Observations of rapid aerosol optical depth enhancements in the vicinity of polluted cumulus clouds
Author:
Eck T. F., Holben B. N., Reid J. S., Arola A.ORCID, Ferrare R. A., Hostetler C. A., Crumeyrolle S. N.ORCID, Berkoff T. A., Welton E. J., Lolli S.ORCID, Lyapustin A.ORCID, Wang Y., Schafer J. S., Giles D. M., Anderson B. E., Thornhill K. L., Minnis P.ORCID, Pickering K. E., Loughner C. P., Smirnov A.ORCID, Sinyuk A.
Abstract
Abstract. During the July 2011 DISCOVER-AQ field experiment in Maryland, significant enhancements in AERONET sun-sky radiometer measured AOD were observed in the immediate vicinity of non-precipitating cumulus clouds on some days. Both measured Angstrom exponents and aerosol size distribution retrievals made before, during and after cumulus development often suggest little change in fine mode particle size, therefore implying possible new particle formation in addition to cloud processing and humidification of existing particles. In addition to sun/sky radiometer measurements of large enhancements of fine mode AOD, lidar measurements made from both ground-based and aircraft-based instruments during the experiment also measured large increases in aerosol signal at altitudes associated with the presence of fair weather cumulus clouds. These data show modifications of the aerosol vertical profile as a result of the aerosol enhancements at and below cloud altitudes. The airborne lidar data were utilized to estimate the spatial extent of these aerosol enhancements, finding increased AOD, backscatter and extinction out to 2.5 km distance from the cloud edge. Furthermore, in situ measurements made from aircraft vertical profiles over an AERONET site during the experiment also showed large increases in aerosol scattering and aerosol volume after cloud formation as compared to before. The 15 year AERONET database of AOD measurements at the GSFC, Maryland site was investigated in order to obtain a climatological perspective of this phenomenon of AOD enhancement. Analysis of the diurnal cycle of AOD in summer showed significant increases in AOD from morning until late afternoon, corresponding to the diurnal cycle of cumulus development.
Funder
National Aeronautics and Space Administration
Publisher
Copernicus GmbH
Reference84 articles.
1. Ackermann, J.: The extinction-to-backscatter ratio of tropospheric aerosol: a numerical study, J. Atmos. Ocean. Tech., 15, 1043–1050, https://doi.org/10.1175/1520-0426(1998), 1998. 2. Anderson, T. L. and Ogren, J. A.: Determining aerosol radiative properties using the TSI 3563 integrating nephelometer, Aerosol Sci. Tech., 29, 57–69, https://doi.org/10.1080/02786829808965551, 1998. 3. Berkoff, T., Hoff, R. M., Delgado, R., Sullivan, J., Thomas, A., Lawrence, W. T., Jones, T., Decola, P., Mathur, S., Zheng, Y., Wyant, G. J., Blucher, R. G., Piatt, R., Abderrahman, M., Martins, D. K., Auvil, R., Woodman, M., Connell, R., Hicks, M., Venable, D. D., Demoz, B., Tzortziou, M., De Rosa, P. J., Pickering, K. E., Starr, D., Welton, E. J., Holben, B. N., Ferrare, R. A., Hostetler, C. A., and Crawford, J. H.: Field deployment and initial results from micro-pulse lidar systems during NASA's DISCOVER AQ campaign, American Geophysical Union, Fall Meeting Abstracts, 2012. 4. Burton, S. P., Ferrare, R. A., Hostetler, C. A., Hair, J. W., Kittaka, C., Vaughan, M. A., Obland, M. D., Rogers, R. R., Cook, A. L., Harper, D. B., and Remer, L. A.: Using airborne high spectral resolution lidar data to evaluate combined active plus passive retrievals of aerosol extinction profiles, J. Geophys. Res.-Atmos., 115, D00H15, https://doi.org/10.1029/2009JD012130, 2010. 5. Burton, S. P., Ferrare, R. A., Vaughan, M. A., Omar, A. H., Rogers, R. R., Hostetler, C. A., and Hair, J. W.: Aerosol classification from airborne HSRL and comparisons with the CALIPSO vertical feature mask, Atmos. Meas. Tech., 6, 1397–1412, https://doi.org/10.5194/amt-6-1397-2013, 2013.
|
|