Predicting the occurrence of surplus and deficit net radiation in Ibadan, Nigeria

Abstract

This study aims at predicting the occurrence of surplus and deficit net radiation in Ibadan, Nigeria. Thirty-four (34) years data (1977-2010) on daily maximum and minimum Relative-Humidity, Solar irradiance and maximum and minimum Air temperature were sourced from the International Institute of Tropical Agriculture (IITA) and used in the analysis. The Penman-Monteith (FAO-56) step by step method was used to compute net radiation in Ibadan. A two – state (surplus and deficit net radiation) Markov Chain model was developed and used in this work. The monthly transition counts, transition probability matrix, n-step transition matrix (power matrix), steady state probability vector and the vector of mean reoccurrence times (in days) were determined each for the two states. The model was also used in predicting the chance occurrence of surplus and deficit net radiation for one year. The average monthly net radiation is surplus (positive) in the months of February, March, April, May, June, October, November and December, while it is deficit (negative) in January, July, August, and September. The study also reveals a 69%, 76%, 76%, 74%, 63%, 63%, 70% and 52% chance occurrence of surplus net radiation in the months of February, March, April, May, June, October, November and December, while a 54%, 64%, 76% and 55% chance of deficit net radiation occurring in the months of January, July, August and September respectively using the Markov Chain model (steady states probabilities). The mean reoccurrences times (in days) analysis reveals that, on the average it takes: 1.4 days for surplus net radiation and 3.5 days for deficit net radiation to reoccur in the months of February, March, April, May, June, October, November and December; 3.9 days for deficit net radiation and 1.3 days for surplus net radiation to reoccur in the months of January, July, August and September. This explains why the air temperature of Ibadan is warmer in the months of February, March, April, May, June, October, November and December, and colder in January, July, August and September. The weather/climate is extremely warm in March and April, and extremely cold in August as revealed by the proportions of surplus and deficit net radiation for each month of the year.