Circulation mechanisms responsible for wet or dry summers over Zimbabwe

Moven Manjowe; Terence Darlington Mushore; Juliet Gwenzi; Collen Mutasa; Electdom Matandirotya; Emmanuel Mashonjowa; Moven Manjowe; Terence Darlington Mushore; Juliet Gwenzi; Collen Mutasa; Electdom Matandirotya; Emmanuel Mashonjowa

doi:10.3934/environsci.2018.3.154

AIMS Environmental Science

2018, Volume 5, Issue 3: 154-172. doi: 10.3934/environsci.2018.3.154

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Research article

Circulation mechanisms responsible for wet or dry summers over Zimbabwe

1.
Department of Physics, University of Zimbabwe, P Bag MP 167, Mount Pleasant, Harare, Zimbabwe
2.
Discipline of Geography, School of Agricultural, Earth and Environmental Sciences, University of KwaZulu-Natal, P/Bag X01, Scottsville, Pietermaritzburg 3209, South Africa

Received: 11 December 2017 Accepted: 03 June 2018 Published: 13 June 2018

Climate change has resulted in increased rainfall variability over many parts of the world including Southern Africa. As such, droughts and floods have become a frequent phenomenon in Zimbabwe and have potential to intensify socio-economic stressors. This study examined possible forcing factors behind the occurrence of extreme summer events using re-analysis datasets. Composite analysis and correlation methods were used to identify circulation mechanisms and their strength in determining rainfall patterns in Zimbabwe. Predominantly northerly airflow in the lower troposphere was found to favor wet while southerly airflow favors dry seasons. Negative geopotential anomalies (minimum of −20 hPa) to the west of Zimbabwe in the middle levels characterize wet summers which swing to positive anomalies (+24 hPa) during dry summers. Positive SST anomalies (maximum of 0.4) exist to the southwest of Madagascar extending to the western shore on the Angola-Namibian border characterize wet summers which swing to negative anomalies (−0.2 ºC) during dry summer seasons. SST anomalies in the South western Indian and South eastern Atlantic oceans are crucial in the determination of the strength of both the South Indian and Atlantic Ocean high pressure systems which in turn control moisture advection and convergence into Zimbabwe during the summer period. If these SST anomalies at lag times of about 3 months can be used to predict the incoming summer circulation patterns then the accuracy of summer seasonal outlook forecasts can be improved. Studying the mechanisms behind drought and flood occurrence is important to the country which is in the process of downscaling regional prediction products to improve the accuracy of seasonal forecasts. These findings are useful in crafting relevant measures to maximize the benefits and minimize the risks of extreme rainfall events.
- Zimbabwe summer rainfall,
- South Atlantic Ocean High,
- South Indian Ocean High,
- Angola Low Pressure
Citation: Moven Manjowe, Terence Darlington Mushore, Juliet Gwenzi, Collen Mutasa, Electdom Matandirotya, Emmanuel Mashonjowa. Circulation mechanisms responsible for wet or dry summers over Zimbabwe[J]. AIMS Environmental Science, 2018, 5(3): 154-172. doi: 10.3934/environsci.2018.3.154

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Abstract

Climate change has resulted in increased rainfall variability over many parts of the world including Southern Africa. As such, droughts and floods have become a frequent phenomenon in Zimbabwe and have potential to intensify socio-economic stressors. This study examined possible forcing factors behind the occurrence of extreme summer events using re-analysis datasets. Composite analysis and correlation methods were used to identify circulation mechanisms and their strength in determining rainfall patterns in Zimbabwe. Predominantly northerly airflow in the lower troposphere was found to favor wet while southerly airflow favors dry seasons. Negative geopotential anomalies (minimum of −20 hPa) to the west of Zimbabwe in the middle levels characterize wet summers which swing to positive anomalies (+24 hPa) during dry summers. Positive SST anomalies (maximum of 0.4) exist to the southwest of Madagascar extending to the western shore on the Angola-Namibian border characterize wet summers which swing to negative anomalies (−0.2 ºC) during dry summer seasons. SST anomalies in the South western Indian and South eastern Atlantic oceans are crucial in the determination of the strength of both the South Indian and Atlantic Ocean high pressure systems which in turn control moisture advection and convergence into Zimbabwe during the summer period. If these SST anomalies at lag times of about 3 months can be used to predict the incoming summer circulation patterns then the accuracy of summer seasonal outlook forecasts can be improved. Studying the mechanisms behind drought and flood occurrence is important to the country which is in the process of downscaling regional prediction products to improve the accuracy of seasonal forecasts. These findings are useful in crafting relevant measures to maximize the benefits and minimize the risks of extreme rainfall events.

References

[1]	ADDIN Mendeley Bibliography CSL_BIBLIOGRAPHY Moyo EN, Nangombe SS (2015) Southern Africa's 2012–13 violent storms: role of climate change. Procedia IUTAM 17: 69–78. doi: 10.1016/j.piutam.2015.06.011
[2]	Wahid H, Ahmad S, Nor MSM, et al. (2017) Prestasi kecekapan pengurusan kewangan dan agihan zakat: perbandingan antara majlis agama islam negeri di Malaysia. J Ekon Malaysia 51: 39–54.
[3]	Mutasa M (2010) Zimbabwe' s Drought Conundrum : vulnerability and coping in Buhera and Chikomba districts. MS thesis, 163.
[4]	Ndlovu S (2010) Coping With Drought. Mainstreaming Livelihood Centred Approaches to Disaster Management.
[5]	Levey KM, Jury MR (1996) Composite intraseasonal oscillations of convection over Southern Africa. J Clim 9: 1910–1920. doi: 10.1175/1520-0442(1996)009<1910:CIOOCO>2.0.CO;2
[6]	Makarau A (1995) Intra-seasonal oscillatory modes of the southern Africa summer circulation, Univ. Cape T. (PhD thesis).
[7]	Zhakata W (1996) Impacts of climate variability and forecasting on agriculture (Zimbabwe experience), in Proc. Workshop on Reducing Climate-Related Vulnerability in Southern Africa, 131–139.
[8]	Jury MR (1993) The structure and possible forcing mechanisms of the 1991–1992 drought in Southern Africa, Suid-Afrikaanse Tydskr. vir Natuurwetenskap en Tegnol 12, 8–16.
[9]	Colberg F (2004) South Atlantic response to El Niño–Southern Oscillation induced climate variability in an ocean general circulation model. J Geophys Res 109: C12015. doi: 10.1029/2004JC002301
[10]	Chikozho C (2010) Applied social research and action priorities for adaptation to climate change and rainfall variability in the rainfed agricultural sector of Zimbabwe. Phys Chem Earth 35: 780–790. doi: 10.1016/j.pce.2010.07.006
[11]	Gwimbi P (2009) Cotton farmers' vulnerability to climate change in Gokwe District (Zimbabwe): impact and influencing factors. JÀMBÁ J Disaster Risk Stud 2: 81–92.
[12]	Alvarez TC, Delgado RC, González PA (2014) Aplicabilidad de los sistemas de triaje prehospitalarios en los incidentes con múltiples víctimas: De la teoría a la práctica. Emergencias 26: 147–154.
[13]	Tome S (2017) Weekly Bulletin on Outbreaks. Week 46, no. July, 1–7.
[14]	Bohle HG, Downing TE, Watts M J (1994) Climate Change and Social Vulnerability. Toward a Sociology and Geography of Food Insecurity. Glob Environ Chang 4: 37–48.
[15]	Mavhura E, Bernard S, Collins AE, et al. (2013) Author' s personal copy International Journal of Disaster Risk Reduction Indigenous knowledge, coping strategies and resilience to floods in Muzarabani, Zimbabwe. Int J Disaster Risk Reduct 5: 38–48. doi: 10.1016/j.ijdrr.2013.07.001
[16]	Mavhura E, Manatsa D, Mushore T (2015) Adaptation to drought in arid and semi-arid environments: Case of the Zambezi Valley, Zimbabwe. Jàmbá J Disaster Risk Stud 7: 1–7.
[17]	Mushore TD (2013) Uptake Of Seasonal Rainfall Forecasts In Zimbabwe. IOSR J Environ Sci Toxicol Food Technol 5: 31–37. doi: 10.9790/2402-0513137
[18]	Cook KH (2000) The South Indian convergence zone and interannual rainfall variability over Southern Africa. J Clim 13: 3789–3804. doi: 10.1175/1520-0442(2000)013<3789:TSICZA>2.0.CO;2
[19]	Mason S, Lindesay J, Tyson J (1994) Simulating drought in Southern Africa using sae surface temperature variations. Water SA 20: 15–22.
[20]	Beilfuss R (2012) A Risky Climate for Southern African Hydro. Int Rivers Berkely, 1–46.
[21]	Mamombe V, Kim WM, Choi YS (2017) Rainfall variability over Zimbabwe and its relation to large-scale atmosphere–ocean processes. Int J Climatol 37: 963–971. doi: 10.1002/joc.4752
[22]	Mwafulirwa ND (1999) Climate variability and predictability in tropical southern africa with a focus on dry spells over Malawi.
[23]	Manatsa D, Chingombe W, Matsikwa H, et al. (2008) The superior influence of Darwin Sea level pressure anomalies over ENSO as a simple drought predictor for Southern Africa. Theor Appl Climatol 92: 1–14. doi: 10.1007/s00704-007-0315-3
[24]	Manatsa D, Mukwada G (2012) Rainfall Mechanisms for the Dominant Rainfall Mode over Zimbabwe Relative to ENSO and/or IODZM. Sci World J 2012: 1–15.
[25]	Gaughan AE, Staub CG, Hoell A, et al. (2016) Inter- and Intra-annual precipitation variability and associated relationships to ENSO and the IOD in southern Africa. Int J Climatol 36: 1643–1656. doi: 10.1002/joc.4448
[26]	Ogwang BA, Guirong T, Haishan C (2012) Diagnosis of September - November Drought and the Associated Circulation Anomalies Over Uganda. Pakistan J Meteorol 9: 11–24.
[27]	Kabanda TA, Jury MR (1999) Inter-annual variability of short rains over northern Tanzania. Clim Res 13: 231–241. doi: 10.3354/cr013231
[28]	Nangombe S, Madyiwa S, Wang J (2018) Precursor conditions related to Zimbabwe's summer droughts. Theor Appl Climatol 131: 413–431. doi: 10.1007/s00704-016-1986-4
[29]	Manatsa D, Reason CJC, Mukwada G (2012) On the decoupling of the IODZM from southern Africa Summer rainfall variability. Int J Climatol 32: 727–746. doi: 10.1002/joc.2306
[30]	Simmonds I, Hope P (1997) Persistence Characteristics of Australian Rainfall Anomalies. Int J Climatol 17: 597–613. doi: 10.1002/(SICI)1097-0088(199705)17:6<597::AID-JOC173>3.0.CO;2-V
[31]	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: 259–274. doi: 10.1007/s00704-015-1632-6
[32]	Department of Meterological Services (1981) Climate Handbook of Zimbabwe, Zimbabwe Meteorol. Serv. Harare, 48.
[33]	Mavhura E, Collins A, Bongo PP (2017) Flood vulnerability and relocation readiness in Zimbabwe. Disaster Prev Manag An Int J 26: 41–54. doi: 10.1108/DPM-05-2016-0101
[34]	Muzenda-Mudavanhu C, Manyena B, Collins AE (2015) Disaster risk reduction knowledge among children in Muzarabani District, Zimbabwe. Nat Hazards 84: 911–931.
[35]	Bohle HG, Downing TE, Watts MJ (1994) Köppen Climate Classification for Bucharest.
[36]	Janus Corporate Solutions (2016) Weather and Climate in Singapore. Longman.
[37]	Matarira CH (1990) Theoretical and Ap. plied Climatology Frequency and Tracks of Anticyclones and Their Effect on Rainfall Pat- terns over Zimbabwe. Theor Appl Climatol 66: 53–66.
[38]	Makarau A, Jury MR (1997) Seasonal Cycle of Convective Spells Over Southern. Int J Climatol 17: 1317–1332. doi: 10.1002/(SICI)1097-0088(199710)17:12<1317::AID-JOC197>3.0.CO;2-A
[39]	Manatsa D, Morioka Y, Behera SK, et al. (2013) Link between Antarctic ozone depletion and summer warming over southern Africa. Nat Geosci 6: 934–939. doi: 10.1038/ngeo1968
[40]	Levitus S, Boyer T (1998) NOAA/OAR/ESRL PSD, Boulder, Colorado, USA.
[41]	Dee DP, Uppala SM, Simmons AJ, et al. (2011) The ERA-Interim reanalysis: Configuration and performance of the data assimilation system. Q J R Meteorol Soc 137: 553–597. doi: 10.1002/qj.828
[42]	Kalnay E, Kanamitsu M, Kistler R, et al. (1996) The NCEP/NCAR 40-year reanalysis project. Bull Am Meteorol Soc 77: 437–471. doi: 10.1175/1520-0477(1996)077<0437:TNYRP>2.0.CO;2
[43]	Smith TM, Reynolds RW, Peterson TC, et al. (2008) Improvements to NOAA's historical merged land–ocean surface temperature analysis (1880–2006). J Clim 21: 2283–2296. doi: 10.1175/2007JCLI2100.1
[44]	Folland CK (1983) Regional-Scale International Variability Of Climate-A Northwest European-Perspective. Meteorol Mag 112: 163–183.
[45]	Mpeta EJ (1997) Intra-seasonal convection dynamics over southwest and northeast Tanzania: an observational study, University of Cape Town.
[46]	Naeraa M, Jury MR (1998) Meteorology and Atmospheric Physics Tropical Cyclone Composite Structure and Impacts over Eastern Madagascar During January-March 1994. Meteorol Atmos Phys 53: 43–53.
[47]	Jury MR, Levey KM (1997) Vertical structure of the atmosphere during wet spells over Southern Africa. Water SA 23: 51–55.
[48]	Hargraves R, Jury M (1997) Composite meteorological structure of flood events over the eastern mountains of South Africa. Water SA 23: 357–363.
[49]	Boschat G, Simmonds L, Purich A, et al. (2016) On the use of composite analyses to form physical hypotheses: An example from heat wave-SST associations. Sci Rep 6: 29599. doi: 10.1038/srep29599
[50]	Rocha A, Simmonds I (1997) Interannual Variability of South-Eastern African Summer Rainfall. Part Ii. Modelling the Impact of Sea-Surface Temperatures on Rainfall and Circulation. Int J Climatol 17: 267–290.
[51]	Simmonds I, Bi D, Hope P (1999) Atmospheric water vapor flux and its association with rainfall over China in summer. J Clim 12: 1353–1367. doi: 10.1175/1520-0442(1999)012<1353:AWVFAI>2.0.CO;2
[52]	Preston-Whyte RA, Tyson PD (1988) The atmosphere and weather of Southern Africa. Oxford University Press.
[53]	Rocha A, Simmonds I (1997) Interannual Variability of South-Eastern African Summer Rainfall. Part 1: Relationships With Air–Sea Interaction Processes. Int J Climatol 17: 235–265.
[54]	Nicholson SE, Entekhabi D (1987) Rainfall Variability in Equatorial and Southern Africa: Relationships with Sea Surface Temperatures along the Southwestern Coast of Africa. J Clim Appl Meteorol 26: 561–578. doi: 10.1175/1520-0450(1987)026<0561:RVIEAS>2.0.CO;2

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