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Inadvertent Weather Modification : Aerosol Indirect Effects

@Since both the radiative properties of clouds and their ability to precipitate are dependent upon the size distribution of cloud droplets for warm clouds and upon the partitioning between supercooled droplets and ice crystals for cold clouds, the activation processes of aerosol particles functioning as cloud condensation nuclei (CCN) and ice nuclei (IN), which determine initial droplet size distribution and number concentration of ice crystals, are important. Through cloud-radiation interaction and precipitation mechanisms, aerosol particles further affect the spatial extent and lifetime of clouds, and consequently influence surface precipitation. To enable better understanding of the effects of aerosol particles on clouds and precipitation, which will help to improve short-range precipitation forecasts and climate change projections, MRI investigated the relationships linking the microphysical properties of various kinds of clouds and the physico-chemical properties of aerosol particles acting as CCN and IN through aircraft observation and laboratory experiments. The indirect effects of aerosols on clouds and precipitation were also quantitatively studied using the NHM with aerosol-cloud-precipitation unified microphysics parameterization.

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Laboratory Study of Aerosol Indirect Effects by Using MRI Cloud Simulation Chamber

@A versatile aerosol species consists of soluble/insoluble matter has a potential ability to act as CCN and/or IN, and some of them actually activate under conditions relevant to the atmosphere. It is an urgent subject to unravel the entanglement of ice formation processes through multiple pathways. To reduce the uncertainty in estimates of the aerosol indirect effects, we attempt to propose novel physics-based parameterizations that link aerosol particles and cloud particles from the experimental approaches. The MRI dynamic cloud chamber experiments of ice formation by soot and external mixing state of mineral dust are under way. We herein describe the overview of this study and the preliminary results on the potential role of these particles as CCN and IN.

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Measurements

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Dust particles

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Soot particles

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Comparison of Dust/Soot

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External mixing particles

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