Relating Point to Area Average Rainfall in Semiarid West Africa and the Implications for Rainfall Estimates Derived from Satellite Data

Flitcroft, Ian D.; Milford, J. R.; Dugdale, G.

doi:10.1175/1520-0450(1989)028<0252:rptaar>2.0.co;2

Cited by 48 publications

(34 citation statements)

References 9 publications

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“…As differences are calculated for the TAMSAT rainfall estimate S minus the gauge observation G (Table 2), negative values indicate relative underestimation and positive values indicate relative overestimation of rainfall by TAMSAT. Although differences between point and pixel rainfall over larger 10-day totals decline substantially and are very much dependent on the particular storm characteristics, these are shown to be as much as 35% (12.5 in 36 mm) in a case study in Niger (Flitcroft et al 1989). The 210-to 10-mm difference thus represents the difference expected from the point-to-area comparison, although this can be much higher depending on the frequency distributions of particular storms (Flitcroft et al 1989).…”

Section: ) Operational Validation Of Dekadal Rainfall Estimatesmentioning

confidence: 86%

“…This partially relates to the optimizing of TAMSAT calibrations for detecting the median rainfall event, whereas point-to-pixel validation effectively compares rainfall estimates against mean gauge observations. Although the point-to-pixel validation method used here introduces a dry bias, which is representative of the point-to-pixel mismatch in estimating rainfall over an area, using the median is more appropriate than the mean for deriving area-averaged rainfall estimates (Flitcroft et al 1989). Figure 6 highlights that TAMSAT has skill outside the main rainy season over parts of southern Africa in both April and August, which is important because in some African regions there can be a secondary rainy season and/or rain events during the dry season that are crucial for crop growth.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Extension of the TAMSAT Satellite-Based Rainfall Monitoring over Africa and from 1983 to Present

Tarnavsky

Grimes

Maidment

et al. 2014

Journal of Applied Meteorology and Climatology

213

149

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Tropical Applications of Meteorology Using Satellite Data and Ground-Based Observations (TAMSAT) rainfall monitoring products have been extended to provide spatially contiguous rainfall estimates across Africa. This has been achieved through a new, climatology-based calibration, which varies in both space and time. As a result, cumulative estimates of rainfall are now issued at the end of each 10-day period (dekad) at 4-km spatial resolution with pan-African coverage. The utility of the products for decision making is improved by the routine provision of validation reports, for which the 10-day (dekadal) TAMSAT rainfall estimates are compared with independent gauge observations. This paper describes the methodology by which the TAMSAT method has been applied to generate the pan-African rainfall monitoring products. It is demonstrated through comparison with gauge measurements that the method provides skillful estimates, although with a systematic dry bias. This study illustrates TAMSAT's value as a complementary method of estimating rainfall through examples of successful operational application.

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Section: ) Operational Validation Of Dekadal Rainfall Estimatesmentioning

confidence: 86%

mentioning

confidence: 99%

Extension of the TAMSAT Satellite-Based Rainfall Monitoring over Africa and from 1983 to Present

Tarnavsky

Grimes

Maidment

et al. 2014

Journal of Applied Meteorology and Climatology

213

149

View full text Add to dashboard Cite

show abstract

“…As far as the error attributable to the gauge data is concerned, a detailed investigation by Flitcroft et al (1989) has demonstrated that raingauge measurements of convective rainfall events in the Sahel typically vary by more than 50% within a single pixel. However, the present study is concerned only with the variability of the rainfall/CCD relationship attributable to different weather regimes.…”

Section: General Approachmentioning

confidence: 99%

Satellite-based rainfall estimation for river flow forecasting in Africa. I: Rainfall estimates and hydrological forecasts

Grimes¹,

Diop²

2003

Hydrological Sciences Journal

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Reliable, real-time river flow forecasting in Africa on a time scale of days can provide enormous humanitarian and economic benefits. This study investigates the feasibility of using daily rainfall estimates based on cold cloud duration (CCD) derived from Meteosat thermal infrared imagery as input to a simple rainfall-runoff model and also whether such estimates can be improved by the inclusion of information from numerical weather prediction (NWP) analysis models. The Bakoye catchment in Mali, West Africa has been used as a test area. The data available for the study covered the main months of the rainy season for three years. The rainfall estimates were initially validated against gauge data. Improvements in quality were observed when information relating to African Easterly Wave phase and storm type was included in a multiple linear regression (MR) algorithm. The estimates were also tested by using them as input to a rainfall-runoff model. When contemporaneous calibrations from raingauges were available for calibration, both CCD-only and MR rainfall estimates gave more accurate river flow forecasts than when using raingauge data alone. In the absence of contemporaneous calibrations, the performance was reduced but the MR did better than the CCDonly input in all years. The use of satellite-derived vegetation index did not improve the quality of the river flow forecasts.Key words satellite rainfall estimates; river flow; hydrological model; NWP model; multiple regression; Africa Estimation par satellite des précipitations pour la prévision des débits fluviaux en Afrique. I: Estimations des précipitations et prévisions hydrologiques Résumé Prévoir en Afrique, avec fiabilité et en temps réel, le débit fluvial à échéance de quelques jours, peut apporter d'énormes bénéfices humanitaires et économiques. Cette étude porte sur la possibilité d'utiliser des estimations journalières de précipitation fondées sur la durée de nuages à sommet froid (DNSF) dérivée d'images infrarouge thermique Meteosat, comme entrée d'un modèle pluie-débit. Le but de l'étude est également de savoir si de telles estimations peuvent être améliorées en incluant des informations provenant de modèles numériques de prévision météorologique. Le bassin de Bakoye au Mali, Afrique de l'Ouest, a été utilisé en tant que test dans cette région. Les données disponibles pour l'étude couvrent les principaux mois de la saison pluvieuse durant trois ans. Les estimations des pluies ont été initialement validées par des données pluviométriques au sol. Une amélioration de la qualité a été observée lors de l'incorporation d'informations concernant la phase des ondes d'est africaines et le type d'orage dans un algorithme de régression multiple. Les estimations ont aussi été testées en tant qu'entrées d'un modèle pluie-débit. Lorsque des calibrations pluviométriques simultanées étaient diponibles, les précipitations estimées par le DNSF seul et la régression multiple ont donné des débits fluviaux plus précis que lorsque seules les données pluviométriques o...

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“…The vastness of the area and the rapid development of weather patterns within the Inter-tropical Convergence Zone present a multitude of problems in obtaining accurate ground measurement of rainfall using traditional meteorological tools. Patterns of rainfall in the Sahel show considerable spatial variability over relatively short distances and rain gauges across the region are too sparsely placed to yield consistently reliable data (Flitcroft et a/., 1989). In much of the Sahel, there may be only one rain gauge per 10 000 km 2 .…”

Section: Rainfall Estimationmentioning

confidence: 99%

Agricultural Production Monitoring in the Sahel Using Remote Sensing: Present Possibilities and Research Needs

Lambin

Cashman

Moody

et al. 1993

Journal of Environmental Management

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Relating Point to Area Average Rainfall in Semiarid West Africa and the Implications for Rainfall Estimates Derived from Satellite Data

Cited by 48 publications

References 9 publications

Extension of the TAMSAT Satellite-Based Rainfall Monitoring over Africa and from 1983 to Present

Extension of the TAMSAT Satellite-Based Rainfall Monitoring over Africa and from 1983 to Present

Satellite-based rainfall estimation for river flow forecasting in Africa. I: Rainfall estimates and hydrological forecasts

Agricultural Production Monitoring in the Sahel Using Remote Sensing: Present Possibilities and Research Needs

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