ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-11-8489-2011 Horizontal variability of aerosol optical depth observed during the ARCTAS airborne experiment Shinozuka Y. 1 Redemann J. 1 Bay Area Environmental Research Institute, Sonoma, California, USA 19 08 2011 11 16 8489 8495 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/11/8489/2011/acp-11-8489-2011.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/11/8489/2011/acp-11-8489-2011.pdf

We present statistics on the horizontal variability of aerosol optical depth (AOD) directly measured from the NASA P-3 aircraft. Our measurements during two contrasting phases (in Alaska and Canada) of the ARCTAS mission arguably constrain the variability in most aerosol environments common over the globe. In the Canada phase, which features local emissions, 499 nm AOD has a median relative standard deviation (std<sub>rel, med</sub>) of 19 % and 9 % and an autocorrelation (<i>r</i>) of 0.37 and 0.71 over 20 km and 6 km horizontal segments, respectively. In the Alaska phase, which features long-range transport, the variability is considerably lower (std<sub>rel, med</sub> = 3 %, <i>r</i> = 0.92 even over 35.2 km). Compared to the magnitude of AOD, its wavelength dependence varies less in the Canada phase, more in the Alaska phase. We translate these findings from straight-line flight tracks into grid boxes and points, to help interpretation and design of satellite remote sensing, suborbital observations and transport modeling.

 References Anderson, T. L., Charlson, R. J., Winker, D. M., Ogren, J. A., and Holmen, K.: Mesoscale variations of tropospheric aerosols, J. Atmos. Sci., 60, 119–136, 2003. Bréon, F. M., Vermeulen, A., and Descloitres, J., An evaluation of satellite aerosol products against sunphotometer measurements, Remote Sens. Environ., in press, 2011. Fuelberg, H. E., Harrigan, D. L., and Sessions, W.: A meteorological overview of the ARCTAS 2008 mission, Atmos. Chem. Phys., 10, 817–842, http://dx.doi.org/10.5194/acp-10-817-2010doi:10.5194/acp-10-817-2010, 2010. Hidy, G. M., Brook, J. R., Chow, J. C., Green, M., Husar, R. B., Lee, C., Scheffe, R. D., Swanson, A., and Watson, J. G.: Remote sensing of particulate pollution from space: have we reached the promised land?, J. Air Waste Manage., 59, 1130–1139, 2009. Ichoku, C., Chu, D. A., Mattoo, S., Kaufman, Y. J., Remer, L. A., Tanré, D., Slutsker, I., and Holben, B. N.: A spatio-temporal approach for global validation and analysis of MODIS aerosol products, Geophys. Res. Lett., 29, 8006, doi:8010.1029/2001GL013206, 2002. Jacob, D. J., Crawford, J. H., Maring, H., Clarke, A. D., Dibb, J. E., Emmons, L. K., Ferrare, R. A., Hostetler, C. A., Russell, P. B., Singh, H. B., Thompson, A. M., Shaw, G. E., McCauley, E., Pederson, J. R., and Fisher, J. A.: The Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) mission: design, execution, and first results, Atmos. Chem. Phys., 10, 5191–5212, http://dx.doi.org/10.5194/acp-10-5191-2010doi:10.5194/acp-10-5191-2010, 2010. Kahn, B. H. and Teixeira, J.: A Global Climatology of Temperature and Water Vapor Variance Scaling from the Atmospheric Infrared Sounder, J. Climate, 22, 5558–5576, 2009. Kahn, R. A., Garay, M. J., Nelson, D. L., Yau, K. K., Bull, M. A., Gaitley, B. J., Martonchik, J. V., and Levy, R. C.: Satellite-derived aerosol optical depth over dark water from MISR and MODIS: Comparisons with AERONET and implications for climatological studies, J. Geophys. Res., 112, D18205, http://dx.doi.org/10.1029/2006JD008175doi:10.1029/2006JD008175, 2007. Loeb, N. G. and Su, W.: Direct Aerosol Radiative Forcing Uncertainty Based on a Radiative Perturbation Analysis, J. Climate, 23, 5288–5293, 2010. Mishchenko, M. I., Cairns, B., Hansen, J. E., Travis, L. D., Burg, R., Kaufman, Y. J., Vanderlei Martins, J., and Shettle, E. P.: Monitoring of aerosol forcing of climate from space: Analysis of measurement requirements, J. Quant. Spectrosc. Ra., 88, 149–161, http://dx.doi.org/10.1016/j.jqsrt.2004.03.030doi:10.1016/j.jqsrt.2004.03.030, 2004. Qian, Y., Gustafson Jr., W. I., and Fast, J. D.: An investigation of the sub-grid variability of trace gases and aerosols for global climate modeling, Atmos. Chem. Phys., 10, 6917–6946, http://dx.doi.org/10.5194/acp-10-6917-2010doi:10.5194/acp-10-6917-2010, 2010. Redemann, J., Zhang, Q., Schmid, B., Russell, P. B., Livingston, J. M., Jonsson, H., and Remer, L. A.: Assessment of MODIS-derived visible and near-IR aerosol optical properties and their spatial variability in the presence of mineral dust, Geophys. Res. Lett., 33, L18814, doi:18810.11029/12006GL026626, 2006. Shinozuka, Y., Clarke, A. D., Howell, S. G., Kapustin, V. N., and Huebert, B. J.: Sea-salt vertical profiles over the Southern and tropical Pacific oceans: Microphysics, optical properties, spatial variability, and variations with wind speed, J. Geophys. Res., 109, D24201, doi:24210.21029/22004JD004975, 2004. Shinozuka, Y., Clarke, A. D., Howell, S. G., Kapustin, V. N., McNaughton, C. S., Zhou, J., and Anderson, B. E.: Aircraft profiles of aerosol microphysics and optical properties over North America: Aerosol optical depth and its association with PM$_2.5$ and water uptake, J. Geophys. Res., 112, D12S20, http://dx.doi.org/10.1029/2006JD007918doi:10.1029/2006JD007918, 2007. Shinozuka, Y., Redemann, J., Livingston, J. M., Russell, P. B., Clarke, A. D., Howell, S. G., Freitag, S., O'Neill, N. T., Reid, E. A., Johnson, R., Ramachandran, S., McNaughton, C. S., Kapustin, V. N., Brekhovskikh, V., Holben, B. N., and McArthur, L. J. B.: Airborne observation of aerosol optical depth during ARCTAS: vertical profiles, inter-comparison and fine-mode fraction, Atmos. Chem. Phys., 11, 3673–3688, http://dx.doi.org/10.5194/acp-11-3673-2011doi:10.5194/acp-11-3673-2011, 2011. Wang, J. and Christopher, S. A.: Intercomparison between satellite-derived aerosol optical thickness and PM$_2.5$ mass: Implications for air quality studies, Geophys. Res. Lett., 30, 2095, doi:2010.1029/2003GL018174, 2003.