Abstract
This paper presents the application of Mann-Kendall trend test and Standard Anomaly index onhydro-meteorological variables in the coastal area of Lagos state in order to determine the nature of trend and level of significance. The hydro-meteorological data such as air temperature, relative humidity, wind speed, rainfall and sea level rise were obtained from Nigeria meteorological agency (NIMET) Oshodi, Lagos. Variables such as rainfall, relative humidity, wind speed and sea level rise exhibited positive Kendall’s (S) values indicate upward trend and imply an increase of the parameters over time. However, temperature showed negative Kendall’s (S) which indicates downward trend and implies decrease over time. Sea level rise, rainfall, relative humidity and wind speed has mean statistics Zs of 3.9855, 1.9668, 3.0895 and 2.2553 respectively which are more than 1.96 (test statistics for a significant level of 5% that is (Z 0.025 =1.96), this implies that the upward trend is significance and there is tendency to continue. Temperature has statistic Zs of 0.0309 which is less than 1.96 and implies no significance, thus the reduction may not be noticed. The auto correlation factor values ranges from 0.59 to 0.99 for all the parameters, indicating a good fit. Standard Anomaly index (SIA) results showed that trends for the temperature depicts downward trend with the slope of the trend equations are negative, this implies that temperature has tendency to decrease. Rainfall, relative humidity and sea level rise exhibited upward trend which implies tendency to increase. However, the mean wind speed exhibited upward trend while both maximum and minimum wind speed exhibited downward trend, but not noticeable. It can be inferred that both Mann-Kendall trend test and standard anomaly index showed that there is tendency for trend increase in rainfall, humidity, windspeed and sea level rise, while temperature has tendency to decrease. This could be due to impact of climate variability which can influence flooding pattern in the coastline of Lagos State. Keywords: Climate variables, Mann-Kendall test, Standard Anomaly index, hydro-Meteorological variables, Lagos coast
Highlights
Global climate change is a sensitive subject that affects all key aspects of human existence, the socioeconomic, political and the biophysical environments that dictate the quality of life on the earth
From the review work a range of potential impacts of climate change and variability on the Hydrological regime for various geographic areas has been hypothesized and the Mann-Kendall on-parametric test (MKNT) and Standard Anomaly Index (SAI) was adopted to detect trends observed by most authors
SAI was used to test for the trend and fluctuation of hydro-meteorological parameters in the study of climate change impact on water resources and adaptation strategies in the Sudano- Sahelian Ecological Zone (SSEZ) of Nigeria (Ojoye, 2012)
Summary
Study Area: Adelekan (2009) reported that Lagos is the fifth largest city in the world and is the foremost manufacturing, port city in West Africa, and the hub of business and economic development in Nigeria. This coastal city is situated within latitudes 6o 23’N and 6o 41’ N and longitudes 2o 42’E and 3o 42’E (Figure 1). In addition to the low topography of these barrier islands, some of them such as Ikoyi, Lagos, Victoria Island and Lekki are either fully or partially developed commercial and residential areas and could be said to constitute the most important commercial and residential parts of the country (Nwilo & Onuoha, 1993).
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