Modulation of Mid‐Holocene African Rainfall by Dust Aerosol Direct and Indirect Effects
Climate model simulations of the mid‐Holocene (MH) consistently underestimate northern African rainfall for reasons not fully understood. While most models incorporate orbital forcing and vegetation feedbacks, they neglect dust reductions associated with greater vegetation cover. Here we simulate th...
| Published in: | Chemical Geology |
|---|---|
| Main Authors: | , , , |
| Format: | Article in Journal/Newspaper |
| Language: | unknown |
| Published: |
Springer Netherlands
2019
|
| Subjects: | |
| Online Access: | https://hdl.handle.net/2027.42/149324 https://doi.org/10.1029/2018GL081225 |
| id |
ftumdeepblue:oai:deepblue.lib.umich.edu:2027.42/149324 |
|---|---|
| record_format |
openpolar |
| institution |
Open Polar |
| collection |
University of Michigan: Deep Blue |
| op_collection_id |
ftumdeepblue |
| language |
unknown |
| topic |
indirect aerosol effects dust aerosols African humid period West African Monsoon Geological Sciences Science |
| spellingShingle |
indirect aerosol effects dust aerosols African humid period West African Monsoon Geological Sciences Science Thompson, Alexander J. Skinner, Christopher B. Poulsen, Christopher J. Zhu, Jiang Modulation of Mid‐Holocene African Rainfall by Dust Aerosol Direct and Indirect Effects |
| topic_facet |
indirect aerosol effects dust aerosols African humid period West African Monsoon Geological Sciences Science |
| description |
Climate model simulations of the mid‐Holocene (MH) consistently underestimate northern African rainfall for reasons not fully understood. While most models incorporate orbital forcing and vegetation feedbacks, they neglect dust reductions associated with greater vegetation cover. Here we simulate the MH climate response to reduced Saharan dust using CESM CAM5‐chem, which resolves direct and indirect dust aerosol effects. Direct aerosol effects increase Saharan and Sahel convective rainfall by ~16% and 8%. In contrast, indirect aerosol effects decrease stratiform rainfall, damping the dust‐induced total rainfall increase by ~13% in the Sahara and ~59% in the Sahel. Sensitivity experiments indicate the dust‐induced precipitation anomaly in the Sahara and Sahel (0.27 and 0.18 mm/day) is smaller than the anomaly from MH vegetation cover (1.19 and 1.08 mm/day). Although sensitive to dust radiative properties, sea surface temperatures, and indirect aerosol effect parameterization, our results suggest that dust reductions had competing effects on MH African rainfall.Plain Language SummarySix thousand years ago, changes in Earth’s orbit led to greater summer season solar radiation over northern Africa. The increase in energy resulted in higher rainfall amounts, widespread vegetation, and reduced dust aerosols over regions that today are desert. In this study we use a climate model, CESM CAM5‐chem, that accounts for the ways dust aerosols interact with sunlight and cloud droplets to examine how the reduction in Saharan dust during this past humid time affected rainfall. When dust aerosols are reduced in the model, more sunlight reaches the surface, the Sahara warms, and convective rainfall from the West African Monsoon increases. However, through dust‐cloud droplet interactions, the same reduction in dust decreases nonconvective rainfall, which is less prevalent during the monsoon season but still important, and thus dampens the total rainfall increase. Overall, dust reduction leads to a rainfall response that is ... |
| format |
Article in Journal/Newspaper |
| author |
Thompson, Alexander J. Skinner, Christopher B. Poulsen, Christopher J. Zhu, Jiang |
| author_facet |
Thompson, Alexander J. Skinner, Christopher B. Poulsen, Christopher J. Zhu, Jiang |
| author_sort |
Thompson, Alexander J. |
| title |
Modulation of Mid‐Holocene African Rainfall by Dust Aerosol Direct and Indirect Effects |
| title_short |
Modulation of Mid‐Holocene African Rainfall by Dust Aerosol Direct and Indirect Effects |
| title_full |
Modulation of Mid‐Holocene African Rainfall by Dust Aerosol Direct and Indirect Effects |
| title_fullStr |
Modulation of Mid‐Holocene African Rainfall by Dust Aerosol Direct and Indirect Effects |
| title_full_unstemmed |
Modulation of Mid‐Holocene African Rainfall by Dust Aerosol Direct and Indirect Effects |
| title_sort |
modulation of mid‐holocene african rainfall by dust aerosol direct and indirect effects |
| publisher |
Springer Netherlands |
| publishDate |
2019 |
| url |
https://hdl.handle.net/2027.42/149324 https://doi.org/10.1029/2018GL081225 |
| genre |
Arctic |
| genre_facet |
Arctic |
| op_relation |
Thompson, Alexander J.; Skinner, Christopher B.; Poulsen, Christopher J.; Zhu, Jiang (2019). "Modulation of Mid‐Holocene African Rainfall by Dust Aerosol Direct and Indirect Effects." Geophysical Research Letters 46(7): 3917-3926. 0094-8276 1944-8007 https://hdl.handle.net/2027.42/149324 doi:10.1029/2018GL081225 Geophysical Research Letters Strong, J. D. O., Vecchi, G. A., & Ginoux, P. ( 2015 ). The response of the tropical Atlantic and West African climate to Saharan dust in a fully coupled GCM. Journal of Climate, 28 ( 18 ), 7071 – 7092. https://doi.org/10.1175/JCLI‐D‐14‐00797.1 Shanahan, T. M., Mckay, N. P., Hughen, K. A., Overpeck, J. T., Otto‐Bliesner, B., Heil, C. W., King, J., Scholz, C. A., & Peck, J. ( 2015 ). The time‐transgressive termination of the African humid period. Nature Geoscience, 8 ( 2 ), 140 – 144. https://doi.org/10.1038/NGEO2329 Skinner, C. B., & Poulsen, C. J. ( 2016 ). The role of fall season tropical plumes in enhancing Saharan rainfall during the African humid period. Geophysical Research Letters, 43, 349 – 358. https://doi.org/10.1002/2015GL066318 Solmon, F., Elguindi, N., & Mallet, M. ( 2012 ). Radiative and climatic effects of dust over West Africa, as simulated by a regional climate model. Climate Research, 52 ( 1 ), 97 – 113. https://doi.org/10.3354/cr01039 Taylor, K. E., Stouffer, R. J., & Meehl, G. A. ( 2012 ). An overview of CMIP5 and the experiment design. Bulletin of the American Meteorological Society, 93 ( 4 ), 485 – 498. https://doi.org/10.1175/BAMS‐D‐11‐00094.1 Tierney, J. E., Pausata, F. S. R., & deMenocal, P. B. ( 2017 ). Rainfall regimes of the green Sahara. Science Advances, 3 ( e1601503 ), 1 – 9. https://doi.org/10.1126/sciadv.1601503 Tilmes, S., Lamarque, J. F., Emmons, L. K., Kinnison, D. E., Ma, P. L., Liu, X., Ghan, S., Bardeen, C., Arnold, S., Deeter, M., Vitt, F., Ryerson, T., Elkins, J. W., Moore, F., Spackman, J. R., & Val Martin, M. ( 2015 ). Description and evaluation of tropospheric chemistry and aerosols in the Community Earth System Model (CESM1.2). Geoscientific Model Development, 8, 1395 – 1426. https://doi.org/10.5194/gmd‐8‐1395‐2015 Tjallingii, R., Claussen, M., Stuut, J. B. W., Fohlmeister, J., Jahn, A., Bickert, T., Lamy, F., & Röhl, U. ( 2008 ). Coherent high‐and low‐latitude control of the northwest African hydrological balance. Nature Geoscience, 1, 670 – 675. https://doi.org/10.1038/ngeo289 Tuenter, E., Weber, S. L., Hilgen, F. J., & Lourens, L. J. ( 2007 ). Simulating sub‐Milankovitch climate variations associated with vegetation dynamics. Climate of the Past, 3, 169 – 180. https://doi.org/10.5194/cp‐3‐169‐2007 Vamborg, F. S. E., Brovkin, V., & Claussen, M. ( 2014 ). Background albedo dynamics improve simulated precipitation variability in the Sahel region. Earth System Dynamics, 5, 89 – 101. https://doi.org/10.5194/esd‐5‐89‐2014 Vergara‐Temprado, J., Murray, B. J., Wilson, T. W., O’Sullivan, D., Browse, J., Pringle, K. J., Ardon‐Dryer, K., Bertram, A. K., Burrows, S. M., Ceburnis, D., DeMott, P. J., Mason, R. H., O’Dowd, C. D., Rinaldi, M., & Carslaw, K. S. ( 2017 ). Contribution of feldspar and marine organic aerosols to global ice nucleating particle concentrations. Atmospheric Chemistry and Physics, 17 ( 5 ), 3637 – 3658. https://doi.org/10.5194/acp‐17‐3637‐2017 Williams, R. H., McGee, D., Kinsley, C. W., Ridley, D. A., Hu, S., Fedorov, A., Tal, I., Murray, R. W., & deMenocal, P. B. ( 2016 ). Glacial to Holocene changes in trans‐Atlantic Saharan dust transport and dust‐climate feedbacks. Science Advances, 2, 1 – 11. https://doi.org/10.1126/sciadv.1600445 Xie, S., Ma, H. Y., Boyle, J. S., Klein, S. A., & Zhang, Y. ( 2012 ). On the correspondence between short‐ and long‐time‐scale systematic errors in CAM4/CAM5 for the year of tropical convection. Journal of Climate, 25 ( 22 ), 7937 – 7955. https://doi.org/10.1175/JCLI‐D‐12‐00134.1 Xie, X., Zhang, H., Liu, X., Peng, Y., & Liu, Y. ( 2017 ). Sensitivity study of cloud parameterizations with relative dispersion in CAM5.1: Impacts on aerosol indirect effects. Atmospheric Chemistry and Physics, 17, 5877 – 5892. https://doi.org/10.5194/acp‐17‐5877‐2017 Yoshioka, M., Mahowald, N. M., Conley, A. J., Collins, W. D., Fillmore, D. W., Zender, C. S., & Coleman, D. B. ( 2007 ). Impact of desert dust radiative forcing on Sahel precipitation: Relative importance of dust compared to sea surface temperature variations, vegetation changes, and greenhouse gas warming. Journal of Climate, 20 ( 8 ), 1445 – 1467. https://doi.org/10.1175/JCLI4056.1 Yu, M., Wang, G., & Pal, J. S. ( 2016 ). Effects of vegetation feedback on future climate change over West Africa. Climate Dynamics, 46 ( 11–12 ), 3669 – 3688. https://doi.org/10.1007/s00382‐015‐2795‐7 Zender, C. S., Bian, H., & Newman, D. ( 2003 ). Mineral dust entrainment and deposition (DEAD) model: Description and 1990s dust climatology. Journal of Geophysical Research, 108 ( D14 ), 4416. https://doi.org/10.1029/2002JD002775 Zhang, Z., Ramstein, G., Schuster, M., Li, C., Contoux, C., & Yan, Q. ( 2014 ). Aridification of the Sahara desert caused by Tethys Sea shrinkage during the Late Miocene. Nature, 513 ( 7518 ), 401 – 404. https://doi.org/10.1038/nature13705 Zhu, Z., Piao, S., Myneni, R. B., Huang, M., Zeng, Z., Canadell, J. G., Ciais, P., Sitch, S., Friedlingstein, P., Arneth, A., Cao, C., Cheng, L., Kato, E., Koven, C., Li, Y., Lian, X., Liu, Y., Liu, R., Mao, J., Pan, Y., Peng, S., Peñuelas, J., Poulter, B., Pugh, T. A. M., Stocker, B. D., Viovy, N., Wang, X., Wang, Y., Xiao, Z., Yang, H., Zaehle, S., & Zeng, N. ( 2016 ). Greening of the Earth and its drivers. Nature Climate Change, 6 ( 8 ), 791 – 795. https://doi.org/10.1038/nclimate3004 Bartlein, P. J., Harrison, S. P., Brewer, S., Connor, S., Davis, B. A. S., Gajewski, K., Guiot, J., Harrison‐Prentice, T. I., Henderson, A., Peyron, O., Prentice, I. C., Scholze, M., Seppä, H., Shuman, B., Sugita, S., Thompson, R. S., Viau, A. E., Williams, J., & Wu, H. ( 2011 ). Pollen‐based continental climate reconstructions at 6 and 21 ka: A global synthesis. Climate Dynamics, 37, 775 – 802. https://doi.org/10.1007/s00382‐010‐0904‐1 Colman, R. ( 2003 ). A comparison of climate feedbacks in general circulation models. Climate Dynamics, 20 ( 7–8 ), 865 – 873. https://doi.org/10.1007/s00382‐003‐0310‐z Conley, A. J., Lamarque, J. F., Vitt, F., Collins, W. D., & Kiehl, J. ( 2013 ). PORT, a CESM tool for the diagnosis of radiative forcing. Geoscientific Model Development, 6 ( 2 ), 469 – 476. https://doi.org/10.5194/gmd‐6‐469‐2013 Gaetani, M., Messori, G., Zhang, Q., Flamant, C., & Pausata, F. S. R. ( 2017 ). Understanding the mechanisms behind the northward extension of the West African Monsoon during the mid‐Holocene. Journal of Climate, 30 ( 19 ), 7621 – 7642. https://doi.org/10.1175/JCLI‐D‐16‐0299.1 Boos, W. R., & Korty, R. L. ( 2016 ). Regional energy budget control of the intertropical convergence zone and application to mid‐Holocene rainfall. Nature Geoscience, 9 ( 12 ), 892 – 897. https://doi.org/10.1038/ngeo2833 Braconnot, P., Harrison, S. P., Otto‐Bliesner, B., Abe‐Ouchi, A., Jungclaus, J., & Peterschmitt, J.‐Y. ( 2011 ). The paleoclimate modeling intercomparison project contribution to CMIP5. CLIVAR Exchanges, 56 ( 16–2 ), 15 – 19. http://www.clivar.org/sites/default/files/documents/Exchanges56.pdf Braconnot, P., Joussaume, S., Marti, O., & de Noblet, N. ( 1999 ). Synergistic feedbacks from ocean and vegetation on the African monsoon response to mid‐Holocene insolation. Geophysical Research Letters, 26, 2481 – 2484. https://doi.org/10.1029/1999GL006047 Bretherton, C. S. ( 2015 ). Insights into low‐latitude cloud feedbacks from high‐resolution models. Philosophical Transactions of the Royal Society A, 373 ( 2054 ), 1 – 19. https://doi.org/10.1098/rsta.2014.0415 Brostrom, A., Coe, M., Harrison, S. P., Gallimore, R., Kutzbach, J. E., Foley, J., Prentice, I. C., & Behling, P. ( 1998 ). Land surface feedbacks and palaeomonsoons in northern Africa. Geophysical Research Letters, 25 ( 19 ), 3615 – 3618. https://doi.org/10.1029/98GL02804 Brovkin, V., Claussen, M., Petoukhov, V., & Ganopolski, A. ( 1998 ). On the stability of the atmosphere‐vegetation system in the Sahara/Sahel region. Journal of Geophysical Research, 103 ( D24 ), 31,613 – 31,624. https://doi.org/10.1029/1998JD200006 Charney, J., Stone, P. H., & Quirk, W. J. ( 1975 ). Drought in the Sahara: A biogeophysical feedback mechanism. Science, 187 ( 4175 ), 434 – 435. https://doi.org/10.1126/science.187.4175.434 Charney, J. G. ( 1975 ). Dynamics of deserts and drought in the Sahel. Quarterly Journal of the Royal Meteorological Society, 101 ( 428 ), 193 – 202. https://doi.org/10.1002/qj.49710142802 Claussen, M., & Gayler, V. ( 1997 ). The greening of the Sahara during the mid‐Holocene: Results of an interactive atmosphere‐biome. Global Ecology and Biogeography Letters, 6 ( 5 ), 369 – 377. https://doi.org/10.2307/2997337 Claussen, M., Kubatzki, C., Brovkin, V., Ganopolski, A., Hoelzmann, P., & Pachur, H.‐J. ( 1999 ). Simulation of an abrupt change in Saharan vegetation in the mid‐Holocene. Geophysical Research Letters, 26 ( 14 ), 2037 – 2040. https://doi.org/10.1029/1999GL900494 Davies, F. J., Renssen, H., Blaschek, M., & Muschitiello, F. ( 2015 ). The impact of Sahara desertification on arctic cooling during the Holocene. Climate of the Past, 11 ( 3 ), 571 – 586. https://doi.org/10.5194/cp‐11‐571‐2015 deMenocal, P. ( 1995 ). Plio‐Pleistocene African climate. Science, 270, 53 – 59. https://doi.org/10.1126/science.270.5233.53 deMenocal, P., Ortiz, J., Guilderson, T., Adkins, J., Sarnthein, M., Baker, L., & Yarusinsky, M. ( 2000 ). Abrupt onset and termination of the African humid period: Rapid climate responses to gradual insolation forcing. Quaternary Science Reviews, 19, 347 – 361. https://doi.org/10.1016/S0277‐3791(99)00081‐5 DeMott, P. J., Sassen, K., Poellot, M. R., Baumgardner, D., Rogers, D. C., Brooks, S. D., Prenni, A. J., & Kreidenweis, S. M. ( 2003 ). African dust aerosols as atmospheric ice nuclei. Geophysical Research Letters, 30 ( 14 ), 1732. https://doi.org/10.1029/2003GL017410 Egerer, S., Claussen, M., Reick, C., & Stanelle, T. ( 2016 ). The link between marine sediment records and changes in Holocene Saharan landscape: Simulating the dust cycle. Climate of the Past, 12, 1009 – 1027. https://doi.org/10.5194/cp‐12‐1009‐2016 Eltahir, E. A. B. ( 1998 ). A soil moisture‐rainfall feedback mechanism: 1. Theory and observations. Water Resources Research, 34 ( 4 ), 765 – 776. https://doi.org/10.1029/97WR03499 Evan, A. T., Flamant, C., Gaetani, M., & Guichard, F. ( 2016 ). The past, present and future of African dust. Nature, 531 ( 7595 ), 493 – 495. https://doi.org/10.1038/nature17149 Forbes, R., Tompkins, A. M., & Untch, A. ( 2011 ). A new prognostic bulk microphysics scheme for the IFS. ECMWF Technical Memorandum. (No. 649). Reading, UK: European Centre for Medium‐Range Weather Forecasts. Gent, P. R., Danabasoglu, G., Donner, L. J., Holland, M. M., Hunke, E. C., Jayne, S. R., Lawrence, D. M., Neale, R. B., Rasch, P. J., Vertenstein, M., Worley, P. H., Yang, Z. L., & Zhang, M. ( 2011 ). The community climate system model version 4. Journal of Climate, 24 ( 19 ), 4973 – 4991. https://doi.org/10.1175/2011JCLI4083.1 Ghan, S. J., Liu, X., Easter, R. C., Zaveri, R., Rasch, P. J., & Yoon, J. ( 2012 ). Toward a minimal representation of aerosols in climate models: Comparative decomposition of aerosol direct, semidirect, and indirect radiative forcing. Journal of Climate, 25, 6461 – 6476. https://doi.org/10.1175/JCLI‐D‐11‐00650.1 Ghan, S. J., Smith, S. J., Wang, M., Zhang, K., Pringle, K., Carslaw, K., Pierce, J., Bauer, S., & Adams, P. ( 2013 ). A simple model of global aerosol indirect effects. Journal of Geophysical Research: Atmospheres, 118, 6688 – 6707. https://doi.org/10.1002/jgrd.50567 |
| op_rights |
IndexNoFollow |
| op_doi |
https://doi.org/10.1029/2018GL08122510.1007/s00382‐003‐0310‐z10.1098/rsta.2014.041510.1002/qj.4971014280210.1126/science.270.5233.5310.1029/97WR0349910.1126/science.214.4516.59 |
| container_title |
Chemical Geology |
| container_volume |
263 |
| container_issue |
1-4 |
| container_start_page |
99 |
| op_container_end_page |
109 |
| _version_ |
1810294165506883584 |
| spelling |
ftumdeepblue:oai:deepblue.lib.umich.edu:2027.42/149324 2024-09-15T17:52:06+00:00 Modulation of Mid‐Holocene African Rainfall by Dust Aerosol Direct and Indirect Effects Thompson, Alexander J. Skinner, Christopher B. Poulsen, Christopher J. Zhu, Jiang 2019-04-16 application/pdf https://hdl.handle.net/2027.42/149324 https://doi.org/10.1029/2018GL081225 unknown Springer Netherlands Wiley Periodicals, Inc. Thompson, Alexander J.; Skinner, Christopher B.; Poulsen, Christopher J.; Zhu, Jiang (2019). "Modulation of Mid‐Holocene African Rainfall by Dust Aerosol Direct and Indirect Effects." Geophysical Research Letters 46(7): 3917-3926. 0094-8276 1944-8007 https://hdl.handle.net/2027.42/149324 doi:10.1029/2018GL081225 Geophysical Research Letters Strong, J. D. O., Vecchi, G. A., & Ginoux, P. ( 2015 ). The response of the tropical Atlantic and West African climate to Saharan dust in a fully coupled GCM. Journal of Climate, 28 ( 18 ), 7071 – 7092. https://doi.org/10.1175/JCLI‐D‐14‐00797.1 Shanahan, T. M., Mckay, N. P., Hughen, K. A., Overpeck, J. T., Otto‐Bliesner, B., Heil, C. W., King, J., Scholz, C. A., & Peck, J. ( 2015 ). The time‐transgressive termination of the African humid period. Nature Geoscience, 8 ( 2 ), 140 – 144. https://doi.org/10.1038/NGEO2329 Skinner, C. B., & Poulsen, C. J. ( 2016 ). The role of fall season tropical plumes in enhancing Saharan rainfall during the African humid period. Geophysical Research Letters, 43, 349 – 358. https://doi.org/10.1002/2015GL066318 Solmon, F., Elguindi, N., & Mallet, M. ( 2012 ). Radiative and climatic effects of dust over West Africa, as simulated by a regional climate model. Climate Research, 52 ( 1 ), 97 – 113. https://doi.org/10.3354/cr01039 Taylor, K. E., Stouffer, R. J., & Meehl, G. A. ( 2012 ). An overview of CMIP5 and the experiment design. Bulletin of the American Meteorological Society, 93 ( 4 ), 485 – 498. https://doi.org/10.1175/BAMS‐D‐11‐00094.1 Tierney, J. E., Pausata, F. S. R., & deMenocal, P. B. ( 2017 ). Rainfall regimes of the green Sahara. Science Advances, 3 ( e1601503 ), 1 – 9. https://doi.org/10.1126/sciadv.1601503 Tilmes, S., Lamarque, J. F., Emmons, L. K., Kinnison, D. E., Ma, P. L., Liu, X., Ghan, S., Bardeen, C., Arnold, S., Deeter, M., Vitt, F., Ryerson, T., Elkins, J. W., Moore, F., Spackman, J. R., & Val Martin, M. ( 2015 ). Description and evaluation of tropospheric chemistry and aerosols in the Community Earth System Model (CESM1.2). Geoscientific Model Development, 8, 1395 – 1426. https://doi.org/10.5194/gmd‐8‐1395‐2015 Tjallingii, R., Claussen, M., Stuut, J. B. W., Fohlmeister, J., Jahn, A., Bickert, T., Lamy, F., & Röhl, U. ( 2008 ). Coherent high‐and low‐latitude control of the northwest African hydrological balance. Nature Geoscience, 1, 670 – 675. https://doi.org/10.1038/ngeo289 Tuenter, E., Weber, S. L., Hilgen, F. J., & Lourens, L. J. ( 2007 ). Simulating sub‐Milankovitch climate variations associated with vegetation dynamics. Climate of the Past, 3, 169 – 180. https://doi.org/10.5194/cp‐3‐169‐2007 Vamborg, F. S. E., Brovkin, V., & Claussen, M. ( 2014 ). Background albedo dynamics improve simulated precipitation variability in the Sahel region. Earth System Dynamics, 5, 89 – 101. https://doi.org/10.5194/esd‐5‐89‐2014 Vergara‐Temprado, J., Murray, B. J., Wilson, T. W., O’Sullivan, D., Browse, J., Pringle, K. J., Ardon‐Dryer, K., Bertram, A. K., Burrows, S. M., Ceburnis, D., DeMott, P. J., Mason, R. H., O’Dowd, C. D., Rinaldi, M., & Carslaw, K. S. ( 2017 ). Contribution of feldspar and marine organic aerosols to global ice nucleating particle concentrations. Atmospheric Chemistry and Physics, 17 ( 5 ), 3637 – 3658. https://doi.org/10.5194/acp‐17‐3637‐2017 Williams, R. H., McGee, D., Kinsley, C. W., Ridley, D. A., Hu, S., Fedorov, A., Tal, I., Murray, R. W., & deMenocal, P. B. ( 2016 ). Glacial to Holocene changes in trans‐Atlantic Saharan dust transport and dust‐climate feedbacks. Science Advances, 2, 1 – 11. https://doi.org/10.1126/sciadv.1600445 Xie, S., Ma, H. Y., Boyle, J. S., Klein, S. A., & Zhang, Y. ( 2012 ). On the correspondence between short‐ and long‐time‐scale systematic errors in CAM4/CAM5 for the year of tropical convection. Journal of Climate, 25 ( 22 ), 7937 – 7955. https://doi.org/10.1175/JCLI‐D‐12‐00134.1 Xie, X., Zhang, H., Liu, X., Peng, Y., & Liu, Y. ( 2017 ). Sensitivity study of cloud parameterizations with relative dispersion in CAM5.1: Impacts on aerosol indirect effects. Atmospheric Chemistry and Physics, 17, 5877 – 5892. https://doi.org/10.5194/acp‐17‐5877‐2017 Yoshioka, M., Mahowald, N. M., Conley, A. J., Collins, W. D., Fillmore, D. W., Zender, C. S., & Coleman, D. B. ( 2007 ). Impact of desert dust radiative forcing on Sahel precipitation: Relative importance of dust compared to sea surface temperature variations, vegetation changes, and greenhouse gas warming. Journal of Climate, 20 ( 8 ), 1445 – 1467. https://doi.org/10.1175/JCLI4056.1 Yu, M., Wang, G., & Pal, J. S. ( 2016 ). Effects of vegetation feedback on future climate change over West Africa. Climate Dynamics, 46 ( 11–12 ), 3669 – 3688. https://doi.org/10.1007/s00382‐015‐2795‐7 Zender, C. S., Bian, H., & Newman, D. ( 2003 ). Mineral dust entrainment and deposition (DEAD) model: Description and 1990s dust climatology. Journal of Geophysical Research, 108 ( D14 ), 4416. https://doi.org/10.1029/2002JD002775 Zhang, Z., Ramstein, G., Schuster, M., Li, C., Contoux, C., & Yan, Q. ( 2014 ). Aridification of the Sahara desert caused by Tethys Sea shrinkage during the Late Miocene. Nature, 513 ( 7518 ), 401 – 404. https://doi.org/10.1038/nature13705 Zhu, Z., Piao, S., Myneni, R. B., Huang, M., Zeng, Z., Canadell, J. G., Ciais, P., Sitch, S., Friedlingstein, P., Arneth, A., Cao, C., Cheng, L., Kato, E., Koven, C., Li, Y., Lian, X., Liu, Y., Liu, R., Mao, J., Pan, Y., Peng, S., Peñuelas, J., Poulter, B., Pugh, T. A. M., Stocker, B. D., Viovy, N., Wang, X., Wang, Y., Xiao, Z., Yang, H., Zaehle, S., & Zeng, N. ( 2016 ). Greening of the Earth and its drivers. Nature Climate Change, 6 ( 8 ), 791 – 795. https://doi.org/10.1038/nclimate3004 Bartlein, P. J., Harrison, S. P., Brewer, S., Connor, S., Davis, B. A. S., Gajewski, K., Guiot, J., Harrison‐Prentice, T. I., Henderson, A., Peyron, O., Prentice, I. C., Scholze, M., Seppä, H., Shuman, B., Sugita, S., Thompson, R. S., Viau, A. E., Williams, J., & Wu, H. ( 2011 ). Pollen‐based continental climate reconstructions at 6 and 21 ka: A global synthesis. Climate Dynamics, 37, 775 – 802. https://doi.org/10.1007/s00382‐010‐0904‐1 Colman, R. ( 2003 ). A comparison of climate feedbacks in general circulation models. Climate Dynamics, 20 ( 7–8 ), 865 – 873. https://doi.org/10.1007/s00382‐003‐0310‐z Conley, A. J., Lamarque, J. F., Vitt, F., Collins, W. D., & Kiehl, J. ( 2013 ). PORT, a CESM tool for the diagnosis of radiative forcing. Geoscientific Model Development, 6 ( 2 ), 469 – 476. https://doi.org/10.5194/gmd‐6‐469‐2013 Gaetani, M., Messori, G., Zhang, Q., Flamant, C., & Pausata, F. S. R. ( 2017 ). Understanding the mechanisms behind the northward extension of the West African Monsoon during the mid‐Holocene. Journal of Climate, 30 ( 19 ), 7621 – 7642. https://doi.org/10.1175/JCLI‐D‐16‐0299.1 Boos, W. R., & Korty, R. L. ( 2016 ). Regional energy budget control of the intertropical convergence zone and application to mid‐Holocene rainfall. Nature Geoscience, 9 ( 12 ), 892 – 897. https://doi.org/10.1038/ngeo2833 Braconnot, P., Harrison, S. P., Otto‐Bliesner, B., Abe‐Ouchi, A., Jungclaus, J., & Peterschmitt, J.‐Y. ( 2011 ). The paleoclimate modeling intercomparison project contribution to CMIP5. CLIVAR Exchanges, 56 ( 16–2 ), 15 – 19. http://www.clivar.org/sites/default/files/documents/Exchanges56.pdf Braconnot, P., Joussaume, S., Marti, O., & de Noblet, N. ( 1999 ). Synergistic feedbacks from ocean and vegetation on the African monsoon response to mid‐Holocene insolation. Geophysical Research Letters, 26, 2481 – 2484. https://doi.org/10.1029/1999GL006047 Bretherton, C. S. ( 2015 ). Insights into low‐latitude cloud feedbacks from high‐resolution models. Philosophical Transactions of the Royal Society A, 373 ( 2054 ), 1 – 19. https://doi.org/10.1098/rsta.2014.0415 Brostrom, A., Coe, M., Harrison, S. P., Gallimore, R., Kutzbach, J. E., Foley, J., Prentice, I. C., & Behling, P. ( 1998 ). Land surface feedbacks and palaeomonsoons in northern Africa. Geophysical Research Letters, 25 ( 19 ), 3615 – 3618. https://doi.org/10.1029/98GL02804 Brovkin, V., Claussen, M., Petoukhov, V., & Ganopolski, A. ( 1998 ). On the stability of the atmosphere‐vegetation system in the Sahara/Sahel region. Journal of Geophysical Research, 103 ( D24 ), 31,613 – 31,624. https://doi.org/10.1029/1998JD200006 Charney, J., Stone, P. H., & Quirk, W. J. ( 1975 ). Drought in the Sahara: A biogeophysical feedback mechanism. Science, 187 ( 4175 ), 434 – 435. https://doi.org/10.1126/science.187.4175.434 Charney, J. G. ( 1975 ). Dynamics of deserts and drought in the Sahel. Quarterly Journal of the Royal Meteorological Society, 101 ( 428 ), 193 – 202. https://doi.org/10.1002/qj.49710142802 Claussen, M., & Gayler, V. ( 1997 ). The greening of the Sahara during the mid‐Holocene: Results of an interactive atmosphere‐biome. Global Ecology and Biogeography Letters, 6 ( 5 ), 369 – 377. https://doi.org/10.2307/2997337 Claussen, M., Kubatzki, C., Brovkin, V., Ganopolski, A., Hoelzmann, P., & Pachur, H.‐J. ( 1999 ). Simulation of an abrupt change in Saharan vegetation in the mid‐Holocene. Geophysical Research Letters, 26 ( 14 ), 2037 – 2040. https://doi.org/10.1029/1999GL900494 Davies, F. J., Renssen, H., Blaschek, M., & Muschitiello, F. ( 2015 ). The impact of Sahara desertification on arctic cooling during the Holocene. Climate of the Past, 11 ( 3 ), 571 – 586. https://doi.org/10.5194/cp‐11‐571‐2015 deMenocal, P. ( 1995 ). Plio‐Pleistocene African climate. Science, 270, 53 – 59. https://doi.org/10.1126/science.270.5233.53 deMenocal, P., Ortiz, J., Guilderson, T., Adkins, J., Sarnthein, M., Baker, L., & Yarusinsky, M. ( 2000 ). Abrupt onset and termination of the African humid period: Rapid climate responses to gradual insolation forcing. Quaternary Science Reviews, 19, 347 – 361. https://doi.org/10.1016/S0277‐3791(99)00081‐5 DeMott, P. J., Sassen, K., Poellot, M. R., Baumgardner, D., Rogers, D. C., Brooks, S. D., Prenni, A. J., & Kreidenweis, S. M. ( 2003 ). African dust aerosols as atmospheric ice nuclei. Geophysical Research Letters, 30 ( 14 ), 1732. https://doi.org/10.1029/2003GL017410 Egerer, S., Claussen, M., Reick, C., & Stanelle, T. ( 2016 ). The link between marine sediment records and changes in Holocene Saharan landscape: Simulating the dust cycle. Climate of the Past, 12, 1009 – 1027. https://doi.org/10.5194/cp‐12‐1009‐2016 Eltahir, E. A. B. ( 1998 ). A soil moisture‐rainfall feedback mechanism: 1. Theory and observations. Water Resources Research, 34 ( 4 ), 765 – 776. https://doi.org/10.1029/97WR03499 Evan, A. T., Flamant, C., Gaetani, M., & Guichard, F. ( 2016 ). The past, present and future of African dust. Nature, 531 ( 7595 ), 493 – 495. https://doi.org/10.1038/nature17149 Forbes, R., Tompkins, A. M., & Untch, A. ( 2011 ). A new prognostic bulk microphysics scheme for the IFS. ECMWF Technical Memorandum. (No. 649). Reading, UK: European Centre for Medium‐Range Weather Forecasts. Gent, P. R., Danabasoglu, G., Donner, L. J., Holland, M. M., Hunke, E. C., Jayne, S. R., Lawrence, D. M., Neale, R. B., Rasch, P. J., Vertenstein, M., Worley, P. H., Yang, Z. L., & Zhang, M. ( 2011 ). The community climate system model version 4. Journal of Climate, 24 ( 19 ), 4973 – 4991. https://doi.org/10.1175/2011JCLI4083.1 Ghan, S. J., Liu, X., Easter, R. C., Zaveri, R., Rasch, P. J., & Yoon, J. ( 2012 ). Toward a minimal representation of aerosols in climate models: Comparative decomposition of aerosol direct, semidirect, and indirect radiative forcing. Journal of Climate, 25, 6461 – 6476. https://doi.org/10.1175/JCLI‐D‐11‐00650.1 Ghan, S. J., Smith, S. J., Wang, M., Zhang, K., Pringle, K., Carslaw, K., Pierce, J., Bauer, S., & Adams, P. ( 2013 ). A simple model of global aerosol indirect effects. Journal of Geophysical Research: Atmospheres, 118, 6688 – 6707. https://doi.org/10.1002/jgrd.50567 IndexNoFollow indirect aerosol effects dust aerosols African humid period West African Monsoon Geological Sciences Science Article 2019 ftumdeepblue https://doi.org/10.1029/2018GL08122510.1007/s00382‐003‐0310‐z10.1098/rsta.2014.041510.1002/qj.4971014280210.1126/science.270.5233.5310.1029/97WR0349910.1126/science.214.4516.59 2024-07-30T04:06:19Z Climate model simulations of the mid‐Holocene (MH) consistently underestimate northern African rainfall for reasons not fully understood. While most models incorporate orbital forcing and vegetation feedbacks, they neglect dust reductions associated with greater vegetation cover. Here we simulate the MH climate response to reduced Saharan dust using CESM CAM5‐chem, which resolves direct and indirect dust aerosol effects. Direct aerosol effects increase Saharan and Sahel convective rainfall by ~16% and 8%. In contrast, indirect aerosol effects decrease stratiform rainfall, damping the dust‐induced total rainfall increase by ~13% in the Sahara and ~59% in the Sahel. Sensitivity experiments indicate the dust‐induced precipitation anomaly in the Sahara and Sahel (0.27 and 0.18 mm/day) is smaller than the anomaly from MH vegetation cover (1.19 and 1.08 mm/day). Although sensitive to dust radiative properties, sea surface temperatures, and indirect aerosol effect parameterization, our results suggest that dust reductions had competing effects on MH African rainfall.Plain Language SummarySix thousand years ago, changes in Earth’s orbit led to greater summer season solar radiation over northern Africa. The increase in energy resulted in higher rainfall amounts, widespread vegetation, and reduced dust aerosols over regions that today are desert. In this study we use a climate model, CESM CAM5‐chem, that accounts for the ways dust aerosols interact with sunlight and cloud droplets to examine how the reduction in Saharan dust during this past humid time affected rainfall. When dust aerosols are reduced in the model, more sunlight reaches the surface, the Sahara warms, and convective rainfall from the West African Monsoon increases. However, through dust‐cloud droplet interactions, the same reduction in dust decreases nonconvective rainfall, which is less prevalent during the monsoon season but still important, and thus dampens the total rainfall increase. Overall, dust reduction leads to a rainfall response that is ... Article in Journal/Newspaper Arctic University of Michigan: Deep Blue Chemical Geology 263 1-4 99 109 |