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This study examines the performance of the outputs of three RCMs (CCLM, REMO, RegCM) that participated in CORDEX phase 2 to dynamically downscaling three CMIP5 GCMs at a resolution of 0.22° × 0.22° in replicating West African rainfall from 1970 to 2005. Using different statistical methods and climatological description at seasonal and annual scale, these nine models, downscaling institution-based ensembles mean (CCLM-ENSEMBLE, REMO-ENSEMBLE, RegCM-ENSEMBLE) and the grand ensemble mean (ENS-RCM), were compared to the ensemble mean (ENS-OBS) of the two observations. In simulating the spatial distribution of mean seasonal rainfall over West Africa, outputs of the three CMIP5 GCMs dynamically downscaled by RegCM and RegCM-ENSEMBLE consistently performed better than other models, just like ENS-RCM with little bias. HadGEM-CCLM, HadGEM-REMO, HadGEM-RegCM, MPI-CCLM, and CCLM-ENSEMBLE showed better performance in replicating annual rainfall cycle evident by the two rainfall peaks simulated over Guinea Coast and a single peak over the Savannah and Sahel, unlike the grand ensemble mean. In MAM and SON seasons, the statistical performance evaluation gives a better agreement between ENS-OBS and most of each model, downscaling institution-based ensemble mean and ENS-RCM with r≥ 0.89. It is further observed that some individual models and ensemble mean from different downscaling institutions outperform the grand ensemble in replicating mean seasonal rainfall over the three climatic zones and entire West Africa in DJF and JJA seasons. Moreover, the annual statistical evaluation revealed a poor performance with low correlation values over the Guinea Coast and better performance over the Sahel by all the models and various ensemble mean. Similar to what is observed with ENS-OBS trend assessment, only MPI-REMO adequately simulates the observed decreasing and increasing trend that is not statistically significant over the south and north of 10° N, respectively. These show that ensemble mean may reduce or amplify uncertainty in climate models. Hence, these results accentuate that using ensemble mean will reduce uncertainty in climate models in projecting rainfall over West Africa and over different periods which may not be necessarily true.

The study validated the use of an updated MCD12Q1 MODIS Land Use Land Cover (LULC) data into Weather Research and Forecasting (WRF) model and investigated the effects of LULC change on the spatiotemporal pattern of dew point temperature (DPT), temperature, precipitation and some associated parameters over West Africa (WA). Series of WRF model simulations were carried out with 6 LULC scenarios, which include Built-up (Bu), Partial Deforest I and II (PDI/PDII), Partial Afforest (PA), Total Afforest (TA) and Total Deforest (TD). MCD12Q1 LULC data was integrated into WRF model to carry out eight simulations from May–September, 2012 at 12 km horizontal resolution over WA. The integration of updated MODIS LU data into WRF model showed improvement with lesser RMSE. The BU and TD scenario generally decreases dew point temperature while the areas with remarkable decrease (increase) in dew point temperature also have a decrease (increase) in evapotranspiration and an increase (decrease) in Sensible Heat (SH). Increased SH could be a factor for the increased precipitation over the urbanized area. All afforestation options decreased the temperature due to weakening of the SH. Afforestation of the Sahel led to an increase in rainfall, which is attributed to increase in ET. Deforestation of the Guinea zone (PDI/PDII) reduced the precipitation in Sahel and Sahel–Sahara interface and the entire area. Only the TA scenario increased precipitation over the Sahel–Sahara interface due to increased ET. The effects of LULC change on precipitation are complex as more in-depth analysis of the effects on major features of the general circulation of WA is recommended for future research.

This study assesses the relative impact of green areas on the surface thermal characteristics of an urban area. From this study, the existence of the Park Cool Island (PCI) around the green areas and surrounding zones of the green area was noted, as surface temperatures were lower at the green areas and higher at the outer boundaries. Agodi gardens had the highest vegetation cover of 62.1% and was the area with the lowest mean surface temperature (26.79 °C), while Agugu green area had the lowest vegetation cover of 20.7% and had the highest mean surface temperature (27.75 °C). Green areas with higher vegetation cover percentages had higher rate of change of PCI with buffer distance compared to the other two green areas that had lower percentages of vegetation cover. The green areas were identified for their cooling roles on surface temperature within the urban centres of Ibadan as the surface temperature intensities were of the order of 1–2 °C lower within the 500-m buffer zone. The findings, therefore, brings to light the need for increased greenery within the urban areas of the city, and also provide information for urban planners and designers on the need for green spaces in mitigating heat island phenomenon in the city.

This study presents results from an investigation of wave energy resources over the mid-Atlantic by using the significant wave height and mean wave period (T_m) data spanning a 37 year (1980–2016) period and derived from the analysis of wave climate predictions generated by the WAVEWATCH-III wind-wave model. The spatiotemporal variations of the wave energy resource are presented and described. Results showed that wave energy is richest (11.5–14 kW/m) in regions such as West Indies, East of Martinique and Guiana basin in the extreme northwestern mid-Atlantic and are therefore ideal locations for the installation of wave power plants for electrical energy generation. Temporal variation revealed that 1992 was a year of relatively rich wave energy in the mid-Atlantic. Also, a characterization of wave energy showed that the wave energy groups 0 ≤ wp ≤ 5 and 5 ≤ wp ≤ 10, prevailed in the mid-Atlantic. Furthermore, spatial trend analysis of the annual and summer mean wave power showed that stronger trends (0.03–0.1 kW/m/year) in both cases, distribute in the southern mid-Atlantic while stronger trends (0.04–0.085 kW/m/year) dominate the northern mid-Atlantic at winter. Temporal trend analysis for the years and seasons showed that wave power exhibits an insignificant trend of approximately 0.022 kW/m/year in the mid-Atlantic.

Background:In recent years the developing world, much of which is located in the tropical countries, has seen dramatic growth of its urban population associated with serious degradation of environmental quality. Climate change is producing major impacts including increasing temperatures in these countries that are considered to be most vulnerable to the impact of climate change due to inadequate public health infrastructure and low income status. However, relevant information and data for informed decision making on human health and comfort are lacking in these countries.Objective:The aim of this paper is to study and compare heat stress conditions in an urban (city centre) and rural (airport) environments in Akure, a medium-sized tropical city in south-western Nigeria during the dry harmattan season (January–March) of 2009.Materials and methods:We analysed heat stress conditions in terms of the mean hourly values of the thermohygrometric index (THI), defined by simultaneous in situair temperature and relative humidity measurements at both sites.Results:The urban heat island (UHI) exists in Akure as the city centre is warmer than the rural airport throughout the day. However, the maximum UHI intensity occurs at night between 1900 and 2200 hours local time. Hot conditions were predominant at both sites, comfortable conditions were only experienced in the morning and evenings of January at both sites, but the rural area has more pleasant morning and evenings and less of very hot and torrid conditions. January has the lowest frequency of hot and torrid conditions at both sites, while March and February has the highest at the city centre and the airport, respectively. The higher frequencies of high temperatures in the city centre suggest a significant heat stress and health risk in this hot humid environment of Akure.Conclusions:More research is needed to achieve better understanding of the seasonal variation of indoor and outdoor heat stress and factors interacting with it in order to improve the health, safety, and productivity of Akure city dwellers.