Using Multi-Decadal Records of Long-Lived Constituents to Understand Dynamical Processes Affecting O3 Trends
Abstract
Ground-based measurements show that the atmospheric concentrations of ozone depleting substances (ODSs) are decreasing because the Montreal Protocol (MP) and its amendments required cessation of their production in the 1990s. This decrease prompts effort to detect and quantify stratospheric ozone increases due to ODS decrease. The present rate of ODS decrease is much smaller than the rate of ODS increase prior to the MP. Detection lower stratospheric ozone increase due to ODS decrease is challenging due to the long ozone lifetime, interannual variability due to dynamics, and the need to combine datasets from various satellite sensors in order to obtain a global dataset of sufficient length. Concurrent ozone changes are also probable due to changes stratospheric climate, circulation and mixing.
Significant effort to identify and quantify the dynamic contributions to ozone trends, i.e., the changes in lower stratospheric transport and mixing that masquerade as changes in photochemical loss due to composition change, began in the late 1990s and early 2000s. We are investigating how the dynamical processes affect detection of expected ozone recovery by quantifying how multi-year satellite and ground-based records of other constituents (e.g., nitrous oxide, hydrogen chloride, nitric acid) are impacted by interannual variability. We will present results from parallel analyses of observations and simulations. Observations include 25+ year records of column HCl and HNO3 from the Network for Detection of Stratospheric Composition Change (NDACC) and 14-year records of N2O, HCl and HNO3 from Aura MLS. Simulations include a hindcast using the Global Modeling Initiative chemistry and transport model driven by meteorological fields from MERRA-2. Preliminary results show that the standard approach to trend detection does not return the known surface N2O growth rate when applied to either MLS N2O records or to longer time series obtained from a simulation with realistic interannual variability. We will also consider how these schemes interact with the annual cycle, noting that for constituents like nitrous oxide the annual cycle is dynamically driven whereas for ozone both dynamics and photochemistry play a role.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.A31A..05D
- Keywords:
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- 0340 Middle atmosphere: composition and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 0341 Middle atmosphere: constituent transport and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 3305 Climate change and variability;
- ATMOSPHERIC PROCESSESDE: 3334 Middle atmosphere dynamics;
- ATMOSPHERIC PROCESSES