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 À1 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 À1) 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 À1 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.
Growing awareness of the impact of monoterpenes on climate, atmospheric chemistry, and indoor air quality has necessitated the development of measurement standards to globally monitor and control their emissions. For National Metrology Institutes to develop such standards, it is essential that they demonstrate measurement equivalence for assigned values at the highest levels of accuracy. This report describes the results of a pilot comparison for 4 key monoterpene species: α-pinene, 3-carene, R-limonene and 1,8-cineole, at a nominal amount-of-substance fraction of 2.5 nmol mol−1. The objective of this comparison is to evaluate participant capabilities to measure trace-level monoterpenes using their own calibration techniques. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).
This key comparison aims to assess the core capabilities of the participants in gas analysis. Such competences include, among others, the capabilities to prepare primary standard gas Mixtures (PSMs), perform the necessary purity analysis on the materials used in the gas mixture preparation, the verification of the composition of newly prepared PSMs against existing ones, and the capability of calibrating the composition of a gas mixture. According to the Strategy for Key Comparisons of the Gas Analysis Working Group, this key comparison is classified as a track A key comparison, which means that the results of this key comparison can be used to underpin calibration and measurement capabilities using the flexible scheme, and for propane under the default scheme. The artefacts were binary mixtures of propane in nitrogen at a nominal amount-of-substance fraction level of 1000 μmol/mol. The values and uncertainties from the gravimetric gas mixture preparation were used as key comparison reference values (KCRVs). Each transfer standard had its own KCRV. The results are generally good. All results but one are within ± 0.2 % of the KCRV. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).
The growing awareness of climate change, and continuing concerns regarding tropospheric and stratospheric chemistry, will require future measurements and standards for compounds linked to these issues. To globally monitor and control the emissions of these species in the atmosphere, it is necessary to demonstrate measurement equivalence at the highest levels of accuracy for assigned values of standards. This report describes the results of a key comparison for several important monoterpene species, which are relevant to atmospheric chemistry and climate. The comparison samples include α-pinene, 3-carene, R-limonene and 1,8-cineole in a nitrogen matrix gas, at a 2.5 nmol mol−1 amount-of-substance fraction. The objective of this key comparison is to evaluate the participants’ capabilities to measure trace-level monoterpenes using their own calibration techniques.
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