Abstract
This study evaluates the role of MCSs in the total rainfall distribution as a function of season from a climatological perspective (1998–2014) over sub-Saharan northern Africa and examines how the diurnal cycle of rainfall changes with season. Tropical Rainfall Measuring Mission (TRMM) 3B42V7 rainfall estimates and European Centre for Medium-Range Weather Forecasts ERA-Interim reanalysis are used to evaluate the climatology. The percentages of the full TRMM precipitation delivered by MCSs have meridional structures in spring, fall and winter, ranging from 0 to 80% across sub-Saharan northern Africa, while the percentages are homogenous in summer (> 80%). The diurnal cycles of MCS-associated precipitation coincide with the full TRMM rainfall. Attributes of MCSs, including size, count, and intensity, vary synchronously with the diurnal cycle of rainfall. The diurnal peaks are classified into three categories: single afternoon peak, continuous afternoon peak, and nocturnal peak. Single afternoon peaks dominate in spring and fall while continuous afternoon and nocturnal peaks are more common in summer, indicating the seasonality of the diurnal cycle. The continuous afternoon peak combines rainfall from two system types—one locally-generated and one propagating. The seasonality of the diurnal cycle is related to the seasonality of MCS lifetimes, and propagation speeds and directions. The moisture component of the MSE profile contributes to the instability most in summer when convection is more frequent. Low-level temperature, which is related to surface warming and sensible heat fluxes, influences the instability more during winter and spring.
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Alapaty K, Pleim JE, Raman S, Niyogi DS, Byun DW (1997) Simulation of atmospheric boundary layer processes using local-and nonlocal-closure schemes. J Appl Meteorol 36(3):214–233. https://doi.org/10.1175/1520-0450(1997)036<0214:SOABLP>2.0.CO;2
Birch CE, Marsham JH, Parker DJ, Taylor CM (2014a) The scale dependence and structure of convergence fields preceding the initiation of deep convection. Geophys Res Lett 41:4769–4776. https://doi.org/10.1002/2014GL060493
Birch CE, Parker DJ, Marsham JH, Copsey D, Garcia-Carreras L (2014b) A seamless assessment of the role of convection in the water cycle of the West African Monsoon. J Geophys Res 119:2890–2912. https://doi.org/10.1002/2013JD020887
Burpee RW (1972) The origin and structure of easterly waves in the lower troposphere of North Africa. J Atmos Sci 29:77–90. https://doi.org/10.1175/1520-0469(1972)029<0077:TOASOE>2.0.CO;2
Cook KH (1999) Generation of the African Easterly jet and its role in determining West African precipitation. J Clim 12:1165–1184. https://doi.org/10.1175/1520-0442(1999)012<1165:GOTAEJ>2.0.CO;2
Crétat J, Vizy EK, Cook KH (2015) The relationship between African easterly waves and daily rainfall over West Africa. Observations and regional climate simulations. Clim Dyn 44:385–404. https://doi.org/10.1007/s00382-014-2120-x
Dee DP, Uppala SM, Simmons AJ et al (2011) The ERA-Interim reanalysis: configuration and performance of the data assimilation system. Q J Roy Meteorol Soc 137:553–597. https://doi.org/10.1002/qj.828
Diedhiou A, Janicot S, Viltard A, de Félice P, Laurent H (1999) Easterly wave regimes and associated convection over West Africa and the tropical Atlantic: results from the NCEP/NCAR and ECMWF reanalyses. Clim Dyn 15:795–822. https://doi.org/10.1007/s003820050316
Duvel J-P (1989) Convection over tropical Africa and the Atlantic Ocean during northern summer. Part I: interannual and diurnal variations. Mon Weather Rev 117:2782–2799. https://doi.org/10.1175/1520-0493(1989)117<2782:COTAAT>2.0.CO;2
Eldridge RH (1957) A synoptic study of West African disturbance lines. Q J Roy Meteorol Soc 83:303–314. https://doi.org/10.1002/qj.49708335704
Fink AH, Reiner A (2003) Spatiotemporal variability of the relation between African easterly waves and West African squall lines in 1998 and 1999. J Geophys Res 108:4332. https://doi.org/10.1029/2002JD002816
Fink AH, Vincent DG, Ermert V (2006) Rainfall types in the West African Sudanian zone during the summer monsoon 2002. Mon Weather Rev 134:2143–2164. https://doi.org/10.1175/MWR3182.1
Fortune M (1980) Properties of African squall lines inferred from time-lapse satellite imagery. Mon Weather Rev 108(2):153–168. https://doi.org/10.1175/1520-0493(1980)108<0153:POASLI>2.0.CO;2
Garcia-Carreras L, Marsham JH, Parker DJ, Bain CL, Milton S, Saci A, Salah-Ferroudj M, Ouchene B, Washington R (2013) The impact of convective cold pool outflows on model biases in the Sahara. Geophys Res Lett 40(8):1647–1652. https://doi.org/10.1002/grl.50239
Gaye A, Viltard A, De Felice P (2005) Squall lines and rainfall over Western Africa during summer 1986 and 87. Meteorol Atmos Phys 90(3):215–224. https://doi.org/10.1007/s00703-005-0116-0
Hodges KI, Thorncroft CD (1997) Distribution and statistics of African mesoscale convective weather systems based on ISCCP METEOSAT imagery. Mon Weather Rev 125:2821–2837. https://doi.org/10.1175/1520-0493(1997)125<2821:DASOAM>2.0.CO;2
Holt TR, Niyogi D, Chen F, Manning K, LeMone MA, Qureshi A (2006) Effect of land–atmosphere interactions on the IHOP 24–25 May 2002 convection case. Mon Weather Rev 134(1):113–133. https://doi.org/10.1175/MWR3057.1
Hopsch SB, Thorncroft CD, Tyle KR (2010) Analysis of African easterly wave structures and their role in influencing tropical cyclogenesis. Mon Weather Rev 138(4):1399–1419. https://doi.org/10.1175/2009MWR2760.1
Houze RA Jr (1993) Cloud dynamics. Academic, San Diego, p 573
Hsieh J-S, Cook KH (2005) Generation of African easterly wave disturbances: relationship to the African easterly jet. Mon Weather Rev 133:1311–1327. https://doi.org/10.1175/MWR2916.1
Hsieh J-S, Cook KH (2007) A study of the energetics of African easterly waves using a regional climate model. J Atmos Sci 64:421–440. https://doi.org/10.1175/JAS3851.1
Hsieh J-S, Cook KH (2008) On the instability of the African easterly jet and the generation of African waves: reversals of the potential vorticity gradiet. J Atmos Sci 65:2130–2151. https://doi.org/10.1175/JAS2552.1
Huffman GJ, Adler RF, Bolvin DT, Gu G, Nelkin EJ, Bowman KP, Hong Y, Stocker EF, Wolff DB (2007) The TRMM multisatellite precipitation analysis (TMPA): quasi-global, multiyear, combined-sensor precipitation estimates at fine scales. J Hydrometeorol 8:38–55. https://doi.org/10.1175/JHM560.1
Issa Lélé M, Lamb PJ (2010) Variability of the intertropical front (ITF) and rainfall over the West African Sudan–Sahel zone. J Clim 23(14):3984–4004. https://doi.org/10.1175/2010JCLI3277.1
Jackson B, Nicholson SE, Klotter D (2009) Mesoscale convective systems over western equatorial Africa and their relationship to large-scale circulation. Mon Weather Rev 137(4):1272–1294. https://doi.org/10.1175/2008MWR2525.1
Janiga MA, Thorncroft CD (2014) Convection over tropical Africa and the east Atlantic during the West African monsoon: regional and diurnal variability. J Clim 27(11):4159–4188. https://doi.org/10.1175/JCLI-D-13-00449.1
Jiang H, Zipser EJ (2010) Contribution of tropical cyclones to the global precipitation from eight seasons of TRMM data: regional, seasonal, and interannual variations. J Clim 23(6):1526–1543. https://doi.org/10.1175/2009JCLI3303.1
Jiang H, Liu C, Zipser EJ (2011) A TRMM-based tropical cyclone cloud and precipitation feature database. J Appl Meteor Climatol 50(6):1255–1274. https://doi.org/10.1175/2011JAMC2662.1
Jirak IL, Cotton WR, McAnelly RL (2003) Satellite and radar survey of mesoscale convective system development. Mon Weather Rev 131(10):2428–2449. https://doi.org/10.1175/1520-0493(2003)131<2428:SARSOM>2.0.CO;2
Knippertz P, Fink AH (2008) Dry-season precipitation in tropical West Africa and its relation to forcing from the extratropics. Mon Weather Rev 136(9):3579–3596. https://doi.org/10.1175/2008MWR2295.1
Knippertz P, Fink AH (2009) Prediction of dry-season precipitation in tropical West Africa and its relation to forcing from the extratropics. Weather Forecasting 24(4):1064–1084. https://doi.org/10.1175/2009WAF2222221.1
Laing AG, Fritsch JM (1993) Mesoscale convective complexes in Africa. Mon Weather Rev 121: 2254–2263. https://doi.org/10.1175/1520-0493(1993)121<2254:MCCIA>2.0.CO;2
Laing AG, Fritsch JM, Negri AJ (1999) Contribution of mesoscale convective complexes to rainfall in Sahelian Africa: estimates from geostationary infrared and passive microwave data. J Appl Meteorol 38:957–964. https://doi.org/10.1175/1520-0450(1999)038<0957:COMCCT>2.0.CO;2
Laing AG, Carbone R, Levizzani V, Tuttle J (2008) The propagation and diurnal cycles of deep convection in northern tropical Africa. Q J Roy Meteorol Soc 134:93–109. https://doi.org/10.1002/qj.194
Laing AG, Carbone RE, Levizzani V (2011) Cycles and propagation of deep convection over equatorial Africa. Mon Weather Rev 139(9):2832–2853. https://doi.org/10.1175/2011MWR3500.1
Landsea CW, Gray WM (1992) The strong association between western Sahelian monsoon rainfall and intense Atlantic hurricanes. J Clim 5(5):435–453. https://doi.org/10.1175/1520-0442(1992)005<0435:TSABWS>2.0.CO;2
Laurent H, D’Amato N, Lebel T (1998) How important is the contribution of the mesoscale convective complexes to the Sahelian rainfall? Phys Chem Earth 23:629–633. https://doi.org/10.1016/S0079-1946(98)00099-8
Liu C, Zipser EJ (2009) “Warm rain” in the tropics: seasonal and regional distributions based on 9 year of TRMM data. J Clim 22(3):767–779. https://doi.org/10.1175/2008JCLI2641.1
Liu C, Zipser EJ, Cecil DJ, Nesbitt SW, Sherwood S (2008) A cloud and precipitation feature database from 9 years of TRMM observations. J Appl Meteor Climatol 47(10):2712–2728. https://doi.org/10.1175/2008JAMC1890.1
Machado LAT, Duvel JP, Desbois M (1993) Diurnal variations and modulation by easterly waves of the size distribution of convective cloud clusters over West Africa and the Atlantic Ocean. Mon Weather Rev 121(1):37–49. https://doi.org/10.1175/1520-0493(1993)121<0037:DVAMBE>2.0.CO;2
Maddox RA (1980) Mesoscale convective complexes. Bull Am Meteorol Soc 61:1374–1387. https://doi.org/10.1175/1520-0477(1980)061<1374:MCC>2.0.CO;2
Marsham JH, Dixon NS, Garcia-Carreras L, Lister G, Parker DJ, Knippertz P, Birch CE (2013) The role of moist convection in the West African monsoon system: insights from continental-scale convection-permitting simulations. Geophys Res Lett 40(9):1843–1849. https://doi.org/10.1002/grl.50347
Mathon V, Laurent H, Lebel T (2002) Mesoscale convective system rainfall in the Sahel. J Appl Meteorol 41:1081–1092. https://doi.org/10.1175/1520-0450(2002)041<1081:MCSRIT>2.0.CO;2
Maurer V, Bischoff-Gauß I, Kalthoff N, Gantner L, Roca R, Panitz HJ (2016) Initiation of deep convection in the Sahel in a convection-permitting climate simulation for northern Africa. Q J R Meteorol Soc 143(703):806–816. https://doi.org/10.1002/qj.2966
Mbourou GNT, Bertrand JJ, Nicholson SE (1997) The diurnal and seasonal cycles of wind-borne dust over Africa north of the equator. J Appl Meteorol 36(7):868–882. https://doi.org/10.1175/1520-0450(1997)036<0868:TDASCO>2.0.CO;2
Miyakawa T, Satomura T (2006) Seasonal variation and environmental properties of southward propagating mesoscale convective systems over the Bay of Bengal. SOLA 2:88–91. https://doi.org/10.2151/sola.2006-023
Mohr KI (2004) Interannual, monthly, and regional variability in the wet season diurnal cycle of precipitation in sub-Saharan Africa. J Clim 17:2441–2453. https://doi.org/10.1175/1520-0442(2004)017<2441:IMARVI>2.0.CO;2
Mohr KI, Thorncroft CD (2006) Intense convective systems in West Africa and their relationship to the African easterly jet. Q J Roy Meteorol Soc 132:163–176. https://doi.org/10.1256/qj.05.55
Mohr KI, Zipser EJ (1996) Mesoscale convective systems defined by their 85-GHz ice scattering signature: size and intensity comparison over tropical oceans and continents. Mon Weather Rev 124:2417–2437. https://doi.org/10.1175/1520-0493(1996)124<2417:MCSDBT>2.0.CO;2
Mohr KI, Famiglietti JS, Zipser EJ (1999) The contribution to tropical rainfall with respect to convective system type, size, and intensity estimated from the 85-GHz ice-scattering signature. J Appl Meteorol 38:596–606. https://doi.org/10.1175/1520-0450(1999)038<0596:TCTTRW>2.0.CO;2
Nesbitt SW, Zipser EJ (2003) The diurnal cycle of rainfall and convective intensity according to 3 years of TRMM measurements. J Clim 16:1456–1475. https://doi.org/10.1175/1520-0442&a>2.0.CO;2
Nesbitt SW, Zipser EJ, Cecil DJ (2000) A census of precipitation features in the tropics using TRMM: radar, ice scattering, and lightning observations. J Clim 13(23):4087–4106. https://doi.org/10.1175/1520-0442(2000)013<4087:ACOPFI>2.0.CO;2
Nesbitt SW, Cifelli R, Rutledge SA (2006) Storm morphology and rainfall characteristics of TRMM precipitation features. Mon Weather Rev 134(10):2702–2721. https://doi.org/10.1175/MWR3200.1
Nicholls SD, Mohr KI (2010) An analysis of the environments of intense convective systems in West Africa in 2003. Mon Weather Rev 138(10):3721–3739. https://doi.org/10.1175/2010MWR3321.1
Payne SW, McGarry MM (1977) The relationship of satellite inferred convective activity to easterly waves over West Africa and the adjacent ocean during phase III of GATE. Mon Weather Rev 105(4):413–420. https://doi.org/10.1175/1520-0493(1977)105<0413:TROSIC>2.0.CO;2
Pielke RA (2001) Influence of the spatial distribution of vegetation and soils on the prediction of cumulus convective rainfall. Rev Geophys 39(2):151–177. https://doi.org/10.1029/1999RG000072
Provod M, Marsham JH, Parker DJ, Birch CE (2016) A characterization of cold pools in the West African Sahel. Mon Weather Rev 144(5):1923–1934. https://doi.org/10.1175/MWR-D-15-0023.1
Pu B, Cook KH (2010) Dynamics of the West African westerly jet. J Clim 23:6263–6276. https://doi.org/10.1175/2010JCLI3648.1
Pu B, Cook KH (2012) Role of the West African westerly jet in Sahel rainfall variations. J Clim 25:2880–2896. https://doi.org/10.1175/JCLI-D-11-00394.1
Reed RJ, Norquist DC, Recker EE (1977) The structure and properties of African wave disturbances as observed during Phase III of GATE. Mon Weather Rev 105:317–333. https://doi.org/10.1175/1520-0493(1977)105<0317:TSAPOA>2.0.CO;2
Schwanghart W, Schütt B (2008) Meteorological causes of Harmattan dust in West Africa. Geomorphology 95(3):412–428. https://doi.org/10.1016/j.geomorph.2007.07.002
Shinoda M, Okatani T, Saloum M (1999) Diurnal variations of rainfall over Niger in the West African Sahel: a comparison between wet and drought years. Int J Climatol 19(1):81–94. https://doi.org/10.1002/(SICI)1097-0088(199901)19:1,81:AID-JOC350.3.0.CO;2-F
Sultan B, Janicot S (2003) The West African monsoon dynamics. Part II: The “preonset” and “onset” of the summer monsoon. J Clim 16(21):3407–3427. https://doi.org/10.1175/1520-0442(2003)016<3407:TWAMDP>2.0.CO;2
Taylor CM, Birch CE, Parker DJ, Dixon N, Guichard F, Nikulin G, Lister GMS (2013) Modeling soil moisture-precipitation feedback in the Sahel: Importance of spatial scale versus convective parameterization. Geophys Res Lett 40:6213–6218. https://doi.org/10.1002/2013GL058511
Tuttle JD, Carbone RE (2004) Coherent regeneration and the role of water vapor and shear in a long-lived convective episode. Mon Weather Rev 132(1):192–208. https://doi.org/10.1175/1520-0493(2004)132<0192:CRATRO>2.0.CO;2
Vizy EK, Cook KH (2017) Mesoscale convective systems and nocturnal rainfall over the West African Sahel: role of the Inter-tropical front. Clim Dyn. https://doi.org/10.1007/s00382-017-3628-7
Yang GY, Slingo J (2001) The diurnal cycle in the tropics. Mon Weather Rev 129(4):784–801. https://doi.org/10.1175/1520-0493(2001)129<0784:TDCITT>2.0.CO;2
Zhang G, Cook KH, Vizy EK (2016a) The diurnal cycle of warm season rainfall over West Africa. Part I: observational analysis. J Clim 29(23):8423–8437. https://doi.org/10.1175/JCLI-d-15-0874.1
Zhang G, Cook KH, Vizy EK (2016b) The diurnal cycle of warm season rainfall over West Africa. Part II: convection-permitting simulations. J Clim 29(23):8439–8454. https://doi.org/10.1175/JCLI-d-15-0875.1
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Support from NSF Award #1444505 is gratefully acknowledged. Dr. Gang Zhang provided much appreciated assistance as well.
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Liu, W., Cook, K.H. & Vizy, E.K. The role of mesoscale convective systems in the diurnal cycle of rainfall and its seasonality over sub-Saharan Northern Africa. Clim Dyn 52, 729–745 (2019). https://doi.org/10.1007/s00382-018-4162-y
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DOI: https://doi.org/10.1007/s00382-018-4162-y