scholarly journals Iodine chemistry in the chemistry–climate model SOCOL-AERv2-I

2021 ◽  
Vol 14 (10) ◽  
pp. 6623-6645
Author(s):  
Arseniy Karagodin-Doyennel ◽  
Eugene Rozanov ◽  
Timofei Sukhodolov ◽  
Tatiana Egorova ◽  
Alfonso Saiz-Lopez ◽  
...  
Keyword(s):  
Lower Stratosphere ◽  
Climate Model ◽  
Geographical Location ◽  
Lower Troposphere ◽  
Fold Increase ◽  
High Latitudes ◽  
Iodine Species ◽  
Low Latitudes ◽  
Iodine Chemistry ◽  
Ozone Column

Abstract. In this paper, we present a new version of the chemistry–climate model SOCOL-AERv2 supplemented by an iodine chemistry module. We perform three 20-year ensemble experiments to assess the validity of the modeled iodine and to quantify the effects of iodine on ozone. The iodine distributions obtained with SOCOL-AERv2-I agree well with AMAX-DOAS observations and with CAM-chem model simulations. For the present-day atmosphere, the model suggests that the iodine-induced chemistry leads to a 3 %–4 % reduction in the ozone column, which is greatest at high latitudes. The model indicates the strongest influence of iodine in the lower stratosphere with 30 ppbv less ozone at low latitudes and up to 100 ppbv less at high latitudes. In the troposphere, the account of the iodine chemistry reduces the tropospheric ozone concentration by 5 %–10 % depending on geographical location. In the lower troposphere, 75 % of the modeled ozone reduction originates from inorganic sources of iodine, 25 % from organic sources of iodine. At 50 hPa, the results show that the impacts of iodine from both sources are comparable. Finally, we determine the sensitivity of ozone to iodine by applying a 2-fold increase in iodine emissions, as it might be representative for iodine by the end of this century. This reduces the ozone column globally by an additional 1.5 %–2.5 %. Our results demonstrate the sensitivity of atmospheric ozone to iodine chemistry for present and future conditions, but uncertainties remain high due to the paucity of observational data of iodine species.

scholarly journals Iodine chemistry in the chemistry-climate model SOCOL-AERv2-iodine

2021 ◽  
Author(s):  
Arseniy Karagodin-Doyennel ◽  
Eugene Rozanov ◽  
Timofei Sukhodolov ◽  
Tatiana Egorova ◽  
Alfonso Saiz-Lopez ◽  
...  
Keyword(s):  
Climate Model ◽  
Geographical Location ◽  
Lower Troposphere ◽  
Fold Increase ◽  
High Latitudes ◽  
Ozone Loss ◽  
Low Latitudes ◽  
Iodine Chemistry ◽  
Ozone Column ◽  
Good Agreement

Abstract. This paper introduces a new version of the chemistry-climate model SOCOL-AERv2, supplemented by an iodine chemistry module. We conducted three twenty-year-long ensemble experiments to assess the validity of modeled iodine and to quantify the effects of iodine on ozone. The obtained iodine distributions with SOCOL-AERv2-iodine show good agreement with the CAM-chem model simulations and AMAX-DOAS observations. For the present-day atmosphere, the model suggests the strongest influence of iodine in the lower stratosphere with an ozone loss of up to 30 ppbv at low latitudes and up to 100 ppbv at high latitudes. Globally averaged, the model suggests iodine-induced chemistry to result in an ozone column reduction of 3–4 %, maximizing at high latitudes. In the troposphere, iodine chemistry lowers tropospheric ozone concentrations by 5–10 % depending on the geographical location. We also determined the sensitivity of ozone to iodine applying a 2-fold increase of iodine emissions, which reduces the ozone column globally by an additional 1.5–2.5 %. We found that in the lower troposphere, the share of ozone loss induced by iodine originating from inorganic sources is 75 % and 25 % by iodine originating from organic sources, and contributions become similar at about 50 hPa. These results constrain the importance of atmospheric iodine chemistry for present and future conditions, even though uncertainties remain high due to the paucity of observational data of iodine species.

RADIO STAR SCINTILLATIONS AND IONOSPHERIC DISTURBANCES

1959 ◽  
Vol 37 (10) ◽  
pp. 1137-1152 ◽  
Author(s):  
T. R. Hartz
Keyword(s):  
Geographical Location ◽  
Generation Mechanism ◽  
Upper Atmosphere ◽  
Ionospheric Disturbances ◽  
High Latitudes ◽  
General Belief ◽  
Auroral Activity ◽  
Middle Latitudes ◽  
Low Latitudes ◽  
Spread F

The generation mechanism for the ionization irregularities in the upper atmosphere which are responsible for radio star scintillations is considered. The general belief that scintillations are related to the spread-F phenomenon observed on ionosonde recordings is found to be an inadequate explanation for the scintillations at 53 Mc/s recorded at Ottawa. An examination of the Ottawa recordings shows that there is a definite association, both in time of occurrence and geographical location, with those ionospheric disturbances that are usually considered to be due to incoming solar particles. Since other workers at more southerly geomagnetic latitudes have associated their scintillation observations with the spread-F phenomenon which they consider to be independent of auroral activity, it would appear that two mechanisms, at least, are responsible for the radio star fluctuations: namely, the precipitation of solar corpuscles and a mechanism linked with the spread-F phenomenon. The former seems to predominate at high latitudes, the latter is probably predominant at low latitudes, while both mechanisms probably are operative in middle latitudes.

scholarly journals Impact of high solar zenith angles on dynamical and chemical processes in a coupled chemistry-climate model

2003 ◽  
Vol 3 (4) ◽  
pp. 3681-3711
Author(s):  
D. Lamago ◽  
M. Dameris ◽  
C. Schnadt ◽  
V. Eyring ◽  
C. Brühl
Keyword(s):  
Atmospheric Chemistry ◽  
Lower Stratosphere ◽  
Climate Model ◽  
Chemical Processes ◽  
Sensitivity Experiment ◽  
Mean Values ◽  
Ozone Destruction ◽  
The Impact ◽  
Fully Coupled ◽  
Ozone Column

Abstract. Actinic fluxes at high solar zenith angles (SZAs) are important for atmospheric chemistry, especially under twilight conditions in polar winter and spring. The results of a sensitivity experiment employing the fully coupled 3D chemistry-climate model ECHAM4.L39(DLR)/CHEM have been analysed to quantify the impact of SZAs greater than 87.5° on dynamical and chemical processes in the lower stratosphere, in particular their influence on the ozone layer. Although the actinic fluxes at SZAs larger than 87.5° are small, ozone concentrations are significantly affected because daytime photolytic ozone destruction is switched on earlier, especially the conversion of Cl2 and Cl2O2 into ClO at the end of polar night in the lower stratosphere. Comparing climatological mean ozone column values of a simulation considering SZAs up to 93° with those of the sensitivity run with SZAs confined to 87.5° total ozone is reduced by about 20% in the polar Southern Hemisphere, i.e., the ozone hole is "deeper'' if twilight conditions are considered in the model because there is 2–3 weeks more time for ozone destruction. This causes an additional cooling of the polar lower stratosphere (50 hPa) up to −4 K with obvious consequences for chemical processes. In the Northern Hemisphere the impact of high SZAs cannot be determined on the basis of climatological mean values due to the pronounced dynamic variability of the stratosphere in winter and spring.

scholarly journals Sensitivity of remote aerosol distributions to representation of cloud-aerosol interactions in a global climate model

2013 ◽  
Vol 6 (1) ◽  
pp. 331-378 ◽  
Author(s):  
H. Wang ◽  
R. C. Easter ◽  
P. J. Rasch ◽  
M. Wang ◽  
X. Liu ◽  
...  
Keyword(s):  
Liquid Water ◽  
Climate Model ◽  
Global Climate Model ◽  
Fold Increase ◽  
Convective Transport ◽  
The Arctic ◽  
Cloud Base ◽  
High Latitudes ◽  
Upper Troposphere ◽  
Wet Removal

Abstract. Many global aerosol and climate models, including the widely used Community Atmosphere Model version 5 (CAM5), have large biases in predicting aerosols in remote regions such as upper troposphere and high latitudes. In this study, we conduct CAM5 sensitivity simulations to understand the role of key processes associated with aerosol transformation and wet removal affecting the vertical and horizontal long-range transport of aerosols to the remote regions. Improvements are made to processes that are currently not well represented in CAM5, which are guided by surface and aircraft measurements together with results from a multi-scale aerosol-climate model (PNNL-MMF) that explicitly represents convection and aerosol-cloud interactions at cloud-resolving scales. We pay particular attention to black carbon (BC) due to its importance in the Earth system and the availability of measurements. We introduce into CAM5 a new unified scheme for convective transport and aerosol wet removal with explicit aerosol activation above convective cloud base. This new implementation reduces the excessive BC aloft to better simulate observed BC profiles that show decreasing mixing ratios in the mid- to upper-troposphere. After implementing this new unified convective scheme, we examine wet removal of submicron aerosols that occurs primarily through cloud processes. The wet removal depends strongly on the sub-grid scale liquid cloud fraction and the rate of conversion of liquid water to precipitation. These processes lead to very strong wet removal of BC and other aerosols over mid- to high latitudes during winter months. With our improvements, the Arctic BC burden has a10-fold (5-fold) increase in the winter (summer) months, resulting in a much better simulation of the BC seasonal cycle as well. Arctic sulphate and other aerosol species also increase but to a lesser extent. An explicit treatment of BC aging with slower aging assumptions produces an additional 30-fold (5-fold) increase in the Arctic winter (summer) BC burden. This BC aging treatment, however, has minimal effect on other under-predicted species. Interestingly, our modifications to CAM5 that aim at improving prediction of high-latitude and upper tropospheric aerosols also produce much better aerosol optical depth over various other regions globally when compared to multi-year AERONET retrievals. The improved aerosol distributions have impacts on other aspects of CAM5, improving the simulation of global mean liquid water path and cloud forcing.

scholarly journals Bromine and iodine chemistry in a global chemistry-climate model: description and evaluation of very short-lived oceanic sources

2012 ◽  
Vol 12 (3) ◽  
pp. 1423-1447 ◽  
Author(s):  
C. Ordóñez ◽  
J.-F. Lamarque ◽  
S. Tilmes ◽  
D. E. Kinnison ◽  
E. L. Atlas ◽  
...  
Keyword(s):  
Lower Stratosphere ◽  
Marine Boundary Layer ◽  
Climate Model ◽  
Heterogeneous Reactions ◽  
Model Description ◽  
Chl A ◽  
Tropical Oceans ◽  
Vertical Distributions ◽  
Iodine Chemistry ◽  
Good Agreement

Abstract. The global chemistry-climate model CAM-Chem has been extended to incorporate an expanded bromine and iodine chemistry scheme that includes natural oceanic sources of very short-lived (VSL) halocarbons, gas-phase photochemistry and heterogeneous reactions on aerosols. Ocean emissions of five VSL bromocarbons (CHBr3, CH2Br2, CH2BrCl, CHBrCl2, CHBr2Cl) and three VSL iodocarbons (CH2ICl, CH2IBr, CH2I2) have been parameterised by a biogenic chlorophyll-a (chl-a) dependent source in the tropical oceans (20° N–20° S). Constant oceanic fluxes with 2.5 coast-to-ocean emission ratios are separately imposed on four different latitudinal bands in the extratropics (20°–50° and above 50° in both hemispheres). Top-down emission estimates of bromocarbons have been derived using available measurements in the troposphere and lower stratosphere, while iodocarbons have been constrained with observations in the marine boundary layer (MBL). Emissions of CH3I are based on a previous inventory and the longer lived CH3Br is set to a surface mixing ratio boundary condition. The global oceanic emissions estimated for the most abundant VSL bromocarbons – 533 Gg yr−1 for CHBr3 and 67.3 Gg yr−1 for CH2Br2 – are within the range of previous estimates. Overall the latitudinal and vertical distributions of modelled bromocarbons are in good agreement with observations. Nevertheless, we identify some issues such as the reduced number of aircraft observations to validate models in the Southern Hemisphere, the overestimation of CH2Br2 in the upper troposphere – lower stratosphere and the underestimation of CH3I in the same region. Despite the difficulties involved in the global modelling of the shortest lived iodocarbons (CH2ICl, CH2IBr, CH2I2), modelled results are in good agreement with published observations in the MBL. Finally, sensitivity simulations show that knowledge of the diurnal emission cycle for these species, in particular for CH2I2, is key to assess their global source strength.

scholarly journals Characterising the Seasonal and Geographical Variability of Tropospheric Ozone, Stratospheric Influence and Recent Changes

2018 ◽  
Author(s):  
Ryan S. Williams ◽  
Michaela I. Hegglin ◽  
Brian J. Kerridge ◽  
Patrick Jöckel ◽  
Barry G. Latter ◽  
...  
Keyword(s):  
Tropospheric Ozone ◽  
Radiative Forcing ◽  
Lower Stratosphere ◽  
Climate Model ◽  
Stratospheric Ozone ◽  
Lower Troposphere ◽  
Data Availability ◽  
Ozone Production ◽  
Upper Troposphere ◽  
The World

Abstract. The stratospheric contribution to tropospheric ozone (O3) has been a subject of much debate in recent decades, but is known to have an important influence. Recent improvements in diagnostic and modelling tools provide new evidence that the stratosphere has a much larger influence than previously thought. This study aims to characterise the seasonal and geographical distribution of tropospheric ozone, its variability and changes, and provide quantification of the stratospheric influence on these measures. To this end, we evaluate hindcast specified dynamics chemistry-climate model (CCM) simulations from the ECHAM/MESSy Atmospheric Chemistry (EMAC) model and the Canadian Middle Atmosphere Model (CMAM), as contributed to the IGAC/SPARC Chemistry Climate Model Initiative (CCMI) activity, together with satellite observations from the Ozone Monitoring Instrument (OMI) and ozonesonde profile measurements from the World Ozone and Ultraviolet Radiation Data Centre (WOUDC) over a period of concurrent data availability (2005–2010). An overall positive, seasonally dependent bias in 1000–450 hPa (~ 0–5.5 km) subcolumn ozone is found for EMAC, ranging from 2–8 Dobson Units (DU), whereas CMAM is found to be in closer agreement with the observations, although with substantial seasonal and regional variation in the sign and magnitude of the bias (~ −4 to +4 DU). Although the application of OMI averaging kernels (AKs) improves agreement with model estimates from both EMAC and CMAM as expected, comparisons with ozonesondes indicate a positive ozone bias in the lower stratosphere in CMAM, together with an underestimation of photochemical ozone production (negative bias) in the troposphere. Model variability is found to be more similar in magnitude to that implied from ozonesondes, in comparison with OMI which has significantly larger variability. Noting the overall consistency of the CCMs, the influence of the model chemistry schemes and internal dynamics is discussed in relation to the inter-model differences found. In particular, it is shown that CMAM simulates a faster and shallower Brewer-Dobson Circulation (BDC) relative to both EMAC and observational estimates, which has implications for the distribution and magnitude of the downward flux of stratospheric ozone, over the most recent climatological period (1980–2010). Nonetheless, it is shown that the stratospheric influence on tropospheric ozone is larger than previously thought and is estimated to exceed 50 % in the wintertime extratropics, even in the lower troposphere. Finally, long term changes in the CCM ozone tracers are calculated for different seasons between 1980–89 and 2001–10. An overall statistically significant increase in tropospheric ozone is found across much of the world, but particularly in the Northern Hemisphere and in the middle to upper troposphere, where the increase is on the order of 4–6 ppbv (5–10 %). Our model study implies that attribution from stratosphere-troposphere exchange (STE) to such ozone changes ranges from 25–30 % at the surface to as much as 50–80 % in the upper troposphere-lower stratosphere (UTLS) across many regions of the world. These findings highlight the importance of a well-resolved stratosphere in simulations of tropospheric ozone and its implications for the radiative forcing, air quality and oxidation capacity of the troposphere.

scholarly journals Stratospheric sudden warming effects on winds and temperature in the middle atmosphere at middle and low latitudes: a study using WACCM

2014 ◽  
Vol 32 (7) ◽  
pp. 859-874 ◽  
Author(s):  
A. Chandran ◽  
R. L. Collins
Keyword(s):  
Climate Model ◽  
Middle Atmosphere ◽  
Planetary Waves ◽  
Lower Latitude ◽  
High Latitudes ◽  
Mean Flow ◽  
Low Latitude ◽  
Quasi Biennial Oscillation ◽  
Stratospheric Sudden Warming ◽  
Low Latitudes

Abstract. A stratospheric sudden warming (SSW) is a dynamical phenomenon of the wintertime stratosphere caused by the interaction between planetary Rossby waves propagating from the troposphere and the stratospheric zonal-mean flow. While the effects of SSW events are seen predominantly in high latitudes, they can also produce significant changes in middle and low latitude temperature and winds. In this study we quantify the middle and low latitude effects of SSW events on temperature and zonal-mean winds using a composite of SSW events between 1988 and 2010 simulated with the specified dynamics version of the Whole Atmosphere Community Climate Model (WACCM). The temperature and wind responses seen in the tropics also extend into the low latitudes in the other hemisphere. There is variability in observed zonal-mean winds and temperature depending on the observing location within the displaced or split polar vortex and propagation direction of the planetary waves. The propagation of planetary waves show that they originate in mid–high latitudes and propagate upward and equatorward into the mid-latitude middle atmosphere where they produce westward forcing reaching peak values of ~ 60–70 m s−1 day−1. These propagation paths in the lower latitude stratosphere appear to depend on the phase of the quasi-biennial oscillation (QBO). During the easterly phase of the QBO, waves originating at high latitudes propagate across the equator, while in the westerly phase of the QBO, the planetary waves break at ~ 20–25° N and there is no propagation across the equator. The propagation of planetary waves across the equator during the easterly phase of the QBO reduces the tropical upwelling and poleward flow in the upper stratosphere.

scholarly journals Chemical contribution to future tropical ozone change in the lower stratosphere

2014 ◽  
Vol 14 (6) ◽  
pp. 2959-2971 ◽  
Author(s):  
S. Meul ◽  
U. Langematz ◽  
S. Oberländer ◽  
H. Garny ◽  
P. Jöckel
Keyword(s):  
Lower Stratosphere ◽  
Climate Model ◽  
Dominant Role ◽  
Ozone Production ◽  
Net Production ◽  
Future Evolution ◽  
Ozone Loss ◽  
The Future ◽  
Ozone Column

Abstract. The future evolution of tropical ozone in a changing climate is investigated by analysing time slice simulations made with the chemistry–climate model EMAC. Between the present and the end of the 21st century a significant increase in ozone is found globally for the upper stratosphere and the extratropical lower stratosphere, while in the tropical lower stratosphere ozone decreases significantly by up to 30%. Previous studies have shown that this decrease is connected to changes in tropical upwelling. Here the dominant role of transport for the future ozone decrease is confirmed, but it is found that in addition changes in chemical ozone production and destruction do contribute to the ozone changes in the tropical lower stratosphere. Between 50 and 30 hPa the dynamically induced ozone decrease of up to 22% is amplified by 11–19% due to a reduced ozone production. This is counteracted by a decrease in the ozone loss causing an ozone increase by 15–28%. At 70 hPa the large ozone decrease due to transport (−52%) is reduced by an enhanced photochemical ozone production (+28%) but slightly increased (−5%) due to an enhanced ozone loss. It is found that the increase in the ozone production in the lowermost stratosphere is mainly due to a transport induced decrease in the overlying ozone column while at higher altitudes the ozone production decreases as a consequence of a chemically induced increase in the overlying ozone column. The ozone increase that is attributed to changes in ozone loss between 50 and 30 hPa is mainly caused by a slowing of the ClOx and NOx loss cycles. The enhanced ozone destruction below 70 hPa can be attributed to an increased efficiency of the HOx loss cycle. The role of ozone transport in determining the ozone trend in this region is found to depend on the changes in the net production as a reduced net production also reduces the amount of ozone that can be transported within an air parcel.

scholarly journals Attribution of recent ozone changes in the Southern Hemisphere mid-latitudes using statistical analysis and chemistry–climate model simulations

2017 ◽  
Vol 17 (17) ◽  
pp. 10495-10513 ◽  
Author(s):  
Guang Zeng ◽  
Olaf Morgenstern ◽  
Hisako Shiona ◽  
Alan J. Thomas ◽  
Richard R. Querel ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Southern Hemisphere ◽  
Lower Stratosphere ◽  
Climate Model ◽  
Lower Troposphere ◽  
Atmospheric Composition ◽  
Positive Trend ◽  
Tropopause Height ◽  
Significant Positive Trend ◽  
Tropopause Region

Abstract. Ozone (O3) trends and variability from a 28-year (1987–2014) ozonesonde record at Lauder, New Zealand, have been analysed and interpreted using a statistical model and a global chemistry–climate model (CCM). Lauder is a clean rural measurement site often representative of the Southern Hemisphere (SH) mid-latitude background atmosphere. O3 trends over this period at this location are characterised by a significant positive trend below 6 km, a significant negative trend in the tropopause region and the lower stratosphere between 9 and 15 km, and no significant trend in the free troposphere (6–9 km) and the stratosphere above 15 km. We find that significant positive trends in lower tropospheric ozone are correlated with increasing temperature and decreasing relative humidity at the surface over this period, whereas significant negative trends in the upper troposphere and the lower stratosphere appear to be strongly linked to an upward trend of the tropopause height. Relative humidity and the tropopause height also dominate O3 variability at Lauder in the lower troposphere and the tropopause region, respectively. We perform an attribution of these trends to anthropogenic forcings including O3 precursors, greenhouse gases (GHGs), and O3-depleting substances (ODSs), using CCM simulations. Results indicate that changes in anthropogenic O3 precursors contribute significantly to stratospheric O3 reduction, changes in ODSs contribute significantly to tropospheric O3 reduction, and increased GHGs contribute significantly to stratospheric O3 increases at Lauder. Methane (CH4) likely contributes positively to O3 trends in both the troposphere and the stratosphere, but the contribution is not significant at the 95 % confidence level over this period. An extended analysis of CCM results covering 1960–2010 (i.e. starting well before the observations) reveals significant contributions from all forcings to O3 trends at Lauder – i.e. increases in GHGs and the increase in CH4 alone all contribute significantly to O3 increases, net increases in ODSs lead to O3 reduction, and increases in non-methane O3 precursors cause O3 increases in the troposphere and reductions in the stratosphere. This study suggests that a long-term ozonesonde record obtained at a SH mid-latitude background site (corroborated by a surface O3 record at a nearby SH mid-latitude site, Baring Head, which also shows a significant positive trend) is a useful indicator for detecting atmospheric composition and climate change associated with human activities.

scholarly journals Bromine and iodine chemistry in a global chemistry-climate model: description and evaluation of very short-lived oceanic sources

2011 ◽  
Vol 11 (10) ◽  
pp. 27421-27474 ◽  
Author(s):  
C. Ordóñez ◽  
J.-F. Lamarque ◽  
S. Tilmes ◽  
D. E. Kinnison ◽  
E. L. Atlas ◽  
...  
Keyword(s):  
Lower Stratosphere ◽  
Marine Boundary Layer ◽  
Climate Model ◽  
Lower Boundary ◽  
Heterogeneous Reactions ◽  
Model Description ◽  
Lower Boundary Condition ◽  
Chl A ◽  
Iodine Chemistry ◽  
Good Agreement

Abstract. The global chemistry-climate model CAM-Chem has been extended to incorporate an expanded bromine and iodine chemistry scheme that includes natural oceanic sources of very short-lived (VSL) halocarbons, gas-phase photochemistry and heterogeneous reactions on aerosols. Ocean emissions of five VSL bromocarbons (CHBr3, CH2Br2, CH2BrCl, CHBrCl2, CHBr2Cl) and three VSL iodocarbons (CH2ICl, CH2IBr, CH2I2) have been parameterised by a biogenic chlorophyll-a (chl-a) dependent source in the tropical oceans (20° N–20° S) as well as constant oceanic fluxes with a 2.5 coast-to-ocean emission ratio for the extratropics (latitudinal bands 20°–50° and 50°–90° in both hemispheres). Top-down emission estimates of bromocarbons have been derived using available measurements in the troposphere and lower stratosphere, while iodocarbons have been constrained with observations in the marine boundary layer (MBL). Emissions of CH3I are based on a previous inventory and the longer lived CH3Br is set to a lower boundary condition. The global oceanic emissions estimated for the most abundant VSL bromocarbons – 533 Gg yr−1 for CHBr3 and 67.3 Gg yr−1 for CH2Br2 – are within the range of previous estimates. Overall the latitudinal and vertical distributions of modelled bromocarbons are in good agreement with observations. Nevertheless, we identify some issues such as the reduced number of aircraft observations to validate models in the Southern Hemisphere, the overestimation of CH2Br2 in the upper troposphere – lower stratosphere and the underestimation of CH3I in the same region. Despite the difficulties involved in the global modelling of the most short-lived iodocarbons (CH2ICl, CH2IBr, CH2I2), modelled results are in good agreement with published observations in the MBL. Finally, sensitivity simulations show that knowledge of the diurnal emission cycle for these species, in particular for CH2I2, is key to assess their global source strength.

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