Aerosol-induced changes of convective cloud anvils produce strong climate warming

By Ilan Koren, Lorraine Remer, O. Altaratz, J. Martins, A. Davidi. 2010

145 citations recorded by the source corpus.

Abstract. The effect of aerosol on clouds poses one of the largest uncertainties in estimating the anthropogenic contribution to climate change. Small human-induced perturbations to cloud characteristics via aerosol pathways can create a change in the top-of-atmosphere radiative forcing of hundreds of Wm−2. Here we focus on links between aerosol and deep convective clouds of the Atlantic and Pacific Intertropical Convergence Zones, noting that the aerosol environment in each region is entirely different. The tops of these vertically developed clouds consisting of mostly ice can reach high levels of the atmosphere, overshooting the lower stratosphere and reaching altitudes greater than 16 km. We show a link between aerosol, clouds and the free atmosphere wind profile that can change the magnitude and sign of the overall climate radiative forcing. We find that increased aerosol loading is associated with taller cloud towers and anvils. The taller clouds reach levels of enhanced wind speeds that act to spread and thin the anvil clouds, increasing areal coverage and decreasing cloud optical depth. The radiative effect of this transition is to create a positive radiative forcing (warming) at top-of-atmosphere. Furthermore we introduce the cloud optical depth (τ), cloud height (Z) forcing space and show that underestimation of radiative forcing is likely to occur in cases of non homogenous clouds. Specifically, the mean radiative forcing of towers and anvils in the same scene can be several times greater than simply calculating the forcing from the mean cloud optical depth in the scene. Limitations of the method are discussed, alternative sources of aerosol loading are tested and meteorological variance is restricted, but the trend of taller clouds, increased and thinner anvils associated with increased aerosol loading remains robust through all the different tests and perturbations.

Subfields: Atmospheric Science, Global and Planetary Change

View Paper: https://www.semanticscholar.org/paper/074cc4bb4377909fdadd9e36a44e3f173fbe08e0

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Atmospheric Science

In Global and Planetary Change

Citations in the corpus

Review of Aerosol–Cloud Interactions: Mechanisms, Significance, and Challenges (2016, background): “On the other hand, numerous observational studies showed the increased cloud-top height and cloud cover with an increase of aerosol loading (e.g., Andreae et al. 2004; Koren et al. 2010; Li et al. 2011;Niu andLi 2012).”
The invigoration of deep convective clouds over the Atlantic: aerosol effect, meteorology or retrieval artifact? (2010, background): “The rain band is associated with deep convective elements, surrounded by thinner ice anvils (Koren et al., 2010).”
A review on regional convection‐permitting climate modeling: Demonstrations, prospects, and challenges (2015, background): “Thus, droplet number concentration and radiative properties of clouds [e.g., Koren et al., 2010] might be misrepresented in CPMs with possibly far-reaching consequences on the dynamics of clouds, e.g., cloud top height, extent, or aggregation, and the resulting precipitation [e.g., Fan et al.,…”
Global observations of aerosol‐cloud‐precipitation‐climate interactions (2014, background): “…demonstrated that this often explains a substantial part of the indicated decrease in cloud-top pressure in association with greater AOD, which has been ascribed to aerosol cloud invigoration [Koren et al., 2005, 2010a, 2010b, 2012; Yuan et al., 2011a, 2011b; Niu and Li, 2012; Koren et al., 2014].”
Aerosol Effects on Microstructure and Intensity of Tropical Cyclones (2012, background): “This hypothesis was supported by additional observations (Koren et al. 2005, 2010) and simulations (Wang 2005; Khain et al. 2008b).”