Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 8 4 2008 10.5194/acpd-8-13233-2008 http://www.atmos-chem-phys-discuss.net/8/13233/2008/ http://www.atmos-chem-phys-discuss.net/8/13233/2008/acpd-8-13233-2008.html http://www.atmos-chem-phys-discuss.net/8/13233/2008/acpd-8-13233-2008.pdf 13233 13263 2008-07-11 Sensitivity of aerosol optical thickness and aerosol direct radiative effect to relative humidity H. Bian huisheng.bian@nasa.gov M. Chin J. Rodriguez H. Yu J. E. Penner S. Strahan Goddard Earth Sciences and Technology Center, University of Maryland, Baltimore County, Baltimore, Maryland, USA Atmospheric Chemistry and Dynamics Branch, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, Michigan, USA We present a sensitivity study on the effects of spatial and temporal resolution of atmospheric relative humidity (RH) on calculated aerosol optical thickness (AOT) and the aerosol direct radiative effects (DRE) in a global model. Using the same aerosol fields simulated in the Global Modeling Initiative (GMI) model, we find that, on a global average, the calculated AOT from RH in 1° latitude by 1.25° longitude spatial resolution is 11% higher than that in 2° by 2.5° resolution, and the corresponding DRE at the top of the atmosphere is 8–9% higher for total aerosols and 15% higher for only anthropogenic aerosols in the finer spatial resolution case. The difference is largest over surface escarpment regions (e.g. >200% over the Andes Mountains) where RH varies substantially with surface terrain. The largest zonal mean AOT difference occurs at 50–60°N (16–21%), where AOT is also relatively larger. A similar increase is also found when the time resolution of RH is increased. This increase of AOT and DRE with the increase of model resolution is due to the highly non-linear relationship between RH and the aerosol mass extinction efficiency (MEE) at high RH (>80%). Our study suggests that caution should be taken in a multi-model comparison (e.g. AeroCom) since the comparison usually deals with results coming from different spatial/temporal resolutions. Bloom, S., da Silva, A., Dee, D., Bosilovich, M., Chern, J. D., et al.: Documentation and Validation of the Goddard Earth Observing System (GEOS) Data Assimilation System-Version 4, NASA/TM-2005-104606, 26, 2005. Chan, M. N., Lee, A. K. Y., and Chan, C. K.: Responses of ammonium sulfate particles coated with glutaric acid to cyclic changes in relative humidity: Hygroscopicity and Raman characterization, Environ. Sci. Tech., 40(22), 6983–6989, 2006. Chin, M., Ginoux, P., Holben, B. N., Chou, M.-D., Kinne, S., and Weaver, C.: The GOCART model study of aerosol composition and radiative forcing, paper presented at 12th Symposium on Global Change and Climate Variations, Am. Meteorol. Soc., Albuquerque, New Mexico, USA, 2001. Chin, M., Ginoux, P., Kinne, S., Torres, O., Holben, B. N., Duncan, B. N., et al.: Tropospheric aerosol optical thickness from the GOCART model and comparisons with satellite and sun photometer measurements, J. Atmos. Sci., 59, 461–483, 2002. Chin, M., Chu, A., Levy, R., Remer, L., Kaufman, Y., Holben, B., Eck, T., Ginoux, P., and Gao, Q.: Aerosol distribution in the Northern Hemisphere during ACE-Asia: results from global model, satellite observations, and sunphotometer measurements, J. Geophys, Res., 109, D23S90, doi:10.1029/2004JD004829, 2004. Chou, M.-D. and Suarez, M. J.: A solar radiation parameterization for atmospheric studies, Technical Report Series on Global Modeling and Data Assimilation, NASA Tech. Memo. 104606, 15, 40 pp., 1999. Christopher, S. A. and Zhang, J.: Shortwave aerosol radiative forcing from MODIS and CERES observations over the oceans, Geophys. Res. Lett., 29, 1859, doi:10.1029/2002GL014803, 2002. Considine, D. B., Connell, P. S., Bergmann, D. J., Rotman, D. A., and Strahan, S. E.: Sensitivity of Global Modeling Initiative model predictions of Antarctic ozone recovery to input meteorological fields, J. Geophys. Res., 109, D15301, doi:10.1029/2003JD004487, 2004. Douglass, A. R., Connell, P. S., Stolarski, R. S., and Strahan, S. E.: Radicals and reservoirs in the GMI chemistry and transport model: comparison to measurements, J. Geophys. Res., 109, D16302, doi:10.1029/2004JD004632, 2004. Douglass, A. R., Stolarski, R. S., Strahan, S. E., and Polansky, B. C.: Sensitivity of Arctic ozone loss to polar stratospheric cloud volume and chlorine and bromine loading in a chemistry and transport model, Geophys. Res. Lett., 33, L17809, doi:10.10.29/2006GL026492, 2006. Patadia, F., Gupta, P., and Christopher, S. A.: First estimates of global shortwave aerosol direct radiative effect over land using merged CERES, MODIS and MISR data, Geophys. Res. Lett., 35, L04810, doi:10.1029/2007GL032314, 2008. Ghan, S. and Easter, R. C.: Comments on "A limited-area-model case study of the effects of sub-grid scale variation in relative humidity and cloud upon the direct radiative forcing of sulfate aerosol", Geophy. Res. Lett., 25(7), 1039–1040, 1998. Ginoux, P., Chin, M., Tegen, I., Prospero, J. M., Holben, B., Dubovik, O., and Lin, S.-J.: Sources and distributions of dust aerosols simulated with the GOCART model, J. Geophys. Res., 106(D17), 20 255–20 273, 2001. Gong, S., Barrie, L. A., and Blanchet, J.-P.: Modeling sea salt aerosols in the atmosphere, 1: Model development, J. Geophys. Res., 102, 3805–1818, 1997. Haywood, J. M., Ramaswany, V., and Donner, L. J.: A limited-area-model case study of the effects of sub-grid scale variation in relative humidity and cloud upon the direct radiative forcing of sulfate aerosol, Geophy. Res. Lett., 24(2), 143–146, 1997. Haywood, J. M., Ramaswany, V., and Donner, L. J., Reply, Geophy. Res. Lett., 25(7), 1041, 1998. Intergovernmental Panel on Climate Change (IPCC): Climate Change 2001: synthesis Report, Third Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, New York, USA, 2001. Jordanov, N. and Zekkberm, R.: Investigations of the hygroscopic properties of ammonium sulfate and mixed ammonium sulfate and glutaric acid micro droplets by means of optical levitation and Raman spectroscopy, Phys. Chem. Chem. Phys., 8(23), 2759–2764, 2006. Kinne, S., Schulz, M., Textor, C., Guibert, S., Balkanski, Y., et al.: An AeroCom initial assessment: optical properties in aerosol component modules of global models, Atmos. Chem. Phys., 6, 1815–1834, 2006. Liu, X., Penner, J. E., Das, B., et al.: Uncertainties in global aerosol simulations: assessment using three meteorological datasets, J. Geophys. Res., 112, D11212, doi:10.1029/2006JD008216, 2007. Malm, W. C., Day, D. E., Kreidenweis, S. M., Collett, J. L., Carrico, C., McMeeking, G., and Lee, T.: Hygroscopic properties of an organic-laden aerosol, Atmos. Environ., 39(27), 4969–4982, 2005. Monahan, E. C., Spiel, D. E., and Davidson, K. L.: A model of marine aerosol generation via whitecaps and wave disruption, Oceanic Witecaps, edited by: Monahan, E. C. and MacNiocaill, G., D. Reidel Publishing, Dordrecht, The Netherlands, 167–174, 1986. Pahlow, M., Feingold, G., Jefferson, A., Andrews, E., Ogren, J. A., Wang, J., Lee, Y. N., Ferrare, R. A., and Turner, D. D.: Comparison between lidar and nephelometer measurements of aerosol hygroscopicity at the Southern Great Plains Atmospheric Radiation Measurement site, J. Geophy. Res., 111(D5), D05S15, doi:10.1029/2004JD005646, 2006. Pant, A., Parsons, M. T., and Bertram, A. K.: Crystallization of aqueous ammonium sulfate particles internally mixed with soot and kaolinite: crystallization relative humidities and nucleation rates, J. Phys. Chem. A, 110(28), 8701–8709, 2005. Quinn, P. K., Bates, T. S., Baynard, T., Clarke, A. D., Onasch, T. B., Wang, W., Rood, M. J., Andrews, E., Allan, J., Carrico, C. M., Coffiman, D., and Worsnop, D.: Impact of particulate organic matter on the relative humidity dependence of light scattering: a simplified parameterization, Geophy. Res. Lett., 32, L22809, doi:10.1029/2005GL024322, 2005. Semeniuk, T. A., Wise, M. E., Martin, S. T., Russell, M., and Buseck, P. R.: Hygroscopic behavior of aerosol particles from biomass fires using environmental transmission electron microscopy, J. Atmos. Chem., 56(3), 259–273, 2007. Schulz, M., Textor, C., Kinne, S., Balkanski, Y., Bauer, S., et al.: Radiative forcing by aerosols as derived from the AeroCom present-day and pre-industrial simulaitons, Atmos. Chem. Phys., 6, 5225–5246, 2006. Strahan, S.E. and Douglass, A. R.: Evaluating the credibility of transport processes in simulations of ozone recovery using the Global Modeling Initiative three-dimensional model, J. Geophys. Res., 109, D05110, doi:10.1029/2003JD004238, 2004. Strahan, S. E. and Polansky, B. C.: Meteorological implementation issues in chemistry and transport models, Atmos. Chem. Phys., 6, 2895–2910, 2006. Strahan, S. E., Duncan, B. N., and Hoor, P.: Observationally derived transport diagnostics for the lowermost stratosphere and their application to the GMI chemistry and transport model, Atmos. Chem. Phys., 7, 2435–2445, 2007. Textor, C., Schulz, M., Guibert, S., Kinne, S., Balkanski, Y., et al.: Analysis and quantification of the diversities of aerosol life cycles within AeroCom, Atmos. Chem. Phys., 6, 1777–1813, 2006. Weaver, C. J., Ginoux, P., Hsu, N. C., Chou, M.-D., and Joiner, J.: Radiative Forcing of Saharan Dust: GOCART model simulations Compared with ERBE data, J. Atmos. Sci., 59(3), 736–747, 2002. Yoon, S. C. and Kim, J.: Influences of relative humidity on aerosol optical properties and aerosol radiative forcing during ACE-Asia, Atmos. Environ., 40(23), 4328–4338, 2006. Yu, H., Kaufman, Y. J., Chin, M., Feingold, G., Remer, L. A., et al.: A review of measurement-based assessments of the aerosol direct radiative effect and forcing, Atmos. Chem. Phys., 6, 613–666, 2006. Zhang, J., Christopher, S. A., Remer, L. A., and Kaufman, Y. J.: Shortwave aerosol radiative forcing over cloud-free oceans from Terra, 2: seasonal and global distribution, J. Geophy., Res., 110, D10S24, doi:10.1029/2004JD005009, 2005.