Iodine chemistry in the eastern pacific marine boundary layer

Journal of Geophysical Research Atmospheres

Volumn 118, Issue 2, 2013, Pages 887-904

  Martín, Juan C Gómez ^a,b   Mahajan, Anoop S ^a,f   Hay, Timothy D ^a   Prados Román, Cristina ^a   Ordóñez, Carlos ^a,g   Macdonald, Samantha M ^b   Plane, John M C ^b   Sorribas, Mar ^c,h   Gil, Manuel ^c   Mora, J Francisco Paredes ^d   Reyes, Mario V Agama ^d   Oram, David E ^e   Leedham, Emma ^e   Saiz Lopez, Alfonso ^a  

^a CSIC   (Spain)

^b UNIVERSITY OF LEEDS   (United Kingdom)

^c INSTITUTO NACIONAL DE TÉCNICA AEROESPACIAL   (Spain)

^d National Institute for Meteorology and Hydrology (INAMHI)   (Ecuador)

^e UNIVERSITY OF EAST ANGLIA   (United Kingdom)

^f INDIAN INSTITUTE OF TROPICAL METEOROLOGY   (India)

^g MET OFFICE   (United Kingdom)

^h UNIVERSITY OF GRANADA   (Spain)

Author keywords

[No Author keywords available]

Indexed keywords

ABSORPTION SPECTROSCOPY; BOUNDARY LAYERS; IODINE; MOLECULES; NITROGEN OXIDES; OZONE LAYER; SUN;

DIFFERENTIAL OPTICAL ABSORPTION SPECTROSCOPY; MARINE BOUNDARY LAYERS; METEOROLOGICAL VARIABLES; NEGATIVE CORRELATION; SATELLITE OBSERVATIONS; SEA SURFACE TEMPERATURE (SST); SLANT COLUMN DENSITIES; ULTRA-FINE AEROSOLS;

LOADING;

AEROSOL; ATMOSPHERIC CHEMISTRY; BENTHIC BOUNDARY LAYER; CHLOROPHYLL A; CONCENTRATION (COMPOSITION); EXPERIMENTAL STUDY; IODINE; MARINE ATMOSPHERE; MIXING RATIO; NUCLEATION; OZONE DEPLETION; SATELLITE IMAGERY; SEA SURFACE TEMPERATURE; TRACE GAS;

PACIFIC OCEAN; PACIFIC OCEAN (EAST);

EID: 84884847654     PISSN: None     EISSN: 21698996     Source Type: Journal    
DOI: 10.1002/jgrd.50132     Document Type: Article

References (81)

1. Allan, B. J., G. McFiggans, J. M. C. Plane, and H. Coe (2000), Observations of iodine monoxide in the remote marine boundary layer, J. Geophys. Res. [Atmos.], 105(D11), 14363-14369, doi:10.1029/1999JD901188.
2. Arnold, S. R., D. V. Spracklen, S. Gebhardt, T. Custer, J. Williams, I. Peeken, and S. Alvain (2010), Relationships between atmospheric organic compounds and air-mass exposure to marine biology, Environ. Chem., 7(3), 232-241, doi:10.1071/EN09144.
3. Bogumil, K., et al. (2003), Measurements of molecular absorption spectra with the SCIAMACHY pre-flight model: Instrument characterization and reference data for atmospheric remote-sensing in the 230-2380 nm region, J. Photochem. Photobiol., A, 157(2-3), 167-184, doi:10.1016/s1010-6030(03)00062-5. (Pubitemid 36519084)
4. Brechtel, F. J., S. M. Kreidenweis, and H. B. Swan (1998), Air mass characteristics, aerosol particle number concentrations, and number size distributions at Macquarie Island during the First Aerosol Characterization Experiment (ACE 1), J. Geophys. Res., 103(D13), 16351-16367, doi:10.1029/97JD03014.
5. Brownell, D. K., R. M. Moore, and J. J. Cullen (2010), Production of methyl halides by Prochlorococcus and Synechococcus, Global Biogeochem. Cycles, 24(2), GB2002, doi:10.1029/2009GB003671.
6. Carpenter, L. J., S. M. MacDonald, M. D. Shaw, R. Kumar, R. W. Saunders, R. Parthipan, J. Wilson, and J. M. C. Plane (2013), Atmospheric iodine levels influenced by sea surface emissions of inorganic iodine, Nat. Geosci., doi:10.1038/ngeo1687.
7. Chameides, W. L., and D. Davis (1980), Iodine: Its possible role in tropospheric photochemistry, J. Geophys. Res., 85(C12), 7383-7398, doi:10.1029/JC085iC12p07383.
8. Chance, K., and R. J. D. Spurr (1997), Ring effect studies; Rayleigh scattering, including molecular parameters for rotational Raman scattering and the Fraunhofer spectrum, Appl. Opt., 36, 5224-5230, doi:10.1364/AO.36.005224.
9. Deser, C., and C. A. Smith (1998), Diurnal and semidiurnal variations of the surface wind field over the tropical Pacific Ocean, J. Clim., 11(7), 1730-1748, doi:10.1175/1520-0442(1998)011<1730:DASVOT>2.0. CO;2. (Pubitemid 128500344)
10. Donguy, J. R., and C. Henin (1980), Surface conditions in the eastern equatorial Pacific related to the Intertropical Convergence Zone of the winds, Deep Sea Res. Part A. Oceanographic Res. Papers, 27(9), 693-714, doi:10.1016/0198-0149(80)90023-0. (Pubitemid 11464830)
11. Draxler, R. R. (1999), HYSPLIT4 user's guide. NOAA Tech. Memo. ERL ARL-230Rep., NOAA Air Resources Laboratory, Silver Spring, MD, USA.
12. Draxler, R. R., and G. D. Hess (1997), Description of the HYSPLIT-4 modeling system. NOAA Tech. Memo. ERL ARL-224Rep., 24 pp, NOAA Air Resources Laboratory, Silver Spring, MD, USA.
13. Draxler, R. R., and G. D. Hess (1998), An overview of the HYSPLIT-4 modeling system of trajectories, dispersion, and deposition, Aust. Meteor. Mag., 47, 295-308. (Pubitemid 128184063)
14. Dubovik, O., B. Holben, T. F. Eck, A. Smirnov, Y. J. Kaufman, M. D. King, D. Tanré, and I. Slutsker (2002), Variability of absorption and optical properties of key aerosol types observed in worldwide locations, J. Atmos. Sci., 59(3), 590-608, doi:10.1175/1520-0469(2002) 059<0590:voaaop>2.0.co;2. (Pubitemid 34838293)
15. Ehn, M., et al. (2010), Growth rates during coastal and marine new particle formation in western Ireland, J. Geophys. Res., 115(D18), D18218, doi:10.1029/2010JD014292.
16. Elderfield, H., and V. W. Truesdale (1980), On the biophilic nature of iodine in seawater, Earth. Planet. Sci. Lett., 50(1), 105-114, doi:10.1016/0012-821x(80)90122-3.
17. Fayt, C., and M. van Roozendael (2011), QDOAS 1.00. Software User Manual.
18. Garland, J. A., and H. Curtis (1981), Emission of iodine from the sea surface in the presence of ozone, J. Geophys. Res., 86, 3183-3186, doi:10.1029/JC086iC04p03183.
19. Gómez Martín, J. C., P. Spietz, and J. P. Burrows (2005), Spectroscopic studies of the I2/O3 photochemistry: Part 1: Determination of the absolute absorption cross sections of iodine oxides of atmospheric relevance, J. Photochem. Photobiol., A, 176(1-3 In Honour of Professor Richard P. Wayne), 15-38, doi:10.1016/j.jphotochem.2005.09.024. (Pubitemid 41722486)
20. Gómez Martín, J. C., J. Blahins, U. Gross, T. Ingham, A. Goddard, A. S. Mahajan, A. Ubelis, and A. Saiz-López (2011), In situ detection of atomic and molecular iodine using resonance and off-resonance fluorescence by lamp excitation: ROFLEX, Atmos. Meas. Tech., 4, 29-45, doi:10.5194/amt-4-29-2011.
21. GOOS (2012), (Global Ocean Observing System), International Argo Program, http://www.argo.ucsd.edu/Accessed: January 2012.
22. Graham, M. H., B. P. Kinlan, L. D. Druehl, L. E. Garske, and S. Banks (2007), Deep-water kelp refugia as potential hotspots of tropical marine diversity and productivity, Proc. Nat. Acad. Sci. U.S.A., 104(42), 16576-16580, doi:10.1073/pnas.0704778104. (Pubitemid 350211060)
23. Grainger, J. F., and J. Ring (1962), Anomalous Fraunhofer line profiles, Nature, 193, 762, doi:10.1038/193762a0.
24. Hartten, L. M., and P. A. Datulayta (2004), Seasonal and interannual variations in the daily cycle of winds over the Galapagos, J. Clim., 17(23), 4522-4530, doi:10.1175/3217.1. (Pubitemid 40098861)
25. Hay, T. D., G. E. Bodeker, K. Kreher, R. Schofield, B. Lileya, M. Scherera, and A. J. McDonald (2012), The NIMO Monte Carlo radiative transfer model for box air-mass-factor and radiance calculations, J. Quant. Spectrosc. Radiat. Transfer, doi:10.1016/j.jqsrt.2012.1002.1005.
26. Hayes, S. P., M. J. McPhaden, and J. M. Wallace (1989), The influence of sea-surface temperature on surface wind in the eastern equatorial Pacific: Weekly to monthly variability, J. Clim., 2(12), 1500-1506, doi:10.1175/1520- 0442(1989)002<1500:TIOSST>2.0.CO;2.
27. Heintzenberg, J., D. C. Covert, and R. Van Dingenen (2000), Size distribution and chemical composition of marine aerosols: A compilation and review, Tellus, 52B, 1104-1122, doi:10.1034/j.1600-0889.2000.00136.x.
28. Hill, V. L., and S. L. Manley (2009), Release of reactive bromine and iodine from diatoms and its possible role in halogen transfer in polar and tropical oceans, Limnol. Oceanogr., 54, 812-822, doi:10.4319/lo.2009.54.3.0812.
29. Hu, R. M., R. V. Martin, and T. D. Fairlie (2007), Global retrieval of columnar aerosol single scattering albedo from space-based observations, J. Geophys. Res., 112(D2), D02204, doi:10.1029/2005jd006832. (Pubitemid 47260879)
30. Jammoul, A., S. Dumas, B. D'Anna, and C. George (2009), Photoinduced oxidation of sea salt halides by aromatic ketones: A source of halogenated radicals, Atmos. Chem. Phys., 9(13), 4229-4237, doi:10.5194/acp-9- 4229-2009.
31. Jones, C. E., K. E. Hornsby, R. Sommariva, R. M. Dunk, R. von Glasow, G. McFiggans, and L. J. Carpenter (2010), Quantifying the contribution of marine organic gases to atmospheric iodine, Geophys. Res. Lett., 37 (18), L18804, doi:10.1029/2010GL043990.
32. Kudo, R., A. Uchiyama, A. Yamazaki, E. Kobayashi, and T. Nishizawa (2008), Retrieval of aerosol single-scattering properties from diffuse and direct irradiances: Numerical studies, J. Geophys. Res., 113(D9), D09204, doi:10.1029/2007jd009239.
33. Lai, S., J. Williams, S. R. Arnold, E. Atlas, S. Gebhardt, and T. Hoffmann (2011), Iodine containing species in the remote marine boundary layer: A link to oceanic phytoplankton, Geophys. Res. Lett., 38, L20801, 20801-20805, doi:10.1029/2011GL049035.
34. Lee, J. D., et al. (2010), Reactive halogens in the marine boundary layer (RHaMBLe): The tropical North Atlantic experiments, Atmos. Chem. Phys., 10(3), 1031-1055, doi:10.5194/acp-10-1031-2010.
35. Mahajan, A. S., M. Sorribas, J. C. Gómez Martín, S. M. MacDonald, M. Gil, J. M. C. Plane, and A. Saiz-Lopez (2010a), Concurrent observations of atomic iodine, molecular iodine and ultrafine particles in a coastal environment, Atmos. Chem. Phys., 10, 27227-27253, doi:10.5194/acp-11- 2545-2011.
36. Mahajan, A. S., J. M. C. Plane, H. Oetjen, L. Mendes, R. W. Saunders, A. Saiz-Lopez, C. E. Jones, L. J. Carpenter, and G. B. McFiggans (2010b), Measurement and modelling of tropospheric reactive halogen species over the tropical Atlantic Ocean, Atmos. Chem. Phys., 10(10), 4611-4624, doi:10.5194/acp-10-4611-2010.
37. Mahajan, A. S., et al. (2010c), Evidence of reactive iodine chemistry in the Arctic boundary layer, J. Geophys. Res., 115, D20303, doi:10.1029/ 2009JD013665.
38. Mahajan, A. S., et al. (2012), Latitudinal distribution of reactive iodine in the eastern Pacific and link to open ocean sources, Atmos. Chem. Phys. Disc., 12, 11609-11617, doi:10.5194/acp-12-11609-2012.
39. Martino, M., G. P. Mills, J. Woeltjen, and P. S. Liss (2009), A new source of volatile organoiodine compounds in surface seawater, Geophys. Res. Lett., 36, L01609, doi:10.1029/2008GL03633.
40. NASA-GSFC (2012), Ocean Color Web, http://oceancolor.gsfc.nasa.gov Accessed: January 2012.
41. NASA (2012), Giovanni 3.1.0.1, http://gdata2.sci.gsfc.nasa.gov/daac-bin/ G3/gui.cgi?instance-id=omil2g, Accessed: January 2012.
42. NOAA (2012), El Niño/Southern Oscillation (ENSO) Diagnostic discussion (Climate Prediction Center/NCEP), http://www.cpc.ncep.noaa.gov/ products/analysis-monitoring/enso-advisory/ensodisc.html, Accessed: January 2012.
43. O'Dowd, C. D., et al. (2002), Coastal new particle formation: Environmental conditions and aerosol physicochemical characteristics during nucleation bursts, J. Geophys. Res. [Atmos.], 107(D19), 8107, doi:10.1029/2000JD000206. (Pubitemid 44793934)
44. O'Dowd, C. D., C. Monahan, and M. Dall'Osto (2010), On the occurrence of open ocean particle production and growth events, Geophys. Res. Lett., 37(19), L19805, doi:10.1029/2010GL044679.
45. Oetjen, H. (2009), Measurements of halogen oxides by scattered sunlight differential optical absorption spectroscopy, PhD Thesis, University of Bremen thesis, Bremen, Germany, Bremen.
46. Ordóñez, C., J.-F. Lamarque, S. Tilmes, D. E. Kinnison, E. L. Atlas, D. R. Blake, G. S. Santos, G. Brasseur, and A. Saiz-Lopez (2012), Bromine and iodine chemistry in a global chemistry-climate model: Description and evaluation of very short-lived oceanic sources, Atmos. Chem. Phys., 12, 1423-1447, doi:10.5194/acp-12-1423-2012.
47. Pak, H., and J. R. V. Zaneveld (1974), Equatorial front in the eastern Pacific Ocean, J. Phys. Oceanogr., 4(4), 570-578, doi:10.1175/1520-0485(1974) 004<0570:efitep>2.0.co;2.
48. Peters, E., K. Grossmann, U. Frieß, F.Wittrock, A. Richte, and J. P. Burrows (2011), MAX-DOAS IO and BrO measurements in the western Pacific boundary layer, Geophys. Res. Abstr., 13, EGU2011-2758.
49. Plane, J. M. C., and A. Saiz-Lopez (2006), UV-visible differential optical absorption spectroscopy (DOAS), in Analytical Techniques for Atmospheric Measurement, edited by D. E. Heard, Blackwell Publishing, Oxford, UK.
50. Read, K. A., et al. (2008), Extensive halogen-mediated ozone destruction over the tropical Atlantic Ocean, Nature, 453(7199), 1232-1235, doi:10.1038/nature07035. (Pubitemid 351913601)
51. Reeser, D. I., A. Jammoul, D. Clifford, M. Brigante, B. D'Anna, C. George, and D. J. Donaldson (2008), Photoenhanced reaction of ozone with chlorophyll at the seawater surface, J. Phys. Chem. C, 113(6), 2071- 2077, doi:10.1021/jp805167d.
52. Rodgers, C. D. (2000), Inverse Methods for Atmospheric Sounding: Theory and Practice, 1st ed., World Scientific Publishing, Singapore.
53. Roemmich, D., and J. Gilson (2009), The 2004-2008 mean and annual cycle of temperature, salinity, and steric height in the global ocean from the Argo Program, Prog. Oceanogr., 82, 81-100, doi:10.1016/j.pocean.2009.03.004.
54. Rothman, L. S., et al. (2003), The HITRAN molecular spectroscopic database: Edition of 2000 including updates through 2001, J. Quant. Spectrosc. Radiat. Transfer, 82(1-4), 5-44, doi:10.1016/S0022-4073(03)00146-8. (Pubitemid 37084481)
55. Saiz-Lopez, A., R. W. Saunders, D. M. Joseph, S. H. Ashworth, and J. M. C. Plane (2004), Absolute absorption cross-section and photolysis rate of I2, Atmos. Chem. Phys., 4, 1443-1450, doi:10.5194/acp-4-1443- 2004. (Pubitemid 39316232)
56. Saiz-Lopez, A., et al. (2008), On the vertical distribution of boundary layer halogens over coastal Antarctica: Implications for O3, HOx, NOx and the Hg lifetime, Atmos. Chem. Phys., 8(4), 887-900, doi:10.5194/acp-8-887- 2008.
57. Saiz-Lopez, A., J. M. C. Plane, A. Baker, L. Carpenter, R. von Glasow, J. C. GómezMartín, G. McFiggans, and R. Saunders (2012a), Atmospheric chemistry of iodine, Chem. Rev., 112(3), 1773-1804, doi:10.1021/cr200029u.
58. Saiz-Lopez, A., et al. (2012b), Climate significance of halogen-driven ozone loss in the tropical marine troposphere, Atmos. Chem. Phys., 12, 3939-3949, doi:10.5194/acp-12-3939-2012.
59. Sakamoto, Y., A. Yabushita, M. Kawasaki, and S. Enami (2009), Direct emission of I2 molecule and IO radical from the heterogeneous reactions of gaseous ozone with aqueous potassium iodide solution, J. Phys. Chem. A, 113, 7707-7713, doi:10.1021/jp903486u.
60. Schaeffer, B. A., J. M. Morrison, D. Kamykowski, G. C. Feldman, L. Xie, Y. Liu, W. Sweet, A. McCulloch, and S. Banks (2008), Phytoplankton biomass distribution and identification of productive habitats within the Galapagos Marine Reserve by MODIS, a surface acquisition system, and in-situ measurements, Remote Sens. Environ., 112(6), 3044-3054, doi:10.1016/j.rse.2008.03.005. (Pubitemid 351715365)
61. Schönhardt, A. (2009), DOAS measurements of iodine monoxide from satellite, Ph.D. Thesis, University of Bremen thesis, Bremen, Germany, Bremen, Germany.
62. Schönhardt, A., A. Richter, F. Wittrock, H. Kirk, H. Oetjen, H. K. Roscoe, and J. P. Burrows (2008), Observations of iodine monoxide columns from satellite, Atmos. Chem. Phys., 8(3), 637-653, doi:10.5194/acp-8-637-2008.
63. Sinreich, R., S. Coburn, B. Dix, and R. Volkamer (2010), Ship-based detection of glyoxal over the remote tropical Pacific Ocean, Atmos. Chem. Phys., 10, 11359-11371, doi:10.5194/acp-10-11359-2010.
64. Smythe-Wright, D., S. M. Boswell, P. Breithaupt, R. D. Davidson, C. H. Dimmer, and L. B. Eiras Diaz (2006), Methyl iodide production in the ocean: Implications for climate change, Global Biogeochem. Cycles, 20, GB3003, doi:10.1029/2005GB002642. (Pubitemid 46761022)
65. Spietz, P., J. C. Gómez Martín, and J. P. Burrows (2005), Spectroscopic studies of the I2/O3 photochemistry: Part 2. Improved spectra of iodine oxides and analysis of the IO absorption spectrum, J. Photochem. Photobiol., A, 176(1-3), 50-67, doi:10.1016/j.jphotochem.2005.08.023. (Pubitemid 41722488)
66. Thompson, A. M., et al. (2003), Southern Hemisphere Additional Ozonesondes (SHADOZ) 1998–2000 tropical ozone climatology 2. Tropospheric variability and the zonal wave-one, J. Geophys. Res., 108 (D2), 8241, doi:10.1029/2002JD002241.
67. Thompson, A. M., S. J. Oltmans, D. W. Tarasick, P. von der Gathen, H. G. J. Smit, and J. C. Witte (2011), Strategic ozone sounding networks: Review of design and accomplishments, Atmos. Environ., 45, 2145-2163, doi:10.1016/j. atmosenv.2010.05.002.
68. Trueman, M., and N. d'Ozouville (2010), Characterizing the Galapagos terrestrial climate in the face of global climate change, Galapagos Res., 67, 26-37.
69. Truesdale, V. W., and G. W. Bailey (2002), Iodine distribution in the Southern Benguela system during an upwelling episode, Cont. Shelf Res., 22(1), 39-49, doi:10.1016/s0278-4343(01)00075-9. (Pubitemid 34115665)
70. Truesdale, V. W., A. J. Bale, and E. M. S. Woodward (2000), The meridional distribution of dissolved iodine in near-surface waters of the Atlantic Ocean, Prog. Oceanogr., 45(3-4), 387-400, doi:10.1016/s0079-6611(00) 00009-4. (Pubitemid 30329554)
71. Tsunogai, S., and T. Henmi (1971), Iodine in the surface water of the ocean, J. Ocean. Soc. Jpn., 27(2), 67-72, doi:10.1007/bf02109332.
72. Ueyama, R., and C. Deser (2008), A climatology of diurnal and semidiurnal surface wind variations over the tropical Pacific Ocean based on the tropical atmosphere ocean moored buoy array, J. Clim., 21(4), 593-607, doi:10.1175/JCLI1666.1. (Pubitemid 351395613)
73. Vandaele, A. C., C. Hermans, P. Simon, M. Carleer, R. Colins, F. Fally, M. F. Merienne, A. Jenouvrier, and B. Coquart (1998), Measurements of NO2 absorption cross-sections at 42000 cm-1 to 10000 cm-1 (238-1000 nm) at 220K and 298 K, J. Quant. Spectrosc. Radiat. Transfer, 59, 171-184, doi:10.1016/S0022-4073(97)00168-4.
74. Volkamer, R., P. Spietz, J. P. Burrows, and U. Platt (2005), High resolution absorption cross-section of glyoxal in the UV/vis and IR spectral ranges, J. Photochem. Photobiol., A, 172, 35-46, doi:10.1016/j. jphotochem.2004.11.011. (Pubitemid 40549551)
75. Volkamer, R., S. Coburn, B. Dix, M. Lechner, R. Sinreich, T. Duhl, and A. Guenther (2011), Dissolved organic matter in the surface microlayer: A heterogeneous iodine source over the open ocean, Geophys. Res. Abstr., 13, EGU2011-13678.
76. Vountas, M., V. V. Rozanov, and J. P. Burrows (1998), Ring effect: Impact of rotational Raman scattering on radiative transfer in Earth's atmosphere, J. Quant. Spectrosc. Radiat. Transfer, 60(6), 943-961, doi:10.1016/S0022-4073(97) 00186-6. (Pubitemid 29105871)
77. Wagner, T., B. Dix, C. V. Friedeburg, U. Friess, S. Sanghavi, R. Sinreich, and U. Platt (2004), MAX-DOAS O4 measurements: A new technique to derive information on atmospheric aerosols-principles and information content, J. Geophys. Res., 109, D22205, doi:10.1029/2004JD004904. (Pubitemid 40294871)
78. Wallace, J. M., T. P. Mitchell, and C. Deser (1989), The influence of seasurface temperature on surface wind in the eastern equatorial Pacific: Seasonal and interannual variability, J. Clim., 2(12), 1492-1499, doi:10.1175/1520-0442(1989)002<1492:TIOSST>2.0.CO;2.
79. Whitehead, J. D., G. B. McFiggans, M. W. Gallagher, and M. J. Flynn (2009), Direct linkage between tidally driven coastal ozone deposition fluxes, particle emission fluxes, and subsequent CCN formation, Geophys. Res. Lett., 36, L04806, doi:10.1029/2008GL035969.
80. Worton, D. R., G. P. Mills, D. E. Oram, and W. T. Sturges (2008), Gas chromatography negative ion chemical ionisation mass spectrometry: Application to the detection of alkyl nitrates and halocarbons in the atmosphere, J. Chromatogr. A, 1201(1), 112-119, doi:10.1016/j. chroma.2008.06.019.
81. Yokouchi, Y., et al. (2008), Global distribution and seasonal concentration change of methyl iodide in the atmosphere, J. Geophys. Res., 113, D18311, doi:10.1029/2008JD009861.