Tropical Medicine and Infectious Disease, Jun 6, 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
African Journal of Environmental Science and Technology
The study's primary objective is to evaluate the LMDZ model's capacity to simulate the cyclogenes... more The study's primary objective is to evaluate the LMDZ model's capacity to simulate the cyclogenesis process, interannual variability of cyclone activity, and associated processes in the tropical Atlantic, focusing on the West African coasts to the central tropical Atlantic region. Two main approaches are used. Firstly, the model's ability to capture the interannual variability in Atlantic cyclogenesis activity is examined through seasonal mean. These seasonal average conditions were identified based on ERAI, along with years characterized by strong and low cyclonic activities. Secondly, a more descriptive approach is undertaken, involving the spatiotemporal monitoring of the Hurricane Karl, which originated near the Cape Verdean coasts on September 16th, 2004, until its dissipation. Horizontal sections of the tropospheric layers most sensitive to the cyclonic phenomenon are used to comprehensively track its progress. The results show a significant variability of cyclonic activity in the tropical Atlantic at different time scales, indicating that the period from July to September and the region along the Intertropical Convergence Zone (ITCZ) are favorable for tropical cyclogenesis. It also revealed that the years of high cyclonic activity are mainly characterized by low sea level pressure, strong 850 hPa relative vorticity, high 700 hPa relative humidity, and strong 200 hPa divergence anomalies, whereas the opposite is observed during the low activity years. The LMDZ model performs well in reproducing cyclonic parameters from the surface to the upper troposphere with mean absolute errors being less important from the surface (11%) to the high troposphere (17%). At the synoptic scale, the model accurately replicates hurricane characteristics, including intensity categories, spatial distribution, and trajectories. However, it falls short in accurately representing the genesis phase, such as tropical depression.
Changes in extreme precipitation events show patterns in line with those of the mean change. The ... more Changes in extreme precipitation events show patterns in line with those of the mean change. The models project different changes in water budget over the Sahel region, where the MPI projects an increased deficit in local moisture supply (E < P) whereas the rest of models project a local surplus (E > P). The E-P change is primarily precipitation driven. The precipitation increases over the eastern and/ or central Sahel are attributed to the increase of moisture convergence due to increased water vapor in the boundary layer air column and surface evaporation. On the other hand, the projected dry conditions over the western Sahel are associated with the strengthening of moisture divergence in the upper level (850-300 hPa) combined to both a southward migration of the African Easterly Jet (AEJ) and a weakening of rising motion between the core of the AEJ and the Tropical Easterly Jet.
To ensure continued food security and economic development in Africa, it is very important to add... more To ensure continued food security and economic development in Africa, it is very important to address and adapt to climate change. Excessive dependence on rainfed agricultural production makes Africa more vulnerable to climate change effects. Weather information and services are essential for farmers to more effectively survive the increasing occurrence of extreme weather events due to climate change. Weather information is important for resource management in agricultural production and helps farmers plan their farming activities in advance. Machine Learning is one of the technologies used in agriculture for weather forecasting and crop disease detection among others. The objective of this study is to develop Machine Learning-based models adapted to the context of daily weather forecasting for Rainfall, Relative Humidity, and Maximum and Minimum Temperature in Senegal. In this study, we made a comparison of ten Machine Learning Regressors with our Ensemble Model. These models were ...
On the climate-health issue, studies have already attempted to understand the influence of climat... more On the climate-health issue, studies have already attempted to understand the influence of climate change on the transmission of malaria. Extreme weather events such as floods, droughts, or heat waves can alter the course and distribution of malaria. This study aims to understand the impact of future climate change on malaria transmission using, for the first time in Senegal, the ICTP’s community-based vector-borne disease model, TRIeste (VECTRI). This biological model is a dynamic mathematical model for the study of malaria transmission that considers the impact of climate and population variability. A new approach for VECTRI input parameters was also used. A bias correction technique, the cumulative distribution function transform (CDF-t) method, was applied to climate simulations to remove systematic biases in the Coupled Model Intercomparison Project Phase 5 (CMIP5) global climate models (GCMs) that could alter impact predictions. Beforehand, we use reference data for validation...
nge studies require comprehensive databases to analyze the climate signal, to monitor its evoluti... more nge studies require comprehensive databases to analyze the climate signal, to monitor its evolution, and to predict more accurately future changes. Since complete observations of any continuous process is almost impossible, it is then inevitable to encounter missing information in meteorological databases. The aim of this work is to evaluate the performance of five ($5$) imputation methods: missForest, $k$-nn, ppca, mice and imputeTS. The results show that missForest is the best performing method to handle missing temperature data. In the case of precipitation data, the imputeTS method is the preferred one.
Rural societies in the face of climatic and environmental changes in West Africa, 2017
Introduction The hydrology of the Sudano-Sahelian strip has evolved rapidly in recent decades. We... more Introduction The hydrology of the Sudano-Sahelian strip has evolved rapidly in recent decades. West Africa has experienced strong climatic and environmental changes that have deeply modified the runoff/infiltration/evapotranspiration balance and, as a result, the conditions of flow formation. The observations and scientific progress that have enabled better understanding of the impact of environmental changes on the hydrological cycle can be summarised in the form of several key stages. Durin..
During 15 August through 30 September 2006, ground and aircraft measurements were obtained from a... more During 15 August through 30 September 2006, ground and aircraft measurements were obtained from a multinational group of students and scientists in Senegal. Key measurements were aimed at investigating and understanding precipitation processes, thermodynamic and dynamic environmental conditions, cloud, aerosol and microphysical processes and spaceborne sensors (TRMM, CloudSat/Calipso) validation. Ground and aircraft instruments include: ground based polarimetric radar, disdrometer measurements, a course and a high-density rain gauge network, surface chemical measurements, a 10 m flux tower, broadband IR, solar and microwave measurements, rawinsonde and radiosonde measurements, FA-20 dropsonde, in situ microphysics and cloud radar measurements. Highlights during SOP3 include ground and aircraft measurements of squall lines, African Easterly Waves (AEWs), Saharan Air Layer advances into Senegal, and aircraft measurements of AEWs-including the perturbation that became Hurricane Isaac.
Eight super-pressure balloons floating at constant level between 50 and 80 hPa and three Infra-Re... more Eight super-pressure balloons floating at constant level between 50 and 80 hPa and three Infra-Red Montgolfier balloons of variable altitude (15 hPa daytime, 40-80 hPa night time) have been launched at 22 • S from Brazil in February-May 2004 in the frame of the HIBISCUS project. The flights lasted for 7 to 79 days residing mainly in the tropics, but some of them passed the tropical barrier and went to southern midlatitudes. Compared to the balloon measurements just above the tropical tropopause the ECMWF operational temperatures show a systematic cold bias of 0.9 K and the easterly zonal winds are too strong by 0.7 m/s. This bias in the zonal wind adds to the ECMWF trajectory errors, but they still are relatively small with e.g. about an error of 700 km after 5 days. The NCEP/NCAR reanalysis trajectory errors are substantially larger (1300 km after 5 days). In the southern midlatitudes the cold bias is the same, but the zonal wind bias is almost zero. The trajectories are generally more accurate than in the tropics, but for one balloon a lot of the calculated trajectories end up on the wrong side of the tropical barrier and this leads to large trajectory errors. 1 Introduction This study provides a new intercomparison between the operational ECMWF (and to some extent the NCEP/NCAR reanalysis) data and independent in-situ measurements valid for the southern tropics and extratropics. These new results are important for research studies which depend on the accuracy of assimilations systems such as for example chemical transport studies in the stratosphere do.
African Journal of Environmental Science and Technology
Addressing data incompleteness issues is crucial for reliable climate studies, especially in regi... more Addressing data incompleteness issues is crucial for reliable climate studies, especially in regions like Africa that commonly experience data gaps. This study aims to evaluate the performance of five imputation methods (knn, ppca, mice, imputeTS, and missForest) on meteorological data from stations in Burkina Faso and Senegal. The imputed data is compared with ERA5 reanalysis data to validate its accuracy. Temperature, relative humidity, and precipitation observations from the GSOD dataset (1973-2020) were used, creating subsets with missing rates of 5, 10, 20, 30 and 40%. An evaluation was conducted using the Taylor diagram and Kling-Gupta Efficiency (KGE). The results show a good estimation of temperature and relative humidity time series, with missForest performing the best for handling missing values. Precipitation estimation was less accurate, but there was strong agreement between estimated and observed data. ImputeTS was recommended for precipitation. Spatial consistency between imputed data and ERA5 reanalysis products was found. This research improves the quality of meteorological data, provides essential information about climatic characteristics, and serves as a foundation for climate change and weather modeling studies.
Climate variability is a key factor in driving malaria outbreaks. As shown in previous studies, c... more Climate variability is a key factor in driving malaria outbreaks. As shown in previous studies, climate-driven malaria modeling provides a better understanding of malaria transmission dynamics, generating malaria-related parameters validated as a reliable benchmark to assess the impact of climate on malaria. In this framework, the present study uses climate observations and reanalysis products to evaluate the predictability of malaria incidence in West Africa. Sea surface temperatures (SSTs) are shown as a skillful predictor of malaria incidence, which is derived from climate-driven simulations with the Liverpool Malaria Model (LMM). Using the SST-based Statistical Seasonal Forecast model (S4CAST) tool, we find robust modes of anomalous SST variability associated with skillful predictability of malaria incidence Accordingly, significant SST anomalies in the tropical Pacific and Atlantic Ocean basins are related to a significant response of malaria incidence over West Africa. For the...
The American Journal of Tropical Medicine and Hygiene, 2020
Malaria is a major public health problem in West Africa. Previous studies have shown that climate... more Malaria is a major public health problem in West Africa. Previous studies have shown that climate variability significantly affects malaria transmission. The lack of continuous observed weather station data and the absence of surveillance data for malaria over long periods have led to the use of reanalysis data to drive malaria models. In this study, we use the Liverpool Malaria Model (LMM) to simulate spatiotemporal variability of malaria in West Africa using daily rainfall and temperature from the following: Twentieth Century Reanalysis (20th CR), National Center for Environmental Prediction (NCEP), European Centre for Medium-Range Weather Forecasts (ECMWF) Atmospheric Reanalysis of the Twentieth Century (ERA20C), and interim ECMWF Re-Analysis (ERA-Interim). Malaria case data from the national surveillance program in Senegal are used for model validation between 2001 and 2016. The warm temperatures found over the Sahelian fringe of West Africa can lead to high malaria transmission...
The use of Tropical Rainfall Measuring Mission (TRMM) data is an option for counteracting challen... more The use of Tropical Rainfall Measuring Mission (TRMM) data is an option for counteracting challenge of the lack of ground based observations, particularly in Kayanga/Gêba. This paper undertakes validation of monthly TRMM rainfall estimates before using it to understand the spatial and temporal variability in the Basin. This validation based on application of statistical study, made it possible to obtain interesting results with correlation coefficients varying from 0.92 to 0.96 and Nash indices close to 1. The analysis of the seasonal rainfall pattern shows consistence with ground based observations. The study of the annual cycle reveals that their interannual variability is similar to that of ground based observations. Finally, the interpolation of average monthly rainfall in the basin highlights the NorthSouth rainfall gradient, which shows that the South is wetter than the North, with differences more pronounced in August and September.
Rural societies in the face of climatic and environmental changes in West Africa, 2017
Introduction A serious drought hit West Africa in the 1970s (Nicholson, 1980; Held et al., 2005) ... more Introduction A serious drought hit West Africa in the 1970s (Nicholson, 1980; Held et al., 2005) whose consequences for agriculture—the main activity of the people in the region—made a serious contribution to late development. Rainfall in the Sahel seems to have recovered since the 2000s, although it is not possible to say whether the trend will last during the coming decades (Paeth and Hense, 2004). This period also coincided with warming that probably resulted from the increase in greenhous..
Tropical Medicine and Infectious Disease, Jun 6, 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
African Journal of Environmental Science and Technology
The study's primary objective is to evaluate the LMDZ model's capacity to simulate the cyclogenes... more The study's primary objective is to evaluate the LMDZ model's capacity to simulate the cyclogenesis process, interannual variability of cyclone activity, and associated processes in the tropical Atlantic, focusing on the West African coasts to the central tropical Atlantic region. Two main approaches are used. Firstly, the model's ability to capture the interannual variability in Atlantic cyclogenesis activity is examined through seasonal mean. These seasonal average conditions were identified based on ERAI, along with years characterized by strong and low cyclonic activities. Secondly, a more descriptive approach is undertaken, involving the spatiotemporal monitoring of the Hurricane Karl, which originated near the Cape Verdean coasts on September 16th, 2004, until its dissipation. Horizontal sections of the tropospheric layers most sensitive to the cyclonic phenomenon are used to comprehensively track its progress. The results show a significant variability of cyclonic activity in the tropical Atlantic at different time scales, indicating that the period from July to September and the region along the Intertropical Convergence Zone (ITCZ) are favorable for tropical cyclogenesis. It also revealed that the years of high cyclonic activity are mainly characterized by low sea level pressure, strong 850 hPa relative vorticity, high 700 hPa relative humidity, and strong 200 hPa divergence anomalies, whereas the opposite is observed during the low activity years. The LMDZ model performs well in reproducing cyclonic parameters from the surface to the upper troposphere with mean absolute errors being less important from the surface (11%) to the high troposphere (17%). At the synoptic scale, the model accurately replicates hurricane characteristics, including intensity categories, spatial distribution, and trajectories. However, it falls short in accurately representing the genesis phase, such as tropical depression.
Changes in extreme precipitation events show patterns in line with those of the mean change. The ... more Changes in extreme precipitation events show patterns in line with those of the mean change. The models project different changes in water budget over the Sahel region, where the MPI projects an increased deficit in local moisture supply (E < P) whereas the rest of models project a local surplus (E > P). The E-P change is primarily precipitation driven. The precipitation increases over the eastern and/ or central Sahel are attributed to the increase of moisture convergence due to increased water vapor in the boundary layer air column and surface evaporation. On the other hand, the projected dry conditions over the western Sahel are associated with the strengthening of moisture divergence in the upper level (850-300 hPa) combined to both a southward migration of the African Easterly Jet (AEJ) and a weakening of rising motion between the core of the AEJ and the Tropical Easterly Jet.
To ensure continued food security and economic development in Africa, it is very important to add... more To ensure continued food security and economic development in Africa, it is very important to address and adapt to climate change. Excessive dependence on rainfed agricultural production makes Africa more vulnerable to climate change effects. Weather information and services are essential for farmers to more effectively survive the increasing occurrence of extreme weather events due to climate change. Weather information is important for resource management in agricultural production and helps farmers plan their farming activities in advance. Machine Learning is one of the technologies used in agriculture for weather forecasting and crop disease detection among others. The objective of this study is to develop Machine Learning-based models adapted to the context of daily weather forecasting for Rainfall, Relative Humidity, and Maximum and Minimum Temperature in Senegal. In this study, we made a comparison of ten Machine Learning Regressors with our Ensemble Model. These models were ...
On the climate-health issue, studies have already attempted to understand the influence of climat... more On the climate-health issue, studies have already attempted to understand the influence of climate change on the transmission of malaria. Extreme weather events such as floods, droughts, or heat waves can alter the course and distribution of malaria. This study aims to understand the impact of future climate change on malaria transmission using, for the first time in Senegal, the ICTP’s community-based vector-borne disease model, TRIeste (VECTRI). This biological model is a dynamic mathematical model for the study of malaria transmission that considers the impact of climate and population variability. A new approach for VECTRI input parameters was also used. A bias correction technique, the cumulative distribution function transform (CDF-t) method, was applied to climate simulations to remove systematic biases in the Coupled Model Intercomparison Project Phase 5 (CMIP5) global climate models (GCMs) that could alter impact predictions. Beforehand, we use reference data for validation...
nge studies require comprehensive databases to analyze the climate signal, to monitor its evoluti... more nge studies require comprehensive databases to analyze the climate signal, to monitor its evolution, and to predict more accurately future changes. Since complete observations of any continuous process is almost impossible, it is then inevitable to encounter missing information in meteorological databases. The aim of this work is to evaluate the performance of five ($5$) imputation methods: missForest, $k$-nn, ppca, mice and imputeTS. The results show that missForest is the best performing method to handle missing temperature data. In the case of precipitation data, the imputeTS method is the preferred one.
Rural societies in the face of climatic and environmental changes in West Africa, 2017
Introduction The hydrology of the Sudano-Sahelian strip has evolved rapidly in recent decades. We... more Introduction The hydrology of the Sudano-Sahelian strip has evolved rapidly in recent decades. West Africa has experienced strong climatic and environmental changes that have deeply modified the runoff/infiltration/evapotranspiration balance and, as a result, the conditions of flow formation. The observations and scientific progress that have enabled better understanding of the impact of environmental changes on the hydrological cycle can be summarised in the form of several key stages. Durin..
During 15 August through 30 September 2006, ground and aircraft measurements were obtained from a... more During 15 August through 30 September 2006, ground and aircraft measurements were obtained from a multinational group of students and scientists in Senegal. Key measurements were aimed at investigating and understanding precipitation processes, thermodynamic and dynamic environmental conditions, cloud, aerosol and microphysical processes and spaceborne sensors (TRMM, CloudSat/Calipso) validation. Ground and aircraft instruments include: ground based polarimetric radar, disdrometer measurements, a course and a high-density rain gauge network, surface chemical measurements, a 10 m flux tower, broadband IR, solar and microwave measurements, rawinsonde and radiosonde measurements, FA-20 dropsonde, in situ microphysics and cloud radar measurements. Highlights during SOP3 include ground and aircraft measurements of squall lines, African Easterly Waves (AEWs), Saharan Air Layer advances into Senegal, and aircraft measurements of AEWs-including the perturbation that became Hurricane Isaac.
Eight super-pressure balloons floating at constant level between 50 and 80 hPa and three Infra-Re... more Eight super-pressure balloons floating at constant level between 50 and 80 hPa and three Infra-Red Montgolfier balloons of variable altitude (15 hPa daytime, 40-80 hPa night time) have been launched at 22 • S from Brazil in February-May 2004 in the frame of the HIBISCUS project. The flights lasted for 7 to 79 days residing mainly in the tropics, but some of them passed the tropical barrier and went to southern midlatitudes. Compared to the balloon measurements just above the tropical tropopause the ECMWF operational temperatures show a systematic cold bias of 0.9 K and the easterly zonal winds are too strong by 0.7 m/s. This bias in the zonal wind adds to the ECMWF trajectory errors, but they still are relatively small with e.g. about an error of 700 km after 5 days. The NCEP/NCAR reanalysis trajectory errors are substantially larger (1300 km after 5 days). In the southern midlatitudes the cold bias is the same, but the zonal wind bias is almost zero. The trajectories are generally more accurate than in the tropics, but for one balloon a lot of the calculated trajectories end up on the wrong side of the tropical barrier and this leads to large trajectory errors. 1 Introduction This study provides a new intercomparison between the operational ECMWF (and to some extent the NCEP/NCAR reanalysis) data and independent in-situ measurements valid for the southern tropics and extratropics. These new results are important for research studies which depend on the accuracy of assimilations systems such as for example chemical transport studies in the stratosphere do.
African Journal of Environmental Science and Technology
Addressing data incompleteness issues is crucial for reliable climate studies, especially in regi... more Addressing data incompleteness issues is crucial for reliable climate studies, especially in regions like Africa that commonly experience data gaps. This study aims to evaluate the performance of five imputation methods (knn, ppca, mice, imputeTS, and missForest) on meteorological data from stations in Burkina Faso and Senegal. The imputed data is compared with ERA5 reanalysis data to validate its accuracy. Temperature, relative humidity, and precipitation observations from the GSOD dataset (1973-2020) were used, creating subsets with missing rates of 5, 10, 20, 30 and 40%. An evaluation was conducted using the Taylor diagram and Kling-Gupta Efficiency (KGE). The results show a good estimation of temperature and relative humidity time series, with missForest performing the best for handling missing values. Precipitation estimation was less accurate, but there was strong agreement between estimated and observed data. ImputeTS was recommended for precipitation. Spatial consistency between imputed data and ERA5 reanalysis products was found. This research improves the quality of meteorological data, provides essential information about climatic characteristics, and serves as a foundation for climate change and weather modeling studies.
Climate variability is a key factor in driving malaria outbreaks. As shown in previous studies, c... more Climate variability is a key factor in driving malaria outbreaks. As shown in previous studies, climate-driven malaria modeling provides a better understanding of malaria transmission dynamics, generating malaria-related parameters validated as a reliable benchmark to assess the impact of climate on malaria. In this framework, the present study uses climate observations and reanalysis products to evaluate the predictability of malaria incidence in West Africa. Sea surface temperatures (SSTs) are shown as a skillful predictor of malaria incidence, which is derived from climate-driven simulations with the Liverpool Malaria Model (LMM). Using the SST-based Statistical Seasonal Forecast model (S4CAST) tool, we find robust modes of anomalous SST variability associated with skillful predictability of malaria incidence Accordingly, significant SST anomalies in the tropical Pacific and Atlantic Ocean basins are related to a significant response of malaria incidence over West Africa. For the...
The American Journal of Tropical Medicine and Hygiene, 2020
Malaria is a major public health problem in West Africa. Previous studies have shown that climate... more Malaria is a major public health problem in West Africa. Previous studies have shown that climate variability significantly affects malaria transmission. The lack of continuous observed weather station data and the absence of surveillance data for malaria over long periods have led to the use of reanalysis data to drive malaria models. In this study, we use the Liverpool Malaria Model (LMM) to simulate spatiotemporal variability of malaria in West Africa using daily rainfall and temperature from the following: Twentieth Century Reanalysis (20th CR), National Center for Environmental Prediction (NCEP), European Centre for Medium-Range Weather Forecasts (ECMWF) Atmospheric Reanalysis of the Twentieth Century (ERA20C), and interim ECMWF Re-Analysis (ERA-Interim). Malaria case data from the national surveillance program in Senegal are used for model validation between 2001 and 2016. The warm temperatures found over the Sahelian fringe of West Africa can lead to high malaria transmission...
The use of Tropical Rainfall Measuring Mission (TRMM) data is an option for counteracting challen... more The use of Tropical Rainfall Measuring Mission (TRMM) data is an option for counteracting challenge of the lack of ground based observations, particularly in Kayanga/Gêba. This paper undertakes validation of monthly TRMM rainfall estimates before using it to understand the spatial and temporal variability in the Basin. This validation based on application of statistical study, made it possible to obtain interesting results with correlation coefficients varying from 0.92 to 0.96 and Nash indices close to 1. The analysis of the seasonal rainfall pattern shows consistence with ground based observations. The study of the annual cycle reveals that their interannual variability is similar to that of ground based observations. Finally, the interpolation of average monthly rainfall in the basin highlights the NorthSouth rainfall gradient, which shows that the South is wetter than the North, with differences more pronounced in August and September.
Rural societies in the face of climatic and environmental changes in West Africa, 2017
Introduction A serious drought hit West Africa in the 1970s (Nicholson, 1980; Held et al., 2005) ... more Introduction A serious drought hit West Africa in the 1970s (Nicholson, 1980; Held et al., 2005) whose consequences for agriculture—the main activity of the people in the region—made a serious contribution to late development. Rainfall in the Sahel seems to have recovered since the 2000s, although it is not possible to say whether the trend will last during the coming decades (Paeth and Hense, 2004). This period also coincided with warming that probably resulted from the increase in greenhous..
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