Space-based evaluation of interactions between aerosols and low-level Arctic clouds during the Spring and Summer of 2008

Abstract

Abstract. This study explores the indirect effects of anthropogenic and biomass burning aerosols on Arctic clouds by co-locating a combination of MODIS and POLDER cloud products with output from the FLEXPART tracer transport model. During the activities of the International Polar Year for the Spring and Summer of 2008, we find a high sensitivity of Arctic cloud radiative properties to both anthropogenic and biomass burning pollution plumes, particularly at air temperatures near freezing or potential temperatures near 286 K. However, the sensitivity is much lower at both colder and warmer temperatures, possibly due to increases in the wet and dry scavenging of cloud condensation nuclei: the pollution plumes remain but the component that influences Arctic clouds has been removed along transport pathways. The analysis shows that, independent of local temperature, cloud optical depth is approximately four times more sensitive to changes in pollution levels than is cloud effective radius. This suggests that some form of feedback mechanism amplifies the radiative response of Arctic clouds to pollution through changes in cloud liquid water path.

Effects of long-range aerosol transport on the microphysical properties of low-level liquid clouds in the Arctic

“…Our study extends the Tietze et al (2011) research by adding 2 years of data, 2009 and 2010, and in addition to temperature, stratifying the results by lower tropospheric stability (LTS) and atmospheric specific humidity (Matsui et al, 2006;Mauger and Norris, 2007). Our results highlight the importance of considering meteorological conditions when assessing the aerosol impact on cloud microphysical properties to show that r e and τ have similar sensitivities to pollution.…”

“…Colocating satellite cloud retrievals with pollution tracer output from a chemical transport model offers an alternative approach for assessing the effect of pollution on clouds Lance et al, 2011;Tietze et al, 2011). Cloud microphysical properties and pollution concentrations can be estimated at the same time, location, and meteorological regime (Schwartz et al, 2002;Kawamoto et al, 2006;Avey et al, 2007).…”

“…CO was colocated with POLDER-3 (POLarization and Directionality of the Earth's Reflectance) and MODIS (MODerate-resolution Imaging Spectroradiometer) observations. Tietze et al (2011) showed that the sensitivity of liquid-cloud-droplet effective radius (r e ) and optical depth (τ ) to pollution has a maximum around the freezing point, and that the sensitivity decreases for both higher and lower temperatures. The optical depth was generally up to 4 times more sensitive than the effective radius.…”

“…Using the approach of colocating a passive tracer from a tracer transport model with satellite observations, Tietze et al (2011) presented an analysis of pollution-cloud interactions over the Arctic from March to July 2008. Anthropogenic and biomass burning aerosol pollution was represented using a CO passive tracer in the FLEXPART (FLEXible PARTicle dispersion model) tracer model (Stohl et al, 2005) as a proxy.…”

Measurements of aerosol and CCN properties in the Mackenzie River delta (Canadian Arctic) during spring–summer transition in May 2014

“…This can change the interaction with incoming shortwave radiation, increasing cloud reflectivity and therefore cooling. This effect might be of limited relevance in the Arctic since its surface is highly reflective due to snow and ice (Tietze et al, 2011). However, a higher droplet number concentration would also lead to increased cloud longwave emissivity, which warms the Earth's surface (Garrett et al, 2002;Lubin and Vogelmann, 2006).…”