Evaluating global reanalysis precipitation datasets with rain gauge measurements in the Sudano‐Sahel region: case study of the Logone catchment, Lake Chad Basin

Nkiaka, Elias; Nawaz, Rizwan; Lovett, Jon C.

doi:10.1002/met.1600

Cited by 48 publications

(31 citation statements)

References 30 publications

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“…This follows the finding of Nkiaka et al [21] who showed that CFSR and ERA-Interim precipitation estimates could replicate the seasonal cycle of rainfall in the catchment. However, from the streamflow hydrographs shown in Figures 3-6 it can be observed that WFDEI and CFSR were able to simulate low flows (baseflow) throughout the period under study while ERA-Interim overestimated low flows in most years during the same period.…”

Section: Resultssupporting

confidence: 72%

“…This suggest that rainfall input plays a significant role in model calibration because it has the potential to influence calibrated parameters as reported by [29]. Nevertheless, the significant variability in CFSR and ERA-Interim datasets in this study follow the findings of [21] in the Logone catchment.…”

Section: Model Evaluationsupporting

confidence: 49%

“…In a previous study in the catchment, the authors of [21] evaluated the quality of precipitation estimates from CFSR and ERA-Interim against observed monthly rainfall covering the period 1979-2002 and concluded that, precipitation estimates from both reanalyses products could reproduce the seasonal rainfall cycle in the catchment albeit significant variability in the data.…”

Section: Introductionmentioning

confidence: 99%

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Evaluating Global Reanalysis Datasets as Input for Hydrological Modelling in the Sudano-Sahel Region

2017

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This paper investigates the potential of using global reanalysis datasets as input for hydrological modelling in the data-scarce Sudano-Sahel region. To achieve this, we used two global atmospheric reanalyses (Climate Forecasting System Reanalysis and European Center for Medium-Range Weather Forecasts (ECMWF) ERA-Interim) datasets and one global meteorological forcing dataset WATCH Forcing Data methodology applied to ERA-Interim (WFDEI). These datasets were used to drive the Soil and Water Assessment Tool (SWAT) in the Logone catchment in the Lake Chad basin. Model performance indicators after calibration showed that, at daily and monthly time steps, only WFDEI produced Nash Sutcliff Efficiency (NSE) and Coefficient of Determination (R 2 ) values above 0.50. Despite a general underperformance compared to WFDEI, CFSR performed better than the ERA-Interim. Model uncertainty analysis after calibration showed that more than 60% of all daily and monthly observed streamflow values at all hydrometric stations were bracketed within the 95 percent prediction uncertainty (95PPU) range for all datasets. Results from this study also show significant differences in simulated actual evapotranspiration estimates from the datasets. Overall results showed that biased corrected WFDEI outperformed the two reanalysis datasets; meanwhile CFSR performed better than the ERA-Interim. We conclude that, in the absence of gauged hydro-meteorological data, WFDEI and CFSR could be used for hydrological modelling in data-scarce areas such as the Sudano-Sahel region.

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Section: Resultssupporting

confidence: 72%

Section: Model Evaluationsupporting

confidence: 49%

Section: Introductionmentioning

confidence: 99%

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Evaluating Global Reanalysis Datasets as Input for Hydrological Modelling in the Sudano-Sahel Region

2017

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“…Although this issue may be resolved by using satellite or reanalysis data sets, these too also need to be validated against in situ rain gauge measurements (e.g. Nkiaka et al ., 2016a). Accuracy, of satellite and reanalysis rainfall forecast models thus depends on the quality of gauge data used for calibration and are inevitably affected by the sparsity of gauge data or temporally incomplete gauge time series in the region under investigation.…”

Section: Introductionmentioning

confidence: 99%

Analysis of rainfall variability in the Logone catchment, Lake Chad basin

Nkiaka

Nawaz

Lovett

2016

Intl Journal of Climatology

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The socio-economic consequences posed by climate change in Africa are giving increasing emphasis to the need for trend analysis and detection of changes in hydro-climatic variables in data deficient areas. This study analyzes rainfall data from seventeen rain gauges unevenly distributed across the Logone catchment in the Lake Chad basin (LCB) over a fifty-year period . After quality control of the rainfall data using homogeneity tests, non-parametric MannKendall (MK) and Spearman rho tests were applied to detect the presence of trends. Trend magnitude was calculated using Sen's Slope Estimator. Results of the homogeneity test showed that rainfall was homogeneous across the catchment. Trend analysis revealed the presence of negative trends for annual rainfall at all the stations. Results of long term trend analysis at a monthly time scale revealed the presence of statistically insignificant positive trends at 32% of the stations. Spatially, the analysis showed a clear distinction in rainfall magnitude between the semi-arid and Sudano zones. The slope of the trend lines for annual rainfall averaged over the respective zones was higher in the semi-arid zone (-4.37) compared to the Sudano zone (-4.02). However, the station with the greatest reduction in annual rainfall (-8.06 mm) was located in the Sudano zone.Keywords: Rainfall analysis, Mann-Kendall, Sudano-Sahel, Logone catchment, Lake Chad basin. 1) IntroductionPrecipitation in the African Sudano-Sahel is highly variable both spatially and temporally, and experiences periods of prolonged drought such as that which affected the region in the 70s and 80s (Boyd et al., 2013;Nicholson, 2013). According to Nicholson (2013), rainfall in the Sudano-Sahel region is controlled by mesoscale convective systems (MCS). Its variability can be attributed to several factors. Firstly, as over the rest of Africa, annual rainfall variability can be attributed to global sea surface temperature (SST) anomalies (Giannini et al., 2008). Secondly, for the Sudano-Sahel, fluctuations in high altitude jet stream circulation is responsible for the spatiotemporal variability of rainfall in the region. This includes the African Easterly Jet (AEJ), the Tropical Easterly Jet (TEJ), the African Westerly Jet (AWJ), Low Level Jets, the West African Westerly Jet (WAWJ), the Nocturnal Low Level Jets (NLLJ), the Saharan Heat Low (SHL), and the Saharan Air Layer (SAL) (Nicholson, 2013).Rainfall variability in the region is also strongly influenced by seasonal regime changes. The oceanic regime (monsoon), characterized by the progressive increase of moist air flow from the Atlantic Ocean into the continent up to about 11°N in May, is associated with seasonal migration of the Intertropical Convergence Zone (ITCZ) from its southern position in the boreal winter to its northern position in the boreal summer (Lebel et al., 2003). The continental regime (harmattan) is characterized by large convective systems during July to September embedded in the easterly circulation (Lebel et al., 2003), an...

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“…For example, Nkiaka et al . () found that there are good correlations between ERA‐Interim and rain gauge datasets over the Lake Chad Basin, such that the bias and mean absolute error of ERA‐Interim were found on average 2% and 6.5 mm month −1 , respectively.…”

Section: Model Description and Methodologymentioning

confidence: 99%

Impacts of global warming on the surface water balance components in Iran as simulated by RegCM4

Moslemzadeh

Irannejad

Alizadeh

2019

Intl Journal of Climatology

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The impacts of future global warming on the climate of semi‐arid to arid regions of Iran have remained mostly unexplored. Using Regional Climate Model version 4.4 (RegCM4) under the RCP4.5 and RCP8.5 scenarios, changes in surface water balance components in Iran are investigated for the future period 2070 to 2099 relative to the base period 1970 to 1999. The initial and boundary conditions for RegCM4 were derived from the CSIRO‐Mk3.6 general circulation model (GCM). Model results during the base period are compared against the European Centre for Medium‐Range Weather Forecasts (ECMWF) reanalysis Interim (ERA‐Interim) and the Climatic Research Unit (CRU) datasets. Analyses of the ERA‐Interim and CRU datasets and model simulations during the base period indicated that due to the large latitudinal extent of Iran and its complex topography, different regions of the country experience a diverse range of climate, with monthly precipitation ranging from 0.1 mm day−1 over arid regions of southeastern Iran to more than 2.5 mm day−1 over wet coastal regions of northern Iran. In the future period, near‐surface temperatures over all regions of Iran will increase under the two scenarios, with more temperature rises under the RCP8.5 scenario. Under the two scenarios, precipitation over most regions of Iran will increase in winter and decrease in summer. As winter will be warmer in the future under the two scenarios, and a warmer air has a higher water vapour storage capacity, precipitation will increase in the future winter climate. On the other hand, the decrease of precipitation in summer is due to an increase of the altitude of the lifting condensation level under the warmer climate. It is shown that increases in the surface temperature and precipitation in the future winter are associated with an increase of evaporatranspiration in nearly all regions of Iran.

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Evaluating global reanalysis precipitation datasets with rain gauge measurements in the Sudano‐Sahel region: case study of the Logone catchment, Lake Chad Basin

Cited by 48 publications

References 30 publications

Evaluating Global Reanalysis Datasets as Input for Hydrological Modelling in the Sudano-Sahel Region

Evaluating Global Reanalysis Datasets as Input for Hydrological Modelling in the Sudano-Sahel Region

Analysis of rainfall variability in the Logone catchment, Lake Chad basin

Impacts of global warming on the surface water balance components in Iran as simulated by RegCM4

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