Abstract
This paperwork describes a comprehensive statistical assessment of rain gauge and satellite- based monthly and annual rainfall measurements over Nigeria during the period of 2001 to 2010. Two statistical methods were empolyed for inter-comparison and validation of the Tropical Rainfall Measuring Mission - TRMM 3B43 V7 rainfall product. TRMM was selected because of the recently developed algorithms to estimate 3D rain distribution from the visual spectrum radiance, radar and microwave sensors. The results of the continuous statistical assessment of the rainfall algorithms show good agreement with rain gauge measurement in term of correlation coefficient and improved mean error tests. The geometric mean of correlation coefficient from all the locations for annual, monthly, wet and dry period are 0.43, 0.79, 0.64, and 0.41 respectively. The categorical analysis assessment is based on the International Telecommunication Union for Radio-communication (ITU-R) recommended threshold for radio propagation. The results of Accuracy and FBI for ITU-R recommendation threshold of 1 to 10% percentage error for radio propagation applications are 0.629 and 0.901 for annual while that of monthly are 0.558 and 0.416. The overall performance of the TRMM based rainfall assessment is encouraging but more improvement is still needed for accurate and sufficient global rainfall estimation. Key words: TRMM 3B43 V6, satellite data, cross-validation, categorical statistics, radio propagation, ITU-R.
Highlights
Advancement in satellite technology and remote sensing techniques have brought about the development and launching of space borne measuring instruments for continuous monitoring of rainfall and its associated parameters in space and time
A number of meteorological weather satellites have been launched in the last few decades and some of these satellite rainfall products are freely available in real time on the internet via the web or File Transfer Protocol (FTP) such as PERSIANN, CMORPH, and GSMAP etc
In the validation study reported on Nigeria rainfall estimate by (Omotosho and Oluwafemi, 2009), Tropical Rainfall Measuring Mission (TRMM) 3B43 V6 among other satellite rainfall products presented by TRMM is found to be in agreement with ground measurement
Summary
Advancement in satellite technology and remote sensing techniques have brought about the development and launching of space borne measuring instruments for continuous monitoring of rainfall and its associated parameters in space and time. In the validation study reported on Nigeria rainfall estimate by (Omotosho and Oluwafemi, 2009), TRMM 3B43 V6 among other satellite rainfall products presented by TRMM is found to be in agreement with ground measurement. In this study, comprehensive categorical statistical analysis is done on satellite-ground rainfall measurement over Nigeria by comparing TRMM 3B43 V7 rainfall product with rain gauge data. TRMM based data for Nigeria The Tropical Rainfall Measuring Mission (TRMM) satellite was the first weather space borne measuring instruments launched in November 1997 (Kummerow et al, 1998). TRMM 3B43 V7 database is a combination scheme for precipitation estimates from different satellite measuring instruments such as microwave infrared, radar data and rain gauge measurements.
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