scholarly journals Latitudinal distribution of reactive iodine in the Eastern Pacific and its link to open ocean sources

2012 ◽  
Vol 12 (6) ◽  
pp. 15541-15564 ◽  
Author(s):  
A. S. Mahajan ◽  
J. C. Gómez Martín ◽  
T. D. Hay ◽  
S.-J. Royer ◽  
S. Yvon-Lewis ◽  
...  
Keyword(s):  
Marine Boundary Layer ◽  
Open Ocean ◽  
Eastern Pacific ◽  
Optical Absorption Spectroscopy ◽  
Chl A ◽  
Mixing Ratios ◽  
Southeastern Pacific ◽  
Remote Environment ◽  
Ocean Environment

Abstract. Ship-based Multi-Axis Differential Optical Absorption Spectroscopy measurements of iodine monoxide (IO) and atmospheric and seawater Gas Chromatography – Mass Spectrometer observations of methyl iodide (CH3I) were made in the Eastern Pacific marine boundary layer during April 2010 as a part of the HaloCarbon Air Sea Transect-Pacific (HaloCAST-P) scientific cruise. The presence of IO in the open ocean environment was confirmed, with a maximum differential slant column density of 5 × 1013 molecules cm−2 (corresponding to approximately 1 pptv) measured in the oligotrophic region of the Southeastern Pacific. Such low IO mixing ratios and their observed geographical distribution are inconsistent with satellite estimates and with previous understanding of oceanic sources of iodine. A strong correlation was observed between reactive iodine (defined as IO + I) and CH3I, suggesting common sources. In situ measurements of meteorological parameters and physical ocean variables, along with satellite-based observations of Chlorophyll a (Chl a) and Chromophoric Dissolved Organic Matter (CDOM) were used to gain insight into the possible sources of iodine in this remote environment. Surprisingly, reactive iodine showed a negative correlation (>99% confidence) to Chl a and CDOM across the cruise transect. However, a significant positive correlation (>99% confidence) with sea surface temperature (SST) and salinity instead suggests a widespread abiotic source related to the availability of aqueous iodine and to temperature.

scholarly journals Latitudinal distribution of reactive iodine in the Eastern Pacific and its link to open ocean sources

2012 ◽  
Vol 12 (23) ◽  
pp. 11609-11617 ◽  
Author(s):  
A. S. Mahajan ◽  
J. C. Gómez Martín ◽  
T. D. Hay ◽  
S.-J. Royer ◽  
S. Yvon-Lewis ◽  
...  
Keyword(s):  
Marine Boundary Layer ◽  
Elevation Angle ◽  
Open Ocean ◽  
Eastern Pacific ◽  
Optical Absorption Spectroscopy ◽  
Chl A ◽  
Mixing Ratios ◽  
Southeastern Pacific ◽  
Remote Environment ◽  
Ocean Environment

Abstract. Ship-based Multi-Axis Differential Optical Absorption Spectroscopy measurements of iodine monoxide (IO) and atmospheric and seawater Gas Chromatography-Mass Spectrometer observations of methyl iodide (CH3I) were made in the Eastern Pacific marine boundary layer during April 2010 as a part of the HaloCarbon Air Sea Transect-Pacific (HaloCAST-P) scientific cruise. The presence of IO in the open ocean environment was confirmed, with a maximum differential slant column density of 5 × 1013 molecules cm−2 along the 1° elevation angle (corresponding to approximately 1 pptv) measured in the oligotrophic region of the Southeastern Pacific. Such low IO mixing ratios and their observed geographical distribution are inconsistent with satellite estimates and with previous understanding of oceanic sources of iodine. A strong correlation was observed between reactive iodine (defined as IO + I) and CH3I, suggesting common sources. In situ measurements of meteorological parameters and physical ocean variables, along with satellite-based observations of Chlorophyll a (Chl a) and Chromophoric Dissolved Organic Matter (CDOM) were used to gain insight into the possible sources of iodine in this remote environment. Surprisingly, reactive iodine showed a negative correlation (> 99% confidence) to Chl a and CDOM across the cruise transect. However, a significant positive correlation (> 99% confidence) with sea surface temperature (SST) and salinity instead suggests a widespread abiotic source related to the availability of aqueous iodine and to temperature.

scholarly journals In situ measurements of molecular iodine in the marine boundary layer: the link to macroalgae and the implications for O<sub>3</sub>, IO, OIO and NO<sub>x</sub>

2010 ◽  
Vol 10 (1) ◽  
pp. 361-390
Author(s):  
R.-J. Huang ◽  
K. Seitz ◽  
J. Buxmann ◽  
D. Poehler ◽  
K. E. Hornsby ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Marine Boundary Layer ◽  
Single Point ◽  
Molecular Iodine ◽  
In Situ Measurements ◽  
Gas Chromatography Mass Spectrometry ◽  
Optical Absorption Spectroscopy ◽  
Mixing Ratios ◽  
Concentration Levels

Abstract. "Single-point" in situ measurements of molecular iodine (I2) were carried out in the coastal marine boundary layer (MBL) using diffusion denuders in combination with a gas chromatography-mass spectrometry (GC-MS) method. Comparison measurements were taken at Mace Head and Mweenish Bay, on the West Coast of Ireland. The observed mixing ratios of I2 at Mweenish Bay are much higher than that at Mace Head, indicating the emissions of I2 are correlated with the local algal biomass density and algae species. The concentration levels of I2 were found to correlate inversely with tidal height and correlate positively with the concentration levels of O3 in the surrounding air. However, the released I2 can also lead to O3 destruction via the reaction of O3 with iodine atoms that are formed by the photolysis of I2 during the day and via the reaction of I2 with NOx at night. IO and OIO were measured by long-path differential optical absorption spectroscopy (LP-DOAS). The results show that the concentrations of both daytime and nighttime IO are correlated with the mixing ratios of I2. OIO was observed not only during the day but also, for the first time at both Mace Head and Mweenish Bay, at night. In addition, I2 was measured simultaneously by the LP-DOAS technique and compared with the "single-point" in situ measurement. The results suggest that the local algae sources dominate the inorganic iodine chemistry at Mace Head and Mweenish Bay.

scholarly journals In situ measurements of molecular iodine in the marine boundary layer: the link to macroalgae and the implications for O<sub>3</sub>, IO, OIO and NO<sub>x</sub>

2010 ◽  
Vol 10 (10) ◽  
pp. 4823-4833 ◽  
Author(s):  
R.-J. Huang ◽  
K. Seitz ◽  
J. Buxmann ◽  
D. Pöhler ◽  
K. E. Hornsby ◽  
...  
Keyword(s):  
Marine Boundary Layer ◽  
Algal Species ◽  
Molecular Iodine ◽  
In Situ Measurements ◽  
Gas Chromatography Mass Spectrometry ◽  
Optical Absorption Spectroscopy ◽  
Atmospheric Measurements ◽  
Mixing Ratios ◽  
Inorganic Iodine

Abstract. Discrete in situ atmospheric measurements of molecular iodine (I2) were carried out at Mace Head and Mweenish Bay on the west coast of Ireland using diffusion denuders in combination with a gas chromatography-mass spectrometry (GC-MS) method. I2, IO and OIO were also measured by long-path differential optical absorption spectroscopy (LP-DOAS). The simultaneous denuder and LP-DOAS I2 measurements were well correlated (R2=0.80) but the denuder method recorded much higher concentrations. This can be attributed to the fact that the in situ measurements were made near to macroalgal sources of I2 in the intertidal zone, whereas the LP-DOAS technique provides distance-averaged mixing ratios of an inhomogeneous distribution along the light-path. The observed mixing ratios of I2 at Mweenish Bay were significantly higher than that at Mace Head, which is consistent with differences in local algal biomass density and algal species composition. Above algal beds, levels of I2 were found to correlate inversely with tidal height and positively with the concentrations of O3 in the surrounding air, indicating a role for O3 in the production of I2 from macroalgae, as has been previously suggested from laboratory studies. However, measurements made ~150 m away from the algal beds showed a negative correlation between O3 and I2 during both day and night. We interpret these results to indicate that the released I2 can also lead to O3 destruction via the reaction of O3 with I atoms that are formed by the photolysis of I2 during the day and via the reaction of I2 with NO3 radicals at night. The results show that the concentrations of daytime IO are correlated with the mixing ratios of I2, and suggest that the local algae sources dominate the inorganic iodine chemistry at Mace Head and Mweenish Bay.

scholarly journals Vertical profiles of NO<sub>2</sub>, SO<sub>2</sub>, HONO, HCHO, CHOCHO, and aerosols derived from MAX-DOAS measurements at a rural site in the central-western North China Plain and their relation to emission sources and effects of regional transport

2018 ◽  
Author(s):  
Yang Wang ◽  
Steffen Dörner ◽  
Sebastian Donner ◽  
Sebastian Böhnke ◽  
Isabelle De Smedt ◽  
...  
Keyword(s):  
Trace Gases ◽  
Rural Site ◽  
Optical Absorption Spectroscopy ◽  
Vertical Profiles ◽  
Regional Transport ◽  
Near Surface ◽  
North West ◽  
Mixing Ratios ◽  
Chemistry Research

Abstract. A Multi Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) instrument was deployed in May and June 2016 at a monitoring station (37.18° N, 114.36° E) in the suburban area of Xingtai (one of the most polluted cities in China) during the Atmosphere-Aerosol-Boundary Layer-Cloud (A2BC) and Air chemistry Research In Asia (ARIAs) joint experiments to derive tropospheric vertical profiles of NO2, SO2, HONO, HCHO, CHOCHO and aerosols. Aerosol optical depths derived from MAX-DOAS were found to be consistent with collocated sun-photometer measurements. Also the derived near-surface aerosol extinction and HCHO mixing ratio agree well with coincident visibility meter and in situ HCHO measurements, with mean HCHO near-surface mixing ratios of ~ 3.5 ppb. Underestimates of MAX-DOAS results compared to in situ measurements of NO2 (~ 60 %), SO2 (~ 20 %) are found expectedly due to vertical and horizontal inhomogeneity of trace gases. Vertical profiles of aerosols and NO2, SO2 are reasonably consistent with those measured by a collocated Raman Lidar and aircraft spirals over the station. The deviations can be attributed to differences in sensitivity as a function of altitude and substantial horizontal gradients of pollutants. Aerosols, HCHO, and CHOCHO profiles typically extended to higher altitudes (with 75 % integrated column located below ~ 1.4 km) than did NO2, SO2, and HONO (with 75 % integrated column below ~ 0.5 km) under polluted condition. Lifted layers were systematically observed for all species, (except HONO), indicating accumulation, secondary formation, or long-range transport of the pollutants at higher altitudes. Maximum values routinely occurred in the morning for NO2, SO2, and HONO, but around noon for aerosols, HCHO, and CHOCHO, mainly dominated by photochemistry, characteristic upslope/downslope circulation and PBL dynamics. Significant day-to-day variations are found for all species due to the effect of regional transport and changes in synoptic pattern analysed with HYSPLIT trajectories. Low pollution was often observed for air masses from the north-west (behind cold fronts), and high pollution from the southern areas such as industrialized Wuan. The contribution of regional transport for the pollutants measured at the site during the observation period was estimated to be about 20 % to 30 % for trace gases, and about 50 % for aerosols. In addition, agricultural burning events impacted the day-to-day variations of HCHO, CHOCHO and aerosols.

The Airyx 2D SkySpec instrument: MAX-DOAS measurements of tropospheric NO2 and HCHO in Munich and the comparison to satellite observations

2020 ◽  
Author(s):  
Johannes Lampel ◽  
Ka Lok Chan ◽  
Denis Pöhler ◽  
Matthias Wiegner ◽  
Carlos Alberti ◽  
...  
Keyword(s):  
Pearson Correlation ◽  
Satellite Observations ◽  
Optical Absorption Spectroscopy ◽  
Aerosol Extinction ◽  
Aerosol Formation ◽  
Mixing Ratios ◽  
Monitor Data ◽  
Sun Light ◽  
Good Agreement

&lt;p&gt;We present the Airyx 2D SkySpec Instrument: A commercially available two-dimensionally scanning Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) setup for the observations of trace gases using spectral measurements of scattered sun light and optionally also direct sun light. The waterproof design of the scanner unit is designed for long-term outdoor deployment. Temperature stabilisation of the spectrometers and automatic calibration spectra measurement are used to ensure high-quality measurement data over months and years of observations.&lt;/p&gt;&lt;p&gt;We show 2.5 years of measurements in Munich. Vertical columns and vertical distribution profiles of aerosol extinction coefficient, NO&lt;sub&gt;2&lt;/sub&gt; and HCHO are retrieved from the 2D MAX-DOAS observations. The measured surface aerosol extinction coefficients and NO&lt;sub&gt;2&lt;/sub&gt; mixing ratios are compared to in-situ monitor data. The retrieved surface NO&lt;sub&gt;2&lt;/sub&gt; mixing ratios show good agreement with in-situ monitor data with a Pearson correlation coefficient (R) of 0.91. Good agreement (R= 0.80) is also found for AOD when compared to sun-photometer measurements. Tropospheric vertical column densities (VCDs) of NO2 and HCHO derived from the MAX-DOAS measurements are also used to validate OMI and TROPOMI satellite observations. Monthly averaged data show good correlation, however, satellite observations are on average 30% lower than the MAX-DOAS measurements. Furthermore, the 2D MAX-DOAS observations are used to investigate the spatio-temporal characteristic of NO2 and HCHO in Munich. Analysis of the relations among aerosol, NO&lt;sub&gt;2&lt;/sub&gt; and HCHO show higher aerosol to HCHO ratios in winter indicating a longer atmospheric lifetime of aerosol and HCHO. The analysis also suggests that secondary aerosol formation is the major source of aerosols in Munich.&lt;/p&gt;

scholarly journals Bromocarbons in the tropical coastal and open ocean atmosphere during the 2009 Prime Expedition Scientific Cruise (PESC-09)

2014 ◽  
Vol 14 (15) ◽  
pp. 8137-8148 ◽  
Author(s):  
M. S. Mohd Nadzir ◽  
S. M. Phang ◽  
M. R. Abas ◽  
N. Abdul Rahman ◽  
A. Abu Samah ◽  
...  
Keyword(s):  
Chlorophyll A ◽  
Statistical Tests ◽  
Open Ocean ◽  
Common Source ◽  
Sampling Point ◽  
Coastal Regions ◽  
Chl A ◽  
June July ◽  
Strait Of Malacca

Abstract. Atmospheric concentrations of very short-lived species (VSLS) bromocarbons, including CHBr3, CH2Br2, CHCl2Br, CHClBr2, and CH2BrCl, were measured in the Strait of Malacca and the South China and Sulu–Sulawesi seas during a two-month research cruise in June–July 2009. The highest bromocarbon concentrations were found in the Strait of Malacca, with smaller enhancements in coastal regions of northern Borneo. CHBr3 was the most abundant bromocarbon, ranging from 5.2 pmol mol−1 in the Strait of Malacca to 0.94 pmol mol−1 over the open ocean. Other bromocarbons showed lower concentrations, in the range of 0.8–1.3 pmol mol−1 for CH2Br2, 0.1–0.5 pmol mol−1 for CHCl2Br, and 0.1–0.4 pmol mol−1 for CHClBr2. There was no significant correlation between bromocarbons and in situ chlorophyll a, but positive correlations with both MODIS and SeaWiFS satellite chlorophyll a. Together, the short-lived bromocarbons contribute an average of 8.9 pmol mol−1 (range 5.2–21.4 pmol mol−1) to tropospheric bromine loading, which is similar to that found in previous studies from global sampling networks (Montzka et al., 2011). Statistical tests showed strong Spearman correlations between brominated compounds, suggesting a common source. Log–log plots of CHBr3/CH2Br2 versus CHBr2Cl/CH2Br2 show that both chemical reactions and dilution into the background atmosphere contribute to the composition of these halocarbons at each sampling point. We have used the correlation to make a crude estimate of the regional emissions of CHBr3 and to derive a value of 32 Gg yr−1 for the Southeast (SE) Asian region (10° N–20° S, 90–150° E). Finally, we note that satellite-derived chlorophyll a (chl a) products do not always agree well with in situ measurements, particularly in coastal regions of high turbidity, meaning that satellite chl a may not always be a good proxy for marine productivity.

scholarly journals Bromocarbons in the tropical coastal and open ocean atmosphere during the Prime Expedition Scientific Cruise 2009 (PESC 09)

2014 ◽  
Vol 14 (1) ◽  
pp. 953-984 ◽  
Author(s):  
M. S. Mohd Nadzir ◽  
S. M. Phang ◽  
M. R. Abas ◽  
N. Abdul Rahman ◽  
A. Abu Samah ◽  
...  
Keyword(s):  
Chlorophyll A ◽  
Statistical Tests ◽  
Open Ocean ◽  
Common Source ◽  
Sampling Point ◽  
The South ◽  
Coastal Regions ◽  
Chl A ◽  
Strait Of Malacca

Abstract. Atmospheric concentrations of very short-lived species (VSLS) bromocarbons, including CHBr3, CH2Br2, CHCl2Br, CHClBr2, CH2BrCl, were measured in the Strait of Malacca and the South China and Sulu-Sulawesi Seas during a two month research cruise in June/July 2009. The highest bromocarbon concentrations were found in the Strait of Malacca, with smaller enhancements in coastal regions of Northern Borneo. CHBr3 was the most abundant bromocarbon, ranging from 5.2 pmol mol−1 in the Strait of Malacca to 0.94 pmol mol−1 over the open ocean. Other bromocarbons showed lower concentrations, in the range of 0.8–1.3 pmol mol−1 for CH2Br2, 0.1–0.5 pmol mol−1 (CHCl2Br) and 0.1–0.4 pmol mol−1 (CHClBr2). There was no significant correlation between bromocarbons and in situ chlorophyll a. Together the short-lived bromocarbons contribute an average of 8.9 pmol mol−1 (range 5.2–21.4 pmol mol−1) to tropospheric bromine load, which is similar to that found in previous studies (Montzka et al., 2011). Statistical tests showed strong Spearman correlations amongst brominated compounds suggesting a common source. Log-log plots of CHBr3/CH2Br2 vs. CHBr2Cl/CH2Br2 show that both chemical reactions and dilution into the background atmosphere contribute to the composition of these halocarbons at each sampling point. We have used the correlation to make a crude estimate of the regional emissions of CHBr3 and derive a value of 63 Gg yr−1 for the South East (S.E.) Asian region (10° N–20° S, 90–150° E). Finally, we note that satellite-derived chlorophyll a (chl a) products do not always agree well with in situ measurements, particularly in coastal regions of high turbidity, meaning that satellite chl a may not always be a good proxy for marine productivity.

scholarly journals Measurements and modelling of molecular iodine emissions, transport and photodestruction in the coastal region around Roscoff

2010 ◽  
Vol 10 (23) ◽  
pp. 11823-11838 ◽  
Author(s):  
R. J. Leigh ◽  
S. M. Ball ◽  
J. Whitehead ◽  
C. Leblanc ◽  
A. J. L. Shillings ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Marine Boundary Layer ◽  
Coastal Region ◽  
Molecular Iodine ◽  
Transport Processes ◽  
Optical Absorption Spectroscopy ◽  
Emission Rates ◽  
Cavity Ringdown Spectroscopy ◽  
The Relationship

Abstract. Iodine emissions from the dominant six macroalgal species in the coastal regions around Roscoff, France, have been modelled to support the Reactive Halogens in the Marine Boundary Layer Experiment (RHaMBLe) undertaken in September 2006. A two-dimensional model is used to explore the relationship between geographically resolved regional emissions (based on maps of seaweed beds in the area and seaweed I2 emission rates previously measured in the laboratory) and in situ point and line measurements of I2 performed respectively by a broadband cavity ringdown spectroscopy (BBCRDS) instrument sited on the shoreline and a long-path differential optical absorption spectroscopy (LP-DOAS) instrument sampling over an extended light path to an off-shore island. The modelled point and line I2 concentrations compare quantitatively with BBCRDS and LP-DOAS measurements, and provide a link between emission fields and the different measurement geometries used to quantify atmospheric I2 concentrations during RHaMBLe. Total I2 emissions over the 100 km2 region around Roscoff are calculated to be 1.7×1019 molecules per second during the lowest tides. During the night, the model replicates I2 concentrations up to 50 pptv measured along the LP-DOAS instrument's line of sight, and predicts spikes of several hundred pptv in certain conditions. Point I2 concentrations up to 50 pptv are also calculated at the measurement site, in broad agreement with the BBCRDS observations. Daytime measured concentrations of I2 at the site correlate with modelled production and transport processes. However substantial recycling of the photodissociated I2 is required for the model to quantitatively match measured concentrations. This result corroborates previous modelling of iodine and NOx chemistry in the semi-polluted marine boundary layer which proposed a mechanism for recycling I2 via the formation, transport and subsequent reactions of the IONO2 reservoir compound. The methodology presented in this paper provides a tool for linking spatially distinct measurements to inhomogeneous and temporally varying emission fields.

scholarly journals Measurements of diurnal variations and eddy covariance (EC) fluxes of glyoxal in the tropical marine boundary layer: description of the Fast LED-CE-DOAS instrument

2014 ◽  
Vol 7 (10) ◽  
pp. 3579-3595 ◽  
Author(s):  
S. Coburn ◽  
I. Ortega ◽  
R. Thalman ◽  
B. Blomquist ◽  
C. W. Fairall ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Eddy Covariance ◽  
Marine Boundary Layer ◽  
Light Emitting Diode ◽  
Chemical Properties ◽  
Diurnal Variations ◽  
Optical Absorption Spectroscopy ◽  
Tropical Ocean ◽  
Mixing Ratios ◽  
Fast Light

Abstract. Here we present first eddy covariance (EC) measurements of fluxes of glyoxal, the smallest α-dicarbonyl product of hydrocarbon oxidation, and a precursor for secondary organic aerosol (SOA). The unique physical and chemical properties of glyoxal – i.e., high solubility in water (effective Henry's law constant, KH = 4.2 × 105 M atm−1) and short atmospheric lifetime (~2 h at solar noon) – make it a unique indicator species for organic carbon oxidation in the marine atmosphere. Previous reports of elevated glyoxal over oceans remain unexplained by atmospheric models. Here we describe a Fast Light-Emitting Diode Cavity-Enhanced Differential Optical Absorption Spectroscopy (Fast LED-CE-DOAS) instrument to measure diurnal variations and EC fluxes of glyoxal and inform about its unknown sources. The fast in situ sensor is described, and first results are presented from a cruise deployment over the eastern tropical Pacific Ocean (20° N to 10° S; 133 to 85° W) as part of the Tropical Ocean tRoposphere Exchange of Reactive halogens and Oxygenated VOCs (TORERO) field experiment (January to March 2012). The Fast LED-CE-DOAS is a multispectral sensor that selectively and simultaneously measures glyoxal (CHOCHO), nitrogen dioxide (NO2), oxygen dimers (O4), and water vapor (H2O) with ~2 Hz time resolution (Nyquist frequency ~1 Hz) and a precision of ~40 pptv Hz−0.5 for glyoxal. The instrument is demonstrated to be a "white-noise" sensor suitable for EC flux measurements. Fluxes of glyoxal are calculated, along with fluxes of NO2, H2O, and O4, which are used to aid the interpretation of the glyoxal fluxes. Further, highly sensitive and inherently calibrated glyoxal measurements are obtained from temporal averaging of data (e.g., detection limit smaller than 2.5 pptv in an hour). The campaign average mixing ratio in the Southern Hemisphere (SH) is found to be 43 ± 9 pptv glyoxal, which is higher than the Northern Hemisphere (NH) average of 32 ± 6 pptv (error reflects variability over multiple days). The diurnal variation of glyoxal in the marine boundary layer (MBL) is measured for the first time, and mixing ratios vary by ~8 pptv (NH) and ~12 pptv (SH) over the course of 24 h. Consistently, maxima are observed at sunrise (NH: 35 ± 5 pptv; SH: 47 ± 7 pptv), and minima at dusk (NH: 27 ± 5 pptv; SH: 35 ± 8 pptv). In both hemispheres, the daytime flux was directed from the atmosphere into the ocean, indicating that the ocean is a net sink for glyoxal during the day. After sunset the ocean was a source for glyoxal to the atmosphere (positive flux) in the SH; this primary ocean source was operative throughout the night. In the NH, the nighttime flux was positive only shortly after sunset and negative during most of the night. Positive EC fluxes of soluble glyoxal over oceans indicate the presence of an ocean surface organic microlayer (SML) and locate a glyoxal source within the SML. The origin of most atmospheric glyoxal, and possibly other oxygenated hydrocarbons over tropical oceans, remains unexplained and warrants further investigation.

scholarly journals Long-path averaged mixing ratios of O<sub>3</sub> and NO<sub>2</sub> in the free troposphere from mountain MAX-DOAS

2013 ◽  
Vol 6 (5) ◽  
pp. 8235-8267
Author(s):  
L. Gomez ◽  
M. Navarro-Comas ◽  
O. Puentedura ◽  
Y. Gonzalez ◽  
E. Cuevas ◽  
...  
Keyword(s):  
Detection Limit ◽  
Optical Absorption ◽  
Radiative Transfer Model ◽  
Optical Absorption Spectroscopy ◽  
Transfer Model ◽  
High Mountain ◽  
Free Troposphere ◽  
Air Masses ◽  
Mixing Ratios

Abstract. A new approximation is proposed to estimate O3 and NO2 mixing ratios in the Northern Subtropics Free Troposphere (FT). Multi Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) high mountain measurements, recorded at Izaña Observatory (28°18' N, 16°29' W), are used in this work. Proposed method uses horizontal and near-zenith geometries to estimate the station level differential path. Two different methods are described. First one uses retrieved Slant Column Densities (SCD) of O4. On second method, path is estimated from LIBRADTRAN radiative transfer model for the region and season. Results show that under low aerosol loading, O3 and NO2 mixing ratios concentrations can be retrieved with moderately low errors. Obtained concentrations have been compared with in situ instrumentation on the observatory. O3 concentration in FT is found to be in the range of 40–80 ppb, approximately. NO2 is in the range of 20–30 ppt, below the detection limit of in situ instrumentation. The different air masses scanned by each instrument have been identified as a cause of discrepancy between O3 observed by MAX-DOAS and in situ.

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