Investigating the diurnal cycle of precipitation over Central Africa

AbstractThe present study investigated the reliability of downscaling tool RegCM4.4 to simulate 2002–2006 June–September diurnal cycle precipitation characteristics. Besides their diurnal cycles, the spatial and temporal patterns in precipitation intensity, amount and frequency over Central Africa (CA) are investigated. Diurnal variance, phase and amplitude based on 3‐hourly model simulations are obtained by diurnal harmonics from each 24‐h period. Two statistical measures are used to evaluate model performance: the root mean square error and the index of agreement. The result shows that the RegCM outputs are well simulated compared with reference data in revealing the temporal and spatial patterns of precipitation amount and frequency over the continental area with some systematic wet biases over Cameroon highlands area. Diurnal variability of precipitation frequency and amount are properly well reproduced by the model with an afternoon peak around 1800 LST over entire domain except Atlantic Ocean sub‐region. The model does not properly describe the observed diurnal variation of precipitation intensity over the study area. One of the prominent results is that the pattern of precipitation frequency is quite similar to that of precipitation amount. This strong relationship between these two precipitation characteristics over the entire region of interest suggests that the diurnal precipitation variability is generally determined by how often it rains

Spatiotemporal Variability, Trends, and Potential Impacts of Extreme Rainfall Events in the Sudano-Sahelian Region of Cameroon

The Sudano-Sahelian region of Cameroon is mainly drained by the Benue, Chari, and Logone rivers; which are very useful for water resources; especially for irrigation, hydropower generation, and navigation. Long-term changes in mean and extreme rainfall events in the region may be of crucial importance in understanding the impacts of climate change. Daily and monthly rainfall data from fifteen climate stations in the study area from 1980 to 2018 and measurements from the Expert Team on Climate Change Detection and Indices (ETCCDI) were estimated using the non-parametric innovative trend analysis (ITA) and the Sen slope estimator. The precipitation concentration index (PCI), the precipitation concentration degree (PCD), and the precipitation concentration period (PCP) were used to explore the spatiotemporal variations in the characteristics of rainfall concentrations. The results showed complex spatial patterns of the annual average PCI values across the Sudano-Sahelian region; which varied from values lower in the south to higher in the far north, which were the characteristic of seasonality and a strong seasonal precipitation distribution throughout the year; respectively. The PCD results revealed that the annual rainy days in a year decreased from the south to the far north. Additionally, the PCP results indicated a slightly later occurrence of precipitation. A significant trend toward more intense–extreme rainfall events was observed in most parts of the study area, but a significant trend toward more humid days was observed in the southeastern part. Trends in dry days significantly increased in the central and southwestern parts of the study area. This could mean that the prevalence of flood and drought risks are higher in the study area. Overall, the increase in annual rainfall could benefit the hydro-power sector, agricultural irrigation, the availability of potable water sources, and food security

Consequences of 1.5 degrees C and 2 degrees C global warming levels for temperature and precipitation changes over Central Africa

Discriminating climate impacts between 1.5 °C and 2 °C warming levels is particularly important for Central Africa, a vulnerable region where multiple biophysical, political, and socioeconomic stresses interact to constrain the region's adaptive capacity. This study uses an ensemble of 25 transient Regional Climate Model (RCM) simulations from the CORDEX initiative, forced with the Representative Concentration Pathway (RCP) 8.5, to investigate the potential temperature and precipitation changes in Central Africa corresponding to 1.5 °C and 2 °C global warming levels. Global climate model simulations from the Coupled Model Intercomparison Project phase 5 (CMIP5) are used to drive the RCMs and determine timing of the targeted global warming levels. The regional warming differs over Central Africa between 1.5 °C and 2 °C global warming levels. Whilst there are large uncertainties associated with projections at 1.5 °C and 2 °C, the 0.5 °C increase in global temperature is associated with larger regional warming response. Compared to changes in temperature, changes in precipitation are more heterogeneous and climate model simulations indicate a lack of consensus across the region, though there is a tendency towards decreasing seasonal precipitation in March–May, and a reduction of consecutive wet days. As a drought indicator, a significant increase in consecutive dry days was found. Consistent changes of maximum 5 day rainfall are also detected between 1.5 °C vs. 2 °C global warming levels