ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-7-3309-2007 Global trends in visibility: implications for dust sources Mahowald N. M. 1 Ballantine J. A. 2 5 Feddema J. 3 Ramankutty N. 4 National Center for Atmospheric Research, Boulder Colorado, USA Institute for Computational Earth System Science, University of California, Santa Barbara, CA, USA Department of Geography, University Kansas, Lawrence, Kansas, USA Department of Geography, McGill University, Montreal, Quebec, Canada now at: United States Geological Survey, Denver, Colorado, USA 26 06 2007 7 12 3309 3339 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/7/3309/2007/acp-7-3309-2007.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/7/3309/2007/acp-7-3309-2007.pdf

There is a large uncertainty in the relative roles of human land use, climate change and carbon dioxide fertilization in changing desert dust source strength over the past 100 years, and the overall sign of human impacts on dust is not known. We used visibility data from meteorological stations in dusty regions to assess the anthropogenic impact on long term trends in desert dust emissions. We did this by looking at time series of visibility derived variables and their correlations with precipitation, drought, winds, land use and grazing. Visibility data are available at thousands of stations globally from 1900 to the present, but we focused on 357 stations with more than 30 years of data in regions where mineral aerosols play a dominant role in visibility observations. We evaluated the 1974 to 2003 time period because most of these stations have reliable records only during this time. We first evaluated the visibility data against AERONET aerosol optical depth data, and found that only in dusty regions are the two moderately correlated. Correlation coefficients between visibility-derived variables and AERONET optical depths indicate a moderate correlation (0.47), consistent with capturing about 20% of the variability in optical depths. Two visibility-derived variables appear to compare the best with AERONET observations: the fraction of observations with visibility less than 5 km (VIS5) and the surface extinction (EXT). Regional trends show that in many dusty places, VIS5 and EXT are statistically significantly correlated with the Palmer drought severity index (based on precipitation and temperature) or surface wind speeds, consistent with dust temporal variability being largely driven by meteorology. This is especially true for North African and Chinese dust sources, but less true in the Middle East, Australia or South America, where there are not consistent patterns in the correlations. Climate indices such as El Nino or the North Atlantic Oscillation are not correlated with visibility-derived variables in this analysis. There are few stations where visibility measures are correlated with cultivation or grazing estimates on a temporal basis, although this may be a function of the very coarse temporal resolution of the land use datasets. On the other hand, spatial analysis of the visibility data suggests that natural topographic lows are not correlated with VIS5 or EXT, but land use is correlated at a moderate level. This analysis is consistent with land use being important in some regions, but meteorology driving interannual variability during 1974–2003.

 References Baker, J., Southhard, R., and Mitchell, J.: Agricultural dust production in standard and conservation tillage systems in the San Joaquin Valley, J. Environ. Qual., 34, 1260–1269, 2006. Baker, J., Ballantine, J.-A. C., Okin, G. S., Prentiss, D. E., and Roberts, D. A.: Mapping landforms in North Africa using continental scale unmixing of MODIS imagery, Rem. Sens. Environ., 97, 470–483, 2005. Bonan, G., Levis, S., Kergoat, L., and Oleson, K.: Landscapes as patches of plant functional types: An integrating concept for climate and ecosystem models, Global Biogeochem. Cy., 16, 5.1–5.23, 2002. Chen, M., Xie, P., Janowiak, J., and Arkin, P.: Global land precipitation: a 50-year monthly analysis based on gauge observations, J. Hydrometeorol., 3, 249–266, 2002. Chiapello, I., Moulin, C., and Prospero, J.: Understanding the long-term variability of African dust transport across the Atlantic as recorrded in both Barbados surface concentrations and large scales TOMS optical thicknesses, J. Geophys. Res., 110, D18S10, doi:10.1029/2004JD005132, 2005. Dai, A., Fung, I. Y., and Del Genio, A. D.: Surface observed global land precipitation variations during 1900–88, J. Climate, 10, 2943–2962, 1997. Dai, A., Trenberth, K. E., and Karl, T. R.: Global Variations in Droughts and Wet Spells, Geophys. Res. Lett., 25, 3367–3370, 1998. Dai, A., Trenberth, K., and Qian, T.: A global dataset of Palmer Drought Severity Index for 1870–2002: Relationship with soil moisture and the effects of surface warming, J. Hydrometeorol., 5, 1117–1130, 2004. DeMott, P., Sassen, K., Poellot, M., et al.: African dust aerosols as atmospheric ice nuclei, Geophys. Res. Lett., 30, 1732, doi:10.1029/2003GL017410, 2003. Dentener, F. J., Carmichael, G. R., Zhang, Y., Lelieveld, J., and Crutzen, P. J.: Role of mineral aerosol as a reactive surface in the global troposphere, J. Geophys. Res., 101, 22 869–22 889, 1996. Engelstaedter, S., Kohfeld, K. E., Tegen, I., and Harrison, S. P.: Controls of dust emissions by vegetation and topographic depressions: An evaluation using dust storm frequency data, Geophys. Res. Lett., 30, 1294, doi:10.1029/2002GL016471, 2003. % %Feddema, J., Lawrence, P., Bauer, J., and Jackson, T.: A global land cover %dataset for use in transient climate simulations, JAMC, submitted\blackbox\bf status?, 2007. Gillette, D. A.: Threshold friction velocities for dust production for agricultural soils, J. Geophys. Res., 93, 12 645–12 662, 1988. Ginoux, P. Chin, M., Tegen, I., et al.: Sources and distribution of dust aerosols with the GOCART model, J. Geophys. Res., 106, 20 255–20 273, 2001. Godish, T.: Air Quality. CRC Press, Boca Raton, Florida, 1997. Goudie, A. and Middleton, N.: Saharan dust storms: nature and consequences, Earth-Sci. Rev., 56, 179–204, 2001. Goudie, A. S. and Middleton, N. J.: The Changing Frequency of Dust Storms Through Time, Climatic Change, 20, 197–225, 1992. Grini, A. and Zender, C.: Roles of saltation, sandblasting, and wind speed variability on mineral dust aerosol size distribution during the Puerto Rican Dust Experiment (PRIDE), J. Geophys. Res., 109, D07202, doi:10.1029/2003JD004233, 2004. Holben, B. N., Eck, T., Slutsker, I., et al.: AERONET-A Federated Instrument Network and Data Archeive for Aerosol Characterization, 2000. Holben, B. N., Tanre, D., Smirnov, A. et al.: An emerging ground-based aerosol climatology:Aerosol optical depth from AERONET, J. Geophys. Res., 106, 12 067–12 097, 2001. Hurrell, J. W.: Decadal Trends in the North Atlantic Oscillation Regional Temperatures and Precipitation, Science, 269, 676–679, 1995. Jickells, T., An, Z., Anderson, K., et al.: Global iron connections between dust, ocean biogeochemistry and climate, Science, 308, 67–71, 2005. Kistler, R., Kalnay, E., Collins, W., et al.: The NCEP-NCAR 50-Year Reanalysis: Monthly Means CD-ROM and Documentation, B. Am. Meteorol. Soc., 82, 247–267, 2001. Klein-Goldewijk, K.: Estimating global land use change over the past 300 years: the HYDE database, Global Biogeochem. Cy., 15, 417–434, 2001. Kurosaki, Y. and Mikami, M.: Recent frequent dust events and their relation to surface wind in East Asia, Geophys. Res. Lett., 30, 1736, doi:10.1029/2003GL017261, 2003. Laurent, B., Maricorena, B., Bergametti, G., Chazette, P., Maignan, F., and Schmetig, C.: Simulation of the mineral dust emission frequencies from desert areas of China and Mongolia using an aerodynamic roughness length map derived from the POLDER/ADEOS 1 surface products, J. Geophys. Res., 110, D18S04, doi:10.1029/2004JD005013, 2005. Liu, X., Yin, Z.-Y., Zhang, X., and Yang, X.: Analyses of the spring dust storm frequency of northern China in relation to antecedent and concurrent wind, precipitation, vegetation and soil moisture conditions, J. Geophys. Res., 109, D16210, doi:10.1029/2004JD004615, 2004. Luo, C., Mahowald, N., and Corral, J. D.: Sensitivity study of meteorological parameters on mineral aerosol mobilization, transport and idstribution, J. Geophys. Res., 108, 4447, doi:10.1029/2003JD0003483, 2003. Mahowald, N., Baker, A., Bergametti, G., et al.: The atmospheric global dust cycle and iron inputs to the ocean, Global Biogeochem. Cy., 19, GB4025, doi:10.1029/2004GB002402, 2005. Mahowald, N., Bryant, R., Corral, J. D., and Steinberger, L.: Ephemeral lakes and desert dust sources, Geophys. Res. Lett., 30, 1074, doi:10.1029/2002GL016041, 2003a. Mahowald, N., Muhs, D., Levis, S., et al.: Change in atmospheric mineral aerosols in response to climate: last glacial period, pre-industrial, modern and doubled-carbon dioxide climates, J. Geophys. Res., 111, D10202, doi:10.1029/2005JD006653, 2006. Mahowald, N. and Dufresne, J.-L.: Sensitivity of TOMS aerosol index to boundary layer height: implications for detection of mineral aerosol sources, Geophys. Res. Lett., 31, L03103, doi:10.1029/2003GL018865, 2004. Mahowald, N., Luo, C., Corral, J. D., and Zender, C.: Interannual variability in atmospheric mineral aerosols from a 22-year model simulation and observational data, J. Geophys. Res., 108, 4352, doi:10.1029/2002JD002821, 2003b. Mahowald, N., Rasch, P., Eaton, B., Whittlestone, S., and Prinn, R.: Transport of 222radon to the remote troposphere using the Model of Atmospheric Transport and Chemistry and assimilated winds from ECMWF and the National Center for Environmental Prediction/NCAR, J. Geophys. Res., 102, 28 139–28 151, 1997. Mahowald, N., Rivera, G., and Luo, C.: Comment on "Relative importance of climate and land use in determining present and future global soil dust emission", Geophys. Res. Lett., 31, L24105, doi:10.1029/2004GL021272, 2004. Mahowald, N., Zender, C., Luo, C., et al.: Understanding the 30-year Barbados desert dust record, J. Geophys. Res., 4561, doi:10.129/2002JD002097, 2002. Mahowald, N. M. and Luo, C.: A less dusty future?, Geophys. Res. Lett., 30, 1903, doi:10.1029/2003GRL017880, 2003. N-Tchayi Mbourou, G., Bertrand, J. J., and Nicholson, S. E.: The Diurnal and Seasonal Cycles of Wind-Borne Dust over Africa North of the Equator, J. Appl. Meteorol., 36, 868–882, 1997. McTainsh, G. H., Burgess, R., and Pitblado, J. R.: Aridity, drought and dust storms in Australia, J. Arid Environ., 16, 11–22, 1989. Middleton, N. and Thomas, D. (Eds.): World Atlas of Desertification, Arnold, London, 182 pp., 1997. Middleton, N. J.: Dust Storms in the Middle East, J. Geophys. Res., 16, 11–22, 1984. Middleton, P., Stewart, T. R., and Leary, J.: On the Use of Human Judgment and Physical/Chemical Measurements in Visual Air Quality Management, J. Air Pollut. Control Assoc., 35, 11–18, 1985. Miller, R. and Tegen, I.: Climate Response to Soil Dust Aerosols, Am. Meteorl. Soc., 11, 3247–3267, 1998. Moulin, C., Lambert, C., Dulac, F., et al.: Long-term daily monitoring of Saharan dust load over ocean using Meteosat ISCCP-B2 data 2. Accuracy of the method and validation using Sun photometer measurements, J. Geophys. Res., 102, 16 959–16 969, 1997a. Moulin, C. and Chiapello, I.: Evidence of the control of summer atmospheric transport of African dust over the Atlantic by Sahel sources from TMS satellites (1979–2000), Geophys. Res. Lett., 31, L02107, doi:10.1029/2003GL018931, 2004. Moulin, C., Lambert, C. E., Dulac, F., and Dayan, U.: Control of atmospheric export of dust from North Africa by the North Atlantic Oscillation, Nature, 387, 691–694, 1997b. Neff, J., Reynolds, R., Belnap, J., and Lamothe, P.: Multi-decadal impacts of grazing on soil physical and biogeochemical properties in southeast Utah, Ecol. Appl., 15, 87–95, 2005. Okin, G. S. and Reheis, M.: An ENSO predictor of wind erosion and dust emission in the Southwestern United States, Geophys. Res. Lett., 29, 1332 ,doi:10.1029/2001GL014494, 2002. Petit, J. R., Jouzel, J., Raynaud, D., et al.: Climate and atmospheric history of hte past 420,000 years from teh Vostok Ice core, Antarctica, Nature, 399, 429–436, 1999. Prospero, J. and Lamb, P.: African droughts and dust transport to the Caribbean: climate change implications, Science, 302, 1024–1027, 2003. Prospero, J., Ginoux, P., Torres, O., and Nicholson, S. E.: Environmental Characterization of Global sources of atmospheric soil dust derived from the NIMBUS-7 TOMS absorbing aerosol product, Rev. Geophys., 40, 1002, doi:10.1029/2000RG000095, 2002. Prospero, J. M. and Nees, R. T.: Impact of the North African drought and El Niño on mineral dust in the Barbados trade winds, Nature, 320, 735–738, 1986. Ramankutty, N. and Foley, J.: Estimating historical changes in global land cover: croplands from 1700 to 1992, Global Biogeochem. Cy., 13, 997–1027, 1999. Rasch, P. J., Collins, W., and Eaton, B. E.: Understanding the Indian ocean Experiment (INDOEX) aerosol distributions with an aerosol assimilation, J. Geophys. Res., 106, 7337–7355, 2001. Rasch, P. J., Mahowald, N. M., and Eaton, B. E.: Representations of transport, convection and the hydrologic cycle in chemical transport models: Implications for the modeling of short-lived and soluble species, J. Geophys. Res., 102, 18 127–28 138, 1997. Rosenfeld, D. and Nirel, R.: Seeding effectiveness-the interaction of desert dust and the southern margins of rain cloud systems in Isreal, J. Appl. Meteorol., 35, 1502–1509, 1996. Seinfeld, J. and Pandis, S.: Atmospheric Chemistry and Physics. John Wiley and Sons, Inc, New York, 1326~pp., 1998. Smith, S., Huxman, T., Zitzer, S., et al.: Elevated CO2 increases productivity and invasive species success in an arid ecosystem, Nature, 408, 79–82, 2000. Sun, J., Zhang, M., and Liu, T.: Spatial and temporal characteristics of dust storms in China and its surrounding regions, 1960–1999:Relations to source area and climate, J. Geophys. Res., 106, 10 325–10 333, 2001. Torres, O., Bhartia, P., Herman, J., et al.: A long-term record of aerosol optical depth from TOMS observations andn comparison to AERONET measurements, J. Atmos. Sci., 59, 398–431, 2002. Torres, O., Bhartia, P. K., Herman, J. R., Ahmad, Z., and Gleason, J.: Derivation of aerosol properties from satellite measurements of backscattered ultraviolet radiation: Theoretical basis, J. Geophys. Res., 103, 17 099–17 110, 1998. Trenberth, K. E. and Stepaniak, D. P.: Letters: indices of El Nino Evolution, J. Climate, 14, 1697–1701, 2001. Zender, C., Bian, H., and Newman, D.: Mineral Dust Entrainment and Deposition (DEAD) model: Description and 1990s dust climatology, J. Geophys. Res., 108, 4416, doi:10.1029/2002JD002775, 2003a. Zender, C. and Kwon, E., Regional contrasts in dust emission responses to climate, J. Geophys. Res., 110, D13201, doi:10.1029/2004JD005501, 2005. Zender, C., Newman, D., and Torres, O.: Spatial Heterogeneity in Aerolian Erodibility: Uniform, Topographic, Geomorphic and Hydrologic Hypotheses, J. Geophys. Res., 108, 4543, doi:10.1029/2002JD003039, 2003b. Zhang, X. Y., Gong, S., Zhao, T., et al.: Sources of Asian dust and role of climate change versus desertification in Asian dust emission, Geophys. Res. Lett., 30, 2272, doi:10.1029/2003GL018206, 2003. Zhao, C., Dabu, X., and Li, Y.: Relationship between climate factors and dust storm frequency in Inner Mongolia of China, Geophys. Res. Lett., 31, L01103, doi:10.1029/2003GL018351, 2004. Zijiang, Z. and Guocai, Z.: Typical severe dust storms in northern China during 1954–2002, Chinese Sci. Bull., 48, 2366–2370, 2003.