Evapotranspiration of soil moisture can affect temperature and humidity in the lower atmosphere, and thereby the development of convective rain storms. Climate models have illustrated the importance of soil-moisture–precipitation feedbacks for weekly rainfall totals in semi-arid regions, such as the Sahel1. However, large variations exist between model feedbacks, and the mechanisms governing the strength and sign of the feedback are uncertain. Here, we use satellite observations of land surface temperatures and convective cloud cover over West Africa—collected during the wet seasons between 2006 and 2010—to determine the impact of soil moisture on rainfall in the Sahel. We show that variations in soil moisture on length scales of approximately 10–40 km exert a strong control on storm initiation—as evidenced by the appearance of convective cloud. The probability of convective initiation is doubled over strong soil-moisture gradients compared with that over uniform soil-moisture conditions. We find that 37% of all storm initiations analysed occurred over the steepest 25% of soil-moisture gradients. We conclude that heterogeneities in soil moisture on scales of tens of kilometres have a pronounced impact on rainfall in the Sahel, and suggest that similar processes may be important throughout the semi-arid tropics.
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Koster, R. D. et al. Regions of strong coupling between soil moisture and precipitation. Science 305, 1138–1140 (2004).
Hastenrath, S. Climate Dynamics of the Tropics (Kluwer, 1995).
Ganopolski, A. et al. The influence of vegetation–atmosphere–ocean interaction on climate during the mid-Holocene. Science 280, 1916–1919 (1998).
Zeng, N., Neelin, J. D., Lau, K. M. & Tucker, C. J. Enhancement of interdecadal climate variability in the Sahel by vegetation interaction. Science 286, 1537–1540 (1999).
Giannini, A., Saravanan, R. & Chang, P. Oceanic forcing of Sahel rainfall on interannual to interdecadal time scales. Science 302, 1027–1030 (2003).
Taylor, C. M. & Ellis, R. J. Satellite detection of soil moisture impacts on convection at the mesoscale. Geophys. Res. Lett. 33, L03404 (2006).
Taylor, C. M. & Lebel, T. Observational evidence of persistent convective-scale rainfall patterns. Mon. Weather Rev. 126, 1597–1607 (1998).
Kohler, M., Kalthoff, N. & Kottmeier, C. The impact of soil moisture modifications on CBL characteristics in West Africa: A case-study from the AMMA campaign. Q. J. R. Meteorol. Soc. 136, 442–455 (2010).
Mathon, V., Laurent, H. & Lebel, T. Mesoscale convective system rainfall in the Sahel. J. Appl. Meteorol. 41, 1081–1092 (2002).
Lebel, T., Taupin, J. D. & D’Amato, N. Rainfall monitoring during HAPEX-Sahel: 1. General rainfall conditions and climatology. J. Hydrol. 189, 74–96 (1997).
Owe, M., de Jeu, R. & Holmes, T. Multisensor historical climatology of satellite-derived global land surface moisture. J. Geophys. Res. 113, F01002 (2008).
Trigo, I. F., Monteiro, I. T., Olesen, F. & Kabsch, E. An assessment of remotely sensed land surface temperature. J. Geophys. Res. 113, D17108 (2008).
Stewart, D. J., Taylor, C. M., Reeves, C. E. & McQuaid, J. B. Biogenic nitrogen oxide emissions from soils: Impact on NOx and ozone over west Africa during AMMA (African Monsoon Multidisciplinary Analysis) observational study. Atmos. Chem. Phys. 8, 2285–2297 (2008).
Taylor, C. M., Harris, P. P. & Parker, D. J. Impact of soil moisture on the development of a sahelian mesoscale convective system: A case study from the AMMA special observing period. Q. J. R. Meteorol. Soc. 136, 456–470 (2010).
Taylor, C. M., Parker, D. J. & Harris, P. P. An observational case study of mesoscale atmospheric circulations induced by soil moisture. Geophys. Res. Lett. 34, L15801 (2007).
Gantner, L. & Kalthoff, N. Sensitivity of a modelled life cycle of a mesoscale convective system to soil conditions over West Africa. Q. J. R. Meteorol. Soc. 136, 471–482 (2010).
Gaertner, M. A., Dominguez, M. & Garvert, M. A modelling case-study of soil moisture–atmosphere coupling. Q. J. R. Meteorol. Soc. 136, 483–495 (2010).
Chen, F. & Avissar, R. Impact of land-surface moisture variability on local shallow convective cumulus and precipitation in large-scale models. J. Appl. Meteorol. 33, 1382–1401 (1994).
Baidya Roy, S., Weaver, C. P., Nolan, D. S. & Avissar, R. A preferred scale for landscape forced mesoscale circulations? J. Geophys. Res. 108, 8854 (2003).
Weaver, C. P. Coupling between large-scale atmospheric processes and mesoscale land–atmosphere interactions in the US Southern Great Plains during summer. Part I: Case studies. J. Hydromet. 5, 1223–1246 (2004).
Pielke, R. A. et al. Nonlinear influence of mesoscale land-use on weather and climate. J. Clim. 4, 1053–1069 (1991).
Mathon, V. & Laurent, H. Life cycle of Sahelian mesoscale convective cloud systems. Q. J. R. Meteorol. Soc. 127, 377–406 (2001).
Carleton, A. M. et al. Summer season land cover—convective cloud associations for the Midwest US ‘Corn Belt’. Geophys. Res. Lett. 28, 1679–1682 (2001).
Wang, J. F. et al. Impact of deforestation in the Amazon basin on cloud climatology. Proc. Natl Acad. Sci. USA. 106, 3670–3674 (2009).
Garcia-Carreras, L. et al. Impact of mesoscale vegetation heterogeneities on the dynamical and thermodynamic properties of the planetary boundary layer. J. Geophys. Res. 115, D03102 (2010).
Garcia-Carreras, L., Parker, D. J. & Marsham, J. H. What is the mechanism for the modification of convective cloud distributions by land surface–induced flows? J. Atmos. Sci. 68, 619–634 (2011).
Morel, C. & Senesi, S. A climatology of mesoscale convective systems over Europe using satellite infrared imagery. I: Methodology. Q. J. R. Meteorol. Soc. 128, 1953–1971 (2002).
Foster, G. Wavelets for period analysis of unevenly sampled time series. Astronomical J. 112, 1709–1729 (1996).
Based on a French initiative, AMMA was built by an international scientific group and is currently funded by a large number of agencies, especially from France, the UK, the US and Africa. The authors were funded by the European Community’s Sixth Framework Research Programme and the UK NERC project NE/B505597/1. We would like to thank D. Parker and J. Polcher for many valuable discussions on this topic. We also thank LandSAF for the provision of land surface temperature data, EUMETSAT for cloud data, R. de Jeu for soil-moisture retrievals and M. Tomasini for assistance with MCS tracking.
The authors declare no competing financial interests.
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Taylor, C., Gounou, A., Guichard, F. et al. Frequency of Sahelian storm initiation enhanced over mesoscale soil-moisture patterns. Nature Geosci 4, 430–433 (2011). https://doi.org/10.1038/ngeo1173
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