Analysis of some meteorological data for some selected Cities in the Eastern and Southern zone of Nigeria

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1 Africa Joural of Evirometal Sciece ad Techology Vol. 4(2), pp , February, 2010 Available olie at ISSN X 2010 Academic Jourals Full Legth Research Paper Aalysis of some meteorological data for some selected ities i the Easter ad Souther zoe of Nigeria. Augustie* ad M. N. Nabuchi Departmet of Idustrial Physics, Eboyi State Uiversity, Abakaliki, Nigeria. Accepted 4 Jauary, 2010 The mothly mea daily global solar radiatio, sushie duratio hours, maximum temperature, loudiess idex ad relative humidity data for some selected cities i the Easter ad Souther zoe of Nigeria coverig a period of sevetee years ( ) were used to geerate several liear ad multiliear regressio equatios. The values of the solar radiatio estimated by the equatios ad the measured solar radiatio were tested usig the mea bias error (MBE), root mea square error (RMSE) ad mea percetage error (MPE) statistical techiques. The values of the correlatio coefficiet (R) ad coefficiet of correlatio (R 2 ) were also determied for each equatio. The equatios with the highest values of R, R 2 ad least values of MBE, RMSE ad MPE are suitable for predictig global solar radiatio i the Easter ad Souther part of Nigeria. The developed equatios ca be used for estimatig solar radiatio i other locatios with similar geographical iformatio. Key words: loudiess idex, solar radiatio, sushie hours, relative humidity, maximum temperature. INTRODUTION Nigeria is blessed with abudat amout of sushie. It has bee foud that there is a estimated 3,000 h of aual sushie. It is also estimated that Nigeria has over 97,000 rural commuities (Oti, 1995), whose populatio is characterized with deprivatio from covetioal eergy, arisig from poor supply ifrastructure. For istace, about 18% oly of the rural populatio had access to electricity by 1991/1992 (FOS, 1996). Where covectioal eergy is available, its supply is ureliable. The readily available ad widely utilized eergy i the rural areas is the reewable eergy type, particularly fuel wood, agricultural ad aimal wastes, wid eergy ad solar eergy; which are maily used for cookig, cottage idustrial applicatios, wiowig ad ope-to su-dryig process. Mii hydropower ad biogas are yet to be popular, as rural eergy i Nigeria, perhaps due to the more advaced coversio techologies associated with them. Solar radiatio data may be cosidered as a essetial *orrespodig author. emmyaustie2003@yahoo.com. requiremet to coduct feasibility studies for solar eergy systems. The kowledge of solar eergy, preferably gaied over a log period should be useful ot oly to the locality where the radiatio data is collected but for the wider world commuity. I developig coutries such as Ghaa, Idia, Nigeria etc, the facility for global radiatio measuremet is available at a few places while bright sushie hours are measured at may locatios. Some caot eve afford the equipmets ad techiques ivolved. For such coutries it is essetial that correlatios be developed so as to predict global solar radiatio from readily measured data. Several such correlatios already exist for some developig coutries (Ibrahim, 1985; Turto, 1987; Abdalla, 1987; Sambo, 1986; Bakhah et al., 1985; Falayi ad Rabiu, 2005; Sausi ad Aliyu, 2005). This paper is a cotiuatio of the effort to develop predictive techiques for several coutries so as to provide a basis for the future regioal iso-radiatio maps. The paper also developed models which ca be used to predict mothly mea daily global solar radiatio icidet o a horizotal surface i some selected cities i the Easter ad Souther zoe i Nigeria.

2 Augustie ad Nabuchi 093 METHODOLOGY The measured mothly mea daily values of sushie hours, maximum temperature, cloud cover ad relative humidity for the cities of Owerri i Imo State, Eugu i Eugu State, Warri i Delta State ad alabar i ross River State collected from the archives of the Nigeria Meteorological Agecy, Oshodi, Lagos State while the global solar radiatio data were collected courtesy of the Reewable Eergy For Rural Idustrializatio ad Developmet i Nigeria. The four cities beig studied lie o the latitudes ad logitudes (lat N, log E) for Owerri, (lat N, log E) for Eugu, (lat N, log E) for Warri ad (lat N, log E) for Uyo respectively. To develop the models, the global solar radiatio data measured i (Kwhm -2 day -1 ) was coverted to usig a factor of 3.6 proposed by Iqbal (1983). The lier regressio model used i correlatig the measured global solar radiatio data with fractio of sushie is give after Agstrom (1924) ad later modified by Page (1964): = a + b Ο (1) Where; a ad b are regressio costats, is the measured mothly mea daily global radiatio, is the mothly mea extraterrestrial solar radiatio o horizotal surface, give by Iqbal (1983) as follows: 24 π = Ι sceο ws siφ siδ + cosφ cosδ si ws π 180 (2) Ι Where; sc E is the solar costat, Ο is the eccetricity correctio ws is the factor, φ is the latitude, δ is the solar decliatio ad hour agle. The expressios for sc (1983): 1367X 3600 Ι sc = 0000 Ι, EΟ, δ ad ws are give by Iqbal (MJm -2 day 1 ) (3) 360N Ε Ο = OS 365 (4) ( N + ) δ = 23.45Si 365 (5) Where N is the characteristic day umber for each moth. ( ta ta ) 1 ws = os φ δ (6) Other regressio models were obtaied by the modificatio of the Agstrom-Page model. The various meteorological data are related to global solar radiatio. Multiple liear regressio ad correlatio aalysis of five c parameters (,, Τ, ad R ) were employed to estimate the global solar radiatio. Where idex, is the fractio of sushie duratio, c is the clearess Τ is the maximum temperature, is the loudliess idex ad R is the relative humidity. SPSS omputer Software Program was used i evaluatig model parameters. The accuracy of the estimated values were tested by calculatig the Mea Bias Error (MBE), Root Mea Square Error (RMSE) ad Mea Percetage Error (MPE). The expressios for the MBE (MJm - 2 day -1 ), RMSE, ad MPE (%) is stated by El Sebaii ad Trabea (2005) as follows: ( ) ΡΕ = i, cal i, meas / i, cal i, meas / ( ) RSΕ = ΡΕ = i, cal ad i, meas i, cal i, meas Χ / (7) (8) (9) i, meas is the ith calculated (predicted) ad Where measured values ad is the total umber of observatios. Iqbal (1983), Halouai (1993), Almorox et al. (2005) ad he et al. (2007) have recommeded that a zero value for MBE is ideal ad a low RMSE is desirable. The RMSE test provides iformatio o the short-term performace of the studied model as it allows a term by term comparism of the actual deviatio betwee the calculated values ad the measured values. The MPE test gives log term performace of the examied regressio equatios, a positive MPE values provide the averages amout of overestimatio i the calculated values, while the egative values gives uderestimatio. A low value of MPE is desirable by Akpabio ad Etuk (2002). The values of the meteorological data ad global solar radiatio data for the four cities are preseted i Tables 1-4. RESULTS AND DISUSSION The regressio costats a ad b for Owerri, Eugu, Delta ad alabar were determied by correlatig the global solar radiatio with the meteorological data. The values of the regressio costats are foud to be differet from those obtaied by Hussai (2005), Bala

3 094 Afr. J. Eviro. Sci. Techol. Table 1. Meteorological data ad global solar radiatio for Owerri. Moth Τ ( o ) c R Κ Τ = JAN FEB MAR APR MAY JUN JUL AUG SEPT OT NOV DE Table 2. Meteorological data ad global solar radiatio for Eugu. Moth Τ ( o ) c R Κ Τ = JAN FEB MAR APR MAY JUN JUL AUG SEPT OT NOV DE (2001), Burari ad Sambo (2001), Awachie ad Okeke (1990), Akpabio ad Etuk (2002), Fagbele (1990), Badamus ad momoh (2005) etc. These differeces suggest that regressio coefficiets associated with sushie hours ad other meteorogical data chages with latitude ad atmospheric coditios. The sum of the regressio coefficiets (a+b) is iterpreted as the trasmissivity of the atmosphere for global solar radiatio uder perfectly clear sky coditios (Revfei, 1983). Similarly the itercept a is iterpreted as the trasmissivity of a overcast atmosphere. It is therefore importat to examie the regressio relatio we have developed ad compare it with others i terms of the value of the atmospheric trasmissivity uder clear skies, which compares favourably with the figure of reported for the tropics (Turto, 1987). I geeral the clear sky trasmissivity of most tropical, regios seems to lie betwee (Ibrahim, 1985; Turto, 1987; Abdalla, 1987; Sambo, 1986; Bakhah et al., 1983). A close examiatio of Tables 5-6 show that the maximum values of the fractio of sushie occurred i the moth of November. These values are withi what is expected of a tropical site (Exell, 2000; Okogbue ad Adedoku, 2005). The moth of occurrece is ot expected because of the harmatta seaso whe aersol mass loadig greatly reduces the itesity of solar radiatio (Babatude, 2001) ad (Babatude ad Aro, 2000). However it should be oted that isolatio istrumet records hours of bright sushie whe solar radiatio flux desity is above the threshold value of 210 Wm -2. Hece durig the moth of November a very high mea daily sushie hours is obtaied because it has a high clear-

4 Augustie ad Nabuchi 095 Table 3. Meteorological data ad global solar radiatio for Warri. Moth Τ ( o ) c R Κ Τ = JAN FEB MAR APR MAY JUN JUL AUG SEPT OT NOV DE Table 4. Meteorological data ad global solar radiatio for Uyo. Moth Τ ( o ) c R Κ Τ = JAN FEB MAR APR MAY JUN JUL AUG SEPT OT NOV DE ess idex. Tables 5-8 cotai summaries of various liear regressio aalyses, obtaied from the applicatio of equatio (1) to the mothly mea value for the five variables uder study. It is clear that the correlatio coefficiet R, coefficiet of determiatio R 2, MBE (MJ/m 2 /day), RMSE (MJ/m 2 /day) ad MPE (%) vary from oe variable to aother variable. It was observed that combiatio of sushie hours, maximum temperature, cloudiess idex ad relative humidity gave better results (Tables 5-8). Figures 1-4 show a remarkable agreemet betwee the observed ad predicted values of global solar radiatio. For better aalysis the developed correlatio will be cosidered that has high value of correlatio coefficiet R ad coefficiet of correlatio R 2. From Tables 5-8, based o the highest values of correlatio coefficiet, coefficiet of determiatio ad least values of MBE, RMSE ad MPE, the followig equatios: = , = , = ,

5 096 Afr. J. Eviro. Sci. Techol. Table 5. Regressio equatios ad statistical idicators for Owerri. Equatios R R 2 MBE RMSE MPE = Ο = Τ Ο R = Ο c = = Τ Ο Table 6. Regressio equatios ad statistical idicators for Eugu. Equatios R R 2 MBE RMSE MPE = + Ο = Τ R = Ο c = = Τ Ο Table 7. Regressio equatios ad statistical idicators for Warri. Equatios R R 2 MBE RMSE MPE = Ο = Τ R = c = + =

6 Augustie ad Nabuchi 097 Table 8. Regressio equatios ad statistical idicators for Uyo. Equatios R R 2 MBE RMSE MPE = + Ο = Τ R = c = = G l o b a l s o l a r ra d i a ti o (M J / m 2 / d a y ) Moth of the year Measured SR Predicted SR Figure 1. omparism betwee the measured ad predicted global solar radiatio for Owerri. = Are the best regressio equatios suitable for estimatig global solar radiatio i Owerri, Eugu, Delta ad Uyo respectively. oclusio SPSS computer software program was used to develop several liear ad multiliear regressio equatios for some selected cities i the Easter ad Souther part of Nigeria. Based o the values of the correlatio coefficiet ad coefficiet of determiatio ad least values of MBE, RMSE ad MPE, the equatios: = , = ,

7 098 Afr. J. Eviro. Sci. Techol. G lo b a l s o l a r ra d ia tio (M J /m 2 /d a y ) Moth of the year Measured SR Predicted SR Figure 2. omparism betwee the measured ad predicted global solar radiatio for Eugu. Figure 3. omparism betwee the measured ad predicted global solar radiatio for Warri. = ad = have bee foud suitable for predictig the mothly mea daily solar radiatio i Owerri, Eugu, Warri ad Uyo respectively. The derived data ad correlatio will provide a useful source of iformatio to desigers of reewable eergy ad air-coditioig systems for these areas. It would also erich the Natioal Eergy data bak. osequetly, the work should be exteded to other zoes of the

8 Augustie ad Nabuchi 099 Figure 4. omparism betwee the measured ad predicted global solar radiatio for Uyo. coutry. AKNOWLEDGEMENTS The authors wish to express their gratitude to the maagemet ad staff of the Nigeria Meteorological Agecy, Oshodi, Lagos for their kidess i supplyig the data for sushie hours for this work ad the Reewable Eergy for Rural Idustrializatio ad Developmet i Nigeria for makig the solar radiatio data available. REFERENES Abdalla YAG (1987). Solar radiatio over Doha (Qatar). It. J. Solar Eergy, 5: 1-9. Agstrom AS (1924). Solar Terr. Radiat. Meteorol. Soc., 50: Almorox J, Beito M, Hotoria (2005). Estimatig of Mothly Agstrom Prescott quatio coefficiets from measured daily data i Toledo, Spai. Reewable Eergy Jourey 30: Akpabio LE, Etuk SE (2002). Relatioship betwee solar radiatio ad sushie duratio for Oe Nigeria. Turk. J. Phys. 27: Awachie IRN, Okeke E (1990). New Empirical Solar Model ad its use i predictig solar Irradiatio, NJST, 9: Bala EJ (2001). Aalysis of some meteorological data for four cities i the North wester zoe of Nigeria. Nig. J. Reewable Eergy 9: Badamus IB, Momoh M (2005). omparism of Models for Estimatig Mothly Average Daily Isolatio o a horizotal surface. 41 st Sciece Associatio Nigeria coferece, Sokoto, April. Burari FW, Sambo AS (2001). Model for the predictio of global solar for Bauchi usig Meteorological Data, Niger. J. Reewable Eergy 91: Bakhah H, Sriivasa V, Bahel V (1985). orrelatio betwee hourly diffuse ad global solar radiatio for Dhahram, Saudi Arabia. Solar Wid Techol. 2: Babatude EB, Aro TD (2000). Variatio characteristics of diffuse solar Radiatio at a tropical statio (llori, Nigeria). Niger. J. Phys. 12: Babatude EB (2001). Determiatio of total wavelegth turbidity ad optical depth of the harmatta dust atmosphere usig total wavelegth trasmittace. Nig. J. Phys. 13: he HZ, Shi GY, Zhag XY, Zhao JQ, Li Y (2007). Aalysis of sky coditio usig 40 years records of solar radiatio data i hia. Theor. Appl. limatol. 89: he AA, Trabea AA (2005). Estimatio of Global Solar Radiatio o Horizotal Surfaces Over Egypt, Egypt. J. Solids, 28: 166. Exell RHB (2000). The itesity of solar radiatio. Kig Mogkut s Uiv. Techol. press Thorburi. Falayi EO, Rabiu AB (2005). Modellig global solar radiatio usig sushie duratio data, Niger. J. Phys. 17: FOS (1996). Aual Abstract of Statistics. Fagbele RO (1990). Estimatio of total solar radiatio i igeria usig Meteorological data. Nig. J. Reewable Eergy, 1: I 10. Ibrahim SMA (1985). Predicted ad measured global solar radiatio i Egypt, Solar Eergy 35: Igbal M (1983). A itroductio to solar radiatio. Academy press. New york. Oti MI (1995). Desig, Maufacture ad Istallatio of Multi-bladed widmill, NJSE 13: Okogbue E, Adedoku JA (2005). The Solar Radiatio limate at a tropical Site, lle-lfe, i South Wester Nigeria. oferece Paper. 28 th Aual oferece. NIP, lle-lfe, Aug Page JK (1964). The estimatio of mothly mea values of daily total short-wave radiatio o vertical ad iclied surfaces from sushie records for latitude 40 0 N 40 0 S. Proceedig UN coferece. New Sources of Eergy. Revfei KJA (1983). A iterpretatio of the coefficiets of the Agstrom equatio. Solar Eergy 31: 415. Sambo AS (1986). Empirical models for the correlatio of global solar radiatio with meteorological data for orther Nigeria. Solar ad wid Techol. 3(2): 89. Sausi YA, Aliyu M (2005). Estimatio of Global Solar Radiatio i Sokoto ad its Eviros Usig Maximum Temperature Data, Niger. Jourey Solar Eergy 15: Turto SMA (1987). The relatioship betwee total irradiatio ad sushie i humid tropics. Solar Eergy 38:

Empirical Models for the Correlation of Global Solar Radiation with Meteorological Data for Enugu, Nigeria.

Empirical Models for the Correlation of Global Solar Radiation with Meteorological Data for Enugu, Nigeria. Empirical Models for the orrelation of Global Solar Radiation with Meteorological Data for Enugu, Nigeria.. Augustine and M.N. Nnabuchi Department of Industrial Physics, Ebonyi State University, Abakaliki,