Inter-Annual Variability Of Rainfall In Some States Of Southern Nigeria

Abstract: The study inter-annual variability of rainfall in some states in Southern Nigeria focuses on analyzing the trends and fluctuations in annual rainfall over six states in Southern Nigeria, covering a period of 1972 � 2012. In order to ascertain the variability�s, and to model the annual rainfall for future prediction to enhance policy implementation, the quantitative and descriptive analysis techniques was employed. The rainfall series were analyzed for fluctuations using Standardized Anomaly Index (SAI), whereas the trends were examined using Statistical Package for Social Science Software (SPSS 17.0). At 95 percent confidence level, observations in the stations may be signals that the wetter period dominates the drier periods in this study. Each of the series contains two distinct periods when the rainfall anomalies (negative and positive) of a particular type were most significant. The period where the annual rainfall is above one standard deviation from the mean annual rainfall is considered Wet, and the period below one standard deviation from the mean annual rainfall is considered Dry for each station. The results of the linear trend lines revealed an increase in rainfall supply over the period of study especially of recent. The annual rate of increase in rainfall over the period of investigation 1972 - 2012 were; 15.21mm/year for Calabar, 2.18mm/year for Port Harcourt, 22.23mm/year for Owerri, 3.25mm/year for Benin City, 5.08mm/year for Enugu, and 16.29mm/year for Uyo respectively. The variability in amount of annual rainfall revealed that, in 2012 Calabar received the highest amount of rainfall of about 4062.70mm and the least value of 2099.4mm in 1973. In Porthacourt, the highest amount of rainfall occurred in 1993 with a value of 3911.70mm and the least value in 1983 with a value of 1816.4mm. Owerri recorded the highest amount of rainfall of about 3064.0mm in 2011, and the least value occurred in 1986 with a value of 1228.4mm. In 1976, Benin received the highest amount in rainfall of 2435.5mm and the least value of 1190.7mm occurred in 1983. Enugu received 2262.4mm as the highest amount of rainfall in 1997 and the least occurred in 1981 with a value of 913.10mm. From the period of investigation, Uyo received 3172.9mm as the highest amount of rainfall in 2011 and the least value of 1562mm in 1983. The predicted values for the modeled data suggests continues increase in amount of annual rainfall in all the locations. From the cumulative mean deviation graphs, Calabar and Uyo indicate a tendency towards flood, while the other stations reveal a tendency towards drought.

REFERENCES

[1] Acheampong, P.K (1987). Rainfall characteristics over African Sahel. The Nigerian example. Singapore Journal of tropical Geography. Pp8, pp72-83.

[2] Ati, O. F, Stigter, C. J, Iguisi,E.O, and Afolayan, J. O (2009). Profile of rainfall changes and variability in the Northern Nigeria, 1953-2002. Research Journal of Environmental and Earth Sciences, 1(2), 58-63

[3] Afangideh, A. I, Francis, E. O, Eje, E.I (2010). A preliminary investigation into the annual rainfall trend and pattern for selected towns in part of South-eastern Nigeria.

[4] British Meteorological Office 1990.

[5] Bowden, D. J. (1980). Rainfall in Sierra Leone. Singapore Journal of Tropical Geography. 1(2): 35 � 38.

[6] Emerson, Brandon (2005). �Raindrop modeling� web.28Apr.2010..

[7] Ewona, I.O and Udo, S.O (2008) characteristics pattern of rainfall in Calabar, Nigeria- a tropical location Nigeria. Nigeria Journal of physics 20(1), 84-91.

[8] Ewona, I. O. and Udo, O. (2009). Seasonal long-term rainfall trend in Cal, Nigeria Global Journal of Pure and Applied Sciences. Vol. 15(2): 247 � 245.

[9] Gregory, S. (1989). The changing fre. Of drought in India, 1871 � 1995. The Geographical Journal. 155(3): 322 � 324.

[10] Haylock , M.& Nicholls, N. 1998. Royal meteorological society, 8, 67.

[11] Hess T.M,Stephen,W & mayan, U.M (1995). Rainfall trends in the north east and zone of Nigeria 1961-1990. Agriculture and forest meterology 74, (1-2), 87-89.

[12] Kandji, S.T, Verchot, L, and Mackensen, J (2006). Climate change and variability in the Sahel region: impacts and adaptation strategies in the agricultural sector. World Agro forestry Centre (ICRAF)/ United Nations Environmental Programme (UNEP). Retrieved February 13, 2009 from http//www.unep.org/themes/freshwater/documents/pdf/climatewww.cpc.ncep.noaa.gov/products/analysis_monitoring/regional_monitoring/palmer.giff.

[13] Karl, T.R, Derr, V.R, Easterting, D.R, Folland, C.K,Hofmann, D,J, Levitus, S., Nicholls, N., Parker, D.E, Wittee, G.W. (1995b). critical issues for long term climate monitory. Climate change, 31, 185-221.

[14] Lamb, H.H. (1968). The changing climate, Methuen,London.

[15] Mcilveen, R. (1992). Fundamentals of weather and climate. Chanpman and Hall(London), 1992. ISBN 0-442-314760.

[16] Mckee, T. J, Doesken, N. J, Kleist, J (1993). The relationship of drought frequencyand duration to timescale. Preprints 8th conference on Applied climatology, Anaheim 17-22 January pp 179-184.

[17] Obot, N. I.; Chendo, M. A.; Odu, S. O. and Ewona, I. O. (2010). Evaluation of rainfall trend in Nigeria for 30 yrs (1978 - 2007). International Journal of the Physical science. Vol. 5(4): 2217 � 2224.

[18] Oladipo, E. O (1995). Some statistical characteristics of drought and variations inthe Savanna region of Nigeria. Journal of Applied Climatology 50 (3-4): 147-155.

[19] Olaniran, O.J (1991b). Rainfall anomaly patterns in the wet and dry years over Nigeria. International Journal of Climatology vol. 11, pp177-204.

[20] Oladipo, E. (2008). Climate change and sustainable livelihoods: Greening options for Nigeria. Report of the first national environmental summit. Theme : Greening the environment for sustainable development. 96-112. Federal ministry of environment , housing and urban development.

[21] Oladipo, E.O. (1993). Some aspects of the spatial characteristics of drought innorthern Nigeria. Natural Hazards. 8, 171-188. Netherlands : Kluwer Academic publisher.

[22] Osang, Jonathan Eyire, Obi, Emmanuel O. And Ewona, Igwe O; Evaluation Of The Effect Of Workshop/Laboratory Accidents And Precautionary Steps Towards Safety Practice. Iosr Journal Of Electronics And Communication Engineering (Iosr-Jece) E-Issn:2278-2834, P-Issn:2278-8735. Volume 6 Issue 3 (May=June 2013) Pp 16-22. Www.Iosrjournal.Org

[23] Osang, J. E, Obi E.O, Ewona, I.O Udoimuk A.B, Nnwankukwu. (2013) Review Of Gas Flaring Activities In Niger Delta Area of Nigeria. International Journal Of Scientific & Engineering Research, Volume 4, Issue 9, September-2013 971issn 2229-5518 Http://Www.Ijsetr.Org.

[24] Osang. J. E.1, Ewona, I.O, Obi E. O., Udoimuk A,B, Kamgba F.A.,(2013); Analyses Of Radiation and Rainfall Pattern In Kano State Northern Nigeria (1978-2007), International Journal Of Scientific & Engineering Research, Volume 4, Issue 9, September-2013 971issn 2229-5518 : Http://Www.Ijser.Org.

[25] Osang, J. E., Udoimuk, A. B., Etta, E. B., Ushie, P. O., Offiong N. E. Methods Of Gathering Data For Research Purpose And Applications Using Ijser Acceptance Rate Of Monthly Paper Publication (March 2012 Edition-May 2013 Edition) Iosr Journal Of Computer Engineering (Iosr-Jce) E-Issn: 2278-0661, P- Issn: 2278-8727volume 15, Issue 2 (Nov. - Dec. 2013), Pp 59-65 Www.Iosrjournals.Org

[26] Obi, E. O., Osang, J. E., Ewona, I. O., Udoimuk A. B., Kamgba, F. A. (2013):, Environmental Health Effect And Air Pollution From Cigarette Smokers In Cross River State, Nigeria; Iosr Journal Of Applied Physics (Iosr-Jap) E-Issn: 2278-4861. Volume 4, Issue 6 (Sep. - Oct. 2013), Pp 61-68; Www.Iosrjournal.Org

[27] Ryan C. Rankin (2005). �Bubble Resonance.� The physics of bubbles, antibubbles, and all that. Retrieved 2006-12-09

[28] Seelye, C. J(1940). Variability of annual rainfall in New Zealand. N.Z.J. Science Tech. 22B (1): 18-21.

[29] S.O. Udo, O.E. Ani and K. Oduro-Afrive; effect of moisture and bulk density on soil temp; Global journal of pure & applied science vol. 8, No.1 Jan. 2002. 125-132.

[30] Sharon E. Nichlson (2000) � The nature of rainfall variability over Africa on time scales of decades to millennia. Florida state university, Tallahassee FL 32306, USA.

[31] Smith, B. I.; Burton, R.; Klein, J. T. and Wandel, J. (2000). An Anatomy of adaptation to climate change and variability climate change. 45: 223 � 251.

[32] Tope, O. S. (2013). Changing rainfall patterns in Nigeria and global warming in special report. Vanguard News paper.

[33] Trenberth, K.E, Jones, P.D, Ambenje, P, Bojariu, R Eastherling, D, Klein Tank A. and Zhai, P(2007). Observations: surface and atmospheric climate change. In Solomon, S. Qin, D. Manning, M, Chen, Z, Marquis, M, Averyt, K.B. Tignor.

[34] United Nations Framework Convention on climate change, UNFCCC. (2007). Climate change: Impacts, vulnerabilities and adaptation in developing countries. Retrieved June 22, 2011 from htt://unfccc.int/resource/does/publications/impacts.pdf

[35] United Nations Framework Convention on Climate Change (UNFCCC) 1992, www.unfcc.int.