scholarly journals Modelling the impacts of iodine chemistry on the northern Indian Ocean marine boundary layer

2021 ◽  
Vol 21 (11) ◽  
pp. 8437-8454
Author(s):  
Anoop S. Mahajan ◽  
Qinyi Li ◽  
Swaleha Inamdar ◽  
Kirpa Ram ◽  
Alba Badia ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Chemical Composition ◽  
Indian Ocean ◽  
Marine Boundary Layer ◽  
Indian Subcontinent ◽  
Winter Period ◽  
Monsoon Period ◽  
Mean Values ◽  
Iodine Chemistry ◽  
Inorganic Iodine

Abstract. Recent observations have shown the ubiquitous presence of iodine oxide (IO) in the Indian Ocean marine boundary layer (MBL). In this study, we use the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem version 3.7.1), including halogen (Br, Cl, and I) sources and chemistry, to quantify the impacts of the observed levels of iodine on the chemical composition of the MBL. The model results show that emissions of inorganic iodine species resulting from the deposition of ozone (O3) on the sea surface are needed to reproduce the observed levels of IO, although the current parameterizations overestimate the atmospheric concentrations. After reducing the inorganic emissions by 40 %, a reasonable match with cruise-based observations is found, with the model predicting values between 0.1 and 1.2 pptv across the model domain MBL. A strong seasonal variation is also observed, with lower iodine concentrations predicted during the monsoon period, when clean oceanic air advects towards the Indian subcontinent, and higher iodine concentrations predicted during the winter period, when polluted air from the Indian subcontinent increases the ozone concentrations in the remote MBL. The results show that significant changes are caused by the inclusion of iodine chemistry, with iodine-catalysed reactions leading to regional changes of up to 25 % in O3, 50 % in nitrogen oxides (NO and NO2), 15 % in hydroxyl radicals (OH), 25 % in hydroperoxyl radicals (HO2), and up to a 50 % change in the nitrate radical (NO3), with lower mean values across the domain. Most of the large relative changes are observed in the open-ocean MBL, although iodine chemistry also affects the chemical composition in the coastal environment and over the Indian subcontinent. These results show the importance of including iodine chemistry in modelling the atmosphere in this region.

scholarly journals Modelling the Impacts of Iodine Chemistry on the Northern Indian Ocean Marine Boundary Layer

2020 ◽  
Author(s):  
Anoop S. Mahajan ◽  
Qinyi Li ◽  
Swaleha Inamdar ◽  
Kirpa Ram ◽  
Alba Badia ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Chemical Composition ◽  
Indian Ocean ◽  
Marine Boundary Layer ◽  
Indian Subcontinent ◽  
Winter Period ◽  
Monsoon Period ◽  
The Indian Ocean ◽  
Iodine Chemistry ◽  
Inorganic Iodine

Abstract. Recent observations have shown the ubiquitous presence of iodine oxide (IO) in the Indian Ocean marine boundary layer (MBL). In this study, we use the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem version 3.7.1), including halogens (Br, Cl and I) sources and chemistry, to quantify the impacts of the observed levels of iodine on the chemical composition of the MBL. The model results show that emissions of inorganic iodine species resulting from the deposition of ozone (O3) on the sea surface are needed to reproduce the observed levels of IO, although the current parameterisations overestimate the atmospheric concentrations. After reducing the inorganic emissions by 40 %, a reasonable match with cruise-based observations is found. A strong seasonal variation is also observed, with lower iodine concentrations predicted during the monsoon period when clean oceanic air advects towards the Indian subcontinent, and higher iodine concentrations predicted during the winter period, when polluted air from the Indian subcontinent increases the ozone concentrations in the remote MBL. The results show that significant changes are caused by the inclusion of iodine chemistry, with iodine catalysed reactions leading to regional changes of up to 25 % in O3, 50 % in nitrogen oxides (NO and NO2), 15 % in hydroxyl radicals (OH), 25 % in hydroperoxyl radicals (HO2), and up to a 50 % change in the nitrate radical (NO3). Most of the large relative changes are observed in the open ocean MBL, although iodine chemistry also affects the chemical composition in the coastal environment and over the Indian subcontinent. These results show the importance of including iodine chemistry in modelling the atmosphere in this region.

Marine Aerosol Iodine Chemistry: The Importance of Soluble Organic Iodine

2005 ◽  
Vol 2 (4) ◽  
pp. 295 ◽  
Author(s):  
Alex R. Baker
Keyword(s):  
Boundary Layer ◽  
Marine Boundary Layer ◽  
Marine Aerosol ◽  
Radiative Balance ◽  
Iodine Species ◽  
Ozone Destruction ◽  
Organic Iodine ◽  
Iodine Chemistry ◽  
Inorganic Iodine ◽  
Complex Chemistry

Environmental Context.Ozone concentrations play a large part in controlling the oxidation capacity of the marine boundary layer, while the production of new aerosol particles affects atmospheric radiative balance. Iodine has a complex chemistry in the marine atmosphere which impacts on both these processes. Much of this iodine chemistry, especially the chemical speciation of iodine in aerosol, is only poorly understood. This study explores the occurrence and abundance of organic forms of iodine, a topic that has received very little attention to date. Abstract.Iodine has a complex chemistry in aerosols in the marine boundary layer (MBL), and is involved in both ozone destruction and new aerosol particle formation processes. Work in this area has focussed almost exclusively on inorganic iodine chemistry. Results from two research cruises in the Atlantic Ocean, covering wide longitude (60°W to 0°W) and latitude (50°N to 50°S) ranges indicate that soluble organic iodine species are both widespread and abundant in marine aerosol. The reactivity of these species is yet to be determined, but may influence the concentrations of some aerosol inorganic iodine species, and may also impact on MBL ozone destruction reactions.

Structure of the marine boundary layer over north western Indian Ocean during 1983 summer monsoon

1990 ◽  
Vol 52 (1-2) ◽  
pp. 177-191
Author(s):  
M. R. Ramesh Kumar ◽  
Y. Sadhuram ◽  
G. S. Michael ◽  
L. V. Gangadhara Rao
Keyword(s):  
Boundary Layer ◽  
Indian Ocean ◽  
Summer Monsoon ◽  
Marine Boundary Layer ◽  
Western Indian Ocean ◽  
North Western

scholarly journals A laboratory characterisation of inorganic iodine emissions from the sea surface: dependence on oceanic variables and parameterisation for global modelling

2013 ◽  
Vol 13 (12) ◽  
pp. 31445-31477 ◽  
Author(s):  
S. M. MacDonald ◽  
J. C. Gómez Martín ◽  
R. Chance ◽  
S. Warriner ◽  
A. Saiz-Lopez ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Atmospheric Chemistry ◽  
Marine Boundary Layer ◽  
Environmental Parameters ◽  
Sea Surface ◽  
Total Iodine ◽  
Iodide Ions ◽  
Iodine Compounds ◽  
Halogen Chemistry ◽  
Inorganic Iodine

Abstract. Reactive iodine compounds play a~significant role in the atmospheric chemistry of the oceanic boundary layer by influencing the oxidising capacity through catalytically removing O3 and altering the HOx and NOx balance. The sea-to-air flux of iodine over the open ocean is therefore an important quantity in assessing these impacts on a global scale. This paper examines the effect of a number of relevant environmental parameters, including water temperature, salinity and organic compounds, on the magnitude of the HOI and I2 fluxes produced from the uptake of O3 and its reaction with iodide ions in aqueous solution. The results of these laboratory experiments and those reported previously (Carpenter et al., 2013), along with sea surface iodide concentrations measured or inferred from measurements of dissolved total iodine and iodate reported in the literature, were then used to produce parameterised expressions for the HOI and I2 fluxes as a function of wind speed, sea-surface temperature and O3. These expressions were used in the Tropospheric HAlogen chemistry MOdel (THAMO) to compare with MAX-DOAS measurements of iodine monoxide (IO) performed during the HaloCAST-P cruise in the Eastern Pacific ocean (Mahajan et al., 2012). The modelled IO agrees reasonably with the field observations, although significant discrepancies are found during a period of low wind speeds (<3 m s−1), when the model overpredicts IO by up to a factor of three. The inorganic iodine flux contributions to IO are found to be comparable to, or even greater than, the contribution of organo-iodine compounds and therefore its inclusion in atmospheric models is important to improve predictions of the influence of halogen chemistry in the marine boundary layer.

Iodine chemistry in the tropical and remote open ocean marine boundary layer

2020 ◽  
Author(s):  
Swaleha Inamdar ◽  
Liselotte Tinel ◽  
Rosie Chance ◽  
Lucy Jane Carpenter ◽  
Sabu Prabhakaran ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Kinetic Model ◽  
Southern Ocean ◽  
Tropospheric Ozone ◽  
Marine Boundary Layer ◽  
Sea Surface ◽  
Iodine Species ◽  
Ocean Region ◽  
Inorganic Iodine

&lt;p&gt;Iodine chemistry plays an essential role in controlling the radiation budget by changing various atmospheric parameters. Iodine in the atmosphere is known to cause depletion of ozone via catalytic reaction cycles. It alters the atmospheric oxidation capacity, and lead to ultrafine particle formation that acts as potential cloud condensation nuclei. The ocean is the primary source of iodine; it enters the atmosphere through fluxes of gaseous reactive iodine species. At the ocean surface, seawater iodide reacts with tropospheric ozone (gas) to form inorganic iodine species in gaseous form. These species namely, hypoiodous acid (HOI) and molecular iodine (I&lt;sub&gt;2&lt;/sub&gt;) quickly photolyse to release reactive iodine (I) in the atmosphere. This process acts as a significant sink for tropospheric ozone contributing to ~16% ozone loss throughout the troposphere. Reactive iodine released in the atmosphere undergoes the formation of iodine monoxide (IO) or higher oxides of iodine (I&lt;sub&gt;x&lt;/sub&gt;O&lt;sub&gt;x&lt;/sub&gt;) via self-recombination reactions. It is known that inorganic iodine fluxes (HOI and I&lt;sub&gt;2&lt;/sub&gt;) contribute to 75% of the detected IO over the Atlantic Ocean. However, we did not observe this from ship-based MAX-DOAS studies between 2014-2017. At present, there are no direct observations of inorganic iodine (HOI; few for I&lt;sub&gt;2&lt;/sub&gt;) and are estimated via empirical methods derived from the interfacial kinetic model by Carpenter et al. in 2013. Based on the kinetic model, estimation of HOI and I&lt;sub&gt;2&lt;/sub&gt; fluxes depends on three parameters, namely, ozone concentration, surface iodide concentration, and the wind speed. This parameterisation for inorganic fluxes assumes a sea surface temperature (SST) of 293 K and has limiting wind speed conditions. Since the parameterisation conditions assumed SST of 293 K higher uncertainties due to errors in activation energy creeps in the estimation of HOI flux compared to I&lt;sub&gt;2&lt;/sub&gt; as the flux of HOI is ~20 times greater than that of I&lt;sub&gt;2&lt;/sub&gt;. For three consecutive expeditions in the Indian and Southern Ocean, we detected ~1 pptv of IO in the marine boundary layer. These levels are not explained by the calculated inorganic fluxes by using observed and predicted sea surface iodide concentrations. This method of iodine flux estimation is currently used in all global models, along with the MacDonald et al. 2014 iodide estimation method. Model output using these parameterisations have not been able to match the observed IO levels in the Indian and Southern Ocean region. This discrepancy suggests that the process of efflux of iodine to the atmosphere may not be fully understood, and the current parametrisation does not do justice to the observations. It also highlights that the flux of organic iodine may also play a role in observed IO levels, especially in the Indian Ocean region. A correlation of 0.7 was achieved above the 99% confidence limit for chlorophyll-a with observed IO concentration in this region. There is a need to carry more observations to improve the estimation technique of iodine sea-air flux thus improving model predictions of IO in the atmosphere.&lt;/p&gt;

scholarly journals Morphological features and mixing states of soot-containing particles in the marine boundary layer over the Indian and Southern Oceans

2018 ◽  
Author(s):  
Sayako Ueda ◽  
Kazuo Osada ◽  
Keiichiro Hara ◽  
Masanori Yabuki ◽  
Fuminori Hashihama ◽  
...  
Keyword(s):  
South Africa ◽  
Boundary Layer ◽  
Indian Ocean ◽  
Marine Boundary Layer ◽  
Aerosol Particles ◽  
Morphological Features ◽  
Absorption Coefficients ◽  
Climatic Effects ◽  
Mixing States ◽  
Carbon Aerosols

Abstract. Mixing states of soot-containing aerosol particles are important information for the simulation of climatic effects of black carbon aerosols in the atmosphere. To elucidate the mixing states and morphological features of soot-containing particles in remote ocean areas, we conducted onboard observations over the southern Indian Ocean and the Southern Ocean during the TR/V Umitaka-maru UM-08-09 cruise, which started from Benoa, Indonesia on 1 December 2008 via Cape Town, South Africa and which terminated in Fremantle, Australia on 6 February 2009. The light absorption coefficients of size-segregated particles (

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