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

KARAGODIN-DOYENNEL, ARSENIY; ROZANOV, EUGENE; SUKHODOLOV, TIMOFEI; EGOROVA, TATIANA; SAIZ-LOPEZ, ALFONSO; CUEVAS, CARLOS A.; FERNANDEZ, RAFAEL P.; SHERWEN, TOMÁS; VOLKAMER, RAINER; KOENIG, THEODORE K.; GIROUD, TANGUY; PETER, THOMAS

Geoscientific Model Development

Copernicus

Año: 2021 vol. 14 p. 6623 - 6645

In  this  paper,  we  present  a  new  version  of  thechemistry?climate model SOCOL-AERv2 supplemented byan iodine chemistry module. We perform three 20-year en-semble  experiments  to  assess  the  validity  of  the  modelediodine and to  quantify the effects of iodine  on ozone. Theiodine  distributions  obtained  with  SOCOL-AERv2-I  agreewell with AMAX-DOAS observations and with CAM-chemmodel  simulations.  For  the  present-day  atmosphere,  themodel suggests that the iodine-induced chemistry leads to a3 %?4 % reduction in the ozone column, which is greatest athigh latitudes. The model indicates the strongest influence ofiodine in the lower stratosphere with 30 ppbv less ozone atlow latitudes and up to 100 ppbv less at high latitudes. In thetroposphere, the account of the iodine chemistry reduces thetropospheric ozone concentration by 5 %?10 % depending ongeographical location. In the lower troposphere, 75 % of themodeled ozone reduction originates from inorganic sourcesof iodine, 25 % from organic sources of iodine. At 50 hPa, theresults show that the impacts of iodine from both sources arecomparable. Finally, we determine the sensitivity of ozoneto iodine by applying a 2-fold increase in iodine emissions,as  it  might  be  representative  for  iodine  by  the  end  of  thiscentury. This reduces the ozone column globally by an addi-tional 1.5 %?2.5 %. Our results demonstrate the sensitivity ofatmospheric ozone to iodine chemistry for present and futureconditions, but uncertainties remain high due to the paucityof observational data of iodine species.