Large‐Scale Industrial Cloud Perturbations Confirm Bidirectional Cloud Water Responses to Anthropogenic Aerosols

Abstract

 Satellite observations confirm aerosol-induced decreases in cloud droplet size in large areas compared to nearby less polluted areas  Aerosol-induced cloud water increases and decreases compensate each other at large spatial scales similarly to ship-track-like perturbations  On average, Twomey effect is more important than the effect of cloud water changes for the aerosol radiative forcing of the Earth's climate

Opportunistic experiments to constrain aerosol effective radiative forcing

“…Stratiform clouds over land responded to isolated pollution sources in much the same manner as marine stratiform clouds did. An expanded analysis, focusing on the Norilsk pollution hotspot in Russia but including some data from the United States, Europe, and eastern Asia in addition to that used in Toll et al (2019) confirmed that competing LWP adjustments in varying conditions average out to a small offset of the Twomey effect ( Trofimov et al, 2020 ). It is noteworthy that this result, where the focus is more in continental areas, contrasts with more significant Twomey effect offsets in the shipping lane study of Diamond and Wood (2020) .…”

“…As an example, copper and nickel production facilities in Norilsk, Russia, emit more than 1 Mt of SO 2 each year, i.e., more than 1 % of global anthropogenic SO 2 emissions ( Fioletov et al, 2016 ). Such strong localized emissions induce a high contrast between clouds affected by the emissions of the Norilsk smelters and nearby less polluted clouds ( Trofimov et al, 2020 ). The opening and closing of large factories and implementation of desulfurization devices can lead to rapid changes in emissions ( Fioletov et al, 2016 ), providing additional insight into aerosol impacts on clouds.…”

“…Some individual wildfire plumes were analyzed in the studies of Toll et al (2019) and Trofimov et al (2020) . Another opportunistic experiment is the smoke–cloud system that develops seasonally over the southeast Atlantic stratocumulus deck ( Zuidema et al, 2016 , 2018 ), where it is obvious that the smoke can be traced to the effects of agricultural burning over the continent rather than processes occurring over the ocean.…”

“… Carn et al (2017) catalog the emission rates of SO 2 from several hundred passive degassing volcanoes using a combination of satellite retrievals and ground-based measurements. In addition, opportunistic experiments resulting from prominent industrial sites such as Norilsk ( Fioletov et al, 2016 ), persistent and weakly explosive volcanic eruptions, (e.g., South Sandwich Islands’ volcanoes and Ambrym), and significant fire “outbreak” seasons have been logged from satellite imagery in Toll et al (2019) and Trofimov et al (2020) . Ship track databases identified from MODIS satellite imagery are available for the tracks: (a) off the California coast during summer months of 2002–2004 ( Coakley and Walsh, 2002 ; Segrin et al, 2007 ; Christensen et al, 2009 ); (b) off the California, Chilean, and Namibian coasts from 2007–2010 collocated to CloudSat and CALIPSO ( Christensen and Stephens, 2011 , 2012 ; Chen et al, 2012 ; Christensen et al, 2014 ); (c) off the California coast for studying recent shipping emission regulations ( Gryspeerdt et al, 2019b ); and (d) globally through the use of machine learning ( Yuan et al, 2019 ).…”

Liquid Containing Clouds at the North Slope of Alaska Demonstrate Sensitivity to Local Industrial Aerosol Emissions

“…If total condensate mass does not change, increased N l results in decreased cloud droplet size, enhancing cloud albedo (Twomey, 1976;Quaas et al, 2020) and longwave emissivity for optically-thin clouds (Garrett & Zhao, 2006;Lubin & Vogelmann, 2006). Aerosols may also impact cloud lifetime through alteration of precipitation processes (Albrecht, 1989), though recent studies (Wood, 2007;Malavelle et al, 2017;Gryspeerdt et al, 2019;Rosenfeld et al, 2019;Toll et al, 2019;Trofimov et al, 2020) show limited relationships between liquid water path (LWP) and aerosol concentration, suggesting system buffering (Stevens & Feingold, 2009). Challenges associated with quantifying these aerosol-cloud effects contribute significantly to uncertainties in understanding the climate system, in particular in the Arctic (Zamora et al, 2018;Engelmann et al, 2020;Schmale et al, 2021).…”