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Article Type:
Research Article

Empirical Relationships of Sea Surface Temperature and Vegetation Activity with Summer Rainfall Variability over the Sahel

Yaqian He Department of Geology and Geography, West Virginia University, Morgantown, West Virginia

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Eungul Lee Department of Geology and Geography, West Virginia University, Morgantown, West Virginia

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Print Publication:
01 Feb 2016
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Biogeophysical Climate Impacts of Land Use and Land Cover Change (LULCC)
DOI:
https://doi.org/10.1175/EI-D-15-0028.1
Page(s):
1–18
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Abstract

Regional land surface and remote ocean variables have been considered as primary forcings altering the variability of summer rainfall over the Sahel. However, previous studies usually examined the two components separately. In this study, the authors apply statistical methods including correlation, multivariate linear regression, and Granger causality analyses to investigate the relative roles of spring–summer sea surface temperature (SST) and vegetation activity in explaining the Sahel summer rainfall variability from 1982 to 2006. The remotely sensed normalized difference vegetation index (NDVI) is used as an indicator of land surface forcing. This study shows that spring and summer SSTs over the subtropical North Atlantic have significant positive correlations with summer rainfall. The spring and summer NDVIs over the Sahel have significant negative and positive correlations, respectively, with summer rainfall. Based on the multivariate linear regression analysis, the adjusted R2 for the integrated model with both the land and ocean variables is 0.70. It is around 2 times larger than the model with SST alone (adjusted R2 = 0.36). To further investigate the causal relationships of summer rainfall with the SST and NDVI variables selected in the integrated multivariate model, the authors perform a Granger causality test. This study finds that summer NDVI over the Sahel does Granger cause summer rainfall over the Sahel, while the summer SST over the subtropical North Atlantic does not Granger cause the summer rainfall. The results indicate that the regional land surface forcing has a relatively strong contribution to Sahel summer rainfall, compared to the remote ocean forcing, during the recent decades.

Supplemental information related to this paper is available at the Journals Online website: http://dx.doi.org/10.1175/EI-D-15-0028.s1.

Corresponding author address: Eungul Lee, Department of Geology and Geography, West Virginia University, 98 Beechurst Avenue, Morgantown, WV 26506. E-mail address: eungul.lee@mail.wvu.edu

This article is included in the Biogeophysical Climate Impacts of Land Use and Land Cover Change (LULCC) special collection.

Abstract

Regional land surface and remote ocean variables have been considered as primary forcings altering the variability of summer rainfall over the Sahel. However, previous studies usually examined the two components separately. In this study, the authors apply statistical methods including correlation, multivariate linear regression, and Granger causality analyses to investigate the relative roles of spring–summer sea surface temperature (SST) and vegetation activity in explaining the Sahel summer rainfall variability from 1982 to 2006. The remotely sensed normalized difference vegetation index (NDVI) is used as an indicator of land surface forcing. This study shows that spring and summer SSTs over the subtropical North Atlantic have significant positive correlations with summer rainfall. The spring and summer NDVIs over the Sahel have significant negative and positive correlations, respectively, with summer rainfall. Based on the multivariate linear regression analysis, the adjusted R2 for the integrated model with both the land and ocean variables is 0.70. It is around 2 times larger than the model with SST alone (adjusted R2 = 0.36). To further investigate the causal relationships of summer rainfall with the SST and NDVI variables selected in the integrated multivariate model, the authors perform a Granger causality test. This study finds that summer NDVI over the Sahel does Granger cause summer rainfall over the Sahel, while the summer SST over the subtropical North Atlantic does not Granger cause the summer rainfall. The results indicate that the regional land surface forcing has a relatively strong contribution to Sahel summer rainfall, compared to the remote ocean forcing, during the recent decades.

Supplemental information related to this paper is available at the Journals Online website: http://dx.doi.org/10.1175/EI-D-15-0028.s1.

Corresponding author address: Eungul Lee, Department of Geology and Geography, West Virginia University, 98 Beechurst Avenue, Morgantown, WV 26506. E-mail address: eungul.lee@mail.wvu.edu

This article is included in the Biogeophysical Climate Impacts of Land Use and Land Cover Change (LULCC) special collection.

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  • Bah, A., 1987: Towards the prediction of Sahelian rainfall from sea surface temperatures in the Gulf of Guinea. Tellus, 39A, 39–48, doi:10.1111/j.1600-0870.1987.tb00287.x.

    • Search Google Scholar
    • Export Citation

  • Biasutti, M., I. Held, A. Sobel, and A. Giannini, 2008: SST forcings and Sahel rainfall variability in simulations of the twentieth and twenty-first centuries. J. Climate, 21, 3471–3486, doi:10.1175/2007JCLI1896.1.

    • Search Google Scholar
    • Export Citation

  • Carlson, T. N., and D. A. Ripley, 1997: On the relation between NDVI, fractional vegetation cover, and leaf area index. Remote Sens. Environ., 62, 241–252, doi:10.1016/S0034-4257(97)00104-1.

    • Search Google Scholar
    • Export Citation

  • Dai, A., P. J. Lamb, K. E. Trenberth, M. Hulme, P. D. Jones, and P. Xie, 2004: The recent Sahel drought is real. Int. J. Climatol., 24, 1323–1331, doi:10.1002/joc.1083.

    • Search Google Scholar
    • Export Citation

  • Dirmeyer, P. A., D. Niyogi, N. de Noblet-Ducoudré, R. E. Dickinson, and P. K. Snyder, 2010: Impacts of land use change on climate. Int. J. Climatol., 30, 1905–1907, doi:10.1002/joc.2157.

    • Search Google Scholar
    • Export Citation

  • Eklundh, L., and L. Olsson, 2003: Vegetation index trends for the African Sahel 1982–1999. Geophys. Res. Lett., 30, 1430, doi:10.1029/2002GL016772.

    • Search Google Scholar
    • Export Citation

  • Eltahir, E. A., 1998: A soil moisture–rainfall feedback mechanism: 1. Theory and observations. Water Resour. Res., 34, 765–776, doi:10.1029/97WR03499.

    • Search Google Scholar
    • Export Citation

  • FAO, 2011: Disaster risk management strategy in West Africa and the Sahel. FAO Rep., 41 pp. [Available online at http://www.fao.org/emergencies/resources/documents/resources-detail/en/c/157580/.]

  • Fink, A., D. Vincent, and V. Ermert, 2006: Rainfall types in the West African Sudanian zone during the summer monsoon 2002. Mon. Wea. Rev., 134, 2143–2164, doi:10.1175/MWR3182.1.

    • Search Google Scholar
    • Export Citation

  • Foley, J. A., M. T. Coe, M. Scheffer, and G. Wang, 2003a: Regime shifts in the Sahara and Sahel: Interactions between ecological and climatic systems in northern Africa. Ecosystems, 6, 524–532, doi:10.1007/s10021-002-0227-0.

    • Search Google Scholar
    • Export Citation

  • Foley, J. A., M. H. Costa, C. Delire, N. Ramankutty, and P. K. Snyder, 2003b: Green surprise? How terrestrial ecosystems could affect Earth’s climate. Front. Ecol. Environ., 1, 38–44, doi:10.1890/1540-9295(2003)001[0038:GSHTEC]2.0.CO;2.

    • Search Google Scholar
    • Export Citation

  • Folland, C., T. Palmer, and D. Parker, 1986: Sahel rainfall and worldwide sea temperatures, 1901–85. Nature, 320, 602–607, doi:10.1038/320602a0.

    • Search Google Scholar
    • Export Citation

  • Ford, T. W., A. D. Rapp, and S. M. Quiring, 2015: Does afternoon precipitation occur preferentially over dry or wet soils in Oklahoma? J. Hydrometeor., 16, 874–888, doi:10.1175/JHM-D-14-0005.1.

    • Search Google Scholar
    • Export Citation

  • Gamon, J. A., C. B. Field, M. L. Goulden, K. L. Griffin, A. E. Hartley, G. Joel, J. Penuelas, and R. Valentini, 1995: Relationships between NDVI, canopy structure, and photosynthesis in three Californian vegetation types. Ecol. Appl., 5, 28–41, doi:10.2307/1942049.

    • Search Google Scholar
    • Export Citation

  • Giannini, A., R. Saravanan, and P. Chang, 2003: Oceanic forcing of Sahel rainfall on interannual to interdecadal time scales. Science, 302, 1027–1030, doi:10.1126/science.1089357.

    • Search Google Scholar
    • Export Citation

  • Granger, C. W., 1969: Investigating causal relations by econometric models and cross-spectral methods. Econometrica, 37, 424–438, doi:10.2307/1912791.

    • Search Google Scholar
    • Export Citation

  • Hagos, S. M., and K. H. Cook, 2008: Ocean warming and late-twentieth-century Sahel drought and recovery. J. Climate, 21, 3797–3814, doi:10.1175/2008JCLI2055.1.

    • Search Google Scholar
    • Export Citation

  • Hameed, S., and N. Riemer, 2012: Relationship of Sahel precipitation and atmospheric centers of action. Adv. Meteor., 2012, 953853, doi:10.1155/2012/953853.

    • Search Google Scholar
    • Export Citation

  • Helsel, D. R., and R. M. Hirsch, 1992: Statistical Methods in Water Resources. U.S. Geological Survey, 522 pp.

  • Hoerling, M., J. Hurrell, J. Eischeid, and A. Phillips, 2006: Detection and attribution of twentieth-century northern and southern African rainfall change. J. Climate, 19, 3989–4008, doi:10.1175/JCLI3842.1.

    • Search Google Scholar
    • Export Citation

  • Jiang, N., W. Zhu, Z. Zheng, G. Chen, and D. Fan, 2013: A comparative analysis between GIMSS NDVIg and NDVI3g for monitoring vegetation activity change in the Northern Hemisphere during 1982–2008. Remote Sens., 5, 4031–4044, doi:10.3390/rs5084031.

    • Search Google Scholar
    • Export Citation

  • Lamprey, H., 1988: Report on the desert encroachment reconnaissance in northern Sudan: 21 October to 10 November 1975. Desertification Control Bull., 17, 1–7.

  • Lee, E., T. N. Chase, and B. Rajagopalan, 2008: Highly improved predictive skill in the forecasting of the East Asian summer monsoon. Water Resour. Res., 44, W10422, doi:10.1029/2007WR006514.

    • Search Google Scholar
    • Export Citation

  • Lee, E., T. N. Chase, B. Rajagopalan, R. G. Barry, T. W. Biggs, and P. J. Lawrence, 2009: Effects of irrigation and vegetation activity on early Indian summer monsoon variability. Int. J. Climatol., 29, 573–581, doi:10.1002/joc.1721.

    • Search Google Scholar
    • Export Citation

  • Lee, E., C. C. Barford, C. J. Kucharik, B. S. Felzer, and J. A. Foley, 2011: Role of turbulent heat fluxes over land in the monsoon over East Asia. Int. J. Geosci., 2, 420–431, doi:10.4236/ijg.2011.24046.

    • Search Google Scholar
    • Export Citation

  • Lee, E., Y. He, M. Zhou, and J. Liang, 2016: Potential feedback of recent vegetation changes on summer rainfall in the Sahel. Phys. Geogr., doi:10.1080/02723646.2015.1120139, in press.

    • Search Google Scholar
    • Export Citation

  • Lo, M.-H., and J. S. Famiglietti, 2013: Irrigation in California’s Central Valley strengthens the southwestern U. S. water cycle. Geophys. Res. Lett., 40, 301–306, doi:10.1002/grl.50108.

    • Search Google Scholar
    • Export Citation

  • Los, S. O., G. P. Weedon, P. North, J. Kaduk, C. Taylor, and P. Cox, 2006: An observation-based estimate of the strength of rainfall-vegetation interactions in the Sahel. Geophys. Res. Lett., 33, L16402, doi:10.1029/2006GL027065.

    • Search Google Scholar
    • Export Citation

  • Lu, J., and T. L. Delworth, 2005: Oceanic forcing of the late 20th century Sahel drought. Geophys. Res. Lett., 32, L22706, doi:10.1029/2005GL023316.

    • Search Google Scholar
    • Export Citation

  • Mahmood, R., and Coauthors, 2014: Land cover changes and their biogeophysical effects on climate. Int. J. Climatol., 34, 929–953, doi:10.1002/joc.3736.

    • Search Google Scholar
    • Export Citation

  • Martin, E. R., and C. D. Thorncroft, 2014: The impact of the AMO on the West African monsoon annual cycle. Quart. J. Roy. Meteor. Soc., 140, 31–46, doi:10.1002/qj.2107.

    • Search Google Scholar
    • Export Citation

  • McPherson, R. A., 2007: A review of vegetation—Atmosphere interactions and their influences on mesoscale phenomena. Prog. Phys. Geogr., 31, 261–285, doi:10.1177/0309133307079055.

    • Search Google Scholar
    • Export Citation

  • Meng, L., D. Long, S. M. Quiring, and Y. Shen, 2014: Statistical analysis of the relationship between spring soil moisture and summer precipitation in East China. Int. J. Climatol., 34, 1511–1523, doi:10.1002/joc.3780.

    • Search Google Scholar
    • Export Citation

  • Mitchell, T. D., T. R. Carter, P. D. Jones, M. Hulme, and M. New, 2004: A comprehensive set of high-resolution grids of monthly climate for Europe and the globe: The observed record (1901–2000) and 16 scenarios (2001–2100). Tyndall Centre for Climate Change Research Working Paper 55, 30 pp. [Available online at http://ipcc-data.org/docs/tyndall_working_papers_wp55.pdf.]

  • Mohino, E., S. Janicot, and J. Bader, 2011: Sahel rainfall and decadal to multi-decadal sea surface temperature variability. Climate Dyn., 37, 419–440, doi:10.1007/s00382-010-0867-2.

    • Search Google Scholar
    • Export Citation

  • Mueller, K. L., V. Yadav, P. S. Curtis, C. Vogel, and A. M. Michalak, 2010: Attributing the variability of eddy-covariance CO2 flux measurements across temporal scales using geostatistical regression for a mixed northern hardwood forest. Global Biogeochem. Cycles, 24, GB3023, doi:10.1029/2009GB003642.

    • Search Google Scholar
    • Export Citation

  • Myneni, R. B., C. Keeling, C. Tucker, G. Asrar, and R. Nemani, 1997: Increased plant growth in the northern high latitudes from 1981 to 1991. Nature, 386, 698–702, doi:10.1038/386698a0.

    • Search Google Scholar
    • Export Citation

  • Neumann, D. W., B. Rajagopalan, and E. A. Zagona, 2003: Regression model for daily maximum stream temperature. J. Environ. Eng., 129, 667–674, doi:10.1061/(ASCE)0733-9372(2003)129:7(667).

    • Search Google Scholar
    • Export Citation

  • Olsson, L., and M. Hall-Beyer, 2008: Greening of the Sahel. Accessed 12 January 2015. [Available online at http://www.eoearth.org/view/article/153150/.]

  • Perez, F., M. De Stefano, F. Disabato, and R. Vigna, 2012: The ITHACA early warning system for drought monitoring: First prototype test for the 2010 Sahel crisis. Ital. J. Remote Sens., 44, 181–195, doi:10.5721/ItJRS201244114.

    • Search Google Scholar
    • Export Citation

  • Pielke, R. A., Sr., 2005: Land use and climate change. Science, 310, 1625–1626, doi:10.1126/science.1120529.

  • Rayner, N., and Coauthors, 2003: Global analyses of sea surface temperature, sea ice, and night marine air temperature since the late nineteenth century. J. Geophys. Res., 108, 4407, doi:10.1029/2002JD002670.

    • Search Google Scholar
    • Export Citation

  • Rouse, J. W., Jr., R. H. Haas, J. A. Schell, and D. W. Deering, 1974: Monitoring vegetation systems in the Great Plains with ERTS. Proc. Third Earth Resources Technology Satellite-1 Symp., Washington, D.C., NASA Goddard Space Flight Center, 309–313.

  • Rowell, D. P., 2003: The impact of Mediterranean SSTs on the Sahelian rainfall season. J. Climate, 16, 849–862, doi:10.1175/1520-0442(2003)016<0849:TIOMSO>2.0.CO;2.

    • Search Google Scholar
    • Export Citation

  • Sanogo, S., A. H. Fink, J. A. Omotosho, A. Ba, R. Redl, and V. Ermert, 2015: Spatio-temporal characteristics of the recent rainfall recovery in West Africa. Int. J. Climatol., 35, 4589–4605, doi:10.1002/joc.4309.

    • Search Google Scholar
    • Export Citation

  • Shanahan, T. M., and Coauthors, 2009: Atlantic forcing of persistent drought in West Africa. Science, 324, 377–380, doi:10.1126/science.1166352.

    • Search Google Scholar
    • Export Citation

  • Tippett, M. K., and A. Giannini, 2006: Potentially predictable components of African summer rainfall in an SST-forced GCM simulation. J. Climate, 19, 3133–3144, doi:10.1175/JCLI3779.1.

    • Search Google Scholar
    • Export Citation

  • Tucker, C. J., and S. E. Nicholson, 1999: Variations in the size of the Sahara Desert from 1980 to 1997. Ambio, 28, 587–591.

  • Tucker, C. J., and Coauthors, 2005: An extended AVHRR 8-km NDVI dataset compatible with MODIS and SPOT vegetation NDVI data. Int. J. Remote Sens., 26, 4485–4498, doi:10.1080/01431160500168686.

    • Search Google Scholar
    • Export Citation

  • Van Noorden, R., 2006: More plants make more rain. Accessed 16 January 2015. [Available online at http://www.nature.com/news/2006/060925/full/news060925-1.html.]

  • Von Storch, H., and F. W. Zwiers, 2001: Statistical Analysis in Climate Research. Cambridge University Press, 496 pp.

  • Wang, W., B. T. Anderson, N. Phillips, R. K. Kaufmann, C. Porter, and R. B. Myneni, 2006: Feedbacks of vegetation on summertime climate variability over the North American grasslands. Part I: Statistical analysis. Earth Interact., 10, doi:10.1175/EI196.1.

    • Search Google Scholar
    • Export Citation

  • Xue, Y., and J. Shukla, 1993: The influence of land surface properties on Sahel climate. Part I: Desertification. J. Climate, 6, 2232–2245, doi:10.1175/1520-0442(1993)006<2232:TIOLSP>2.0.CO;2.

    • Search Google Scholar
    • Export Citation

  • Xue, Y., A. Boone, and C. M. Taylor, 2012: Review of recent developments and the future prospective in West African atmosphere/land interaction studies. Int. J. Geophys., 2012, 748921, doi:10.1155/2012/748921.

    • Search Google Scholar
    • Export Citation

  • Zhang, R., and T. L. Delworth, 2006: Impact of Atlantic multidecadal oscillations on India/Sahel rainfall and Atlantic hurricanes. Geophys. Res. Lett., 33, L17712, doi:10.1029/2006GL026267.

    • Search Google Scholar
    • Export Citation

  • Zheng, X., E. A. Eltahir, and K. A. Emanuel, 1999: A mechanism relating tropical Atlantic spring sea surface temperature and West African rainfall. Quart. J. Roy. Meteor. Soc., 125, 1129–1163, doi:10.1002/qj.1999.49712555604.

    • Search Google Scholar
    • Export Citation
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