Aerosol–cloud interaction is the most uncertain component of the overall anthropogenic forcing of
the climate, in which cloud droplet number concentration (Nd) sensitivity to aerosol (S) is a key term for the
overall estimation. However, satellite-based estimates of S are especially challenging, mainly due to the difficulty in disentangling aerosol effects on Nd from possible confounders. By combining multiple satellite observations and reanalysis, this study investigates the impacts of (a) updraft, (b) precipitation, (c) retrieval errors,
and (d) vertical co-location between aerosol and cloud on the assessment of S in the context of marine warm
(liquid) clouds. Our analysis suggests that S increases remarkably with both cloud-base height and cloud geometric thickness (proxies for vertical velocity at cloud base), consistent with stronger aerosol–cloud interactions
at larger updraft velocity for midlatitude and low-latitude clouds. In turn, introducing the confounding effect
of aerosol–precipitation interaction can artificially amplify S by an estimated 21 %, highlighting the necessity
of removing precipitating clouds from analyses of S. It is noted that the retrieval biases in aerosol and cloud
appear to underestimate S, in which cloud fraction acts as a key modulator, making it practically difficult to balance the accuracies of aerosol–cloud retrievals at aggregate scales (e.g., 1◦ × 1
◦ grid). Moreover, we show that
using column-integrated sulfate mass concentration (SO4C) to approximate sulfate concentration at cloud base
(SO4B) can result in a degradation of correlation with Nd, along with a nearly twofold enhancement of S, mostly
attributed to the inability of SO4C to capture the full spatiotemporal variability of SO4B. These findings point
to several potential ways forward to practically account for the major influential factors by means of satellite
observations and reanalysis, aiming at optimal observational estimates of global radiative forcings due to the
Twomey effect and also cloud adjustments.
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:82031 |
| Date | 08 November 2022 |
| Creators | Jia, Hailing, Quaas, Johannes, Gryspeerdt, Edward, Böhm, Christoph, Sourdeval, Odran |
| Publisher | European Geosciences Union, Copernicus Publications |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, doc-type:article, info:eu-repo/semantics/article, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | 10.5194/acp-22-7353-2022 |
Page generated in 0.0027 seconds