This study evaluates the ability of three Regional Climate Models (RCMs) used in Coordinated Regional Climate Downscaling Experiment (CORDEX) to simulate the characteristics of rainfall pattern during the West Africa Summer Monsoon from 1998 to 2008 The seasonal climatology, annual rainfall cycles, and wind fields of the RCMs output were assessed over three homogenous subregions and validated using precipitation data from eighty-one (81) ground observation stations and TRMM satellite data Furthermore, the ability of the RCMs to simulate response to El Nino and La Nina events was assessed Results show that two of the RCMs (RCA and REMO) simulated the main features of the rainfall climatology and associated dynamics over the three subregions (Guinea Coast, Savannah, and Sahel) of West Africa The RCMs also capture the African Easterly Jet (AEJ) and Tropical Easterly Jet (TEJ) with little variations in position and intensity Analysis shows significant biases in individual models depending on subregion and season under consideration which may be attributed to strong cyclonic circulation observed at 850 mb pressure level In general, the study shows RCA and REMO fairly simulate West Africa rainfall adequately and can therefore be used for the assessment of West African Summer Monsoon and future climate projections

/pdf/assessing-the-capabilities-of-three-regional-climate-models-1tck8jo9qk.pdf

Assessing the Capabilities of Three Regional Climate Models over CORDEX Africa in Simulating West African Summer Monsoon Precipitation

The work described in this paper was supported by the European Commission (EC) Education, Audiovisual and Cultural Executive Agency (EACEA) Erasmus Mundus scholarship. The authors also gratefully appreciate the Information Management School of the Universidade Nova de Lisboa (NOVA IMS), Department of Geoinformatics at the University of Munster and Universitat Jaume I.

/pdf/geospatial-analysis-of-extreme-weather-events-in-nigeria-1vd9nz2ewx.pdf

Geospatial Analysis of Extreme Weather Events in Nigeria (1985–2015) Using Self-Organizing Maps

Accurately predicting precipitation trends is vital in the economic development of a country. Ground observed data from the Nigeria Meteorological Agency (NIMET) was analyzed to study the long-term spatio-temporal trends of rainfall on annual and seasonal scales for 23 stations in Nigeria during a 40-year period spanning from 1974 to 2013. After testing the presence of autocorrelation, Mann–Kendall (modified Mann–Kendall) test was applied to non-autocorrelated (autocorrelated) series to detect the trends in rainfall data. Theil and Sen’s slope estimator test was used to find the magnitude of change over a time period. Pettitt’s test, Standard Normal Homogeneity Test, and Buishand’s test were further used to test the homogeneity of the rainfall series. The results show an increasing trend in annual rainfall; however, only nine stations have a significant increase during the period of study. On the seasonal time scale, a significant increasing trend was observed in the pre- and post-monsoon seasons, while only nine stations show a significant increasing trend in monsoon rainfall and a significant decreasing trend in the winter rainfall over the last 40 years. During the study period, 15.4 and 13.90 % increase were estimated for annual and monsoonal rainfall, respectively. Furthermore, seven stations exhibit changes in mean rainfall while majority of the stations considered (Eighteen stations) exhibit homogeneous trends in annual and seasonal rainfall over the country. The performance of the different tests used in this study was consistent at the verified significance level.

Recent homogeneity analysis and long-term spatio-temporal rainfall trends in Nigeria

The paper aimed at assessing the capabilities and limitations of five different precipitation products to describe rainfall over West Africa. Five gridded precipitation datasets of the Tropical Rainfall Measurement Mission (TRMM) Multi-Platform Analysis (TMPA 3B43v7); University of Delaware (UDEL version 3.01); Climatic Research Unit (CRU version 3.1); Global Precipitation Climatology Centre (GPCC version 7) and African Rainfall Climatology (ARC version 2) were compared and validated with reference ground observation data from 81 stations spanning a 19-year period, from January 1990 to December 2008. Spatial investigation of the precipitation datasets was performed, and their capability to replicate the inter-annual and intra-seasonal variability was also assessed. The ability of the products to capture the El Nino and La Nina events were also assessed. Results show that all the five datasets depicted similar spatial distribution of mean rainfall climatology, although differences exist in the total rainfall amount for each precipitation dataset. Further analysis shows that the three distinct phases of the mean annual cycle of the West Africa Monsoon precipitation were well captured by the datasets. However, CRU, GPCC and UDEL failed to capture the little dry season in the month of August while UDEL and GPCC underestimated rainfall amount in the Sahel region. Results of the inter-annual precipitation anomalies shows that ARC2 fail to capture about 46% of the observed variability while the other four datasets exhibits a greater performance (r > 0.9). All the precipitation dataset except ARC2 were consistent with the ground observation in capturing the dry and wet conditions associated with El Nino and La Nina events, respectively. ARC2 tends to overestimate the El Nino event and failed to capture the La Nina event in all the years considered. In general GPCC, CRU and TRMM were found to be the most outstanding datasets and can, therefore, be used for precipitation assessment over West Africa.

Comparison of five gridded precipitation products at climatological scales over West Africa

The objective of this study was to identify potential runoff storage zones based on the various physical characteristics of the Vishwamitri watershed using a GIS-based conceptual framework that com...

https://www.tandfonline.com/doi/pdf/10.1080/19475683.2020.1733083

GIS-based multi criteria decision making method to identify potential runoff storage zones within watershed

This study investigates rainfall and temperature variabilities in Nigeria using observations of air temperature (oC) and rainfall (mm) from 25 synoptic stations from 1971-2000 (30years). The data were analyzed for the occurrences of abrupt changes in temperature and rainfall values over Nigeria while temporal and spatial trends were also investigated. Statistical approach was deployed to determine the confidence levels, coefficients of kurtosis, skewness and coefficient of variations. Analysis of air temperature indicated that in the first decade of 1971-1980 anomalies between -0.2 and -1.6 were predominant, in the second decade of 1981-1990, only five stations (Lokoja, Kaduna, Bida, Bauchi and Warri) shows positive anomaly while greater portion of the country were normal with evidence of warming in the third decade of 1991-2000. Results further indicated that there have been statistically significant increases in precipitation and air temperature in vast majority of the country. Analyses of long time trends and decadal trends in the time series further suggest a sequence of alternately decreasing and increasing trends in mean annual precipitation and air temperature in Nigeria during the study period.

Analysis of Rainfall and Temperature Variability over Nigeria

The Sahelian West Africa (Long 20W:20E, Lat 0:30N) by its climatological and geographical conditions is a key region for the characterization of global atmospheric aerosol optical properties This study evaluates the spatial and temporal variation of the Aerosol Optical Depth (AOD440nm), aerosol particle size characterization (Angstrom exponent (I±440-675nm) at four locations (Agoufou, Banizoumbou, Cape Verde and Ilorin) over a period of January 2005 to December 2009 Results of the day-to-day AOD440nm variations as well as the seasonal and annual variations are presented in order to establish the aerosol climatology in the region We compared satellite derived data of Total Ozone Mapping Spectrometer - Aerosol Index (TOMSAI), MODIS (Terra and Aqua) with those of ground-based Sunphotometer AERONET measurements In general, there exits good relationship between MODIS (Terra and Aqua) and the ground-based AERONET measurements with correlation coefficients, R2 â€o 08 reported in all stations However low coefficients (as low as 040) were obtained in all the stations for regressions between TOMS AI and ground-based Sunphotometer AERONET data

Ogunjobi K.O

Papers

Analysis of Rainfall and Temperature Variability over Nigeria

Multiyear Analysis of Ground-Based Sunphotometer (AERONET) Aerosol Optical Properties and Its Comparison with Satellite Observations over West Africa

Projected changes in wind energy potential using CORDEX ensemble simulation over West Africa