Abstract. A number of the compounds proposed as replacements for substances controlled under the Montreal Protocol have extremely short atmospheric lifetimes, on the order of days to a few months. An important example is n-propyl bromide (also referred to as 1-bromopropane, CH2BrCH2CH 3 or simplified as 1-C3H7Br or nPB). This compound, useful as a solvent, has an atmospheric lifetime of less than 20 days due to its reaction with hydroxyl. Because nPB contains bromine, any amount reaching the stratosphere has the potential to affect concentrations of stratospheric ozone. The definition of Ozone Depletion Potentials (ODP) needs to be modified for such short-lived compounds to account for the location and timing of emissions. It is not adequate to treat these chemicals as if they were uniformly emitted at all latitudes and longitudes as normally done for longer-lived gases. Thus, for short-lived compounds, policymakers will need a table of ODP values instead of the single value generally provided in past studies. This study uses the MOZART2 three-dimensional chemical-transport model in combination with studies with our less computationally expensive two-dimensional model to examine potential effects of nPB on stratospheric ozone. Multiple facets of this study examine key questions regarding the amount of bromine reaching the stratosphere following emission of nPB. Our most significant findings from this study for the purposes of short-lived replacement compound ozone effects are summarized as follows. The degradation of nPB produces a significant quantity of bromoacetone which increases the amount of bromine transported to the stratosphere due to nPB. However, much of that effect is not due to bromoacetone itself, but instead to inorganic bromine which is produced from tropospheric oxidation of nPB, bromoacetone, and other degradation products and is transported above the dry and wet deposition processes of the model. The
We have also derived the adjusted and instantaneous radiative forcings for CFC-11 and 20 other halocarbons using our radiative transfer model. The sensitivity of radiative forcings to the vertical distribution of these gases is investigated in this study and is shown to be significant. The difference in the global radiative forcing arising from the assumption of a constant vertical profile for these gases is found to range from 0 to 36%, with higher difference for short-lived gases. Global Warming Potentials (GWPs) for the compounds are determined using the lifetimes and radiative forcings evaluated in this study and are found to differ from values reported by Granier et al. [1999] owing to the differences in our calculated radiative forcings and lifetimes.
Future projections of near-surface ozone concentrations depend on the climate/emissions scenario used to drive future simulations, the direct effects of the changing climate on the atmosphere, and the indirect effects of changing temperatures and CO2 levels on biogenic ozone precursor emissions. The authors investigate the influence of these factors on potential future changes in summertime daily 8-h maximum ozone over the United States and China by comparing Model for Ozone and Related Chemical Tracers, version 2.4, (MOZART-2.4) simulations for the period 1996–2000 with 2095–99, using climate projections from NCAR–Department of Energy Parallel Climate Model simulations driven by the Intergovernmental Panel on Climate Change Special Report on Emissions Scenarios A1fi (higher) and B1 (lower) emission scenarios, with corresponding changes in biogenic emissions. The effect of projected climate changes alone on surface ozone is generally less than 3 ppb over most regions. Regional ozone increases and decreases are driven mainly by local warming and marine air dilution enhancement, respectively. Changes are approximately the same magnitude under both scenarios, although spatial patterns of responses differ. Projected increases in isoprene emissions (32%–94% over both countries), however, result in significantly greater changes in surface ozone. Increases of 1–15 ppb are found under A1fi and of 0–7 ppb are found under B1. These increases not only raise the frequency of “high ozone days,” but are also projected to occur nearly uniformly across the distribution of daily ozone maxima. Thus, projected future ozone changes appear to be more sensitive to changes in biogenic emissions than to direct climate changes, and the spatial patterns and magnitude of future ozone changes depend strongly on the future emissions scenarios used.
The long‐term data collection of total ozone estimates from the Solar Backscatter Ultraviolet Ozone Sensors (SBUV and SBUV/2) began with the launch of SBUV on NASA's Nimbus‐7 spacecraft in 1978. Following this successful demonstration, the National Oceanic and Atmospheric Administration (NOAA) adopted the slightly modified SBUV/2 instruments for placement on the afternoon Polar‐Orbiting Operational Environmental Satellites (POES). The SBUV/2 instruments have flown on NOAA‐9, ‐11, ‐14, and ‐16 in the POES series, with NOAA‐16 launched in late 2000. Three more instruments are scheduled for launches in the next 6 years. While the absolute calibrations of individual instruments are good, they give total ozone accuracies of approximately 2%. However, without further adjustment, such interinstrument differences pose significant problems for atmospheric ozone trend analysis. In this paper we use the differences between total ozone estimates from the instruments during periods with overlapping coverage to account for these possible calibration biases. We use the NOAA‐9 SBUV/2 record as the reference standard because of the length of its record and the amount of overlap with other instruments' records. By applying adjustments to the other data sets based on these differences, a complete, unified data set is created for use in analysis of long‐term changes. The monthly‐averaged total ozone time series for 50°S to 50°N and the hemispheric subsets are compared to the results from two 2‐D chemistry models as a demonstration of the usefulness of the unified data sets.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.