    Figure 2.  Power spectra of BSISO-related anomalies of the lower-tropospheric ozone column (700 hPa to the surface) in the (a) Maritime Continent and (b) western North Pacific. The red curve is the red-noise spectrum. The lower and upper blue dashed curves are 5% and 95% red-noise significance levels respectively.

  • The lifecycle of BSISO is 30-60 days, as also reported by (Lee et al., 2013). They divided the BSISO's lifecycle into eight phases according to the location of deep convection. The composite 30-60-day bandpass-filtered (BSISO-related) OLR anomalies represent the location of deep convection in each BSISO phase (Figs. 3a-h). The enhanced/suppressed convection (negative/positive OLR anomalies), accompanied by a negative/positive lower-tropospheric ozone column (700 hPa to the surface) anomalies, show a northwest-southeast pattern, which propagates northeastward, during phases 1-8. The BSISO-related deep convection (negative OLR anomalies) generate over the equatorial eastern Indian Ocean in BSISO phase 1 and enhance in phase 2. Simultaneously, negative BSISO-related anomalies of ozone are observed over the eastern Indian Ocean and Maritime Continent. During phases 3-4, the BSISO-related convection weakens slightly and gradually propagates northeastward to India, the Bay of Bengal, and the Maritime Continent. The negative BSISO-related ozone anomalies over the eastern Indian Ocean and Maritime Continent are also reduced in this period. After phase 5, the negative BSISO-related OLR anomalies and the negative ozone anomalies gradually propagate to the western North Pacific, until the start of the next BSISO lifecycle. Similarly, suppressed convection (positive BSISO-related OLR anomalies) develops over the equatorial Indian Ocean in phase 4, and enhances during phases 5-7 with a northeastward propagation. The positive anomalies of BSISO-related ozone are observed over the eastern Indian Ocean and Maritime Continent during this period. As the suppressed convection propagates to the western North Pacific after phase 8, positive ozone anomalies also gradually propagate to the Northwest Pacific until the next phase 5, when positive ozone anomalies develop over the eastern Indian Ocean and Maritime Continent.

    Figure 3.  Composites of BSISO-related (a-h) OLR anomalies (units: W m-2) and (i-p) lower-tropospheric column (700 hPa to the surface) ozone anomalies (units: DU). Positive and negative anomalies are indicated by red solid and blue dashed lines, respectively. The shaded areas are statistically significant at the 95% confidence level, based on a two-tailed Student's t-test with reduced degrees of freedom. The top-right number in each panel indicates the number of days used for each composite.

    However, there are slight inconsistencies between the locations of BSISO-related OLR anomalies and ozone anomalies. For example, when negative/positive OLR anomalies are in the eastern Indian Ocean in phases 1-2/5-6, the most significant negative/positive ozone anomalies are not, instead being situated in the Maritime Continent. These inconsistences indicate that there are more complicated factors influencing the BSISO of lower-tropospheric ozone. Thus, we investigate the factors that might influence the production and transport of lower-tropospheric ozone. Limited by the availability of data, we only find two factors that are closely related to the BSISO of lower-tropospheric ozone: precipitation anomalies and horizontal circulation anomalies. Precipitation will clean ozone precursors like volatile organic compounds in the troposphere and reduce temperature, resulting in a reduction of generated ozone. Horizontal circulation anomalies can transport ozone across the horizontal gradients of ozone, especially in the midlatitudes, where the most significant ozone gradients are observed (Fig. 1a). Furthermore, the composite BSISO-related precipitation anomalies, stream function anomalies, and horizontal wind anomalies (Fig. 4) show the important roles played by the precipitation and horizontal transport caused by BSISO in modulating the BSISO of lower-tropospheric ozone.

    Figure 4.  As in Fig. 3 but for (a-h) TRMM precipitation anomalies (units: mm) and (i-p) stream function anomalies (contours; units: 106 m2 s-1) and horizontal wind anomalies (vectors; units: m s-1) at 850 hPa. The red vectors are statistically significant at the 95% confidence level, based on a two-tailed Student's t-test with reduced degrees of freedom.

    Compared to OLR, BSISO-related positive/negative precipitation anomalies are more consistent with negative/ positive ozone anomalies. In phases 1-3, positive precipitation anomalies extend form the eastern Indian Ocean to the equatorial Western Pacific, resulting in negative ozone anomalies over the Maritime Continent (Figs. 3i and k). At the same time, there is a cyclonic anomaly over the Maritime Continent and an anticyclonic anomaly over the north of the Maritime Continent (Figs. 4i-k). Strong easterly flow between them brings air containing low ozone (Fig. 1a) from the Pacific to the Maritime Continent, reducing the level of tropospheric ozone in the latter. Positive precipitation and anticyclonic anomalies gradually propagate northeastward to the western Pacific after phase 4. In the following phases 5-7, negative precipitation anomalies occur in the Maritime Continent (Figs. 4e-g), causing positive ozone anomalies (Figs. 3e-g). In this period, there is a cyclonic anomaly (Figs. 4m-o) north of the Maritime Continent, which is more powerful than the anticyclonic anomaly over the Maritime Continent. The northwesterly winds at the edge of the cyclone bring air containing more ozone (Fig. 1a) from mainland Southeast Asia to the Maritime Continent, increasing the tropospheric ozone in this area until phase 8, when the cyclonic anomaly propagates northeastward to the western North Pacific.

    It is worth noting that when positive precipitation anomalies propagate to the western North Pacific in phase 6 (Fig. 4f), the negative ozone anomalies become too weak to be observed (Fig. 3n). However, in the following phases 7 and 8, negative ozone anomalies once again occur in the western North Pacific (Figs. 3o and p), which seems inconsistent with disappearing positive precipitation anomalies (Figs. 4g and h). This is because of the strengthened cyclonic anomalies over the western North Pacific (Figs. 4o and p). The southerly winds at the eastern edge of the cyclone bring air containing less ozone in the tropics to the north, reducing the tropospheric ozone in the western North Pacific. Similarly, the positive ozone anomalies in the western North Pacific in phases 3 and 4 (Figs. 3k and l) are caused by northerly winds at the edge of anticyclonic anomalies (Figs. 4k and l).

    In order to elucidate the relative importance of precipitation and horizontal transport, we calculate the correlation between the BSISO-related ozone anomalies and the precipitation anomalies (Fig. 5a) as well as the stream function anomalies at 850 hPa (Fig. 5b). BSISO-related ozone is better correlated with precipitation anomalies in the eastern Indian Ocean and Maritime Continent; however, in the western North Pacific, ozone is better correlated with stream function anomalies. Based on the above analysis, one can conclude that precipitation plays a dominant role in modulating the BSISO of lower-tropospheric ozone in the tropics (eastern Indian Ocean and Maritime Continent). However, horizontal transport is relatively more important for the BSISO of lower-tropospheric ozone in the extratropics (western North Pacific).

    Figure 5.  Correlation coefficients of BSISO-related anomalies of lower-tropospheric column (700 hPa to the surface) ozone with (a) precipitation and (b) 850-hPa stream function (only correlation coefficients greater than 0.5 are plotted).

  • To investigate the vertical structure of the BSISO-related ozone anomaly, we choose two transect locations: northward, almost across AAR station; and northeastward, across SEP station and close to NAH station (Fig. 1). Vertical cross sections of BSISO-related ozone anomalies and stream function anomalies along these two transect locations are compared in Fig. 6. In both cross sections, BSISO-related ozone anomalies are most remarkable in the tropics, where they extend from the surface to almost 300 hPa. Besides, the ozone anomalies in the tropics have a northward tilt as the height increases. When the ozone anomalies propagate to extratropical regions, they quickly weaken with a limited vertical range from the surface to about 700 hPa. As the BSISO-related anomalies continue to propagate northeastward, ozone anomalies are observed over the western North Pacific along the northeastward transect and South Asia along the northward transect.

    Along the northeastward transect, the nearest locations from SEP and NAH stations are marked as vertical red lines (Fig. 6). SEP station experiences the most significant negative/positive ozone anomalies in phases 1-2/5-6; however, in the subtropics, NAH station shows the most significant negative/positive ozone anomalies in phases 8-1/4-5. Along the northward transect, locations nearest to SEP and AAR stations are marked as vertical red lines (Fig. 6). AAR station experiences the most significant negative/positive ozone anomalies in phases 2/6. Therefore, we test ozone profiles in these BSISO phases based on ozonesonde data from SEP, NAH and AAR stations (Fig. 7). At SEP station, the ozonesonde data show larger ozone partial pressure in phases 5-6 than in phases 1-2 at almost every height from the surface to 500 hPa. This is consistent with the most significant positive ozone anomalies in phases 5-6 (Figs. 6e and f) and negative ones in phases 1-2 (Figs. 6a and b), which extend from the surface to 500 hPa in the tropics. When BSISO propagates northeastward to the western North Pacific, the most significant positive/negative ozone anomalies are in phases 4-5/8-1 (Figs. 6d, e, h and a). This is proved by the ozonesonde data from NAH station, which suggest that the lower-tropospheric ozone partial pressure is larger in phases 4-5 than in phases 8-1. At AAR station, the ozone partial pressure in phase 2 is larger than in phase 5 in the lower troposphere, which is also consistent with the positive ozone anomaly in phase 2 (Fig. 6j) and negative one in phase 6 (Fig. 6n).

    Figure 6.  Vertical cross sections of BSISO-related ozone anomalies (units: DU km-1, colored contours) and stream function anomalies (units: 106 m2 s-1, black contours) at two transect locations: (a-h) northeastward transect location (blue solid line in Fig. 1); (i-p) northward transect location (blue dashed line in Fig. 1). The color-shaded areas are statistically significant at the 95% confidence level, based on a two-tailed Student's t-test with reduced degrees of freedom. The top-left number in each panel indicates the number of days used for each composite. The red vertical lines in (a-h) mark the locations nearest to SEP and NAH stations, while those in (i-p) mark the locations nearest to SEP and AAR stations. The values in parentheses denote degrees of latitude (positive for °N, negative for °S) and longitude (°E), respectively.

    Figure 7.  Average ozone profiles (ozone partial pressure) in (a) BSISO phases 1-2 and 5-6 at SEP station, (b) BSISO phases 2 and 5 at AAR station, and (c) BSISO phases 8-1 and 4-5 at NAH station, from WOUDC.

4. Lower-tropospheric ozone anomalies during active/break periods of the ISM
  • The ISM exhibits intraseasonal variability both in terms of its dynamics and chemistry. We demonstrated in section 3 that 30-60-day BSISO exists in the lower-tropospheric ozone of the ISM region. With northeastward propagation, negative and positive tropospheric ozone anomalies occur alternately in the ISM region. Active and break periods are the two extreme conditions of the ISM. During the summer monsoon season, there are opposite patterns of convection and rainfall in these active and break periods of the ISM. An active/break spell of the ISM is defined as a period in which the convection and rainfall in the core of the ISM region are extremely enhanced/suppressed during the peak monsoon months (July and August). In order to reveal the characteristics of 30-60-day BSISO-related tropospheric ozone in active/break spells of the ISM, we first produce a phase plot (Fig. 8) to see the BSISO phases when the active and break spells of the ISM occur.

    Figure 8.  Phase points for active ISM dates (red dots) and break ISM dates (blue dots) in July-August.

    Phase plots are widely used in ISO studies to show the daily location of deep convection, which is then used to define the phase of each day. The normalized PC1 and PC2 of the MV-EOF analysis of OLR and zonal wind at 850 hPa are taken as the y- and x-axis of the plot, respectively, indicating the location of 30-60-day BSISO deep convection in the ISM region. Figure 8 suggests that most active ISM events occur in BSISO phases 4-7, when the 30-60-day bandpass-filtered deep convection (negative BSISO-related OLR anomalies) is over India, the Bay of Bengal, and the South China Sea (Fig. 9a). At the same time, cyclonic anomalies (Fig. 9e) and positive precipitation anomalies (Fig. 9c) are observed in these regions, causing negative ozone anomalies in the lower troposphere (Fig. 9g). Simultaneously, suppressed convection (positive BSISO-related OLR anomalies) exists over the eastern Indian Ocean (Fig. 9a). Anticyclonic anomalies (Fig. 9e) and negative precipitation anomalies (Fig. 9c) extend from the eastern Indian Ocean to the Maritime Continent, resulting in remarkable positive lower-tropospheric ozone anomalies in this area (Fig. 9g).

    Figure 9.  BSISO-related (30-60-day bandpass-filtered) (a, b) OLR anomalies, (c, d) precipitation anomalies, (e, f) stream function anomalies (contours) and horizontal wind anomalies (vectors), and (g, h) lower-tropospheric column (700 hPa to the surface) ozone anomalies, in active (left-hand panels) and break (right-hand panels) periods of the ISM. The shaded areas are statistically significant at the 95% confidence level, based on a two-tailed Student's t-test with reduced degrees of freedom. The top-right number in each panel indicates the number of days used for each composite.

    On the contrary, most break events of the ISM occur in BSISO phases 8-3 (Fig. 8), when the 30-60-day bandpass-filtered deep convection (negative BSISO-related OLR anomalies) is over the eastern Indian Ocean (Fig. 9b). At this time, cyclonic anomalies (Fig. 9f) and positive precipitation anomalies (Fig. 9d) extend from the eastern Indian Ocean to the Maritime Continent, causing the prominent negative ozone anomalies in this area (Fig. 9h). In break spells of the ISM, suppressed convection (positive BSISO-related OLR anomalies) exists over India, the Bay of Bengal, and the South China Sea (Fig. 9b), accompanied by anticyclonic anomalies (Fig. 9f) and negative precipitation anomalies (Fig. 9d). In this scenario, there are positive lower-tropospheric ozone anomalies in these regions.

    It is worth noting that the blue dots are farther from the center circle than the red dots in Fig. 8. This difference means that the amplitudes of BSISO are greater in break spells of the ISM than active spells, especially on some break days during phases 8-2 (Fig. 9). It suggests that BSISO conviction anomalies in break spells of the ISM are greater than in active spells (compare the amplitudes of OLR anomalies in Figs. 10a and b). As a result, BSISO-related ozone anomalies over India and the Maritime Continent seem more significant in break spells than active spells of the ISM.

    To test the difference in ozone between active and break spells in the Maritime Continent, South Asia, and the western North Pacific, we also compare the ozone profiles in active and break spells of the ISM at SEP, AAR and NAH stations, based on ozonesonde observations from WOUDC (Fig. 10). At SEP station, the ozone partial pressure in active spells is greater than in break spells at almost every level under 300 hPa (Fig. 10a). This is consistent with positive ozone anomalies in active spells and negative ozone anomalies in break spells of the ISM over the Maritime Continent (Figs. 9g and h). At almost every level under about 550 hPa at AAR station, the level of ozone in break spells is greater than in active spells (Fig. 10b). This is also consistent with positive ozone anomalies in break spells and negative ozone anomaly in active spells of the ISM over South Asia (Figs. 9g and h). NAH station, located in the northwestern Pacific, where ozone anomalies possess the same BSISO variation as in the Maritime Continent (Figs. 9g and h). This is proven by the ozonesonde data at NAH station, which show that the ozone partial pressure is greater in active spells than in break spells (Fig. 10c).

    Figure 10.  Average ozone profiles (ozone partial pressure) in active (red line) and break (blue line) periods of the ISM at (a) SEP, (b) AAR and (c) NAH ozonesonde stations, from WOUDC.

5. Conclusions
  • In this paper, we prove the existence of a 30-60-day BSISO of lower-tropospheric ozone in the ISM region, with the most significant ozone variances existing in the Maritime Continent and over the western North Pacific. Lower-tropospheric ozone anomalies caused by BSISO in the tropics can extend from the surface, with a northward tilt, to 300 hPa. However, when they propagate northeastward to extratropical areas, they are only observed under 500 hPa.

    Unlike wintertime MJO, which propagates eastward along the equator, BSISO shows a northeastward propagation, which means that the lower-tropospheric ozone anomalies caused by BSISO have the potentially to move further to the north to influence East Asia and the western North Pacific. The 30-60-day negative/positive ozone anomalies, accompanied by enhanced/suppressed convection, show a northwest-southeast distribution, with northeastward propagation, in the ISM region. However, there are some inconsistences between the OLR and ozone anomalies, indicating the existence of other factors that control the BSISO of lower-tropospheric ozone. Among the factors considered influential on tropospheric ozone, we find that precipitation and horizontal circulation anomalies are closely related to the BSISO of lower-tropospheric ozone. Results show that precipitation plays a dominant role in modulating the BSISO of ozone in the tropics, as it reduces precursors and temperature. The most significant negative and positive ozone anomalies occur consistently over the Maritime Continent in phases 1-3 and in phases 4-6. When BSISO propagates northeastward to the western North Pacific, horizontal transport caused by BSISO becomes relatively more important in modulating the BSISO of lower-tropospheric ozone. The southerly winds at the eastern edge of the cyclonic anomaly in the western North Pacific bring air containing low ozone in the tropics to the north, reducing the tropospheric ozone in this region in BSISO phases 7 and 8. Similarly, the positive ozone anomalies in the western North Pacific in phases 3 and 4 are caused by northerly winds at the edge of anticyclonic anomalies.

    We compare the 30-60-day variations of BSISO in active and break spells of the ISM, in which the convection and rainfall in the core ISM region are extremely enhanced and suppressed, respectively. It is shown that most active ISM events occur in BSISO phases 4-7, when suppressed 30-60-day convection appears over the equatorial Indian Ocean and enhanced convection appears over India, the Bay of Bengal, and the South China Sea. Most break events occur in BSISO phases 8-3, when the convection shows an opposite pattern to that in active periods. As a result, the 30-60-day variation of tropospheric ozone shows significant positive/negative anomalies over the Maritime Continent in active/break spell of the ISM, as well as negative/positive anomalies over India, the Bay of Bengal, and the South China Sea. Also, the BSISO in break spells has larger amplitudes than in active spells, suggesting that BSISO in break spells is stronger than in active spells. Therefore, BSISO-related lower-tropospheric ozone anomalies over India and the Maritime Continent are more significant in break spells of the ISM than in active spells.

    Ozone profiles observed at three ozonesonde stations from WOUDC are used in this study. The ozone at Hanoi (AAR) station represents the BSISO-related ozone variation in South Asia, while that at Sepang Airport (SEP) station represents the variation in the Maritime Continent and that at Naha (NAH) station the western North Pacific. By comparing the ozone profiles in different BSISO phases and in active/break spells of ISM, we further confirm the results regarding BSISO-related lower-tropospheric ozone from the ERA-Interim data. However, due to the limited number of stations and frequency of observation, we are unable to provide any further detail regarding BSISO-related tropospheric ozone from the WOUDC ozonesonde dataset.

    Building upon previous studies of dynamic BSISO in the summer monsoon system, we focus here on the related ozone variation in the lower troposphere. As suggest in our study, BSISO in the summer monsoon region potentially modulates lower-tropospheric ozone via the precipitation and horizontal transport among the regions of mainland Asia, the western North Pacific, and the Maritime Continent. The comparison of tropospheric ozone anomalies caused by BSISO between active and break spells of the ISM warns us that BSISO-related ozone anomalies should not be ignored in the ISM region. However, the ISO of tropospheric ozone is a complicated issue, since it is influenced by emissions, transport, and other factors like air-sea interaction, which has recently been proven to be associated with ISM ISO (Zhang et al., 2018). Thus, there remains a a long way to go until we reveal the mystery of the intraseasonal variation of tropospheric ozone and other atmospheric components.

Reference

Catalog

    /

    DownLoad:  Full-Size Img  PowerPoint
    Return
    Return