Abstract
Three sub-regions of the Indian Ocean in which SSTs significantly influence the equatorial East African short rains on interannual timescales are identified, and the physical processes of this influence are studied using regional climate model simulations from the Weather Research and Forecasting model (WRF). Five 20-year ensemble integrations are generated to represent a control climate and to simulate the individual and combined effects of SSTAs in the influential regions. SSTAs in the western Indian Ocean exert a stronger influence on the equatorial East African short rains than central and eastern Indian Ocean SSTAs both in terms of the coverage of significantly-changed precipitation and the magnitude of the precipitation response. Positive western Indian Ocean SSTAs significantly increase the short rains over 95% of the equatorial East Africa domain (30°–40°E, 5°S–5°N), while only 30% of the region responds to central and eastern Indian Ocean SSTAs. Evidence of an influential Indian Ocean dipole mode does not emerge from the analysis. The mechanisms of this influence are diagnosed using atmospheric moisture budget and moist static energy analyses, with reference to Kelvin and Rossby wave generation as in the Gill model, but in the presence of complicated topography and nonzero background flows. Wind convergence anomalies in a moist environment primarily support precipitation anomalies in all cases, while changes in atmospheric instability are largely controlled by low-level moisture. Central and eastern Indian Ocean SSTAs change circulations and precipitation locally, but the remote influence on East Africa is weaker than that of the western Indian Ocean SSTAs.
Similar content being viewed by others
References
Anyah RO, Qiu W (2012) Characteristic 20th and 21st century precipitation and temperature patterns and changes over the Greater Horn of Africa. Int J Climatol 32(3):347–363. https://doi.org/10.1002/joc.2270
Argent R, Sun X, Semazzi F, Xie L, Liu B (2015) The development of a customization framework for the WRF Model over the Lake Victoria basin, Eastern Africa on seasonal timescales. Adv Meteorol. https://doi.org/10.1155/2015/653473
Ashouri H, Hsu KL, Sorooshian S, Braithwaite DK, Knapp KR, Cecil LD, Nelson BR, Prat OP (2015) PERSIANN-CDR: Daily precipitation climate data record from multisatellite observations for hydrological and climate studies. Bull Am Meteorol Soc 96(1):69–83. https://doi.org/10.1175/BAMS-D-13-00068.1
Bahaga TK, Mengistu Tsidu G, Kucharski F, Diro GT (2015) Potential predictability of the sea-surface temperature forced equatorial East African short rains interannual variability in the 20th century. Q J Roy Meteorol Soc 141(686):16–26. https://doi.org/10.1002/qj.2338
Behera SK, Luo JJ, Masson S, Delecluse P, Gualdi S, Navarra A, Yamagata T (2005) Paramount impact of the Indian Ocean dipole on the EA short rains: a CGCM study. J Clim 18(21):4514–4530. https://doi.org/10.1175/JCLI3541.1
Black E, Slingo J, Sperber KR (2003) An observational study of the relationship between excessively strong short rains in coastal East Africa and Indian Ocean SST. Mon Weather Rev 131(1):74–94. https://doi.org/10.1175/1520-0493(2003)131%3c0074:AOSOTR%3e2.0.CO;2
Crétat J, Vizy EK, Cook KH (2014) How well are daily intense rainfall events captured by current climate models over Africa? Clim Dyn 42(9–10):2691–2711. https://doi.org/10.1007/s00382-013-1796-7
Chen F, Dudhia J (2001) Coupling an advanced land surface–hydrology model with the Penn State–NCAR MM5 modeling system. Part I : Model implementation and sensitivity. Mon Weather Rev 129:569–585. https://doi.org/10.1175/1520-0493(2001)129,0569:CAALSH.2.0.CO;2
Chen SH, Sun WY (2002) A one-dimensional time dependent cloud model. J Meteor Soc Jpn 80:99–118. https://doi.org/10.2151/jmsj.80.99
Clark CO, Webster PJ, Cole JE (2003) Interdecadal variability of the relationship between the Indian Ocean zonal mode and EA coastal rainfall anomalies. J Clim 16(3):548–554. https://doi.org/10.1175/1520-0442(2003)016%3c0548:IVOTRB%3e2.0.CO;2
Cook KH, Vizy EK (2012) Impact of climate change on mid-twenty-first century growing seasons in Africa. Clim Dyn 39:2937–2955. https://doi.org/10.1007/s00382-012-1324-1
Cook KH, Vizy EK (2013) Projected changes in EA rainy seasons. J Clim 26(16):5931–5948. https://doi.org/10.1175/JCLI-D-12-00455.1
Dee DP, Uppala SM et al (2011) The ERA-Interim reanalysis: Configuration and performance of the data assimilation system. Q J Roy Meteorol Soc 137(656):553–597. https://doi.org/10.1002/qj.828
Dommenget D, Latif M (2002) A cautionary note on the interpretation of EOFs. J Clim 15(2):216–225. https://doi.org/10.1175/1520-0442(2002)015%3c0216:ACNOTI%3e2.0.CO;2
Donlon CJ, Martin M, Stark J, Roberts-Jones J, Fiedler E, Wimmer W (2012) The operational sea surface temperature and sea ice analysis (OSTIA) system. Remote Sens Environ 116:140–158. https://doi.org/10.1016/j.rse.2010.10.017
Dudhia J (1989) Numerical study of convection observed during the winter monsoon experiment using a mesoscale two dimensional model. J Atmos Sci 46:3077–3107. https://doi.org/10.1175/1520-0469(1989)046,3077:NSOCOD.2.0.CO;2
Endris HS, Omondi P et al (2013) Assessment of the performance of CORDEX regional climate models in simulating East African rainfall. J Clim 26(21):8453–8475. https://doi.org/10.1175/JCLI-D-12-00708.1
Funk C, Peterson P, Landsfeld M, Pedreros D, Verdin J, Shukla S, Husak G, Rowland J, Harrison L, Hoell A, Michaelsen J (2015) The climate hazards infrared precipitation with stations—a new environmental record for monitoring extremes. Sci Data 2:150066. https://doi.org/10.1038/sdata.2015.66
Gill AE (1980) Some simple solutions for heat-induced tropical circulation. Q J Roy Meteorol Soc 106(449):447–462. https://doi.org/10.1002/qj.49710644905
Han F, Cook KH, Vizy EK (2019) Changes in intense rainfall events and dry periods across Africa in the twenty-first century. Clim Dyn. https://doi.org/10.1007/s00382-019-04653-z
Hastenrath S, Nicklis A, Greischar L (1993) Atmospheric-hydrospheric mechanisms of climate anomalies in the western equatorial Indian Ocean. J Geophs Res: Oceans 98(C11):20219–20235. https://doi.org/10.1029/93JC02330
Hastenrath S, Polzin D, Mutai C (2011) Circulation mechanisms of Kenya rainfall anomalies. J Clim 24(2):404–412. https://doi.org/10.1175/2010JCLI3599.1
Herrmann SM, Mohr KI (2011) A continental-scale classification of rainfall seasonality regimes in Africa based on gridded precipitation and land surface temperature products. J Appl Meteorol 50(12):2504–2513. https://doi.org/10.1175/JAMC-D-11-024.1
Hession SL, Moore N (2011) A spatial regression analysis of the influence of topography on monthly rainfall in East Africa. Int J Climatol 31(10):1440–1456. https://doi.org/10.1002/joc.2174
Hirons L, Turner A (2018) The impact of Indian Ocean mean-state biases in climate models on the representation of the East African short rains. J Clim 31(16):6611–6631. https://doi.org/10.1175/JCLI-D-17-0804.1
Hong SY, Noh Y, Dudhia J (2006) A new vertical diffusion package with an explicit treatment of entrainment processes. Mon Weather Rev 134:2318–2341. https://doi.org/10.1175/MWR3199.1
Huffman GJ, Bolvin DT, Nelkin EJ et al (2007) The TRMM multisatellite precipitation analysis (TMPA): Quasi-global, multiyear, combined-sensor precipitation estimates at fine scales. J Hydrometeorol 8(1):38–55. https://doi.org/10.1175/JHM560.1
Joyce RJ, Janowiak JE, Arkin PA, Xie P (2004) CMORPH: a method that produces global precipitation estimates from passive microwave and infrared data at high spatial and temporal resolution. J Hydrometeorol 5:487–503. https://doi.org/10.1175/1525-7541(2004)005%3c0487:CAMTPG%3e2.0.CO;2
Kain JS, Fritsch JM (1993) Convective parameterization for mesoscale models: The Kain–Fritsch scheme. The Representation of Cumulus Convection in Numerical Models, Meteor Monogr No. 46, Amer Meteor Soc 165–170. doi: 10.1007/978–1–935704–13–3_16
Kobayashi S, Ota Y, Harada Y, Ebita A, Moriya M, Onoda H, Onogi K, Kamahori H, Kobayashi C, Endo H, Miyaoka K, Takahashi K (2015) The JRA-55 reanalysis: General specifications and basic characteristics. J Meteorol Soc Jpn Ser II 93(1):5–48. https://doi.org/10.2151/jmsj.2015-001
Lenters JD, Cook KH (1995) Simulation and diagnosis of the regional summertime precipitation climatology of South America. J Clim 8(12):2988–3005. https://doi.org/10.1175/1520-0442(1995)008%3c2988:SADOTR%3e2.0.CO;2
Li T, Wang B, Chang CP, Zhang Y (2003) A theory for the Indian Ocean Dipole zonal mode. J Atmos Sci 60:2119–2135. https://doi.org/10.1175/1520-0469(2003)060<2119:ATFTIO>2.0.CO;2
Liebmann B, Bladé I et al (2012) Seasonality of African precipitation from 1996 to 2009. J Clim 25(12):4304–4322. https://doi.org/10.1175/JCLI-D-11-00157.1
Lin YL, Farley RD, Orville HD (1983) Bulk parameterization of the snow field in a cloud model. J Clim Appl Meteorol 22(6):1065–1092. https://doi.org/10.1175/1520-0450(1983)022%3c1065:BPOTSF%3e2.0.CO;2
Luo JJ, Zhang R, Behera SK, Masumoto Y, Jin FF, Lukas R, Yamagata T (2010) Interaction between El Nino and extreme Indian ocean dipole. J Clim 23(3):726–742. https://doi.org/10.1175/2009JCLI3104.1
Lyon B (2014) Seasonal drought in the Greater Horn of Africa and its recent increase during the March–May long rains. J Clim 27(21):7953–7975
Lyon B, De Witt DG (2012) A recent and abrupt decline in the East African long rains. Geophys Res Lett. https://doi.org/10.1029/2011GL050337
Mlawer EJ, Taubman SJ, Brown PD, Iacono MJ, Clough SA (1997) Radiative transfer for inhomogeneous atmospheres: RRTM, a validated correlated-k model for the longwave. J Geophys Res 102:16 663–16 682. https://doi.org/10.1029/97JD00237
Nicholson SE (1996) A review of climate dynamics and climate variability in Eastern Africa. In: Johnson TC, Odada E (eds) The limnology, climatology and paleoclimatology of the East African lakes. Gordon and Breach, Amsterdam, pp 25–56
Nicholson SE (1998) Historical fluctuations of Lake Victoria and other lakes in the northern rift valley of East Africa. In: Lehman JT (ed) Environmental change and response in East African lakes. Kluwer Academic Publishers, Dordrecht, pp 7–35
Nicholson SE (2000) The nature of rainfall variability over Africa on time scales of decades to millenia. Glob Planet Chang 26(2000):137–158. https://doi.org/10.1016/S0921-8181(00)00040-0(00)00040-0
Nicholson SE (2016) An analysis of recent rainfall conditions in eastern Africa. Int J Climatol 36(1):526–532. https://doi.org/10.1002/joc.4358
Nicholls N, Drosdowsky W (2001) Is there an equatorial Indian Ocean SST Dipole, independent of the El Nino Southern Oscillation. Preprints. In Symp. on Climate Variability, the Oceans, and Societal Impacts (pp. 17–18). Available online at https://ams.confex.com/ams/annual2001/techprogram/paper_17337.htm
Ogwang BA, Chen H, Li X, Gao C (2016) Evaluation of the capability of RegCM4.0 in simulating East African climate. Theor Appl Climatol 124(1–2):303–313. https://doi.org/10.1007/s00704-015-1420-3
Rayner NAA, Parker DE et al (2003) Global analyses of sea surface temperature, sea ice, and night marine air temperature since the late nineteenth century. J Geophys Res Atmos. https://doi.org/10.1029/2002JD002670
Reynolds RW, Smith TM, Liu C, Chelton DB, Casey KS, Schlax MG (2007) Daily high-resolution-blended analyses for sea surface temperature. J Clim 20(22):5473–5496. https://doi.org/10.1175/2007JCLI1824.1
Rutledge SA, Hobbs PV (1984) The mesoscale and microscale structure and organization of clouds and precipitation in midlatitude cyclones. XII: A diagnostic modeling study of precipitation development in narrow cold-frontal rainbands. J Atmos Sci 41(20), 2949–2972. doi: 10.1175/1520-0469(1984)041%3c2949:TMAMSA%3e2.0.CO;2
Saji NH, Goswami BN, Vinayachandran PN, Yamagata T (1999) A dipole mode in the tropical Indian Ocean. Nature 401(6751):360. https://doi.org/10.1038/43854
Saji NH, Yamagata T (2003) Possible impacts of Indian Ocean dipole mode events on global climate. Clim Res 25(2):151–169. https://doi.org/10.3354/cr025151
Segele ZT, Lamb PJ, Leslie LM (2009) Large-scale atmospheric circulation and global sea surface temperature associations with Horn of Africa June–September rainfall. Int J Climatol 29(8):1075–1100. https://doi.org/10.1002/joc.1751
Shongwe ME, van Oldenborgh GJ, van den Hurk B, van Aalst M (2011) Projected changes in mean and extreme precipitation in Africa under global warming. Part II: East Africa. J Clim 24(14):3718–3733. https://doi.org/10.1175/2010JCLI2883.1
Skamarock WC et al (2008) A description of the Advanced Research WRF version 3. NCAR Tech. Note NCAR/TN-4751STR, 113 pp., doi:10.5065/D68S4MVH.
Sun L, Semazzi FH, Giorgi F, Ogallo L (1999) Application of the NCAR regional climate model to eastern Africa: 1. Simulation of the short rains of 1988. J Geophys Res: Atmos 104(D6), 6529–6548. doi: 10.1029/1998JD200051
Thiery W, Davin EL, Panitz HJ, Demuzere M, Lhermitte S, Van Lipzig N (2015) The impact of the African Great Lakes on the regional climate. J Clim 28(10):4061–4085. https://doi.org/10.1175/JCLI-D-14-00565.1
Ummenhofer CC, Sen Gupta A, England MH, Reason CJ (2009) Contributions of Indian Ocean sea surface temperatures to enhanced East African rainfall. J Clim 22(4):993–1013. https://doi.org/10.1175/2008JCLI2493.1
Vizy EK, Cook KH (2001) Mechanisms by which Gulf of Guinea and eastern North Atlantic sea surface temperature anomalies can influence African rainfall. J Clim 14(5):795–821. https://doi.org/10.1175/1520-0442(2001)014%3c0795:MBWGOG%3e2.0.CO;2
Vizy EK, Cook KH (2009) Tropical storm development from African easterly waves in the eastern Atlantic: a comparison of two successive waves using a regional model as part of NASA AMMA 2006. J Atmos Sci 66(11):3313–3334. https://doi.org/10.1175/2009JAS3064.1
Vizy EK, Cook KH (2012) Mid-twenty-first-century changes in extreme events over northern and tropical Africa. J Clim 25(17):5748–5767. https://doi.org/10.1175/JCLI-D-11-00693.1
Vizy EK, Cook KH (2019) Observed relationship between the Turkana low-level jet and boreal summer convection. Clim Dyn. https://doi.org/10.1007/s00382-019-04769-2
Vizy EK, Cook KH, Crétat J, Neupane N (2013) Projections of a wetter Sahel in the twenty-first century from global and regional models. J Clim 26(13):4664–4687. https://doi.org/10.1175/JCLI-D-12-00533.1
Vizy EK, Cook KH, Chimphamba J, McCusker B (2015) Projected changes in Malawi’s growing season. Clim Dyn 45(5–6):1673–1698. https://doi.org/10.1007/s00382-014-2424-x
Wang T, Lu X, Yang S (2019) Impact of south Indian Ocean Dipole on tropical cyclone genesis over the South China Sea. Int J Climatol 39(1):101–111. https://doi.org/10.1002/joc.5785
Wenhaji Ndomeni C, Cattani E, Merino A, Levizzani V (2018) An observational study of the variability of EA rainfall with respect to sea surface temperature and soil moisture. Q J Roy Meteorol Soc 144:384–404. https://doi.org/10.1002/qj.3255
Woodhams BJ, Birch CE, Marsham JH, Bain CL, Roberts NM, Boyd DF (2018) What Is the added value of a convection-permitting model for forecasting extreme rainfall over tropical East Africa? Mon Weather Rev 146(9):2757–2780. https://doi.org/10.1175/MWR-D-17-0396.1
Yang W, Seager R, Cane MA, Lyon B (2015) The annual cycle of EA precipitation. J Clim 28(6):2385–2404. https://doi.org/10.1175/JCLI-D-14-00484.1
Zhao Y, Nigam S (2015) The Indian Ocean dipole: a monopole in SST. J Clim 28(1):3–19. https://doi.org/10.1175/JCLI-D-14-00047.1
Acknowledgements
This work was funded by NSF Award #1701520. The authors acknowledge the Texas Advanced Computing Center (TACC) at The University of Texas at Austin for providing HPC and database resources that have contributed to the research results reported within this paper. URL: https://www.tacc.utexas.edu. The Grid Analysis and Display System software (GrADS) developed at COLA/IGES was used for generating the figures.
Author information
Authors and Affiliations
Corresponding author
Additional information
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
About this article
Cite this article
Liu, W., Cook, K.H. & Vizy, E.K. Influence of Indian Ocean SST regionality on the East African short rains. Clim Dyn 54, 4991–5011 (2020). https://doi.org/10.1007/s00382-020-05265-8
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00382-020-05265-8