Articles | Volume 8, issue 1
https://doi.org/10.5194/ascmo-8-31-2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/ascmo-8-31-2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Spatial heterogeneity in rain-bearing winds, seasonality and rainfall variability in southern Africa's winter rainfall zone
Willem Stefaan Conradie
CORRESPONDING AUTHOR
Climate System Analysis Group, University of Cape Town, Cape Town, South Africa
Piotr Wolski
Climate System Analysis Group, University of Cape Town, Cape Town, South Africa
Bruce Charles Hewitson
Climate System Analysis Group, University of Cape Town, Cape Town, South Africa
Related authors
Willem Stefaan Conradie, Piotr Wolski, and Bruce Charles Hewitson
Adv. Stat. Clim. Meteorol. Oceanogr., 8, 63–81, https://doi.org/10.5194/ascmo-8-63-2022, https://doi.org/10.5194/ascmo-8-63-2022, 2022
Short summary
Short summary
The
Day Zerowater crisis affecting Cape Town after the severe 2015–2017 drought motivated renewed research interest into causes and projections of rainfall variability and change in this water-stressed region. Unusually few wet months and very wet days characterised the Day Zero Drought. Its extent expanded as it shifted gradually north-eastward, concurrent with changes in the weather systems driving drought. Our results emphasise the need to consider the interplay between drought drivers.
Nathan P. Gillett, Isla R. Simpson, Gabi Hegerl, Reto Knutti, Dann Mitchell, Aurélien Ribes, Hideo Shiogama, Dáithí Stone, Claudia Tebaldi, Piotr Wolski, Wenxia Zhang, and Vivek K. Arora
Geosci. Model Dev., 18, 4399–4416, https://doi.org/10.5194/gmd-18-4399-2025, https://doi.org/10.5194/gmd-18-4399-2025, 2025
Short summary
Short summary
Climate model simulations of the response to human and natural influences together, natural climate influences alone and greenhouse gases alone are key to quantifying human influence on the climate. The last set of such coordinated simulations underpinned key findings in the last Intergovernmental Panel on Climate Change (IPCC) report. Here we propose a new set of such simulations to be used in the next generation of attribution studies and to underpin the next IPCC report.
Robin van der Schalie, Mendy van der Vliet, Clément Albergel, Wouter Dorigo, Piotr Wolski, and Richard de Jeu
Hydrol. Earth Syst. Sci., 26, 3611–3627, https://doi.org/10.5194/hess-26-3611-2022, https://doi.org/10.5194/hess-26-3611-2022, 2022
Short summary
Short summary
Climate data records of surface soil moisture, vegetation optical depth, and land surface temperature can be derived from passive microwave observations. The ability of these datasets to properly detect anomalies and extremes is very valuable in climate research and can especially help to improve our insight in complex regions where the current climate reanalysis datasets reach their limitations. Here, we present a case study over the Okavango Delta, where we focus on inter-annual variability.
Shakirudeen Lawal, Stephen Sitch, Danica Lombardozzi, Julia E. M. S. Nabel, Hao-Wei Wey, Pierre Friedlingstein, Hanqin Tian, and Bruce Hewitson
Hydrol. Earth Syst. Sci., 26, 2045–2071, https://doi.org/10.5194/hess-26-2045-2022, https://doi.org/10.5194/hess-26-2045-2022, 2022
Short summary
Short summary
To investigate the impacts of drought on vegetation, which few studies have done due to various limitations, we used the leaf area index as proxy and dynamic global vegetation models (DGVMs) to simulate drought impacts because the models use observationally derived climate. We found that the semi-desert biome responds strongly to drought in the summer season, while the tropical forest biome shows a weak response. This study could help target areas to improve drought monitoring and simulation.
Willem Stefaan Conradie, Piotr Wolski, and Bruce Charles Hewitson
Adv. Stat. Clim. Meteorol. Oceanogr., 8, 63–81, https://doi.org/10.5194/ascmo-8-63-2022, https://doi.org/10.5194/ascmo-8-63-2022, 2022
Short summary
Short summary
The
Day Zerowater crisis affecting Cape Town after the severe 2015–2017 drought motivated renewed research interest into causes and projections of rainfall variability and change in this water-stressed region. Unusually few wet months and very wet days characterised the Day Zero Drought. Its extent expanded as it shifted gradually north-eastward, concurrent with changes in the weather systems driving drought. Our results emphasise the need to consider the interplay between drought drivers.
Cited articles
Abba Omar, S. and Abiodun, B. J.: Characteristics of cut-off lows during the 2015–2017 drought in the Western Cape, South Africa, Atmos. Res., 235, 104772, https://doi.org/10.1016/j.atmosres.2019.104772, 2020. a, b, c, d
Abba Omar, S. and Abiodun, B. J.: Simulating the characteristics of cut-off low rainfall over the Western Cape using WRF, Clim. Dynam., 56, 1265–1283, https://doi.org/10.1007/s00382-020-05532-8, 2021. a
Archer, E., Landman, W., Malherbe, J., Tadross, M. A., and Pretorius, S.: South Africa's winter rainfall region drought: A region in transition?, Clim. Risk Manage., 25, 100188, https://doi.org/10.1016/j.crm.2019.100188, 2019. a
Aschmann, H.: Distribution and Peculiarity of Mediterranean Ecosystems, in: Mediterranean Type Ecosystems, edited by: di Castri, F. and Mooney, H. A., Springer, Berlin, Heidelberg, Chap. 1, 11–19, https://doi.org/10.1007/978-3-642-65520-3_2, 1973. a, b, c
Barrable, A., Meadows, M. E., and Hewitson, B. C.: Environmental reconstruction and climate modelling of the Late Quaternary in the winter rainfall region of the Western Cape, South Africa, S. Afr. J. Sci., 98, 611–616, 2002. a
Bayer, M. B.: The Cape flora and the Karoo – a winter rainfall biome versus a fynbos biome, Veld and Flora, 70, 17–19, 1984. a
Becker, A., Finger, P., Meyer-Christoffer, A., Rudolf, B., Schamm, K., Schneider, U., and Ziese, M.: A description of the global land-surface precipitation data products of the Global Precipitation Climatology Centre with sample applications including centennial (trend) analysis from 1901–present, Earth Syst. Sci. Data, 5, 71–99, https://doi.org/10.5194/essd-5-71-2013, 2013. a
Blamey, R. C., Ramos, A. M., Trigo, R. M., Tomé, R., and Reason, C. J. C.: The influence of Atmospheric Rivers over the South Atlantic on Winter Rainfall in South Africa, J. Hydrometeorol., 19, JHM-D-17-0111.1, https://doi.org/10.1175/JHM-D-17-0111.1, 2017. a
Born, J., Linder, H. P., and Desmet, P. G.: The Greater Cape Floristic Region, J. Biogeogr., 34, 147–162, https://doi.org/10.1111/j.1365-2699.2006.01595.x, 2007. a
Campitelli, E.: metR: Tools for Easier Analysis of Meteorological Fields, R package version 0.8.0, Zenodo [code], https://doi.org/10.5281/zenodo.2593516, 2020. a
Chase, B. M. and Meadows, M. E.: Late Quaternary dynamics of southern Africa's winter rainfall zone, Earth-Sci. Rev., 84, 103–138, https://doi.org/10.1016/J.EARSCIREV.2007.06.002, 2007. a, b
Chase, B. M., Quick, L. J., Meadows, M. E., Scott, L., Thomas, D. S., and Reimer, P. J.: Late glacial interhemispheric climate dynamics revealed in South African hyrax middens, Geology, 39, 19–22, https://doi.org/10.1130/G31129.1, 2011. a
Chase, B. M., Boom, A., Carr, A. S., Carré, M., Chevalier, M., Meadows, M. E., Pedro, J. B., Stager, J. C., and Reimer, P. J.: Evolving southwest African response to abrupt deglacial North Atlantic climate change events, Quaternary Sci. Rev., 121, 132–136, https://doi.org/10.1016/j.quascirev.2015.05.023, 2015. a
Chase, B. M., Chevalier, M., Boom, A., and Carr, A. S.: The dynamic relationship between temperate and tropical circulation systems across South Africa since the last glacial maximum, Quaternary Sci. Rev., 174, 54–62, https://doi.org/10.1016/j.quascirev.2017.08.011, 2017. a
Chase, B. M., Boom, A., Carr, A. S., Chevalier, M., Quick, L. J., Verboom, G. A., and Reimer, P. J.: Extreme hydroclimate response gradients within the western Cape Floristic region of South Africa since the Last Glacial Maximum, Quaternary Sci. Rev., 219, 297–307, https://doi.org/10.1016/j.quascirev.2019.07.006, 2019. a, b, c, d
Compton, J. S.: The rocks and mountains of Cape Town, Double Storey Books, ISBN 9781919930701, 2004. a
Conradie, S., Hewitson, B., and Wolski, P.: Python code to analyse the association between rainfall data and synoptic wind direction, ZivaHub [code], https://doi.org/10.25375/UCT.16546008.V1, 2021. a
Conradie, S., Hewitson, B., and Wolski, P.: Rainfall quality control and gap-filling procedure using Generalised Additive Models for Location, Scale and Shape (GAMLSS), Ziva Hub [code], https://doi.org/10.25375/uct.18856337, 2022a. a
Conradie, W. S., Wolski, P., and Hewitson, B. C.: Spatial heterogeneity of 2015–2017 drought intensity in South Africa's winter rainfall zone, Adv. Stat. Clim. Meteorol. Oceanogr., 8, 63–81,
https://doi.org/10.5194/ascmo-8-63-2022, 2022b. a, b
Conradie, W. S., Slabbert, P. C., Wolski, P., and Hewitson, B. C.: A new frontal identification methodology applied to the South Atlantic Ocean, in preparation, 2022c. a
Cowling, R. M. and Lombard, A. T.: Heterogeneity, speciation/extinction history and climate: Explaining regional plant diversity patterns in the Cape Floristic Region, Divers. Distrib., 8, 163–179, https://doi.org/10.1046/j.1472-4642.2002.00143.x, 2002. a
Cowling, R. M., Esler, K. J., and Rundel, P. W.: Namaqualand, South Africa – An overview of a unique winter-rainfall desert ecosystem, Plant Ecol., 142, 3–21, https://doi.org/10.1023/A:1009831308074, 1999. a, b, c
Cowling, R. M., Ojeda, F., Lamont, B. B., Rundel, P. W., and Lechmere-Oertel, R.: Rainfall reliability, a neglected factor in explaining convergence and divergence of plant traits in fire-prone mediterranean-climate ecosystems, Global Ecol. Biogeogr., 14, 509–519, https://doi.org/10.1111/j.1466-822X.2005.00166.x, 2005. a, b
Cowling, R. M., Procheş, Ş., and Partridge, T. C.: Explaining the uniqueness of the Cape flora: Incorporating geomorphic evolution as a factor for explaining its diversification, Molec. Phylogen. Evol., 51, 64–74, https://doi.org/10.1016/j.ympev.2008.05.034, 2009. a
Cowling, R. M., Bradshaw, P. L., Colville, J. F., and Forest, F.: Levyns' Law: explaining the evolution of a remarkable longitudinal gradient in Cape plant diversity, T. Roy. Soc. S. Afr., 72, 184–201, https://doi.org/10.1080/0035919X.2016.1274277, 2017. a
de Buys, A.: Dwarsberg weather station (1214 m), event rainfall, 03/2013–09/2019, SAEON [data set], https://doi.org/10.15493/SAEON.FYNBOS.10000008, 2019. a
Dee, D. P., Uppala, S. M., Simmons, A. J., Berrisford, P., Poli, P., Kobayashi, S., Andrae, U., Balmaseda, M. A., Balsamo, G., Bauer, P., Bechtold, P., Beljaars, A. C. M., van de Berg, L., Bidlot, J., Bormann, N., Delsol, C., Dragani, R., Fuentes, M., Geer, A. J., Haimberger, L., Healy, S. B., Hersbach, H., Hólm, E. V., Isaksen, L., Kållberg, P., Köhler, M., Matricardi, M., McNally, A. P., Monge-Sanz, B. M., Morcrette, J.-J., Park, B.-K., Peubey, C., de Rosnay, P., Tavolato, C., Thépaut, J.-N., and Vitart, F.: The ERA-Interim reanalysis: configuration and performance of the data assimilation system, Q. J. Roy. Meteor. Soc., 137, 553–597, https://doi.org/10.1002/qj.828, 2011. a
Deitch, M., Sapundjieff, M., and Feirer, S.: Characterizing Precipitation Variability and Trends in the World's Mediterranean-Climate Areas, Water, 9, 259, https://doi.org/10.3390/w9040259, 2017. a, b
Dent, M., Lynch, S., and Schulze, R.: Mapping mean annual and other rainfall statistics over southern Africa, Tech. Rep. 109/1/89, Water Research Commission, ISBN 0-947447-16-4, 1987. a
Desmet, P. G.: Namaqualand-A brief overview of the physical and floristic environment, J. Arid Environ., 70, 570–587, https://doi.org/10.1016/j.jaridenv.2006.11.019, 2007. a, b
Desmet, P. G. and Cowling, R. M.: The climate of the Karoo: a functional approach, in: The Karoo, Cambridge University Press, 3–16, https://doi.org/10.1017/CBO9780511541988.004, 1999. a, b, c, d
Dieppois, B., Pohl, B., Rouault, M., New, M., Lawler, D., and Keenlyside, N. S.: Interannual to interdecadal variability of winter and summer southern African rainfall, and their teleconnections, J. Geophys. Res.-Atmos., 121, 6215–6239, https://doi.org/10.1016/j.egypro.2016.11.209, 2016. a, b
Du Plessis, J. and Schloms, B.: An investigation into the evidence of seasonal rainfall pattern shifts in the Western Cape, South Africa, J. S. Afr. Inst. Civ. Eng., 59, 47–55, https://doi.org/10.17159/2309-8775/2017/v59n4a5, 2017. a
DWS – South African National Department of Water Affairs and Sanitation: Drainage Regions Station Catalogue, https://www.dws.gov.za/Hydrology/Verified/hymain.aspx, last access: 7 August 2020. a
Engelbrecht, C. J. and Landman, W. A.: Interannual variability of seasonal rainfall over the Cape south coast of South Africa and synoptic type association, Clim. Dynam., 47, 295–313, https://doi.org/10.1007/s00382-015-2836-2, 2016. a, b
Engelbrecht, C. J., Landman, W. A., Engelbrecht, F. A., and Malherbe, J.: A synoptic decomposition of rainfall over the Cape south coast of South Africa, Clim. Dynam., 44, 2589–2607, https://doi.org/10.1007/s00382-014-2230-5, 2015. a, b, c, d
Engelbrecht, F. A., Marean, C. W., Cowling, R. M., Engelbrecht, C. J., Neumann, F. H., Scott, L., Nkoana, R., O'Neal, D., Fisher, E., Shook, E., Franklin, J., Thatcher, M., McGregor, J. L., Van der Merwe, J., Dedekind, Z., and Difford, M.: Downscaling Last Glacial Maximum climate over southern Africa, Quaternary Sci. Rev., 226, 105879, https://doi.org/10.1016/J.QUASCIREV.2019.105879, 2019. a, b, c
Faith, J. T., Chase, B. M., and Avery, D. M.: Late Quaternary micromammals and the precipitation history of the southern Cape, South Africa, Quaternary Res., 91, 848–860, https://doi.org/10.1017/qua.2018.105, 2019. a
Favre, A., Hewitson, B. C., Lennard, C., Cerezo-Mota, R., and Tadross, M.: Cut-off Lows in the South Africa region and their contribution to precipitation, Clim. Dynam., 41, 2331–2351, https://doi.org/10.1007/s00382-012-1579-6, 2013. a, b, c, d
Fick, S. E. and Hijmans, R. J.: WorldClim 2: new 1 km spatial resolution climate surfaces for global land areas, Int. J. Climatol., 37, 4302–4315, https://doi.org/10.1002/joc.5086, 2017. a
Goldblatt, P. and Manning, J. C.: Plant Diversity of the Cape Region of Southern Africa, Ann. Mo. Bot. Gard., 89, 281, https://doi.org/10.2307/3298566, 2002. a
Granger, R., Meadows, M. E., Hahn, A., Zabel, M., Stuut, J.-B. W., Herrmann, N., and Schefuß, E.: Late-Holocene dynamics of sea-surface temperature and terrestrial hydrology in southwestern Africa, Holocene, 28, 695–705, https://doi.org/10.1177/0959683617744259, 2018. a
Helme, N. and Schmiedel, U.: Namaqualand nightmare, Veld and Flora, 14–19, https://botanicalsociety.org.za/d043-veld-flora-june-2020-issue/ (last access: 3 March 2022), 2020. a
Hersbach, H., Bell, B., Berrisford, P., Biavati, G., Horányi, A., Muñoz Sabater, J., Nicolas, J., Peubey, C., Radu, R., Rozum, I., Schepers, D., Simmons, A., Soci, C., Dee, D., and Thépaut, J.-N.: ERA5 hourly data on single levels from 1979 to present, Copernicus Climate Change Service (C3S) Climate Data Store (CDS) [data set], https://doi.org/10.24381/cds.adbb2d47, 2018 a
Hersbach, H., Bell, B., Berrisford, P., Hirahara, S., Horányi, A., Muñoz-Sabater, J., Nicolas, J., Peubey, C., Radu, R., Schepers, D., Simmons, A., Soci, C., Abdalla, S., Abellan, X., Balsamo, G., Bechtold, P., Biavati, G., Bidlot, J., Bonavita, M., De Chiara, G., Dahlgren, P., Dee, D., Diamantakis, M., Dragani, R., Flemming, J., Forbes, R., Fuentes, M., Geer, A., Haimberger, L., Healy, S., Hogan, R. J., Hólm, E., Janisková, M., Keeley, S., Laloyaux, P., Lopez, P., Lupu, C., Radnoti, G., de Rosnay, P., Rozum, I., Vamborg, F., Villaume, S., and Thépaut, J.-N. N.: The ERA5 global reanalysis, Q. J. Roy. Meteorol. Soc., 146, 1999–2049, https://doi.org/10.1002/qj.3803, 2020. a
Hijmans, R. J., Cameron, S. E., Parra, J. L., Jones, P. G., and Jarvis, A.: Very high resolution interpolated climate surfaces for global land areas, Int. J. Climatol., 25, 1965–1978, https://doi.org/10.1002/joc.1276, 2005. a
Hoffman, M. T., Carrick, P. J., Gillson, L., and West, A. G.: Drought, climate change and vegetation response in the succulent karoo, South Africa, S. Afr. J. Sci., 105, 54–60, https://doi.org/10.1590/S0038-23532009000100021, 2009. a
Hoyer, S. and Hamman, J. J.: xarray: N-D labeled Arrays and Datasets in Python, Journal of Open Research Software, 5, 10, https://doi.org/10.5334/jors.148, 2017. a
Hoyer, S., Fitzgerald, C., Hamman, J., akleeman, Kluyver, T., Roos, M., Helmus, J. J., Markel, Cable, P., Maussion, F., Miles, A., Kanmae, T., Wolfram, P., Sinclair, S., Bovy, B., ebrevdo, Guedes, R., Abernathey, R., Spencer Hill, F., Richards, N., Lee, A., Koldunov, N., Graham, M., maciekswat, Gerard, J., Babuschkin, I., Deil, C., Welch, E., and Hilboll, A.: xarray: v0.8.0, Zenodo [code], https://doi.org/10.5281/zenodo.59499, 2016. a
Kam, J., Min, S.-K., Wolski, P., and Kug, J.-S.: CMIP6 Model-Based Assessment of Anthropogenic Influence on the Long Sustained Western Cape Drought over 2015–19, B. Am. Meteorol. Soc., 102, S45–S50, https://doi.org/10.1175/BAMS-D-20-0159.1, 2021. a
Kloppers, P.-L.: Investigating the relationships between wheat-specific rainfall characteristics, large-scale modes of climate variability and wheat yields in the Swartland region, South Africa, MS thesis, University of Cape Town, http://hdl.handle.net/11427/13214 (last access: 3 March 2022), 2014. a
Lakhraj-Govender, R., Grab, S. W., and Beukes Yali Woyessa, N.: Rainfall and river flow trends for the Western Cape Province, South Africa, S. Afr. J. Sci., 115, 1–6, https://doi.org/10.17159/sajs.2019/6028, 2019. a
Liebmann, B., Bladé, I., Kiladis, G. N., Carvalho, L. M., Senay, G. B., Allured, D., Leroux, S., and Funk, C.: Seasonality of African precipitation from 1996 to 2009, J. Climate, 25, 4304–4322, https://doi.org/10.1175/JCLI-D-11-00157.1, 2012. a
MacKellar, N., Hewitson, B. C., and Tadross, M. A.: Namaqualand's climate: Recent historical changes and future scenarios, J. Arid Environ., 70, 604–614, https://doi.org/10.1016/j.jaridenv.2006.03.024, 2007. a
MacPherson, A. J. A., Gillson, L., and Hoffman, M. T.: Climatic buffering and anthropogenic degradation of a Mediterranean-type shrubland refugium at its semi-arid boundary, South Africa, Holocene, 28, 651–666, https://doi.org/10.1177/0959683617735582, 2018. a, b
Mahlalela, P. T., Blamey, R. C., and Reason, C. J. C.: Mechanisms behind early winter rainfall variability in the southwestern Cape, South Africa, Clim. Dynam., 53, 21–39, https://doi.org/10.1007/s00382-018-4571-y, 2019. a, b, c
Masante, D., McCormick, N., Vogt, J., Carmona-Moreno, C., Cordano, E., and Ameztoy, I.: 2018 Drought and Water Crisis in Southern Africa, Tech. rep., European Commission, Ispra, https://doi.org/10.2760/81873, 2018. a
Mbali, S.: Improving estimation of precipitation and prediction of river flows in the Jonkershoek mountain catchment, PhD thesis, University of the Western Cape, http://etd.uwc.ac.za/handle/11394/2760 (last access: 6 March 2022), 2016. a
Mbokodo, I., Bopape, M.-J. M., Chikoore, H., Engelbrecht, F. A., and Nethengwe, N.: Heatwaves in the Future Warmer Climate of South Africa, Atmosphere, 11, 712, https://doi.org/10.3390/atmos11070712, 2020. a
Met Office: Cartopy: a cartographic python library with a matplotlib interface, Exeter, Devon, http://scitools.org.uk/cartopy (last access: 6 March 2022), 2010–2020. a
Meyer-Christoffer, A., Becker, A., Finger, P., Schneider, U., and Ziese, M.: GPCC Climatology Version 2018 at 0.25∘: Monthly Land-Surface Precipitation Climatology for Every Month and the Total Year from Rain-Gauges built on GTS-based and Historical Data, DWD [data set], https://doi.org/10.5676/DWD_GPCC/CLIM_M_V2018_025, 2018. a, b
Moses, G.: The establishment of the long-term rainfall trends in the annual rainfall patterns in the Jonkershoek Valley, Western Cape, South Africa, Master's thesis, University of the Western Cape, http://etd.uwc.ac.za/xmlui/handle/11394/2760 (last access: 3 March 2022), 2008. a
Myers, N., Mittermeler, R. A., Mittermeler, C. G., Da Fonseca, G. A., and Kent, J.: Biodiversity hotspots for conservation priorities, Nature, 403, 853–858, https://doi.org/10.1038/35002501, 2000. a
Naik, M. and Abiodun, B. J.: Projected changes in drought characteristics over the Western Cape, South Africa, Meteorol. Appl., 27, e1802, https://doi.org/10.1002/met.1802, 2019. a
Ndebele, N. E., Grab, S., and Turasie, A.: Characterizing rainfall in the south-western Cape, South Africa: 1841–2016, Int. J. Climatol., 40, joc.6314, https://doi.org/10.1002/joc.6314, 2019. a, b
Nicholson, S. E.: The nature of rainfall variability over Africa on time scales of decades to millenia, Global Planet. Change, 26, 137–158, https://doi.org/10.1016/S0921-8181(00)00040-0, 2000. a
Pascale, S., Kapnick, S. B., Delworth, T. L., and Cooke, W. F.: Increasing risk of another Cape Town “Day Zero” drought in the 21st century, P. Natl. Acad. Sci. USA, 117, 202009144, https://doi.org/10.1073/pnas.2009144117, 2020. a
Pedregosa, F., Varoquaux, G., Gramfort, A., Michel, V., Thirion, B., Grisel, O., Blondel, M., Prettenhofer, P., Weiss, R., Dubourg, V., Vanderplas, J., Passos, A., Cournapeau, D., Brucher, M., Perrot, M., and Duchesnay, E.: Scikit-learn: Machine Learning in Python, J. Mach. Learn. Res., 12, 2825–2830, 2011. a
Pegram, G. and Bárdossy, A.: Downscaling Regional Circulation Model rainfall to gauge sites using recorrelation and circulation pattern dependent quantile–quantile transforms for quantifying climate change, J. Hydrol., 504, 142–159, https://doi.org/10.1016/J.JHYDROL.2013.09.014, 2013. a
Philippon, N., Rouault, M., Richard, Y., and Favre, A.: The influence of ENSO on winter rainfall in South Africa, Int. J. Climatol., 32, 2333–2347, https://doi.org/10.1002/joc.3403, 2012. a, b, c
Polade, S. D., Gershunov, A., Cayan, D. R., Dettinger, M. D., and Pierce, D. W.: Precipitation in a warming world: Assessing projected hydro-climate changes in California and other Mediterranean climate regions, Sci. Rep., 7, 1–10, https://doi.org/10.1038/s41598-017-11285-y, 2017. a
Procheş, C., Cowling, R. M., and Du Preez, D. R.: Patterns of geophyte diversity and storage organ size in the winter-rainfall region of southern Africa, Divers. Distrib., 11, 101–109, https://doi.org/10.1111/j.1366-9516.2005.00132.x, 2005. a, b, c
Quick, L. J., Meadows, M. E., Bateman, M. D., Kirsten, K. L., Mäusbacher, R., Haberzettl, T., and Chase, B. M.: Vegetation and climate dynamics during the last glacial period in the fynbos-afrotemperate forest ecotone, southern Cape, South Africa, Quaternary Int., 404, 136–149, https://doi.org/10.1016/J.QUAINT.2015.08.027, 2016. a
R Core Team: R 3.4.6: A Language and Environment for Statistical Computing, R Foundation for Statistical Computing, Vienna, Austria, https://www.R-project.org/ (last access: 6 March 2022), 2018. a
Reason, C. J. C.: Climate of Southern Africa, in: Oxford Research Encyclopedia of Climate Science, Oxford University Press, https://doi.org/10.1093/acrefore/9780190228620.013.513, 2017. a, b, c
Reason, C. J. C. and Rouault, M.: Links between the Antarctic Oscillation and winter rainfall over western South Africa, Geophys. Res. Lett., 32, 1–4, https://doi.org/10.1029/2005GL022419, 2005. a
Rebelo, A. G., Boucher, C., Helme, N., Mucina, L., Rutherford, M. C., Smit, W. J., Powrie, L. W., Ellis, F., Lambrechts, J. J. N., Scott, L., Radloff, F. G. T., Johnson, S. D., Richardson, D. M., Ward, R. A., Procheš, Š. M., Oliver, E. G. H., Manning, J. C., Jürgens, N., McDonald, D. J., Janssen, J. A. M., Walton, B. A., le Roux, A., Skowno, A. L., Todd, S. W., and Hoare, D. B.: Fynbos Biome, in: The vegetation of South Africa, Lesotho and Swaziland, 52–219, ISBN 10 1-919976-21-3, ISBN 13 978-1-919976-21-1, 2006. a, b, c
Rigby, R. A. and Stasinopoulos, D. M.: Generalized additive models for location, scale and shape, J. Roy. Stat. Soc. C-Appl., 54, 507–554, https://doi.org/10.1111/J.1467-9876.2005.00510.X, 2005. a, b
Roffe, S. J., Fitchett, J. M., and Curtis, C. J.: Classifying and mapping rainfall seasonality in South Africa: a review, S. Afr. Geogr. J., 101, 158–174, https://doi.org/10.1080/03736245.2019.1573151, 2019. a, b, c
Roffe, S. J., Fitchett, J. M., and Curtis, C. J.: Determining the utility of a percentile-based wet-season start- and end-date metrics across South Africa, Theor. Appl. Climatol., 140, 1331–1347, https://doi.org/10.1007/s00704-020-03162-y, 2020. a, b
Roffe, S. J., Fitchett, J. M., and Curtis, C. J.: Investigating changes in rainfall seasonality across South Africa: 1987–2016, Int. J. Climatol., 41, E2031–E2050, https://doi.org/10.1002/joc.6830, 2021a. a
Rudeva, I., Simmonds, I., Crock, D., and Boschat, G.: Midlatitude fronts and variability in the Southern Hemisphere tropical width, J. Climate, 32, JCLI-D-18-0782.1, https://doi.org/10.1175/jcli-d-18-0782.1, 2019. a
Schneider, U., Finger, P., Meyer-Christoffer, A., Rustemeier, E., Ziese, M., and Becker, A.: Evaluating the Hydrological Cycle over Land Using the Newly-Corrected Precipitation Climatology from the Global Precipitation Climatology Centre (GPCC), Atmosphere, 8, 52, https://doi.org/10.3390/atmos8030052, 2017. a
Schneider, U., Becker, A., Finger, P., Meyer-Christoffer, A., and Ziese, M.: GPCC Full Data Monthly Version 2018.0 at 0.25∘: Monthly Land-Surface Precipitation from Rain-Gauges built on GTS-based and Historic Data, DWD [data set], https://doi.org/10.5676/DWD_GPCC/FD_M_V2018_025, 2018. a
Schoenach, D., Simon, T., and Mayr, G. J.: Postprocessing ensemble forecasts of vertical temperature profiles, Adv. Stat. Clim. Meteorol. Oceanogr., 6, 45–60, https://doi.org/10.5194/ascmo-6-45-2020, 2020. a
Schulzweida, U.: CDO User Guide, Zenodo, https://doi.org/10.5281/zenodo.3539275, 2019. a
Schumann, T. E. W. and Hofmeyr, W. L.: The partition of a region into rainfall districts: With special reference to South Africa, Q. J. Roy. Meteorol. Soc., 64, 482–488, https://doi.org/10.1002/qj.49706427612, 1938. a, b, c, d
Schwarz, G.: Estimating the Dimension of a Model, Ann. Stat., 6, 461–464, https://doi.org/10.1214/aos/1176344136, 1978. a
Seager, R., Osborn, T. J., Kushnir, Y., Simpson, I. R., Nakamura, J., and Liu, H.: Climate variability and change of mediterranean-type climates, J. Climate, 32, 2887–2915, https://doi.org/10.1175/JCLI-D-18-0472.1, 2019. a
Sinclair-Smith, K. and Winter, K.: Water demand management in Cape Town: managing water security in a changing climate, Mainstreaming Climate Change in Urban Development: lessons from Cape Town, 100–133, https://www.researchgate.net/publication/325626526_Water_demand_management_in_Cape_Town (last access: 3 March 2022), 2019. a, b
Slingsby, J. A., Buys, A., Simmers, A. D. A., Prinsloo, E., Forsyth, G. G., Glenday, J., and Allsopp, N.: Jonkershoek: Africa's oldest catchment experiment – 80 years and counting, Hydrol. Process., 35, e14101, https://doi.org/10.1002/hyp.14101, 2021. a, b, c
Sousa, P. M., Blamey, R., Reason, C., Ramos, A. M., and Trigo, R. M.: The “Day Zero” Cape Town drought and the poleward migration of moisture corridors, Environ. Res. Lett., 13, 124025, https://doi.org/10.1088/1748-9326/aaebc7, 2018. a, b, c
South African Forestry Research Institute (SAFRI) and Council for Scientific and Industrial Research (CSIR): 17B manual monthly rainfall February 1945–September 1991, https://doi.org/10.15493/SAEON.FYNBOS.17B4591, 2020a. a
South African Forestry Research Institute (SAFRI) and Council for Scientific and Industrial Research (CSIR): 18B manual monthly rainfall February 1945–September 1991, https://doi.org/10.15493/SAEON.FYNBOS.18B4591, 2020b. a
Stager, J. C., Mayewski, P. A., White, J., Chase, B. M., Neumann, F. H., Meadows, M. E., King, C. D., and Dixon, D. A.: Precipitation variability in the winter rainfall zone of South Africa during the last 1400 yr linked to the austral westerlies, Clim. Past, 8, 877–887, https://doi.org/10.5194/cp-8-877-2012, 2012. a
Stasinopoulos, D. M. and Rigby, R. A.: Generalized additive models for location scale and shape (GAMLSS) in R, J. Stat. Softw., 23, 1–46, https://doi.org/10.18637/jss.v023.i07, 2007. a
Statistics South Africa: Mid-year population estimates 2020: P0302, Tech. Rep. July, Statistics South Africa, https://www.statssa.gov.za, last access: 16 November 2020. a
Sun, X., Cook, K. H., Vizy, E. K., Sun, X., Cook, K. H., and Vizy, E. K.: The South Atlantic subtropical high: Climatology and interannual variability, J. Climate, 30, 3279–3296, https://doi.org/10.1175/JCLI-D-16-0705.1, 2017.
a
Theron, S., Archer, E. R. M., Midgley, S., and Walker, S.: Agricultural perspectives on the 2015–2018 Western Cape drought, South Africa: Characteristics and spatial variability in the core wheat growing regions, Agr. Forest Meteorol., 304–305, 108405, https://doi.org/10.1016/j.agrformet.2021.108405, 2021. a
Trigo, R. M. and DaCamara, C. C.: Circulation weather types y their influence on the precipitation regime in Portugal, Int. J. Climatol., 20, 1559–1581,
https://doi.org/10.1002/1097-0088(20001115)20:13<1559::AID-JOC555>3.0.CO;2-5, 2000. a, b
Tyson, P. D.: Atmospheric circulation changes and palaeoclimates of southern Africa, S. Afr. J. Sci., 95, 194–201, https://hdl.handle.net/10520/AJA00382353_8248 (last access: 7 March 2022), 1999. a
Van Niekerk, A. and Joubert, S. J.: Input variable selection for interpolating high-resolution climate surfaces for the Western Cape, Water SA, 37, 271–280, https://doi.org/10.4314/wsa.v37i3.68475, 2011. a, b
van Oldenborgh, G. J., Drijfhout, S., van Ulden, A., Haarsma, R., Sterl, A., Severijns, C., Hazeleger, W., and Dijkstra, H.: Western Europe is warming much faster than expected, Clim. Past, 5, 1–12, https://doi.org/10.5194/cp-5-1-2009, 2009. a
van Rooy, M. P.: Influence of berg winds on the temperatures along the west coast of South Africa, Q. J. Roy. Meteorol. Soc., 62, 528–537, https://doi.org/10.1002/qj.49706226707, 1936. a
Veitch, J. A. and Penven, P.: The role of the Agulhas in the Benguela Current system: A numerical modeling approach, J. Geophys. Res.-Oceans, 122, 3375–3393, https://doi.org/10.1002/2016JC012247, 2017. a
Ward, J. H.: Hierarchical Grouping to Optimize an Objective Function, J. Am. Stat. Assoc., 58, 236–244, https://doi.org/10.1080/01621459.1963.10500845, 1963. a
Wicht, C. L.: A preliminary account of rainfall in jonkershoek, T. Roy. Soc. S. Afr., 28, 161–173, https://doi.org/10.1080/00359194009520010, 1940. a
Wickham, H.: ggplot2: Elegant Graphics for Data Analysis, Use R!, Springer, https://doi.org/10.1007/978-0-387-98141-3, 2009. a
Wickham, H., Averick, M., Bryan, J., Chang, W., McGowan, L., François, R., Grolemund, G., Hayes, A., Henry, L., Hester, J., Kuhn, M., Pedersen, T., Miller, E., Bache, S., Müller, K., Ooms, J., Robinson, D., Seidel, D., Spinu, V., Takahashi, K., Vaughan, D., Wilke, C., Woo, K., and Yutani, H.: Welcome to the Tidyverse, Journal of Open Source Software, 4, 1686, https://doi.org/10.21105/joss.01686, 2019. a
Wolski, P., Conradie, S., Jack, C., and Tadross, M.: Spatio-temporal patterns of rainfall trends and the 2015–2017 drought over the winter rainfall region of South Africa, Int. J. Climatol., 41, E1303–1319, joc.6768, https://doi.org/10.1002/joc.6768, 2021. a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p
Wong, B.: Color blindness, Nat. Meth., 8, 441, https://doi.org/10.1038/nmeth.1618, 2011. a
Short summary
Cape Town is situated in a small but ecologically and climatically highly diverse and vulnerable pocket of South Africa uniquely receiving its rain mostly in winter. We show complex structures in the spatial patterns of rainfall seasonality and year-to-year changes in rainfall within this domain, tied to spatial differences in the rain-bearing winds. This allows us to develop a new spatial subdivision of the region to help future studies distinguish spatially distinct climate change responses.
Cape Town is situated in a small but ecologically and climatically highly diverse and vulnerable...