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 GEP  Vol.5 No.12 , December 2017
Anomalous Atmospheric Circulation Associated with Recent West African Monsoon Rainfall Variability
Abstract: The recent West African Monsoon (WAM) wet season (May to October) rainfall’s interannual variability has been examined with emphasis on the rainfall zones of Guinea Coast (GC), Western Sudano Sahel (WSS) and Eastern Sudano Sahel (ESS) in wet and dry years. Rainfall observations from Climate Research Unit (CRU) and Climate Prediction Center (CPC) Merged Analysis of Precipitation (CMAP), and atmospheric circulation fields from National Center for Environmental Prediction (NCEP) were evaluated from 1979 to 2014. The objectives are to evaluate the trends across the zones and their linear relationship with the identified oceanic pulsations, as well as examine the evolution of the anomalous atmospheric circulation associated with the wet and dry years during the wet season months. The results show remarkable variability across the rainfall zones. The areal averaged rainfall anomalies show significant correlation values of -0.2 with Ocean Nino Index (ONI) only on WSS and ESS respectively, whereas with South Atlantic Ocean Dipole Index (SAODI) it shows significant correlation value of 0.3 only on GC, at 95% Confidence Level from a t-test. The analysis of trends in spatial and temporal patterns of the atmospheric circulation fields has extensively presented attributes associated with the wet seasonal rainfall anomalies in the wet and dry years. FGOALS-s2 model showed an outstanding simulation of the spatial and temporal patterns of these attributes, with the discrepancies noted, hence presenting itself as a viable tool in the prediction of seasonal rainfall extremes over West Africa.
Cite this paper: Okoro, U. , Chen, W. , Chineke, C. and Nwofor, O. (2017) Anomalous Atmospheric Circulation Associated with Recent West African Monsoon Rainfall Variability. Journal of Geoscience and Environment Protection, 5, 1-27. doi: 10.4236/gep.2017.512001.
References

[1]   FAO (2008) Water and the Rural Poor. Interventions for Improving Livelihoods in Sub-Saharan Africa. Food and Agriculture Organization of the United Nations, 93.

[2]   IAASTD (2009) Agriculture at a Crossroads. Sub-Saharan Africa (SSA) Report. International Assessment of Agricultural Knowledge, Science and Technology for Development, 147.

[3]   Linard, C., Gilbert, M., Snow, R.W., Noor, A.M. and Tatem, A.J. (2012) Population Distribution, Settlement Patterns and Accessibility across Africa in 2010. PLoS ONE, 7, e31743.
https://doi.org/10.1371/journal.pone.0031743

[4]   Bayo Omotosho, J. (1985) The Separate Contributions of Squall Lines, Thunderstorms and the Monsoon to the Total Rainfall in Nigeria. International Journal of Climatology, 5, 543-552.
https://doi.org/10.1002/joc.3370050507

[5]   Abiodun, B.J., Pal, J.S., Afiesimama, E.A., Gutowski, W.J. and Adedoyin, A. (2008) Simulation of West African Monsoon Using RegCM3 Part II: Impacts of Deforestation and Desertification. Theoretical and Applied Climatology, 93, 245-261.
https://doi.org/10.1007/s00704-007-0333-1

[6]   Burpee, R.W. (1972) The Origin and Structure of Easterly Waves in the Lower Troposphere of North Africa. Journal of the Atmospheric Sciences, 29, 77-90.
https://doi.org/10.1175/1520-0469(1972)029<0077:TOASOE>2.0.CO;2

[7]   Reed, R.J., Norquist, D.C. and Recker, E.E. (1977) The Structure and Properties of African Wave Disturbances as Observed during Phase III of GATE. Monthly Weather Review, 105, 317-333.
https://doi.org/10.1175/1520-0493(1977)105<0317:TSAPOA>2.0.CO;2

[8]   Thorncroft, C.D. (1995) An Idealized Study of African Easterly Waves. III: More Realistic Basic States. Quarterly Journal of the Royal Meteorological Society, 121, 1589-1614.
https://doi.org/10.1002/qj.49712152706

[9]   Pytharoulis, I. and Thorncroft, C.D. (1999) The Low-Level Structure of African Easterly Waves in 1995. Monthly Weather Review, 127, 2266-2280.
https://doi.org/10.1175/1520-0493(1999)127<2266:TLLSOA>2.0.CO;2

[10]   Thorncroft, C.D. and Blackburn, M. (1999) Maintenance of the African Easterly Jet. Quarterly Journal of the Royal Meteorological Society, 125, 763-786.
https://doi.org/10.1002/qj.49712555502

[11]   Hsieh, J.-S. and Cook, K.H. (2008) On the Instability of the African Easterly Jet and the Generation of African Waves: Reversals of the Potential Vorticity Gradient. Journal of the Atmospheric Sciences, 65, 2130-2151.
https://doi.org/10.1175/2007JAS2552.1

[12]   Nicholson, S.E. and Webster, P.J. (2007) A Physical Basis for the Interannual Variability of Rainfall in the Sahel. Quarterly Journal of the Royal Meteorological Society, 133, 2065-2084.
https://doi.org/10.1002/qj.104

[13]   Nicholson, S.E., Barcilon, A.I. and Challa, M. (2008) An Analysis of West African Dynamics Using a Linearized GCM. Journal of the Atmospheric Sciences, 65, 1182-1203.
https://doi.org/10.1175/2007JAS2194.1

[14]   Kalapureddy, M.C.R., Lothon, M., Campistron, B., Lohou, F. and Said, F. (2010) Wind Profiler Analysis of the African Easterly Jet in Relation with the Boundary Layer and the Saharan Heat-Low. Quarterly Journal of the Royal Meteorological Society, 136, 77-91.
https://doi.org/10.1002/qj.494

[15]   Thorncroft, C.D., Parker, D.J., Burton, R.R., Diop, M., Ayers, J.H., Barjat, H., Devereau, S., Diongue, A., Dumelow, R., Kindred, D.R., Price, N.M., Saloum, M., Taylor, C.M. and Tompkins, A.M. (2003) The JET2000 Project: Aircraft Observations of the African Easterly Jet and African Easterly Waves. Bulletin of the American Meteorological Society, 84, 337-351.
https://doi.org/10.1175/BAMS-84-3-337

[16]   Parker, D.J., Burton, R.R., Diongue-Niang, A., Ellis, R.J., Felton, M., Taylor, C.M., Thorncroft, C.D., Bessemoulin, P. and Tompkins, A.M. (2005) The Diurnal Cycle of the West African Monsoon Circulation. Quarterly Journal of the Royal Meteorological Society, 131, 2839-2860.
https://doi.org/10.1256/qj.04.52

[17]   Lavaysse, C., Flamant, C., Janicot, S. and Knippertz, P. (2009) Dynamics and Impacts on Convection of the Intra-Seasonal Variabilities of the West African Heat Low. Quarterly Journal of the Royal Meteorological Society, 136, 142-159.

[18]   Lavaysse, C., Flamant, C., Janicot, S., Parker, D.J., Lafore, J.-P., Sultan, B. and Pelon, J. (2009) Seasonal Evolution of the West African Heat Low: A Climatological Perspective. Climate Dynamics, 33, 313-330.
https://doi.org/10.1007/s00382-009-0553-4

[19]   Cuesta, J., Lavaysse, C., Flamant, C., Mimouni, M. and Knippertz, P. (2010) Northward Bursts of the West African Monsoon Leading to Rainfall over the Hoggar Massif, Algeria. Quarterly Journal of the Royal Meteorological Society, 136, 174-189.
https://doi.org/10.1002/qj.439

[20]   Lafore, J.-P., Flamant, C., Giraud, V., Guichard, F., Knippertz, P., Mahfouf, J.-F., Mascart, P. and Williams, E.R. (2010) Editorial Introduction to the AMMA Special Issue on “Advances in Understanding Atmospheric Processes over West Africa through the AMMA Field Campaign”. Quarterly Journal of the Royal Meteorological Society, 136, 2-7.
https://doi.org/10.1002/qj.583

[21]   Nicholson, S.E. (2013) The West African Sahel: A Review of Recent Studies on the Rainfall Regime and Its Interannual Variability. ISRN Meteorology, 2013, Article ID: 453521.
https://doi.org/10.1155/2013/453521

[22]   Peter, M. and Tetzlaff, G. (1998) The Structure of West African Squall Lines and Their Environmental Moisture Budget. Meteorology and Atmospheric Physics, 39, 74-84.
https://doi.org/10.1007/BF01041933

[23]   Sultan, B. and Janicot, S. (2000) Abrupt Shift of the ITCZ over West Africa and Intra-Seasonal Variability. Geophysical Research Letters, 27, 3353-3356.
https://doi.org/10.1029/1999GL011285

[24]   Lamb, P.J. (1982) Persistence of Subsaharan Drought. Nature, 299, 46-47.
https://doi.org/10.1038/299046a0

[25]   Nicholson, S.E. (1985) Sub-Saharan Rainfall 1981-84. Journal of Climate and Applied Meteorology, 24, 1388-1391.
https://doi.org/10.1175/1520-0450(1985)024<1388:SSR>2.0.CO;2

[26]   Folland, C.K., Palmer, T.N. and Parker, D.E. (1986) Sahel Rainfall and Worldwide Sea Temperature 1901-85. Nature, 320, 602-607.
https://doi.org/10.1038/320602a0

[27]   Rowell, D.P, Folland, C.K., Maskell, K. and Ward, M.N. (1995) Variability of Summer Rainfall over Tropical North Africa (1906-1992): Observations and Modeling. Quarterly Journal of the Royal Meteorological Society, 121, 669-704.

[28]   Fontaine, B. and Janicot, S. (1996) Sea Surface Temperature Fields Associated with West African Rainfall Anomaly Types. Journal of Climate, 9, 2935-2940.
https://doi.org/10.1175/1520-0442(1996)009<2935:SSTFAW>2.0.CO;2

[29]   Ward, M.N. (1998) Diagnosis and Short-Lead Time Prediction of Summer Rainfall in Tropical North Africa at Interannual and Multidecadal Timescales. Journal of Climate, 11, 3167-3191.
https://doi.org/10.1175/1520-0442(1998)011<3167:DASLTP>2.0.CO;2

[30]   Taylor, C.M., Parker, D.J. and Harris, P.P. (2007) An Observational Case Study of Mesoscale Atmospheric Circulations Induced by Soil Moisture. Geophysical Research Letters, 34, L15801.
https://doi.org/10.1029/2007GL030572

[31]   Nicholson, S.E. and Entekhabi, D. (1986) The Quasi-Periodic Behavior of Rainfall Variability in Africa and Its Relationship to the Southern Oscillation. Archives for Meteorology, Geophysics, and Bioclimatology, Series A, 34, 311-348.

[32]   Ropelewski, C.F. and Halpert, M.S. (1987) Global and Regional Scale Precipitation Associated with El Nino/Southern Oscillation. Monthly Weather Review, 115, 985-996.
https://doi.org/10.1175/1520-0493(1987)115<1606:GARSPP>2.0.CO;2

[33]   Semazzi, F.H.M., Mehta, V. and Sud, Y.C. (1988) An Investigation of the Relationship between Sub-Saharan Rainfall and Global Sea Surface Temperatures. Atmosphere-Ocean, 26, 118-138.

[34]   Wolter, K. (1989) Modes of Tropical Circulation, Southern Oscillation, and Sahel Rainfall Anomalies. Journal of Climate, 2, 149-172.
https://doi.org/10.1175/1520-0442(1989)002<0149:MOTCSO>2.0.CO;2

[35]   Hastenrath, S. (1990) The Relationship of Highly Reflective Clouds to Tropical Climate Anomalies. Journal of Climate, 3, 353-365.
https://doi.org/10.1175/1520-0442(1990)003<0353:TROHRC>2.0.CO;2

[36]   Nicholson, S.E. and Kim, J. (1997) The Relationship of the El Nino-Southern Oscillation to African Rainfall. International Journal of Climatology, 17, 117-135.
https://doi.org/10.1002/(SICI)1097-0088(199702)17:2<117::AID-JOC84>3.0.CO;2-O

[37]   Moron, V. and Ward, M.N. (1998) ENSO Teleconnections with Climate Variability in the European and African Sectors. Weather, 53, 287-295.
https://doi.org/10.1002/j.1477-8696.1998.tb06403.x

[38]   Joly, M. and Voldoire, A. (2009) Influence of ENSO on the West African Monsoon: Temporal Aspects and Atmospheric Processes. Journal of Climate, 22, 3193-3210.
https://doi.org/10.1175/2008JCLI2450.1

[39]   Zebiak, S.E. (1993) Air-Sea Interaction in Equatorial Atlantic Region. Journal of Climate, 6, 1567-1586.
https://doi.org/10.1175/1520-0442(1993)006<1567:AIITEA>2.0.CO;2

[40]   Wagner, R.G. and Da Silva, A.M. (1994) Surface Conditions Associated with Anomalous Rainfall in the Guinea Coastal Region. International Journal of Climatology, 14, 179-199.
https://doi.org/10.1002/joc.3370140205

[41]   Vizy, E.K. and Cook, K.H. (2001) Mechanisms by Which Gulf of Guinea and Eastern North Atlantic Sea Surface Temperature Anomalies Can Influence African Rainfall. Journal of Climate, 14, 795-821.
https://doi.org/10.1175/1520-0442(2001)014<0795:MBWGOG>2.0.CO;2

[42]   Chang, P., Fang, Y., Saravanan, R., Ji, L. and Seidel, H. (2006) The Cause of the Fragile Relationship between the Pacific El Nino and the Atlantic Nino. Nature, 443, 324-328.
https://doi.org/10.1038/nature05053

[43]   Nnamchi, H.C. and Li, J. (2011) Influence of the South Atlantic Ocean Dipole on West African Summer Precipitation. Journal of Climate, 24, 1184-1197.
https://doi.org/10.1175/2010JCLI3668.1

[44]   Nnamchi, H.C., Li, J.P. and Anyadike, R.N.C. (2011) Does a Dipole Mode Really Exist in the South Atlantic Ocean? Journal of Geophysical Research, 116, D15104.
https://doi.org/10.1029/2010JD015579

[45]   Nnamchi, H.C., Li, J., Kang, I.-S. and Kucharski F. (2013) Simulated Impacts of the South Atlantic Ocean Dipole on Summer Precipitation at the Guinea Coast. Climate Dynamics, 41, 677-694.
https://doi.org/10.1007/s00382-012-1629-0

[46]   Motha, R.P., Leduc, S.K., Steyaert, L.T., Sakamoto, C.M. and Strommen, N.D. (1980) Precipitation Patterns in West Africa. Monthly Weather Review, 108, 1567-1578.
https://doi.org/10.1175/1520-0493(1980)108<1567:PPIWA>2.0.CO;2

[47]   Nicholson, S.E. (1980) The Nature of Rainfall Fluctuations in Subtropical West Africa. Monthly Weather Review, 108, 473-487.
https://doi.org/10.1175/1520-0493(1980)108<0473:TNORFI>2.0.CO;2

[48]   Janowiak, J.E. (1988) An Investigation of Interannual Rainfall Variability in Africa. Journal of Climate, 1, 240-255.
https://doi.org/10.1175/1520-0442(1988)001<0240:AIOIRV>2.0.CO;2

[49]   Fontaine, B., Janicot, S. and Moron, V. (1995) Rainfall Anomaly Patterns and Wind Field Signals over West Africa in August (1958-1989). Journal of Climate, 8, 1503-1510.
https://doi.org/10.1175/1520-0442(1995)008<1503:RAPAWF>2.0.CO;2

[50]   Nicholson, S.E., Some, B. and Kone, B. (2000) An Analysis of Recent Rainfall Conditions in West Africa, Including the Rainy Seasons of the 1997 El Nino and the 1998 La Nina Years. Journal of Climate, 13, 2628-2640.
https://doi.org/10.1175/1520-0442(2000)013<2628:AAORRC>2.0.CO;2

[51]   Le Barbé, L., Lebel, T. and Tapsoba, D. (2002) Rainfall Variability in West Africa during the Years 1950-90. Journal of Climate, 15, 187-202.
https://doi.org/10.1175/1520-0442(2002)015<0187:RVIWAD>2.0.CO;2

[52]   L’Hote, Y., Mahé, G., Somé, B. and Triboulet, J.P. (2002) Analysis of a Sahelian Annual Rainfall Index from 1896 to 2000; the Drought Continues. Hydrological Sciences Journal, 47, 563-572.
https://doi.org/10.1080/02626660209492960

[53]   Li, J. and Zeng, Q. (2003) A New Monsoon Index and the Geographical Distribution of the Global Monsoon. Advances in Atmospheric Sciences, 20, 299-302.
https://doi.org/10.1007/s00376-003-0016-5

[54]   Ali, A. and Lebel, T. (2009) The Sahelian Standardized Rainfall Index Revisited. International Journal of Climatology, 29, 1705-1714.
https://doi.org/10.1002/joc.1832

[55]   Lebel, T. and Ali, A. (2009) Recent Trends in the Central and Western Sahel Rainfall Regime (1990-2007). Journal of Hydrology, 375, 52-64.
https://doi.org/10.1016/j.jhydrol.2008.11.030

[56]   Nicholson, S.E. (1981) Rainfall and Atmospheric Circulation during Drought Periods and Wetter Years in West Africa. Monthly Weather Review, 109, 2191-2208.
https://doi.org/10.1175/1520-0493(1981)109<2191:RAACDD>2.0.CO;2

[57]   Nicholson, S.E. (1986) The Spatial Coherence of African Rainfall Anomalies: Interhemispheric Teleconnections. Journal of Climate and Applied Meteorology, 25, 1365-1381.
https://doi.org/10.1175/1520-0450(1986)025<1365:TSCOAR>2.0.CO;2

[58]   Eltahir, E.A.B. and Gong, C. (1996) Dynamics of Wet and Dry Years in West Africa. Journal of Climate, 9, 1030-1042.
https://doi.org/10.1175/1520-0442(1996)009<1030:DOWADY>2.0.CO;2

[59]   Janicot, S., Harzallah, A., Fontaine, B. and Moron, V. (1998) West-African Monsoon Dynamics and Eastern Equatorial Atlantic and Pacific SST Anomalies (1970-88). Journal of Climate, 11, 1874-1882.
https://doi.org/10.1175/1520-0442-11.8.1874

[60]   Long, M., Entekhabi, D. and Nicholson, S.E. (2000) Interannual Variability of Rainfall, Water Vapor Flux, and Vertical Motion over West Africa. Journal of Climate, 13, 3827-3841.
https://doi.org/10.1175/1520-0442(2000)013<3827:IVIRWV>2.0.CO;2

[61]   Nicholson, S.E. and Grist, J.P. (2001) A Conceptual Model for Understanding Rainfall Variability in the West African Sahel on Interannual and Interdecadal Timescales. International Journal of Climatology, 21, 1733-1757.
https://doi.org/10.1002/joc.648

[62]   Dai, A.D., Lamb, P.J., Trenberth, K.E., Hulme, M., Jones, P.D. and Xie, P. (2004) The Recent Sahel Drought Is Real. International Journal of Climatology, 24, 1323-1331.
https://doi.org/10.1002/joc.1083

[63]   Sanogo, S., Fink, A.H., Omotosho, J.A., Ba, A., Redl, R. and Ermert, V. (2015) Spatio-Temporal Characteristics of the Recent Rainfall Recovery in West Africa. International Journal of Climatology, 35, 4589-4605.
https://doi.org/10.1002/joc.4309

[64]   Mitchell, T.D. and Jones, P.D. (2005) An Improved Method of Constructing a Database of Monthly Climate Observations and Associated High-Resolution Grids. International Journal of Climatology, 25, 693-712.
https://doi.org/10.1002/joc.1181

[65]   Xie, P. and Arkin, P.A. (1997) Global Precipitation: A 17-Year Monthly Analysis Based on Gauge Observations, Satellite Estimates, and Numerical Model Outputs. Bulletin of the American Meteorological Society, 78, 2539-2558.
https://doi.org/10.1175/1520-0477(1997)078<2539:GPAYMA>2.0.CO;2

[66]   Okoro, U.K., Chen, W., Chineke, C. and Nwofor, O. (2014) Comparative Analysis of Gridded Datasets and Gauge Measurements of Rainfall in the Niger Delta Region. Research Journal of Environmental Sciences, 8, 373-390.
https://doi.org/10.3923/rjes.2014.373.390

[67]   Kalnay, E., Kanamitsu, M., Kistler, R., Collins, W., Deaven, D., Gandin, L., Iredell, M., Saha, S., White, G., Woollen, J., Zhu, Y., Leetmaa, A., Reynolds, R., Chelliah, M., Ebisuzaki, W., Higgins, W., Janowiak, J., Mo, K.C., Ropelewski, C., Wang, J., Jenne, R. and Joseph, D. (1996) The NCEP/NCAR 40-Year Reanalysis Project. Bulletin of the American Meteorological Society, 77, 437-471.
https://doi.org/10.1175/1520-0477(1996)077<0437:TNYRP>2.0.CO;2

[68]   Kanamitsu, M., Ebisuzaki, W., Woollen, J., Yang, S.-K., Hnilo, J.J., Fiorino, M. and Potter, G.L. (2002) NCEP-DOE AMIP-II Reanalysis (R-2). Bulletin of the American Meteorological Society, 83, 1631-1643.
https://doi.org/10.1175/BAMS-83-11-1631

[69]   Bosilovich, M.G., Junye, C., Robertson, F.R. and Adler, R.F. (2008) Evaluation of Global Precipitation in Reanalyses. Journal of Applied Meteorology and Climatology, 47, 2279-2299.
https://doi.org/10.1175/2008JAMC1921.1

[70]   Diedhiou, A., Janicot, S., Viltard, A., de Felice, P. and Laurent, H. (1999) Easterly Wave Regimes and Associated Convection over West Africa and the Tropical Atlantic: Results from NCEP/NCAR and ECMWF Reanalyses. Climate Dynamics, 15, 795-822.
https://doi.org/10.1007/s003820050316

[71]   Poccard, I., Janicot, S. and Camberlin, P. (2000) Comparison of Rainfall Structures between NCEP/NCAR Reanalysis and Observed Data over Tropical Africa. Climate Dynamics, 16, 897-915.
https://doi.org/10.1007/s003820000087

[72]   Janicot, S., Trzaska, S. and Poccard, I. (2001) Summer Sahel-ENSO Teleconnection and Decadal Time Scale SST Variations. Climate Dynamics, 18, 303-320.
https://doi.org/10.1007/s003820100172

[73]   Sultan, B. and Janicot, S. (2003) The West African Monsoon Dynamics. Part II: The “Preonset” and “Onset” of the Summer Monsoon. Journal of Climate, 16, 3407-3427.
https://doi.org/10.1175/1520-0442(2003)016<3407:TWAMDP>2.0.CO;2

[74]   Zhou, T., Chen, X., Dong, L., Wu, B., Man, W., Zhang, L., Lin, R., Yao, J., Song, F. and Zhao, C. (2014) Chinese Contribution to CMIP5: An Overview of Five Chinese Models’ Performances. Journal of Meteorological Research, 28, 481-509.
https://doi.org/10.1007/s13351-014-4001-y

[75]   Bao, Q., Lin, P., Zhou, T., Liu, Y., Yu, Y., Wu, G., He, B., He, J., Li, L., Li, J., Li, Y., Liu, H., Qiao, F., Song, Z., Wang, B., Wang, J., Wang, P., Wang, X., Wang, Z., Wu, B., Wu, T., Xu, Y., Yu, H., Zhao, W., Zheng, W. and Zhou, L. (2013) The Flexible Global Ocean-Atmosphere-Land System Model, Spectral Version 2: FGOALS-s2. Advances in Atmospheric Sciences, 30, 561-576.
https://doi.org/10.1007/s00376-012-2113-9

[76]   Taylor, K.E., Stouffer, R.J. and Meehl, G.A. (2012) An Overview of CMIP5 and the Experiment Design. Bulletin of the American Meteorological Society, 93, 485-498.
https://doi.org/10.1175/BAMS-D-11-00094.1

[77]   Huang, B., Banzon, V.F., Freeman, E., Lawrimore, J., Liu, W., Peterson, T.C., Smith, T.M., Thorne, P.W., Woodruff, S.D. and Zhang, H.M. (2015) Extended Reconstructed Sea Surface Temperature Version 4 (ERSST. v4). Part I: Upgrades and Intercomparisons. Journal of Climate, 28, 911-930.
https://doi.org/10.1175/JCLI-D-14-00006.1

[78]   Janicot, S. (1992) Spatiotemporal Variability of West African Rainfall. Part 1: Regionalizations and Typings. Journal of Climate, 5, 489-497.
https://doi.org/10.1175/1520-0442(1992)005<0489:SVOWAR>2.0.CO;2

[79]   Ba, M.B., Frouin R. and Nicholson, S.E. (1995) Satellite-Derived Interannual Variability of West African Rainfall during 1983-88. Journal of Applied Meteorology, 34, 411-431.
https://doi.org/10.1175/1520-0450(1995)034<0411:SDIVOW>2.0.CO;2

[80]   Afiesimama, E.A., Pal, J.S., Abiodun, B.J., Gutowski, W.J. and Adedoyin, A. (2006) Simulation of West African Monsoon Using the RegCM3. Part I: Model Validation and Inter Annual Variability. Theoretical and Applied Climatology, 86, 23-37.
https://doi.org/10.1007/s00704-005-0202-8

[81]   Lamptey, B.L. (2008) Comparison of Gridded Multisatellite Rainfall Estimates with Gridded Gauge Rainfall over West Africa. Journal of Applied Meteorology and Climatology, 47, 185-205.
https://doi.org/10.1175/2007JAMC1586.1

[82]   Sultan, B., Janicot, S. and Diedhiou, A. (2003) The West African Monsoon Dynamics. Part I. Documentation of Intra-Seasonal Variability. Journal of Climate, 16, 3389-3406.
https://doi.org/10.1175/1520-0442(2003)016<3389:TWAMDP>2.0.CO;2

[83]   Bock, O., Bouin, M.N., Doerflinger, E., Collard, P., Masson, F., Meynadier, R., Nahmani, S., Koite, M., Gaptia Lawan Balawan, K., Didé, F., Ouedraogo, D., Pokperlaar, S., Ngamini, J.-B., Lafore, J.-P., Janicot, S., Guichard, F. and Nuret, M. (2008) West African Monsoon Observed with Ground-Based GPS Receivers during African Monsoon Multidisciplinary Analysis (AMMA). Journal of Geophysical Research, 113, D21105.
https://doi.org/10.1029/2008JD010327

[84]   Couvreux, F., Guichard, F., Bock, O., Lafore, J.-P. and Redelsperger, J.-L. (2009) Monsoon Flux Pulsations over West Africa Prior to the Monsoon Onset. Quarterly Journal of the Royal Meteorological Society, 136, 160-174.

[85]   Guichard, F., Kergoat, L., Mougin, E., Timouk, F., Baup, F., Hiernaux, P. and Lavenu, F. (2009) Surface Thermodynamics and Radiative Budget in the Sahelian Gourma: Seasonal and Diurnal Cycles. Journal of Hydrology, 375, 161-177.
https://doi.org/10.1016/j.jhydrol.2008.09.007

[86]   Druyan, L.M., Feng, J., Cook, K.H., Xue, Y., Fulakeza, M., Hagos, S.M., Konar, A., Moufouma-Okia, W., Rowell, D.P., Vizy, E.K. and Ibrah, S.S. (2010) The WAMME Regional Model Intercomparison Study. Climate Dynamics, 35, 175-192.
https://doi.org/10.1007/s00382-009-0676-7

[87]   Xue, Y., De Sales, F., Lau, W., Boone, A., Feng, J., Dirmeyer, P., Guo, Z., Kim, K., Kitoh, A., Kumar, V., Poccard-Leclercq, I., Mahowald, N., Moufouma-Okia, W., Pegion, P., Rowell, D., Schemm, J., Schubert, S., Sealy, A., Thiaw, W., Vintzileos, A., Williams, S. and Wu, M. (2010) Intercomparison and Analyses of the Climatology of the West African Monsoon in the West African Monsoon Modeling and Evaluation Project (WAMME) First Model Intercomparison Experiment. Climate Dynamics, 35, 3-27.
https://doi.org/10.1007/s00382-010-0778-2

[88]   Moron, V., Robertson, A.W. and Ward, M.N. (2006) Seasonal Predictability and Spatial Coherence of Rainfall Characteristics in the Tropical Setting of Senegal. Monthly Weather Review, 134, 3248-3262.
https://doi.org/10.1175/MWR3252.1

[89]   Oguntunde, P.G., Abiodun, B.J. and Lischeid, G. (2011) Rainfall Trends in Nigeria, 1901-2000. Journal of Hydrology, 411, 207-218.
https://doi.org/10.1016/j.jhydrol.2011.09.037

[90]   Nnamchi, H.C. and Li, J. (2016) Floods and Droughts along the Guinea Coast in Connection with the South Atlantic Dipole. In: Li, J., Swinbank, R., Grotjahn, R. and Volkert, H., Eds., Dynamics and Predictability of Large-Scale High-Impact Weather and Climate Events, Cambridge University Press, Cambridge, UK, 271-279.
https://doi.org/10.1017/CBO9781107775541.023

[91]   Flohn, H. and Korff, H.C. (1965) Studies on the Water Vapor Transport over North Africa: Bonner Meteorologische Abhandlungen, Vol. 6. Meteorologishes Institüt der Universitat Bonn, Germany, 36.

[92]   Trenberth, K.E. and Guillemot, C.J. (1996) Physical Processes Involved in the 1988 Drought and 1993 Floods in North America. Journal of Climate, 9, 1288-1298.
https://doi.org/10.1175/1520-0442(1996)009<1288:PPIITD>2.0.CO;2

[93]   Zhou, T.-J. and Yu, R.-C. (2005) Atmospheric Water Vapor Transport Associated with Typical Anomalous Summer Rainfall Patterns in China. Journal of Geophysical Research, 110, D08104.
https://doi.org/10.1029/2004JD005413

[94]   Park, J.-S., Jhun, J.-G. and Lee, E.-J. (2009) Characteristic Large-Scale Circulation Anomalies Associated with Persistent Features of Extreme Precipitation over Northeast Asia from Premonsoon Season to Monsoon Season. Journal of Geophysical Research, 114, D11108.
https://doi.org/10.1029/2008JD011031

[95]   IFRC (1999) International Federation of Red Cross and Red Crescent Societies—WEST AFRICA FLOODS (Appeal 26/99)—Situation Report 1.
http://www.ifrc.org/docs/appeals/99/269901.PDF

[96]   Banacos, P.C. and Schultz, D.M. (2005) The Use of Moisture Flux Convergence in Forecasting Convective Initiation: Historical and Operational Perspectives. Forecaster’s Forum. Weather and Forecasting, 20, 351-366.
https://doi.org/10.1175/WAF858.1

[97]   Viste, E. and Sorteberg, A. (2013) Moisture Transport into the Ethiopian Highlands. International Journal of Climatology, 33, 249-263.
https://doi.org/10.1002/joc.3409

[98]   Leroux, S., Hall, N.M.J. and Kiladis, G.N. (2010) A Climatological Study of Transient-Mean-Flow Interactions over West Africa. Quarterly Journal of the Royal Meteorological Society, 136, 397-410.
https://doi.org/10.1002/qj.474

[99]   Janicot, S. (1994) The Recent West African Rainfall Variability through Empirical and Modelling Investigations. In: Desbois, M. and Désalmand, F., Eds., Global Precipitations and Climate Change. NATO ASI Series (Series I: Global Environmental Change), Vol. 26, Springer, Berlin, Heidelberg, 135-149.
https://doi.org/10.1007/978-3-642-79268-7_7

[100]   Couvreux, F., Guichard, F., Bock, O., Campistron, B., Lafore, J.-P. and Redelsperger, J.-L. (2010) Synoptic Variability of the Monsoon Flux over West Africa Prior to the Onset. Quarterly Journal of the Royal Meteorological Society, 136, 159-173.
https://doi.org/10.1002/qj.473

[101]   Sathiyamoorthy, V., Pal, P.K. and Joshi, P.C. (2007) Intraseasonal Variability of the Tropical Easterly Jet. Meteorology and Atmospheric Physics, 96, 305-316.
https://doi.org/10.1007/s00703-006-0214-7

[102]   Knaff, J.A. (1997) Implications of Summertime Sea Level Pressure Anomalies in the Tropical Atlantic Region. Journal of Climate, 10, 789-804.
https://doi.org/10.1175/1520-0442(1997)010<0789:IOSSLP>2.0.CO;2

[103]   Pu, B. and Cook, K.H. (2010) Dynamics of the West African Westerly Jet. Journal of Climate, 23, 6263-6276.
https://doi.org/10.1175/2010JCLI3648.1

 
 
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