Roles of transport and chemistry processes in global ozone change on interannual and multidecadal time scales

Abstract

This study investigates ozone changes and the individual impacts of transport and chemistry on those changes. We specifically examine (1) variation related to El Niño Southern Oscillation, which is a dominant mode of interannual variation of tropospheric ozone, and (2) long‐term change between the 2000s and 2100s. During El Niño, the simulated ozone shows an increase (1 ppbv/K) over Indonesia, a decrease (2–10 ppbv/K) over the eastern Pacific in the tropical troposphere, and an increase (50 ppbv/K) over the eastern Pacific in the midlatitude lower stratosphere. These variations fundamentally agree with those observed by Microwave Limb Sounder/Tropospheric Emission Spectrometer instruments. The model demonstrates that tropospheric chemistry has a strong impact on the variation over the eastern Pacific in the tropical lower troposphere and that transport dominates the variation in the midlatitude lower stratosphere. Between the 2000s and 2100s, the model predicts an increase in the global burden of stratospheric ozone (0.24%/decade) and a decrease in the global burden of tropospheric ozone (0.82%/decade). The increase in the stratospheric burden is controlled by stratospheric chemistry. Tropospheric chemistry reduces the tropospheric burden by 1.07%/decade. However, transport (i.e., stratosphere‐troposphere exchange and tropospheric circulation) causes an increase in the burden (0.25%/decade). Additionally, we test the sensitivity of ozone changes to increased horizontal resolution of the representation of atmospheric circulation and advection apart from any aspects of the nonlinearity of chemistry sensitivity to horizontal resolution. No marked difference is found in medium‐resolution or high‐resolution simulations, suggesting that the increased horizontal resolution of transport has a minor impact.

Tropospheric ozone and its precursors from the urban to the global scale from air quality to short-lived climate forcer

“…ENSO has been shown to modulate the tropospheric ozone burden across the tropical Pacific Ocean with lower tropospheric column ozone corresponding to the cloudiest regions (Ziemke and Chandra, 2003;Sekiya and Sudo, 2014). Zeng and Pyle (2005) calculated an anomalously large increase in stratosphere-troposphere exchange following a typical El Niño year, increasing the global tropospheric ozone burden.…”

Tropospheric Ozone Assessment Report: Assessment of global-scale model performance for global and regional ozone distributions, variability, and trends

“…therein). A few studies show that CCMs driven by observed SSTs (AMIP mode; see Section 2.1) are able to capture the overall pattern and magnitude of the tropical ozone response to ENSO obtained from satellite measurements (Oman et al, 2013;Sekiya and Sudo, 2014), including the observed ozone-ENSO index (Ziemke et al, 2010;Oman et al, 2011). This is calculated as the difference between observed monthly mean column ozone over two broad regions in the western and eastern Pacific ocean; see Figure 8 for an example.…”

The Impacts of Meteorology on the Seasonal and Interannual Variabilities of Ozone Transport From North America to East Asia

“…Because our interest is to study how meteorology influences the interannual variation of ozone transport from North America to East Asia, we allow the meteorology to vary from year to year between 1987 and 2006 but keep the chemistry the same for all years, i.e., we use the archived daily ozone production and loss data in 2005 for all years (year 2005 was randomly chosen). This is an effective approach that has also been used in previous studies (Li et al, ; Liu et al, ; Liu et al, ; Sekiya & Sudo, ). Therefore, the interannual variability of the NA ozone presented in section 5 is driven by meteorology only, while the seasonality of the GEOS‐Chem simulations presented in section 4 is the result of the combined effects of meteorology and chemistry.…”