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We examine the distribution of aerosol optical depth (AOD) across 27,707 northern hemisphere (NH) midlatitude cyclones for 2005–2018 using retrievals from the Moderate Resolution Spectroradiometer (MODIS) sensor on the Aqua satellite. Cyclone‐centered composites show AOD enhancements of 20%–45% relative to background conditions in the warm conveyor belt (WCB) airstream. Fine mode AOD accounts for 68% of this enhancement annually. Relative to background conditions, coarse mode AOD is enhanced by more than a factor of two near the center of the composite cyclone, co‐located with high surface wind speeds. Within the WCB, MODIS AOD maximizes in spring, with a secondary maximum in summer. Cyclone‐centered composites of AOD from the Modern Era Retrospective analysis for Research and Applications, version 2 Global Modeling Initiative (M2GMI) simulation reproduce the magnitude and seasonality of the MODIS AOD composites and enhancements. M2GMI simulations show that the AOD enhancement in the WCB is dominated by sulfate (37%) and organic aerosol (25%), with dust and sea salt each accounting for 15%. MODIS and M2GMI AOD are 60% larger in North Pacific WCBs compared to North Atlantic WCBs and show a strong relationship with anthropogenic pollution. We infer that NH midlatitude cyclones account for 355 Tg yr⁻¹of sea salt aerosol emissions annually, or 60% of the 30–80°N total. We find that deposition within WCBs is responsible for up to 35% of the total aerosol deposition over the NH ocean basins. Furthermore, the cloudy environment of WCBs leads to efficient secondary sulfate production.

Summertime surface‐level ozone (O₃) is known to vary with temperature, but the relative roles of different processes responsible for causing the O₃‐temperature relationship are not well quantified. In this study we use simulations of NASA's Global Modeling Initiative chemical transport model to isolate and assess the relative impact of atmospheric transport, chemistry, and emissions on large‐scale O₃variability, events, and and the covariance of O₃with temperature. Using observations from the Clean Air Status and Trends Network in the contiguous United States, we show that the Global Modeling Initiative chemical transport model reproduces the spatiotemporal variability of O₃and its relationship with temperature during the summer. We use the change in O₃given a change in temperature (dO₃/dT) along with other metrics to understand differences between our simulations. In regions with moderate to strong positive correlations between temperature and O₃such as the northeast, Great Lakes, and Great Plains, temperature's association with transport yields a majority of the total O₃‐temperature relationship (∼60%), while temperature‐dependent chemistry and anthropogenic NO emissions play smaller roles (∼30% and ∼10%, respectively). There are regions, however, with insignificant correlations between temperature and O₃, and our findings suggest that transport is still an important driver of O₃variability in these regions, albeit not correlated with temperature. Transport is not directly dependent on temperature but rather is linked through an indirect association, and it is therefore important to understand the exact mechanisms that link transport to O₃and how these mechanisms will change in a warming world.