Spatial and temporal variation of precipitation in Sudan and their possible causes during 1948–2005

Temporal and spatial patterns of precipitation are essential to the understanding of soil moisture status which is vital for vegetation regeneration in the arid ecosystems. The purposes of this study are (1) to understand the temporal and spatial variations of precipitation in Sudan during 1948–2005 by using high quality global precipitation data known as Precipitation REConstruction (PREC), which has been constructed at the National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Center, and (2) to discuss the relationship between precipitation variability and moisture flux based on the NCEP/NCAR reanalysis data in order to ascertain the potential causes of the spatial and temporal variations of precipitation in the region. Results showed that (1) annual and monthly precipitation in Sudan had great spatial variability, and mean annual precipitation varied from almost nil in the North to about 1500 mm in the extreme Southwest; (2) precipitation of the main rain season, i.e., July, August and September, and annual total precipitation in the central part of Sudan decreased significantly during 1948–2005; (3) abrupt change points were found in the annual, July, August and September in the late 1960s, when precipitation decreased more rapidly than in other periods; and (4) the decreasing precipitation was associated with the weakening African summer monsoon. The summer moisture flux over Sudan tended to be decreasing after the late 1960s which decreased the northward propagation of moisture flux in North Africa. This study provides a complementary view to the previous studies that attempted to explain the Sahel persistent drought and possible causes.

[1]  P. Lamb.  Sub-Saharan rainfall update for 1982: continued drought , 1983 .

[2]  S. Hastenrath,et al.  On the synoptic climatology of summer rainfall over central Sudan , 1969 .

[3]  H. B. Mann.  Nonparametric Tests Against Trend , 1945 .

[4]  C. F. Kossack,et al.  Rank Correlation Methods , 1949 .

[5]  William P. Kustas,et al.  Aerodynamic parameters and sensible heat flux estimates for a semi-arid ecosystem , 2004 .

[6]  Pierre Camberlin,et al.  Comparison of rainfall structures between NCEP/NCAR reanalyses and observed data over tropical Africa , 2000 .

[7]  M. Hulme,et al.  Recent rainfall changes in central Sudan and their physical and human implications , 1984 .

[8]  M. Neil Ward,et al.  Variability of summer rainfall over tropical north Africa (1906–92): Observations and modelling , 1995 .

[9]  D. Entekhabi,et al.  Interannual Variability in Rainfall, Water Vapor Flux, and Vertical Motion over West Africa , 2000 .

[10]  Friedrich-Wilhelm Gerstengarbe,et al.  Estimation of the beginning and end of recurrent events within a climate regime , 1999 .

[11]  John E. Janowiak,et al.  AN investigation of interannual rainfall variability in Africa , 1988 .

[12]  H. Storch,et al.  Analysis of climate variability : applications of statistical techniques : proceedings of an autumn school organized by the Commission of the European Community on Elba from October 30 to November 6, 1993 , 1995 .

[13]  M. Kendall,et al.  Rank Correlation Methods , 1949 .

[14]  K. Cook,et al.  Coupled Model Simulations of the West African Monsoon System: Twentieth- and Twenty-First-Century Simulations , 2006 .

[15]  M. Hulme,et al.  The Tropical easterly Jet and Sudan rainfall: A review , 1989 .

[16]  Sheng Yue,et al.  Applicability of prewhitening to eliminate the influence of serial correlation on the Mann‐Kendall test , 2002 .

[17]  J. Janowiak,et al.  Global Land Precipitation: A 50-yr Monthly Analysis Based on Gauge Observations , 2002 .

[18]  M. Hulme.  Secular changes in wet season structure in central Sudan , 1987, Journal of Arid Environments.

[19]  S. Nicholson.  African drought: Characteristics, causal theories and global teleconnections , 2013 .

[20]  E. Eltahir.  Drought frequency analysis of annual rainfall series in central and western Sudan , 1992 .

[21]  A. Haque.  Climatic changes, desertification and the Republic of Sudan , 1994 .

[22]  M. Hulme.  The changing rainfall resources of Sudan , 1990 .

[23]  Peter J. Lamb,et al.  Persistence of Subsaharan drought , 1982, Nature.

[24]  S. Yue,et al.  Power of the Mann–Kendall and Spearman's rho tests for detecting monotonic trends in hydrological series , 2002 .

[25]  André Berger,et al.  Understanding climate change , 1989 .

[26]  S. Nicholson,et al.  An Analysis of Recent Rainfall Conditions in West Africa, Including the Rainy Seasons of the 1997 El Nino and the 1998 La Nina Years , 2000 .

[27]  P. Lamb.  Case Studies of Tropical Atlantic Surface Circulation Patterns During Recent Sub-Saharan Weather Anomalies: 1967 and 1968 , 1978 .

[28]  S. Nicholson.  The Spatial Coherence of African Rainfall Anomalies: Interhemispheric Teleconnections , 1986 .

[29]  R. E. Livezey,et al.  A Comparison of the NCEP-NCAR Reanalysis Precipitation and the GPCP Rain Gauge-Satellite Combined Dataset with Observational Error Considerations , 1998 .

[30]  Shi Neng,et al.  A preliminary study on the global land annual precipitation associated with ENSO during 1948–2000 , 2002 .

[31]  Chong-Yu Xu,et al.  Statistical Analysis of Parameters and Residuals of a Conceptual Water Balance Model – Methodology and Case Study , 2001 .

[32]  Bernard Fontaine,et al.  Atmospheric water cycle and moisture fluxes in the West African monsoon: mean annual cycles and relationship using NCEP/NCAR reanalysis , 2003 .

[33]  H. Diaz,et al.  Interdecadal change in the Asia–Africa summer monsoon and its associated changes in global atmospheric circulation , 2003 .

[34]  Chong-Yu Xu,et al.  Climate changes and their impacts on water resources in the arid regions: a case study of the Tarim River basin, China , 2010 .

[35]  S. Yue,et al.  A study of variability of annual river flow of the southern African region , 2002 .

[36]  D. Cadet,et al.  Water Vapour Transport Over Africa and the Atlantic Ocean During Summer 1979 , 2007 .

[37]  Hans von Storch,et al.  Misuses of Statistical Analysis in Climate Research , 1995 .

[38]  J. M. Mitchell.  Climatic change : report of a working group of the Commission for Climatology , 1966 .

[39]  T. Palmer.  Influence of the Atlantic, Pacific and Indian Oceans on Sahel rainfall , 1986, Nature.

[40]  Chong-yu Xu,et al.  Spatial and temporal variability of precipitation over China, 1951–2005 , 2009 .

[41]  H. Tao,et al.  Moisture budget variations in the Yangtze River Basin, China, and possible associations with large-scale circulation , 2010 .

[42]  M. Hulme,et al.  Recent rainfall changes and their impact on hydrology and water supply in the semi-arid zone of the Sudan , 1988 .

[43]  P. Camberlin.  June‐september rainfall in north‐eastern Africa and atmospheric signals over the tropics: A zonal perspective , 1995 .

[44]  R. Sneyers.  On the statistical analysis of series of observations. , 1991 .

[45]  A. Shamseldin,et al.  Qualitative rainfall prediction models for central and southern Sudan using El Niño–southern oscillation and Indian Ocean sea surface temperature Indices , 2002 .

[46]  P. Lamb.  Large-scale Tropical Atlantic surface circulation patterns associated with Subsaharan weather anomalies , 1978 .