Advertisement

Climate Dynamics

, Volume 50, Issue 9–10, pp 3219–3236 | Cite as

Austral summer Southern Africa precipitation extremes forced by the El Niño-Southern oscillation and the subtropical Indian Ocean dipole

  • Andrew Hoell
  • Linyin Cheng
Article

Abstract

Southern Africa, defined here as the African continent south of 15°S latitude, is prone to seasonal precipitation extremes during December–March that have profound effects on large populations of people. The intensity of summertime precipitation extremes can be remarkable, with wet seasons experiencing up to a doubling of the seasonal average precipitation. Recognizing the importance of understanding the causes of Southern Africa precipitation extremes for the purpose of improved early warning, an 80-member ensemble of atmospheric model simulations forced by observed time-varying boundary conditions during 1979–2016 is used to examine the mechanisms by which December–March precipitation extremes are delivered to Southern Africa and whether the El Niño-Southern Oscillation (ENSO) and the Subtropical Indian Ocean Dipole (SIOD) modify the probabilities of extreme seasonal precipitation occurrences. The model simulations reveal that the synchronous ENSO and SIOD phasing conditions the probability of December–March extreme precipitation occurrences. The probability of extreme wet seasons is greatly increased by La Niña, especially so when combined with a positive SIOD, and greatly decreased by El Niño regardless of SIOD phasing. By contrast, the probability of extreme dry seasons is increased by El Niño and is decreased by La Niña. The mechanisms by which extreme precipitation are delivered are the same regardless of ENSO and SIOD phase. Extreme wet seasons are a result of an anomalous lower tropospheric cyclone over Southern Africa that increases convergence and moisture fluxes into the region while extreme dry seasons are a result of an anomalous lower tropospheric anticyclone that decreases convergence and moisture fluxes into the region.

Notes

Acknowledgements

The authors thank Dave Allured for completing the ECHAM5 simulations and Tao Zhang for completing the GFS simulations. The authors also thank Judith Perlwitz and Marty Hoerling for thought-provoking discussions during the preparation of this manuscript. The authors are grateful for support from the Famine Early Warning Systems Network.

References

  1. Ash KD, Matyas CJ (2012) The influences of ENSO and the subtropical Indian Ocean Dipole on tropical cyclone trajectories in the southwestern Indian Ocean. Int J Climatol 32:41–56CrossRefGoogle Scholar
  2. Behera SK, Yamagata T (2001) Subtropical SST dipole events in the southern Indian Ocean. Geophys Res Lett 28:327–330CrossRefGoogle Scholar
  3. Behera SK, Salvekar PS, Yamagata T (2000) Simulation of interannual SST variability in the tropical Indian Ocean. J Clim 13:3487–3499CrossRefGoogle Scholar
  4. Bellenger H, Guilyardi E, Leloup J, Lengaigne M, Vialard J (2014) ENSO representation in climate models: from CMIP3 to CMIP5. Clim Dyn 42:1999–2018CrossRefGoogle Scholar
  5. Capotondi A (2013) El Niño–southern oscillation ocean dynamics: simulation by coupled general circulation models. In: Sun D-Z, Bryan F (eds) Climate dynamics: why does climate vary? American Geophysical Union, Washington, DC, pp 105–122Google Scholar
  6. Capotondi A, Wittenberg A, Masina S (2006) Spatial and temporal structure of Tropical Pacific interannual variability in 20th century coupled simulations. Ocean Model 15:274–298CrossRefGoogle Scholar
  7. Capotondi A et al (2014) Understanding ENSO diversity. Bull Am Meteorol Soc 96:921–938CrossRefGoogle Scholar
  8. Cheng L, AghaKouchak A, Gilleland E, Katz RW (2014) Non-stationary extreme value analysis in a changing climate. Clim Change 127:353–369CrossRefGoogle Scholar
  9. Coles S, Pericchi L (2003) Anticipating catastrophes through extreme value modelling. J R Stat Soc: Ser C (Appl Stat) 52:405–416CrossRefGoogle Scholar
  10. Coles SG, Powell EA (1996) Bayesian methods in extreme value modelling: a review and new developments. Int Stat Rev/Revue Internationale de Statistique 64:119–136Google Scholar
  11. Coles S, Bawa J, Trenner L, Dorazio P (2001) An introduction to statistical modeling of extreme values, vol 208. Springer, LondonCrossRefGoogle Scholar
  12. Cook KH, Hsieh JS, Hagos SM (2004) The Africa–South America intercontinental teleconnection. J Climate 17:2851–2865CrossRefGoogle Scholar
  13. Copsey D, Sutton R, Knight JR (2006) Recent trends in sea level pressure in the Indian Ocean region. Geophys Res Lett 33:L19712. doi: 10.1029/2006GL027175 CrossRefGoogle Scholar
  14. D’Abreton PC, Lindesay JA (1993) Water vapour transport over Southern Africa during wet and dry early and late summer months. Int J Climatol 13:151–170CrossRefGoogle Scholar
  15. D’Abreton PC, Tyson PD (1995) Divergent and non-divergent water vapour transport over southern Africa during wet and dry conditions. Meteorol Atmos Phys 55:47–59CrossRefGoogle Scholar
  16. Davison AC, Smith RL (1990) Models for exceedances over high thresholds. J R Stat Soc Ser B (Methodological) 52:393–442Google Scholar
  17. de Haan L, Ferreira A (2006) Extreme value theory: an introduction. Springer-Verlag, New YorkCrossRefGoogle Scholar
  18. Dupuis DJ (1999) Exceedances over high thresholds: a guide to threshold selection. Extremes 1:251–261CrossRefGoogle Scholar
  19. Gates WL (1992) AMIP: the atmospheric model intercomparison project. Bull Am Meteorol Soc 73:1962–1970CrossRefGoogle Scholar
  20. Goddard L, Dilley M (2005) El Niño: catastrophe or opportunity. J Clim 18:651–665CrossRefGoogle Scholar
  21. Guilyardi E et al (2009) Understanding El Niño in ocean–atmosphere general circulation models: progress and challenges. Bull Am Meteorol Soc 90:325–340CrossRefGoogle Scholar
  22. Hastenrath S, Greischar L, van Heerden J (1995) Prediction of the summer rainfall over South Africa. J Clim 8:1511–1518CrossRefGoogle Scholar
  23. Hoell A, Funk C, Magadzire T, Zinke J, Husak G (2015) El Niño-Southern Oscillation diversity and Southern Africa teleconnections during Austral Summer. Clim Dyn 45:1583–1599CrossRefGoogle Scholar
  24. Hoell A, Funk C, Zinke J, Harrison L (2017) Modulation of the Southern Africa precipitation response to the El Niño Southern Oscillation by the subtropical Indian Ocean Dipole. Clim Dyn 48:2529–2540CrossRefGoogle Scholar
  25. Hurrell JW, Hack JJ, Shea D, Caron JM, Rosinski J (2008) A new sea surface temperature and sea ice boundary dataset for the community atmosphere model. J Clim 21:5145–5153CrossRefGoogle Scholar
  26. IFRC (2017) Southern Africa floods. http://www.ifrc.org/southern-africa-floods. Accessed 5 Mar 2017
  27. Jury MR (2013) Variability in the tropical southwest Indian Ocean and Influence on Southern Africa climate. Int J Mar Sci 3:46–64Google Scholar
  28. Jury MR, McQueen C, Levey K (1994) SOI and QBO signals in the African region. Theor Appl Climatol 50:103–115CrossRefGoogle Scholar
  29. Kalnay E et al (1996) The NCEP/NCAR 40-year reanalysis project. Bull Am Meteorol Soc 77:437–471CrossRefGoogle Scholar
  30. Kuhnel I (1989) Tropical-extratropical cloudband climatology based on satellite data. Int J Climatol 9:441–463CrossRefGoogle Scholar
  31. Landman WA, Goddard L (2005) Predicting southern African summer rainfall using a combination of MOS and perfect prognosis. Geophys Res Lett 32:L15809. doi: 10.1029/2005GL022910 CrossRefGoogle Scholar
  32. Landman WA, Beraki A, DeWitt D, Lötter D (2014) SST prediction methodologies and verification considerations for dynamical mid-summer rainfall forecasts for South Africa. Water SA 40(4):615–622CrossRefGoogle Scholar
  33. Lindesay JA (1988) South African rainfall, the Southern Oscillation and a Southern Hemisphere semi-annual cycle. J Climatol 8:17–30CrossRefGoogle Scholar
  34. Lyon B, Mason SJ (2009) The 1997/98 summer rainfall season in Southern Africa. Part II: Model simulations and coupled model forecasts. J Clim 22:3802–3818CrossRefGoogle Scholar
  35. Manatsa D, Matarira CH, Mukwada G (2011) Relative impacts of ENSO and Indian Ocean dipole/zonal mode on east SADC rainfall. Int J Climatol 31:558–577CrossRefGoogle Scholar
  36. Manatsa D, Reason CJC, Mukwada G (2012) On the decoupling of the IODZM from southern Africa Summer rainfall variability. Int J Climatol 32:727–746CrossRefGoogle Scholar
  37. Manatsa D, Mushore T, Lenouo A (2017) Improved predictability of droughts over southern Africa using the standardized precipitation evapotranspiration index and ENSO. Theor Appl Climatol 127:259–274CrossRefGoogle Scholar
  38. Mason SJ, Jury MR (1997) Climatic variability and change over southern Africa: a reflection on underlying processes. Prog Phys Geogr 21:23–50CrossRefGoogle Scholar
  39. Misra V (2003) The influence of Pacific SST variability on the precipitation over Southern Africa. J Clim 16:2408–2418CrossRefGoogle Scholar
  40. Nicholson S, Entekhabi D (1986) The quasi-periodic behavior of rainfall variability in Africa and its relationship to the southern oscillation. Arch Met Geoph Biocl A 34:311–348CrossRefGoogle Scholar
  41. Nicholson SE, Kim J (1997) The relationship of the El Niño-Southern oscillation to African rainfall. Int J Climatol 17:117–135CrossRefGoogle Scholar
  42. Parent E, Bernier J (2003) Bayesian POT modeling for historical data. J Hydrol 274:95–108CrossRefGoogle Scholar
  43. Ratnam JV, Behera SK, Masumoto Y, Yamagata T (2014) Remote effects of El Niño and Modoki events on the austral summer precipitation of Southern Africa. J Clim 27:3802–3815CrossRefGoogle Scholar
  44. Reason CJC (1998) Warm and cold events in the southeast Atlantic/southwest Indian Ocean region and potential impacts on circulation and rainfall over southern Africa. Meteorol Atmos Phys 69:49–65CrossRefGoogle Scholar
  45. Reason CJC (1999) Interannual warm and cool events in the subtropical/mid-latitude South Indian Ocean Region. Geophys Res Lett 26:215–218CrossRefGoogle Scholar
  46. Reason CJC (2001) Subtropical Indian Ocean SST dipole events and southern African rainfall. Geophys Res Lett 28:2225–2227CrossRefGoogle Scholar
  47. Reason CJC, Jagadheesha D (2005) A model investigation of recent ENSO impacts over southern Africa. Meteorol Atmos Phys 89:181–205CrossRefGoogle Scholar
  48. Reason CJC, Mulenga H (1999) Relationships between South African rainfall and SST anomalies in the Southwest Indian Ocean. Int J Climatol 19:1651–1673CrossRefGoogle Scholar
  49. Reason CJC, Allan RJ, Lindesay JA, Ansell TJ (2000) ENSO and climatic signals across the Indian Ocean Basin in the global context: part I, interannual composite patterns. Int J Climatol 20:1285–1327CrossRefGoogle Scholar
  50. Rocha A, Simmonds IAN (1997) Interannual variability of south-eastern African summer rainfall. Part 1: relationships with air–sea interaction processes. Int J Climatol 17:235–265CrossRefGoogle Scholar
  51. Roeckner E et al (2006) Sensitivity of simulated climate to horizontal and vertical resolution in the ECHAM5 atmosphere model. J Clim 19:3771–3791CrossRefGoogle Scholar
  52. Ropelewski CF, Halpert MS (1987) Global and regional scale precipitation patterns associated with the El Niño/Southern oscillation. Mon Weather Rev 115:1606–1626CrossRefGoogle Scholar
  53. Rouault M, Florenchie P, Fauchereau N, Reason CJC (2003) South East tropical Atlantic warm events and southern African rainfall. Geophys Res Lett 30:8009. doi: 10.1029/2002GL014840 CrossRefGoogle Scholar
  54. Saha S et al (2013) The NCEP climate forecast system version 2. J Clim 27:2185–2208CrossRefGoogle Scholar
  55. Schneider U, Becker A, Finger P, Meyer-Christoffer A, Ziese M, Rudolf B (2013) GPCC’s new land surface precipitation climatology based on quality-controlled in situ data and its role in quantifying the global water cycle. Theor Appl Climatol 115:15–40CrossRefGoogle Scholar
  56. Todd M, Washington R (1999) Circulation anomalies associated with tropical-temperate troughs in southern Africa and the south west Indian Ocean. Clim Dyn 15:937–951CrossRefGoogle Scholar
  57. Vidal J (2016) Southern Africa cries for help as El Niño and climate change savage maize harvest. The GuardianGoogle Scholar
  58. Wang F (2010) Subtropical dipole mode in the southern hemisphere: a global view. Geophys Res Lett 37:L10702. doi: 10.1029/2010GL042750 Google Scholar
  59. Wang B et al (2009) Advance and prospectus of seasonal prediction: assessment of the APCC/CliPAS 14-model ensemble retrospective seasonal prediction (1980–2004). Clim Dyn 33:93–117CrossRefGoogle Scholar
  60. Washington R, Preston A (2006) Extreme wet years over southern Africa: role of Indian Ocean sea surface temperatures. J Geophys Res Atmos 111:D15Google Scholar
  61. Wyrtki K (1975) El Niño—the dynamic response of the equatorial Pacific Ocean to atmospheric forcing. J Phys Oceanogr 5:572–584CrossRefGoogle Scholar
  62. Yang C, Giese BS (2013) El Niño Southern Oscillation in an ensemble ocean reanalysis and coupled climate models. J Geophys Res Oceans 118:4052–4071CrossRefGoogle Scholar
  63. Yuan C, Tozuka T, Landman W, Yamagata T (2014) Dynamical seasonal prediction of Southern African summer precipitation. Clim Dyn 42:3357–3374CrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg (outside the USA) 2017

Authors and Affiliations

  1. 1.NOAA/Earth System Research Laboratory Physical Sciences DivisionBoulderUSA
  2. 2.Cooperative Institute for Research in the Environmental SciencesUniversity of Colorado BoulderBoulderUSA

Personalised recommendations