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Tracing the Boundary Layer Sources of Carbon Monoxide in the Asian Summer Monsoon Anticyclone Using WRF-Chem


doi: 10.1007/s00376-014-4130-3

  • The Asian summer monsoon (ASM) anticyclone is a dominant feature of the circulation in the upper troposphere-lower stratosphere (UTLS) during boreal summer, which is found to have persistent maxima in carbon monoxide (CO). This enhancement is due to the upward transport of air with high CO from the planetary boundary layer (PBL), and confinement within the anticyclonic circulation. With rapid urbanization and industrialization, CO surface emissions are relatively high in the ASM region, especially in India and East China. To reveal the transport pathway of CO surface emissions over these two regions, and investigate the contribution of these to the CO distribution within the ASM anticyclone, a source sensitivity experiment was performed using the Weather Research and Forecasting (WRF) with chemistry model (WRF-Chem). According to the experiment results, the CO within the ASM anticyclone mostly comes from India, while the contribution from East China is insignificant. The result is mainly caused by the different transportation mechanisms. In India, CO transportation is primarily affected by convection. The surface air with high CO over India is directly transported to the upper troposphere, and then confined within the ASM anticyclone, leading to a maximum value in the UTLS region. The CO transportation over East China is affected by deep convection and large-scale circulation, resulting mainly in transportation to Korea, Japan, and the North Pacific Ocean, with little upward transport to the anticyclone, leading to a high CO value at 215 hPa over these regions.
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  • Bergman J. W., F. Fierli, E. J. Jensen, S. Honomichl, and L. L. Pan, 2013: Boundary layer sources for the Asian anticyclone: Regional contributions to a vertical conduit. J. Geophys. Res.: Atmos., 118, 2560-2575.
    Berthet G., J. G. Esler, and P. H. Haynes, 2007: A Lagrangian perspective of the tropopause and the ventilation of the lowermost stratosphere. J. Geophys. Res.,112(D18), doi: 10.1029/2006JD008295.
    Chen B., X. D. Xu, J. C. Bian, and X. H. Shi, 2010: Sources, pathways and timescales for the troposphere to stratosphere transport over Asian monsoon regions in boreal summer. Chinese J. Atmos. Sci., 34( 3), 495- 505. (in Chinese)
    Chen B., X. D. Xu, S. Yang, and T. L. Zhao, 2012: Climatological perspectives of air transport from atmospheric boundary layer to tropopause layer over Asian monsoon regions during boreal summer inferred from Lagrangian approach. Atmos. Chem. Phys.,12, 4185-4219, doi: 10.5194/acp-12-5827-2012.
    Chen F., J. Dudhia, 2001: Coupling an advanced land-surface/hydrology model with the Penn State/NCAR MM5 modeling system. Part I: Model description and implementation. Mon. Wea. Rev., 129( 4), 569- 585.
    Ding Y. H., J. C. L. Chan, 2005: The East Asian summer monsoon: An overview. Meteor. Atmos. Phys.,89, 117-142, doi: 10.1007/s00703-005-0125-z.
    Dudhia J., 1989: Numerical study of convection observed during the winter monsoon experiment using a mesoscale two-dimensional model. J. Atmos. Sci., 46( 20), 3077- 3107.
    Emmons L.K., Coauthors, 2010: Description and evaluation of the Model for Ozone and Relatedchemical Tracers,version 4 (MOZART-4).Geoscientific Model Development, 3, 43-67, doi: 10.5194/gmd-3-43-2010.
    Gettelman A., D. E. Kinnison, T. J. Dunkerton, and G.P. Brasseur, 2004: Impact of monsoon circulations on the upper troposphere and lower stratosphere. J. Geophys. Res.,109(D22), doi: 10.1029/2004JD004878.
    Grell G.A., D. D\'ev\'enyi, 2002: A generalized approach to parameterizing convection combining ensemble and data assimilation techniques. Geophys. Res. Lett. ,29, 38-1-38-4, doi:10.1029/2002GL015311.
    Hofmann D. J., J. Barnes, M. O'Neill1 M. Trudeau, and R. Neely, 2009: Increase in background stratospheric aerosol observed with lidar at Mauna Loa Observatory and Boulder, Colorado. Geophys. Res. Lett.,36(15), doi: 10.1029/2009GL039008.
    Hong S. Y., J.-O. J. Lim, 2006: The WRF Single-Moment 6-Class Microphysics Scheme (WSM6). Journal of the Korean Meteorological Society, 42( 2), 129- 151.
    Hoskins B. J., M. J. Rodwell, 1995: A model of the Asian summer monsoon I. The global scale. J. Atmos. Sci., 52( 9), 1329- 1340.
    Livesey N.J., Coauthors, 2007: EOS MLS version 2.2 Level 2 data quality and description document. JPL Tech. Doc. JPL D-33509, Jet Propulsion Lab.,Pasadena
    Livesey N.J., Coauthors, 2008: Validation of Aura Microwave Limb Sounder O3and CO observations in the upper troposphere and lower stratosphere. J. Geophys. Res.,113(D15), doi: 10.1029/2007JD008805.
    Li, Q. B., Coauthors, 2005: Convective outflow of South Asianpollution: A global CTM simulation compared with EOS MLS observations. Geophys. Res. Lett.,32(14), doi: 10.1029/2005GL022762.
    Mlawer E. J., S. J. Taubman, P. D. Brown, M. J. Lacono, and S. Clough, 1997: Radiative transfer for inhomogeneous atmospheres: RRTM, a validated correlated-k model for the longwave. J. Geophys. Res., 102( D14), 16663- 16682.
    Neely III, R. R., Coauthors, 2013: Recent anthropogenic increases in SO2 from Asia have minimal impact on stratospheric aerosol. Geophys. Res. Lett.,40(5), 999 -1004, doi: 10.1002/grl.50263.
    Neely III, R. R., P. Yu, K. H. Rosenlof, O.B.Toon, J. S. Daniel, S. Solomon, H. L. Miller, 2014: The contribution of anthropogenic SO2 emissions to the Asian tropopause aerosol layer. J. Geophys. Res.,119, 1571-1579, doi: 10.1002/2013 JD020578.
    Park M., W. J. Rand el, D. E. Kinnison, R. R. Garcia, and W. Choi, 2004: Seasonal variation of methane, water vapor, and nitrogen oxides near the tropopause: Satellite observations and model simulations. J. Geophys. Res.,109(D13), doi: 10.1029/ 2003JD003706.
    Park M., W. J. Rand el, A. Gettelman, S. T. Massie, and J. H. Jiang, 2007: Transport above the Asian summer monsoon anticyclone inferred from Aura Microwave Limb Sounder tracers. J. Geophys. Res.,112(D16), doi: 10.1029/2006JD008294.
    Park M., W. J. Rand el, L. K. Emmons, and N. J. Livesey, 2009: Transport pathways of carbon monoxide in the Asian summer monsoon diagnosed from Model of Ozone and Related Tracers (MOZART). J. Geophys. Res.,114(D8), doi: 10.1029/ 2008JD010621.
    Rand el, W. J., M. Park, 2006: Deep convective influence on the Asian summer monsoon anticyclone and associated tracer variability observed with Atmospheric Infrared Sounder (AIRS). J. Geophys. Res.,111(12), doi: 10.1029/ 2005JD006490.
    Rand el, W. J., F. Wu, A. Gettelman, J. M. Russell III, J. M. Zawodny, S. J. Oltma, 2001: Seasonal variation of water vapor in the lower stratosphere observed in Halogen occultation experiment data. J. Geophys. Res., 106( D13), 14313- 14325.
    Rand el, W. J., M. Park, L. Emmons, D. Kinnison, P. Bernath, K. A. Walker, C. Boone, H. Pumphrey, 2010: Asian monsoon transport of pollution to the stratosphere. Science, 328( 5978), 611- 613.
    Rosenlof K. H., A. F. Tuck, K. K. Kelly, J. M. Russell III, and M. P.McCormick, 1997: Hemispheric asymmetries in water vapor and inferences about transport in the lower stratosphere. J. Geophys. Res.,102(D11), 13213-13234, doi: 10.1029/97JD00873.
    Schoeberl, M. R., Coauthors, 2006: Overview of the EOS aura mission. IEEE Trans. Geosci. Remote Sens.,44(5), 1066-1074, doi: 10.1109/TGRS.2005.861950.
    Skamarock, W. C., Coauthors, 2008: A description of the Advanced Research WRF Version 3. NCAR Tech. Note, NCAR/TN-475+STR, 8 pp.
    Solomon S., J. S. Daniel, R. R. Neely III, J.-P. Vernier, E. G. Dutton, and L. W. Thomason, 2011: The persistently variable background stratospheric aerosol layer and global climate change. Science,333(6044), 866-870, doi: 10.1126/science.1206027.
    Thomason L. W., J. P. Vernier, 2013: Improved SAGE II cloud/aerosol categorization and observations of the Asian tropopause aerosol layer: 1989-2005. Atmos. Chem. Phys., 13( 9), 4605- 4616.
    Thompson G., R. M. Rasmussen, and K. Manning, 2004: Explicit forecasts of winter precipitation using an improved bulk microphysics scheme, Part I: Description and sensitivity analysis. Mon. Wea. Rev., 132, 519- 542.
    Vernier, J. P., Coauthors, 2011: Major influence of tropical volcanic eruptions on the stratospheric aerosol layer during the last decade. Geophys. Res. Lett., 38(12),L12807, doi: 10.1029/2011GL047563.
    Waters, J. W., Coauthors, 2006: The Earth Observing System microwave limb sounder (EOS MLS) on the Aura satellite. IEEE Trans. Geosci. Remote Sens., 44( 5), 1075- 1092.
    Wang P. X., S. Clemens, L. Beaufort, P. Braconnot, G. Ganssen, Z. M. Jian, P. Kershaw, and M. Sarnthein, 2005: Evolution and variability of the Asian monsoon system: State of the art and outstanding issues. Quaternary Science Reviews, 24, 595- 629.
    Wright J. S., R. Fu, S. Fueglistaler, Y. S. Liu, and Y. Zhang , 2011: The influence of summertime convection over Southeast Asia on water vapor in the tropical stratosphere. J. Geophys. Res.,116(D12302), doi: 10.1029/2010JD015416.
    Xiao Y. P., D. J. Jacob, and S. Turquety, 2007: Atmospheric acetylene and its relationship with CO as an indicator of air mass age. J. Geophys. Res., 112,D12305, doi: 10.1029/2006JD008268.
    Zhang Q., Coauthors, 2009: Asian emissions in 2006 for the NASA INTEX-B mission. Atmos. Chem. Phys., 9, 5131- 5153.
  • [1] LU Riyu*, DONG Huilin, SU Qin, and Hui DING, 2014: The 30-60-day Intraseasonal Oscillations over the Subtropical Western North Pacific during the Summer of 1998, ADVANCES IN ATMOSPHERIC SCIENCES, 31, 1-7.  doi: 10.1007/s00376-013-3019-x
    [2] Ren Baohua, Huang Ronghui, 2002: 10-25-Day Intraseasonal Variations of Convection and Circulation Associated with Thermal State of the Western Pacific Warm Pool during Boreal Summer, ADVANCES IN ATMOSPHERIC SCIENCES, 19, 321-336.  doi: 10.1007/s00376-002-0025-9
    [3] REN Baohua, HUANG Ronghui, 2003: 30-60-day Oscillations of Convection and Circulation Associated with the Thermal State of the Western Pacific Warm Pool during Boreal Summer, ADVANCES IN ATMOSPHERIC SCIENCES, 20, 781-793.  doi: 10.1007/BF02915403
    [4] Li Chongyin, Wu Jingbo, 2000: On the Onset of the South China Sea Summer Monsoon in 1998, ADVANCES IN ATMOSPHERIC SCIENCES, 17, 193-204.  doi: 10.1007/s00376-000-0003-z
    [5] Debashis NATH, CHEN Wen, 2013: Investigating the Dominant Source for the Generation of Gravity Waves during Indian Summer Monsoon Using Ground-based Measurements, ADVANCES IN ATMOSPHERIC SCIENCES, 30, 153-166.  doi: 10.1007/s00376-012-1273-y
    [6] Minghao BI, Ke XU, Riyu LU, 2023: Monsoon Break over the South China Sea during Summer: Statistical Features and Associated Atmospheric Anomalies, ADVANCES IN ATMOSPHERIC SCIENCES, 40, 1749-1765.  doi: 10.1007/s00376-023-2377-2
    [7] Kalim ULLAH, GAO Shouting, 2012: Moisture Transport over the Arabian Sea Associated with Summer Rainfall over Pakistan in 1994 and 2002, ADVANCES IN ATMOSPHERIC SCIENCES, 29, 501-508.  doi: 10.1007/s00376-011-0200-y
    [8] Wenshou TIAN, GUO Zhenhai, YU Rucong, 2004: Treatment of LBCs in 2D Simulation of Convection over Hills, ADVANCES IN ATMOSPHERIC SCIENCES, 21, 573-586.  doi: 10.1007/BF02915725
    [9] ZHU Yali, 2012: Variations of the Summer Somali and Australia Cross-Equatorial Flows and the Implications for the Asian Summer Monsoon, ADVANCES IN ATMOSPHERIC SCIENCES, 29, 509-518.  doi: 10.1007/s00376-011-1120-6
    [10] Bueh Cholaw, Ji Liren, Sun Shuqing, Cui Maochang, 2001: EAWM-Related Air-Sea-Land Interaction and the Asian Summer Monsoon Circulation, ADVANCES IN ATMOSPHERIC SCIENCES, 18, 659-673.
    [11] LIU Xiangwen, WU Tongwen, YANG Song, JIE Weihua, NIE Suping, LI Qiaoping, CHENG Yanjie, LIANG Xiaoyun, 2015: Performance of the Seasonal Forecasting of the Asian Summer Monsoon by BCC_CSM1.1(m), ADVANCES IN ATMOSPHERIC SCIENCES, 32, 1156-1172.  doi: 10.1007/s00376-015-4194-8
    [12] ZOU Liwei, ZHOU Tianjun, 2015: Asian Summer Monsoon Onset in Simulations and CMIP5 Projections Using Four Chinese Climate Models, ADVANCES IN ATMOSPHERIC SCIENCES, 32, 794-806.  doi: 10.1007/s00376-014-4053-z
    [13] Song YANG, WEN Min, Rongqian YANG, Wayne HIGGINS, ZHANG Renhe, 2011: Impacts of Land Process on the Onset and Evolution of Asian Summer Monsoon in the NCEP Climate Forecast System, ADVANCES IN ATMOSPHERIC SCIENCES, 28, 1301-1317.  doi: 10.1007/s00376-011-0167-8
    [14] BIAN Jianchun, YAN Renchang, CHEN Hongbin, Lu Daren, Steven T. MASSIE, 2011: Formation of the Summertime Ozone Valley over the Tibetan Plateau: The Asian Summer Monsoon and Air Column Variations, ADVANCES IN ATMOSPHERIC SCIENCES, 28, 1318-1325.  doi: 10.1007/s00376-011-0174-9
    [15] Lu Peisheng, 1995: Evolution of Asian Summer Monsoon and the Slowly Varying Disturbances, ADVANCES IN ATMOSPHERIC SCIENCES, 12, 311-318.  doi: 10.1007/BF02656979
    [16] Yiran GUO, Jie CAO, Hui LI, Jian WANG, Yuchao DING, 2016: Simulation of the Interface between the Indian Summer Monsoon and the East Asian Summer Monsoon: Intercomparison between MPI-ESM and ECHAM5/MPI-OM, ADVANCES IN ATMOSPHERIC SCIENCES, 33, 294-308.  doi: 10.1007/s00376-015-5073-z
    [17] LU Riyu, Buwen DONG, 2008: Response of the Asian Summer Monsoon to Weakening of Atlantic Thermohaline Circulation, ADVANCES IN ATMOSPHERIC SCIENCES, 25, 723-736.  doi: 10.1007/s00376-008-0723-z
    [18] Min WEI, 2005: A Coupled Model Study on the Intensification of the Asian Summer Monsoon in IPCC SRES Scenarios, ADVANCES IN ATMOSPHERIC SCIENCES, 22, 798-806.  doi: 10.1007/BF02918680
    [19] CHEN Bin, XU Xiang-De, YANG Shuai, ZHANG Wei, 2012: On the Temporal and Spatial Structure of Troposphere-to- Stratosphere Transport in the Lowermost Stratosphere over the Asian Monsoon Region during Boreal Summer, ADVANCES IN ATMOSPHERIC SCIENCES, 29, 1305-1317.  doi: 10.1007/s00376-012-1171-3
    [20] WU Bingyi, WANG Dongxiao, HUANG Ronghui, 2003: Relationship between Sea Level Pressures of the Winter Tropical Western Pacific and the Subsequent Asian Summer Monsoon, ADVANCES IN ATMOSPHERIC SCIENCES, 20, 496-510.  doi: 10.1007/BF02915494

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Manuscript received: 23 June 2014
Manuscript revised: 07 November 2014
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Tracing the Boundary Layer Sources of Carbon Monoxide in the Asian Summer Monsoon Anticyclone Using WRF-Chem

  • 1. Key Laboratory of Middle Atmosphere and Global Environment Observation, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029

Abstract: The Asian summer monsoon (ASM) anticyclone is a dominant feature of the circulation in the upper troposphere-lower stratosphere (UTLS) during boreal summer, which is found to have persistent maxima in carbon monoxide (CO). This enhancement is due to the upward transport of air with high CO from the planetary boundary layer (PBL), and confinement within the anticyclonic circulation. With rapid urbanization and industrialization, CO surface emissions are relatively high in the ASM region, especially in India and East China. To reveal the transport pathway of CO surface emissions over these two regions, and investigate the contribution of these to the CO distribution within the ASM anticyclone, a source sensitivity experiment was performed using the Weather Research and Forecasting (WRF) with chemistry model (WRF-Chem). According to the experiment results, the CO within the ASM anticyclone mostly comes from India, while the contribution from East China is insignificant. The result is mainly caused by the different transportation mechanisms. In India, CO transportation is primarily affected by convection. The surface air with high CO over India is directly transported to the upper troposphere, and then confined within the ASM anticyclone, leading to a maximum value in the UTLS region. The CO transportation over East China is affected by deep convection and large-scale circulation, resulting mainly in transportation to Korea, Japan, and the North Pacific Ocean, with little upward transport to the anticyclone, leading to a high CO value at 215 hPa over these regions.

1. Introduction
  • In boreal summer, the Asian summer monsoon (ASM) anticyclone is a dominant feature of the circulation in the upper troposphere-lower stratosphere (UTLS). The anticyclone is a closed circulation, which is primarily a response to the diabatic heating associated with the presence of persistent deep convection (Hoskins and Rodwell, 1995). Analyses of satellite data show that the anticyclone also has persistent maxima (or minima) in various trace constituents in the UTLS region (Rosenlof et al., 1997; Randel et al., 2001; Park et al., 2004; Li et al., 2005; Vernier et al., 2011). The extrema of these constituents are attributed to the trapping effect of the strong winds and closed streamlines associated with the anticyclone, which act to confine air within the anticyclone for a few weeks (Li et al., 2005; Randel and Park, 2006).

    Asia is thought to currently have the fastest growing economy and be the most densely populated region in the world. Thus, anthropogenic emissions over the region are relatively high. Research has shown that the ASM is a key pathway for water vapor and pollutants at low levels to transport into the stratosphere (Randel et al., 2010). However, the source region and upward transport pathway of surface pollutants over the ASM regions remains an issue of uncertainty (Li et al., 2005; Berthet et al., 2007; Park et al., 2009; Randel et al., 2010; Wright et al., 2011; Bergman et al., 2013). (Li et al., 2005) suggested that the surface air from northeast India and southwest China is lifted to the upper troposphere by deep convection and then trapped within the anticyclone. Other research has revealed that planetary boundary layer (PBL) particles from India and East Asia are transported to the anticyclone and to the tropics, respectively (Chen et al., 2010; Chen et al., 2012). (Bergman et al., 2013) indicated that the PBL source from the Tibetan Plateau is also very important for the distribution of atmospheric composition within the anticyclone.

    Tropospheric pollutants, including black carbon, reactive nitrogen species (NO x), sulfur dioxide (SO2), and carbon monoxide (CO), entering the stratosphere, have a significant influence on stratospheric ozone chemistry, microphysics, radiation balance, and the distribution of atmospheric composition. Based on observed data, an increasing trend of stratospheric aerosols was found from 2000 to 2010 (Hofmann et al., 2009; Solomon et al., 2011). During the same period, SO2 emissions from coal combustion in China increased by about 60%, which are believed to one of the most important reasons for the increase in stratospheric aerosols (Hofmann et al., 2009). But (Neely III et al., 2013) offered a different opinion on this. Their simulation results showed that moderate volcanic eruptions are the primary source of the observed increases in stratospheric aerosol. Satellite observations reveal the existence of a layer of aerosol extending vertically from about 13 km to 18 km in the ASM region, which has been termed the Asian tropopause aerosol layer (ATAL) (Vernier et al., 2011; Thomason and Vernier, 2013). The existence of the ATAL is most likely due to anthropogenic emissions. The aerosol microphysical model simulation indicates that Chinese and Indian SO2 emissions contribute about 30% of the sulfate aerosol extinction in the ATAL during volcanically quiescent periods (Neely III et al., 2014).

    Pollutants from the ASM region are rapidly transported to the stratosphere by the vigorous summertime circulation patterns associated with the Asian monsoon. The huge Asian monsoon system can be divided into two subsystems: the Indian (South Asian) and the East Asian monsoon system (Ding and Chan, 2005). These two subsystems have significant differences, dictated by the contrasting sea-land distributions (Wang et al., 2005). In summer, the former features prevailing southwesterly winds, while the latter features prevailing southeasterly winds. India and East China, the two primary sources of pollution emissions, are respectively located in the South Asian and East Asian monsoon system. Thus, the pollutants in these two regions may have different upward transport pathways due to the differences of their monsoon circulation. Using the MOZART-4 (Model for Ozone and Relatedchemical Tracers, version 4), (Park et al., 2009) indicated that the pollution sources over India and East China are the significant source of CO at 100 hPa. But the horizontal resolution they used was 2.8°× 2.8°, meaning that small and medium-scale convection systems may not have been reproduced in the model. The resolution of the Weather Research and Forecasting (WRF) model with chemistry (WRF-Chem) can be customized as required. In this study, we use WRF-Chem to examine the importance of deep convective dynamical transport and the contribution of emissions from India and East China to the CO distribution within the ASM anticyclone. We chose to focus on CO because of the availability of high-resolution global observation products in the UTLS for this gas. Furthermore, CO emissions, whose photochemical lifetime is 1-2 months in the troposphere (Xiao et al., 2007), can act as an index of all anthropogenic emissions.

2. Method and data
  • Version 3.3.1 of WRF-Chem was used in this study. The dynamic scheme and microphysical processes of the WRF model is coupled with a chemistry model in WRF-Chem. The WRF (Skamarock et al., 2008) model uses terrain-following hydrostatic pressure as the vertical coordinate and the Arakawa-C grid for grid staggering. In this work, the simulation domain covers the entire Asia region, with a 60 km horizontal resolution, and there are 41 vertical levels in the model from the surface to about 10 hPa. The model used the Thompson microphysics scheme (Thompson et al., 2004), the Dudhia shortwave radiation algorithm (Dudhia, 1989), the Rapid Radiative Transfer Model (RRTM) (Mlawer et al., 1997) for longwave radiation, the Grell-D\'ev\'enyi ensemble convective parameterization (Grell and D\'ev\'enyi, 2002), the Noah land-surface scheme (Chen and Dudhia, 2001), and the Yonsei University (YSU) atmospheric boundary layer (ABL) scheme (Hong and Lim, 2006). The initial and lateral boundary conditions for meteorological variables were obtained from National Centers for Environmental Prediction (NCEP) Final analysis (FNL) fields, available every 6 h at the spatial resolution of 1°× 1°.

    In this study, we attempted to simulate the transport of CO surface emissions over India and East China, and the chemical reactions were ignored in the model. Initial and boundary conditions for the chemical species in WRF-Chem were extracted from the output of the MOZART-4 global chemical transport model (Emmons et al., 2010). Anthropogenic emissions came from the Intercontinental Chemical Transport Experiment-Phase B inventory, with a horizontal resolution of 0.5°× 0.5° (Zhang et al., 2009). The Reanalysis of Tropospheric Chemical Composition (RETRO) inventories (http://retro.enes.org/data_emissions.shtml), with a horizontal resolution of 0.5°× 0.5°, were used for the regions where the INTEX-B inventory does not provide data. The INTEX-B emissions are representative of the year 2006, and RETRO emissions are representative of the year 2000. The biomass burning emissions came from the Global Fire Emissions Database, version 3, with a horizontal resolution of 0.5°× 0.5°.

    Figure 1.  Horizontal distribution of CO (ppbv) at (a) 215 hPa, (b) 146 hPa, (c) 100 hPa, and (d) 68 hPa during summer (Jun-Aug) 2005-12. Horizontal wind vectors are from NCEP/NCAR reanalysis data.

  • The microwave limb sounder (MLS) instrument aboard the Aura spacecraft, one of the National Aeronautics and Space Administration (NASA) Earth Observing System (EOS) platforms, has been measuring atmospheric parameters since August 2004 (Schoeberl et al., 2006). The MLS field of view vertically scans the limb in the orbit plane and gives 82°S-82°N latitudinal coverage in each orbit (Waters et al., 2006). The horizontal resolution is 3° along the orbit, with 14 orbits per day. Vertical profiles of CO were obtained from version 2.2/level 2 MLS products. The available vertical coverage for CO varies from 215 hPa to 1 hPa (Livesey et al., 2007). We constructed gridded data on 4° (lat) × 8° (lon) grids by averaging profiles. The quality screening of individual profiles was conducted according to the instructions given by (Livesey et al., 2007), and about 80% of the data were retained.

3. Experimental design
  • It is known that there are persistent maxima of CO within the anticyclonic circulation in the UTLS over the ASM region (Li et al., 2005; Park et al., 2007). A global climatological distribution of CO averaged in June-August from 2005 to 2012 in the UTLS is shown in Figure 1. CO has a broad maximum at 215 hPa, 146 hPa, 100 hPa and 68 hPa in the ASM region. At 215 hPa, the distribution of CO reveals three peak areas corresponding to the Asian, North American, and African monsoons, respectively. In the ASM region, the areas of enhanced CO cover the Indian peninsula, East China, and Korea, and the maximum concentration is about 217 ppbv over Southeast China (Fig. 1a). These peaks are associated with the transport of near surface air with high CO, which was transported to the height by the persistent deep convection (Gettelman et al., 2004). From 146 hPa to 68 hPa, the spatial structure of CO is somewhat different to that of 215 hPa. At 146 hPa, 100 hPa, and 68 hPa, the distribution of CO has only a high concentration region linked to the structure of the ASM anticyclonic circulation, and the center of the maximum is located in the southeast of the anticyclone. The CO distribution differences between these regions are primarily due to the difference of the monsoon circulation (Gettelman et al., 2004). The Asian monsoon circulation is higher and deeper, which results in more tropospheric air with high CO being transported to the upper levels. And the isolation of the ASM anticyclone prevents mixing between the inside and outside of the anticyclone, leading to a high CO concentration within the anticyclone. The relatively high CO in the UTLS over the ASM region is evidence of transport from near-surface levels (Li et al., 2005). The North American and African monsoons are smaller, do not reach well into the stratosphere, and are not isolated circulations. At the upper levels, there is more significant mixing of tropospheric air with stratospheric air containing low CO (Gettelman et al., 2004). Therefore, a maximum of CO cannot be formed in these two areas.

    Figure 2.  Mean distributions of CO (ppbv) at 100 hPa during 15 Jun 2006 to 15 Jul 2006 obtained from (a) MLS and (b) WRF. Mean CO (ppbv) concentration at 100 hPa from (c) Indian emissions and (d) East China emissions. Horizontal wind vectors obtained from (a) NCEP/NCAR reanalysis and (b) model results. Inside (15°-30°N, 60°-100°E) and outside (15°-30°N, 150°-180°E) the anticyclone are marked as white rectangles.

    Based on the above analysis, the ASM circulation can transport more surface air with high CO to the UTLS and confine it inside the anticyclone. The CO comes from INTEX-B anthropogenic emissions, and Global Fire Emissions Database (http://www.globalfiredata.org/) during the summer in 2006 are shown in Fig. 2. There are two main surface emission sources——one over India and one over East China. In this study, we address the transport pathway of CO surface emissions over these two regions using WRF-Chem to isolate the transport of specific surface sources of CO. The model simulation was performed with CO tagged in the two regions: India (10°-35°N, 65°-100°E) and East China (20°-40°N, 100°-120°E) (see Fig. 2). The MOZART-4 CO results, which were used for the chemical species initial and boundary conditions, already contained CO global emissions. To reflect the individual contribution of CO emissions over India and East China, the CO emissions over these two regions were additionally superimposed in the model. The contributions of CO emissions were calculated using the model results for India or East China CO emissions minus the model results without these sources. Since it took some time for the surface emissions to be transported to the upper troposphere, during which the CO concentration in the upper troposphere did not achieve a quasi-steady state, the simulated results for the first 15 days are not included in the analysis.

    Figure 3.  CO surface emissions (kg km-2 d-1), including anthropogenic emissions and global fire during summer 2006. Two geographical regions defined in the CO tagged run [India: 10°-35°N, 65°-100°E); East China: (20°-40°N, 100°-120E)] are marked by the purple rectangles.

    Figure 4.  Mean CO (ppbv) concentration at (a) 700 hPa, (b) 500 hPa, (c) 215 hPa, and (d) 146 hPa from Indian emissions. Horizontal wind vectors are from the model results.

4. Results
  • Figures 3a and b present the horizontal structure of MLS and WRF-Chem CO at 100 hPa from 15 June to 15 July 2006.Note that the CO surface emissions in Fig. 3b come from the entire simulation region. The two figures show that the results of the model correspond well with the MLS observations. The MLS results show an area with enhanced CO over the ASM anticyclone at 100 hPa (Fig. 3a), and the model presents the same results. The magnitude in the model result is slightly reduced due to the MLS-observed CO appearing to be a bit higher in the UTLS (Livesey et al., 2008). Figures 3c and d show the mean CO concentration at 100 hPa from CO surface emissions over India and East China, respectively. The horizontal winds for the corresponding pressure levels are plotted in Figs. 3a and b, which come from the NCEP/NCAR (National Center for Atmospheric Research) reanalysis data and WRF results, respectively. To compare the CO concentration inside and outside the ASM anticyclone, we chose two regions according to the horizontal structure of winds. In this paper, the area of (15°-30°N, 60°-100°E) is defined as "inside the anticyclone", and that of (15°-30°N, 150°-180°E) is defined as "outside the anticyclone" (see Fig. 3). Here, we calculate the mean CO concentration differences between these two regions by "inside minus outside". The results are shown in Table 1. The difference in the MLS observations is about 30 ppbv. The difference in the model results is about 19.8 ppbv, of which about 13 ppbv (∼67%) comes from Indian emissions (Fig. 3c) and about 2 ppbv (∼11%) from East China emissions (Fig. 3d). The distribution difference between inside and outside the anticyclone is due to the trapping effect of the strong and closed circulation of the anticyclone (Li et al., 2005). The MLS observations feature a much larger difference of CO concentrations between the inside and outside of the anticyclone than the simulation, which may be caused by many factors, such as the simulated transport flux, source emissions given in the model, CO retrieval uncertainty, and so on. The calculation results suggest the relatively high CO concentration within the anticyclone is from Indian emissions, while the contribution from East China emissions is insignificant. In addition, the CO surface emissions from other regions are also important, contributing ∼ 22% of the distribution of CO within the anticyclone.

    The CO concentration difference between Indian and East China emissions reaches up to 100 hPa, and is thought to be the result of different transport pathways. The CO concentrations at 700 hPa, 500 hPa, 215 hPa, and 146 hPa that come from India and East China are shown in Fig. 4 and Fig. 5, respectively. In the summer of the Northern Hemisphere, the strongest deep convection behavior mainly occurs over North India. The Indian emissions are transported to the upper troposphere (∼200 hPa) by deep convection, where the South Asian High (SAH) anticyclone circulation has formed. The anticyclonic circulation center is located over the Tibetan Plateau. The CO coming from India is confined effectively within the anticyclone, and results in a high concentration center in the UTLS. Compared with India, the convection over East China has lower frequency and a lower level of convection outflow. Thus, the transport of CO is mainly affected by large-scale circulation. Eastern China is located on the east edge of the anticyclone. The southwest airflow at lower levels transports CO toward the northeast (Fig. 5), leading to a maximum over Korea, Japan, and the North Pacific Ocean. The air is then transported southward above 200 hPa due to the northeast airflow on the east side of the anticyclonic circulation. According to this result, it is concluded that the high CO concentrations at 215 hPa (Fig. 1a) over Korea, Japan, and the North Pacific mainly come from East China emissions.

    Figure 5.  The same as in Fig. 4, but for CO surface emissions from East China.

    Figure 6.  Vertical crosssections of simulated CO (ppbv) with convection: (a) 75°-95°E, (b) 100°-120°E; and without convection: (c) 75°-95°E, (d) 100°-120°E. The thermal tropopause derived from the model is denoted as a black dashed line.

    To isolate the effect of convection, a sensitivity experiment was conducted in which latent heating in the model microphysics was turned off. The development of deep convection was subsequently suppressed. Figure 6 shows the vertical crosssections of mean CO from 75°-95°E and 100°-120°E with and without convection. With the effect of deep convection (Figs. 6a and b), there is a plume of high CO from the surface up to around 16 km over 75°-95°E, and the CO extremum center is located at around 14km. On the eastern side (100°-120°E), there is also a plume of high CO from the surface to the upper troposphere. The highest height is about 14 km, which is lower than the region of 75°-95°E, and the CO extremum center is located at about 12 km. Without the effect of deep convection (Figs. 6c and d), both the high CO plume and CO high value center in the upper troposphere disappear over the region 75°-95°E (Fig. 6c). But there is still a slightly higher plume over100°-120°E (Fig. 6d), and the CO extremum center is located at about 10 km.

    The high value plume of CO shown in Fig. 6a corresponds to the strongest deep convection over North India, and the high value plume of CO shown in Fig. 6b corresponds to the deep convection activity of East China. The convection sensitivity experiment shows that the CO surface emissions over India are mainly transported via convection. In India, the strongest deep convection can transport more air to the upper troposphere. The anticyclone circulation over the region then prevents the air from mixing with the air outside. This is the main reason for the high CO concentration distribution over India at the height of between 12 km and 16 km. Whereas, the deep convective activity is relatively weak in East China, and the CO transport is affected by both deep convection and the large-scale circulation. Therefore, even though without convection behavior, there is still a slightly higher plume of CO.

5. Conclusion
  • The ASM anticyclone is a dominant feature of the circulation in the UTLS during summer in the Northern Hemisphere. Observed data show that there are persistent maxima in tropospheric trace constituents, such as HCN, CH4, and CO. Owing to rapid industrialization and urbanization, surface emissions are relatively higher in the ASM region, especially India and East China. The present study used the WRF-Chem model to examine the importance of deep convective dynamical transport and the contributions of Indian and East China emissions to the CO distribution within the ASM anticyclone. To analyze the dynamical transport, we ignored the chemical reaction processes in the model.

    The model results show that most of the CO within the ASM anticyclone comes from India, while the contribution from East China is much smaller. According to the horizontal structure of the wind field at 100 hPa, we defined the area (15°-30°N, 60°-100°E) as "inside the anticyclone". Inside this area, about 67% CO comes from Indian emissions. East China emissions contribute ∼ 2% of the CO concentration within the anticyclone.

    Deep convection over North India is much stronger than that over eastern China, which can transport more air to the upper troposphere. In India, the air with high CO is transported to the upper troposphere via deep convection and confined within the ASM anticyclone, leading to a maximum CO in the UTLS. The CO surface emissions over East China are affected by both deep convection and large-scale circulation. The CO emissions are mainly transported to Korea, Japan, and the North Pacific Ocean, with little upward transport to the anticyclone, leading to high CO concentrations at 215 hPa over these regions.

    This paper focuses mainly on the transport of CO coming from Indian and East China emissions. Furthermore, chemical reaction processes were not considered in the model. There are in fact a number of different transport pathways for different chemical compositions. Thus, more analysis of the transport of near-surface emissions should be carried out, especially short-lived chemical species.

Reference

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