Observational Insights into the Factors that Modulate Aerosol Impacts on Warm Clouds
Abstract
A large number of modern satellite datasets provide complementary evidence of aerosol influences on the microphysical, macrophysical, and radiative properties of warm clouds. This presentation will demonstrate that these observations are now sufficiently mature and abundant to qualitatively distinguish a wide range of independent, robust aerosol signatures from transient effects that may be artifacts of the methodology or datasets adopted. In some cases, modeled and observed aerosol influences on cloud properties diverge to such a degree that we can identify model biases with some confidence. More generally, however, quantitative relationships derived from satellite datasets are subject to numerous sources of uncertainty owing to inaccurate retrieval methodologies, a lack of knowledge of aerosol nucleation rate, and the strong covariation of cloud properties, aerosol abundance, and environmental conditions. To establish the significance of new observationally-derived estimates of aerosol effects we will examine their sensitivity to uncertainties in observed aerosol and cloud properties, the source of aerosol proxy adopted, local environmental conditions, and the relative vertical placement of cloud and aerosol layers. The analysis reveals that while some aerosol signatures are robust, others depend on the specific choice of datasets employed or fail to exceed realistic noise levels imposed by uncertainties in current satellite products. For example, many relationships that are robust in specific regions at certain times of year are not universal globally. Common to all observed relationships is the fact that aerosol signatures exhibit profound sensitivity to local meteorology and cloud morphology reinforcing the notion that aerosol-cloud interactions vary significantly between scenes, even over relatively large time and space domains. The results caution against the use of universal relationships to represent aerosol-cloud interactions globally but provide a pathway for exploiting the diverse modern satellite record to develop robust statistical estimates of the magnitude of albedo and cloud lifetime effects that transcend these limitations and yield predictive skill.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.A43N..02L
- Keywords:
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- 0305 Aerosols and particles;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 3311 Clouds and aerosols;
- ATMOSPHERIC PROCESSESDE: 3337 Global climate models;
- ATMOSPHERIC PROCESSESDE: 3275 Uncertainty quantification;
- MATHEMATICAL GEOPHYSICS