Wilfried M. PokamUniversity of Yaounde I | UY1 · Department of Physics
Wilfried M. Pokam
PhD
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54
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Publications (54)
The time-varying September-November relationship between the Indian Ocean Dipole (IOD) and Central African (CA) rainfall has strengthened since the 1990s, implying an increasing IOD influence over CA rainfall. Using observational and reanalysis datasets covering the 1980–2016 period, this study examines the CA circulation response associated with t...
This study examines the skill of the North American Multi-Model Ensemble (NMME) seasonal precipitation forecast and the influence of tropical sea surface temperature (SST) anomalies and their teleconnections on precipitation prediction skill over Central Africa (CA). The skill is assessed for December–February (DJF), March–May (MAM), June–August (J...
The Working Group II contribution to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) provides a comprehensive assessment of the scientific literature relevant to climate change impacts, adaptation and vulnerability. The report recognizes the interactions of climate, ecosystems and biodiversity, and human societie...
Climate models are vital to the assessment of the impacts of climate change in the Central African regions. Establishing how well models reproduce key processes is important to the confidence we attach to these tools. This study examines model representation of the September to November characteristics, such as location and intensity, of the Africa...
We evaluate and compare the simulation of the main features (low-level westerlies (LLWs) and the Congo basin (CB) cell) of low-level circulation in Central Equatorial Africa (CEA) with eight climate models from Phase 6 of the Coupled Model Intercomparison Project (CMIP6) and the corresponding eight previous models from CMIP5. Results reveal that, a...
The synoptic precipitation variability over Central Africa (CA) in the March-to-May (MAM) and September-to-November (SON) seasons is investigated in this study. The composite analysis is used to highlight the evolution of synoptic precipitation, related convection, and dynamic fields. Composite analysis findings show that synoptic precipitation ano...
Although climate models are important for making projections of future climate, little attention has been devoted to model simulation of the complex climate of Central Africa (CA). This study investigates rainfall biases through processes in three versions of the Met Office Unified Model over CA with both coupled and atmosphere‐only formulations fo...
Jusqu'ici, très peu d'attention est accordée à l’étude du climat de l'Afrique centrale, à tel point que de nombreux concepts, qui y sont appliqués, ont été importés d'autres régions du globe. Cette étude met en exergue les informations trompeuses dues à la vision simpliste des mécanismes régissant par exemple le régime pluviométrique annuel, un con...
Les produits pluviométriques quotidiens (3B42) et mensuels (3B43) de Tropical Rainfall Measuring Mission (TRMM) sont évalués par rapport aux observations des stations météorologiques synoptiques au Cameroun et selon les principales zones agroclimatiques. Pour atteindre cet objectif, des métriques déterministes et catégorielles ont été utilisées, ai...
The Tropical Rainfall Measuring Mission (TRMM) daily (3B42) and monthly (3B43) rainfall products are evaluated relative to synoptic weather station observations in Cameroon and according to the main agro‐climatic regions. In order to achieve this goal, deterministic and categorical metrics were used, as well as interannual variability and seasonal...
Less attention is given to the study of the central African climate, such that many concepts were imported from other regions of the globe. This study underlines misleading information due to the simplistic view of mechanisms driving annual rainfall regime based on the intertropical convergence zone concept, and presents recent advances in regional...
Using both observational and reanalysis datasets, this study examines the influence of extreme Indian Ocean Dipole (IOD) events on Central Africa (CA) rainfall from September to December over the period 1980–2016. It is shown that during extreme positive IOD events (hereafter pIOD), CA experiences enhanced moisture supply from the Indian Ocean that...
With the recurrence of extreme weather events in Central Africa, it becomes imperative to provide high-resolution forecasts for better decision-making by the Early warning systems. This study assesses the performance of the Weather Research and Forecasting (WRF) model to simulate heavy rainfall that affected the city of Douala in Cameroon during 19...
This chapter assesses multiple lines of evidence to evaluate past, present and future changes in the global water cycle. It complements material in Chapters 2, 3, and 4 on observed and projected changes in the water cycle, and Chapters 10 and 11 on regional climate change and extreme events. The assessment includes the physical basis for water cycl...
Outputs from 25 regional climate models within the coordinated regional downscaling experiments—Africa are used to assess the impacts of the 1.5°C and 2°C global warming levels (GWLs) over Madagascar. A robust increase in the annual mean temperature ranging from 0.9°C to 1.2°C (1.3°C–1.8°C) is projected in the 1.5°C (2°C) GWL. The west and southwes...
The interannual variations in the intraseasonal oscillations (ISO) activity have long been investigated in different geographical areas around the world. However, Central Africa (CA) remains a serious gap in climate variability studies, especially at intraseasonal timescales because very few of these studies focused on this region. In this paper, w...
A comprehensive study on the anomalous propagation (AP) conditions occurring over the central and west African stations was made from 2 years (January 2005-December 2006) high-resolution data measured by GPS (Global Positioning System) radio survey observations. Through data quality control and diagnostic analysis, the probability of AP occurrence...
This paper investigates the performance of 10 Regional Climate Models (RCMs) hindcasts from the Coordinated Regional Climate Downscaling Experiments (CORDEX) over Central Africa, covering the period 1998–2008 and performed over a common model grid spacing 0.44° ( ∼50 km). Multiple observational data sets are used to evaluate model performances over...
The African Easterly Jet South (AEJ-S) is an important feature of the central African mid tropospheric circulation and has been identified as a key contributor to convection over the region. This study uses 21-year (1983–2003) Reanalysis data sets of ERA-Interim, NCEP2 and MERRA2 to establish mechanisms related to AEJ-S dynamics. Results demonstrat...
In this study, an analysis of present day climate simulation (1998–2008) is presented for the Central African (CA) region with the COnsortium for Small‐scale MOdelling in CLimate Mode (CCLM) regional climate model, forced by the ERA‐Interim (ERAINT) reanalysis data. The ability of the CCLM to simulate the observed precipitation with particular focu...
Climate models provide a key component of climate risk information. However, it is difficult to use climate model output for Africa due to model biases and/or limited understanding of how models represent African regions.
Most climate models are developed outside of Africa, whilst many experts in African weather and climate have limited access to...
In this paper, daily characteristics of the Central Africa rainfall are
assessed using the regional model REMO in the framework of
contributions to the CORDEX-Africa project. The model is used to
dynamically downscale two global climate models (MPI-ESM-LR
and EC-EARTH) for the present (1981–2005) and future
(2041–2065, 2071–2095) climate under the...
This paper studies sensitivity of Standardized Precipitation Index (SPI) to statistical distribution functions used in SPI computation procedure, in order to find out which are more appropriate and to assess SPI shift if using inappropriate distribution functions. Results may explain one of the reasons why spatial SPI computed with unique distribut...
Understanding the processes responsible for precipitation and its future change is important to develop plausible and sustainable climate change adaptation strategies, especially in regions with few available observed data like Congo Basin (CB). This paper investigates the atmospheric circulation processes associated with climate model biases in CB...
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 CO...
In this paper, the regional climate model REMO is used to investigate the added value of downscaling low resolutions global climate models (GCMs) and the climate change projections over Central Africa. REMO was forced by two GCMs (EC-Earth and MPI-ESM), for the period from 1950 to 2100 under the Representative Concentration Pathway 8.5 scenario. Th...
Climate models are becoming evermore complex and increasingly relied upon to inform climate change adaptation. Yet progress in model development is lagging behind in many of the regions that need the information most, including in Africa. Targeted model development for Africa is crucial and so too is targeted model evaluation. Assessment of model p...
In this work, the regional climate model REMO is used to investigate the added value of downscaling low resolutions global climate models and the climate change projections over Central Africa.
Ce travail fait un état des lieux de la qualité temporelle et de la densité spatiale des séries pluviométriques du Cameroun, Gabon, Congo, RCA et RDC, en particulier sur la période récente (1973-2014) grâce à la base de données internationale GSOD. Face aux énormes lacunes observées, ces résultats vont permettre d'orienter les choix métrologiques e...
Daily characteristics of precipitation is investigated over Central Africa using REMO model.
Evaluation of CORDEX Regional Climate Models
Fourth Conference on Climate Change and Development in Africa (CCDA-IV)
This paper investigates and characterizes the control mechanisms of the low-level circulation over west equatorial Africa (WEA) using four reanalysis datasets. Emphasis is placed on the contribution of the divergent and rotational circulation to the total flow. Additional focus is made on analyzing the zonal wind component, in order to gain insight...
The characteristics of the main components of the water cycle over Equatorial Central Africa (ECA) were analysed using the 32-year period, spanning from 1968 to 2000, of the National Centers for Environmental Prediction-National Censearch (NCEP-) reanalysis project database. A special emphasis was given to identifying the causes of annual and inter...
The Congo Basin is one of three key convective regions on the planet which, during the transition seasons, dominates global tropical rainfall. There is little agreement as to the distribution and quantity of rainfall across the basin with datasets differing by an order of magnitude in some seasons. The location of maximum rainfall is in the far eas...
A procedure is presented for the computation of equivalent static stability measure in the atmosphere as briefly discussed. The development of the procedure involves empirical formulas for the saturated vapor pressure from Bolton (1980), the equivalent potential temperature, the equivalent stability parameter and the lapse rates for pseudo-adiabati...