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Sensitivity of tropical tropospheric composition to lightning NO x production as determined by replay simulations with GEOS‐5
Author(s) -
Liaskos Christina E.,
Allen Dale J.,
Pickering Kenneth E.
Publication year - 2015
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2014jd022987
Subject(s) - troposphere , tropopause , atmospheric sciences , lightning (connector) , altitude (triangle) , environmental science , climatology , ozone , radiative transfer , physics , meteorology , thermodynamics , mathematics , geology , power (physics) , geometry , quantum mechanics
The sensitivity of tropical tropospheric composition to the source strength of nitrogen oxides (NO x ) produced by lightning (LNO x ) is analyzed for September through November 2007 using the NASA GEOS‐5 model constrained by MERRA fields, with full GMI stratospheric‐tropospheric chemistry and an LNO x algorithm that is appropriate for use in a climate modeling setting; satellite retrievals from OMI, TES, and OMI/MLS; and in situ measurements from SHADOZ ozonesondes. Global mean LNO x production rates of 0 to 492 mol NO flash −1 and the subsequent responses of NO x , ozone (O 3 ), hydroxyl radical (OH), nitric acid (HNO 3 ), peroxyacetyl nitrate (PAN), and NO y (NO x + HNO 3 + PAN) are investigated. The radiative implications associated with LNO x ‐induced changes in tropospheric O 3 are assessed. Increasing the LNO x production rate by a factor of 4 (from 123 to 492 mol flash −1 ) leads to tropical upper tropospheric enhancements of greater than 100% in NO x , OH, HNO 3 , and PAN. This increase in LNO x production also leads to O 3 enhancements of up to 60%, which subsequently yields a factor‐of‐three increase in the mean net radiative flux at the tropopause. An LNO x source of 246 mol flash −1 agrees reasonably well with measurements, with an approximate factor‐of‐two uncertainty due to the short length of the study, inconsistencies in the observational data sets, and systematic biases in modeled LNO x production. Further research into the regional dependencies of lightning flash rates and LNO x production per flash, along with improvements in satellite retrievals, should help resolve the discrepancies that currently exist between the model and observations.