Global Journal of Science Frontier Research, H: Environment & Earth Science, Volume 21 Issue 6

David (2010) observed in southern Nigeria that at the onset and end of rainy season, the rains are in the form of heavy showers of short duration, staring with maximum intensity of up to 75mm/hour and more, declining the intensity after about 30 minutes when the sun gives way to a steady downpour with a lower intensity of about 12.5mm/hour and less. The amount of rainfall has also been show to be at variance with intensity. For instance, David (2010) found that rainfall intensity is not associated with amount or number of raindrop size. The intensity and time period of the rainfall event determine the amount of rainfall in an area at a time and the average amount of rainfall in an area over years, sum up to the mean annual rainfall of the area. Also with the spread of rainfall characteristics, the productivity of the area may be determined. The nature of rainfall over northern Nigeria is highly variable and the variability includes rainfall amount, time and duration, intensities and spatial coverage. According to the Nigeria Meteorological Agency (NIMET, 2012), Nigeria’s climate is characterized by strong latitudinal zone with which becomes progressively drier as one moves northwards from the coast. Rainfall is the key climatic variable and there is a marked difference between the wet and dry seasons in most areas. Rainfall characteristics in Nigeria have been examined for dominant trend notably by (IPCC, 2014). II. M aterials and M ethods a) Types and Sources of Data The types of data required and used were mostly secondary data. The annual rainfall and temperature data of Lafia station for the period of 2001 to 2015 covering a 15 years period. The data was obtained from Nigeria Meteorological Agency (NIMET, 2015) in Lafia. The data on crop yield were data collected from documented crop output by the Nasarawa Agricultural development Project (NADP) Lafia for the period of 2001 to 2015. b) Method of Data Analysis The study employed the annual rainfall variability and annual temperature patterns and annual yam yield were analyzed using Pearson correlation, linear regression, ANOVA, and coefficients Beta for the period of 15 years (2001-2015). III. R esults and D iscussion a) Mean Rainfall, Average Minimum And Maximum Temperature Trend In Nasarawa State Table 1: Annual rainfall data, average minimum and maximum temperature data (2001-2015) S/No. Average Min. Temperature Average Max. Temperature Mean Rainfall (Mm) Years Total Rainfall (Mm) 1. 21.96 33.97 117.86 2001 1414.1 2. 22.16 34.34 99.39 2002 1192.7 3. 22.52 34.3 117.23 2003 1406.8 4. 22.24 33.93 108.75 2004 1305 5. 22.83 34.27 107.55 2005 1290.7 6. 23.03 34.58 109.99 2006 1319.9 7. 21.05 34.76 132.97 2007 1595.7 8. 20.93 35.06 94.83 2008 1138 9. 23.13 34.84 132.97 2009 1595.7 10. 24.09 34.67 110.16 2010 1322 11. 22.58 34.03 104.46 2011 1253.6 12. 22.58 33.63 110.39 2012 1324.7 13. 23.06 33.61 104.91 2013 1259 14. 22.73 37.13 111.00 2014 1332 15. 23.88 33.71 105.08 2015 1261 Culled: Nigerian Meteorological Agency, Lafia (NIMET, 2001-2015) Table 1 give the detailed account of the rainfall variability trend in Nasarawa State. The annual rainfall amount portrays an increasing trend at the first year and a decreasing trend in the second year. There was an increase in annual rainfall from 2000 to 2010 followed by a slight decrease in 2002 of 1192.7mm. An increase in the amount of annual rainfall in Nasarawa state was then recorded in 2003. Then a decrease is recorded between 2004 and 2005 respectively. The amount of rainfall increase again in year 2006 and 2007 from 1319.9mm to 1595.7mm respectively. In the second decade, the amount of rainfall increase again in year 2009 while a fall occurred in 2010. The annual rainfall experience increase as from 2014-2015. It is obvious from the graph, that rainfall indeed experienced a number of variations over the period under consideration (2001-2015) with the highest rainfall (1595.7mm) occurring in 2009. This means that even though rainfall seems to be increasing over the period, the trend of increase is generally, gradual. This gives an indication of an increase in rainfall in the stud area. The implication of the inter-annual rainfall analysis shows that the increase in rainfall in the district has the potential to affect crops which do not need abundant rainfall. Analysis of Rainfall and Temperature Patterns on Yam Yield in Lafia, Nasarawa State, Nigeria © 2021 Global Journals 1 Global Journal of Science Frontier Research Volume XXI Issue VI Year 2021 36 ( H ) Version I