Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
doi:10.5194/acp-2016-1000
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
06 Dec 2016
Review status
A revision of this discussion paper is under review for the journal Atmospheric Chemistry and Physics (ACP).
Satellite observed indications of aerosol effects on warm cloud properties over Yangtze River Delta of China
Yuqin Liu1,2,3, Gerrit de Leeuw1,3,4, Veli-Matti Kerminen3, Jiahua Zhang1, Putian Zhou3, Wei Nie5, Ximeng Qi5, Juan Hong3, Yonghong Wang3, Aijun Ding5, Huadong Guo1, Olaf Krüger3, Markku Kulmala3, and Tuukka Petäjä3 1Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, Beijing, China
2University of Chinese Academy of Sciences, Beijing, China
3Department of Physics, P.O. Box 64, 00014 University of Helsinki, Helsinki, Finland
4Finish Meteorological Institute, Climate Change Unit, P.O. Box 503, 00101 Helsinki, Finland
5Institute for Climate and Global Change Research & School of Atmospheric Sciences, Nanjing University, 210023 Nanjing, China
Abstract. Aerosol effects on summertime low warm clouds over the Yangtze River Delta (YRD) are examined using co-located MODIS, CALIOP and CloudSat observations. By taking the vertical locations of aerosol and cloud layers into account, we use simultaneously observed aerosol and cloud data to investigate relationships between cloud properties and the amount of aerosol particles (using aerosol optical depth, AOD, as a proxy). Also, we investigate the impact of aerosol types on the variation of cloud properties with AOD. Finally, we explore how meteorological conditions affect these relationships using ERA Interim Reanalysis data. This study shows that the relation between cloud droplet effective radius (CDR) and AOD depends on the aerosol abundance, with a different behaviour for low and high AOD (i.e. AOD <> 0.3). Cloud fraction (CF) is found to be little dependent on the AOD when aerosol and cloud physically interact, but has a positive relation in case of well-separated clouds. Cloud optical Thickness (COT) is found to decrease when AOD increases, which may be due to radiative effects and retrieval artefacts caused by absorbing aerosol. Conversely, cloud top pressure (CTP) tends to increase with elevated AOD, indicating that the aerosol is not always prone to expand the vertical extension. Furthermore, separation of cases with either polluted dust or smoke aerosol shows that COT and CF are smaller for clouds mixed with smoke aerosol which is ascribed to the higher absorption efficiency of smoke than dust. The variation of cloud properties with AOD is analysed for different values of relative humidity (RH) and boundary layer thermodynamic and dynamic conditions, showing that high relative humidity and upward motion of air parcels can enhance the strength of aerosol-cloud interaction, especially pronounced in heavily polluted conditions than in moderately polluted conditions. Meteorological conditions play a weak role in the COT-AOD and CTP-AOD relationships throughout the range of AOD. Overall, the interpretation of the observed relationships between cloud properties and AOD requires that ambient environmental conditions are considered in addition to the aerosol and cloud parameters.

Citation: Liu, Y., de Leeuw, G., Kerminen, V.-M., Zhang, J., Zhou, P., Nie, W., Qi, X., Hong, J., Wang, Y., Ding, A., Guo, H., Krüger, O., Kulmala, M., and Petäjä, T.: Satellite observed indications of aerosol effects on warm cloud properties over Yangtze River Delta of China, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-1000, in review, 2016.
Yuqin Liu et al.
Yuqin Liu et al.
Yuqin Liu et al.

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Short summary
The response of warm cloud parameters to aerosol loading over Yangtze River Delta are systematically examined using multi-sensor retrievals. Cloud droplet effective radius shows different behaviours for low and high AOD. Cloud fraction is found to be little dependent on the AOD when aerosol and cloud are mixed. Cloud optical thickness and cloud fraction are smaller for clouds mixed with smoke aerosol than dust. Meteorological conditions play a weak role in the COT-AOD and CTP-AOD relationships.
The response of warm cloud parameters to aerosol loading over Yangtze River Delta are...
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