TITLE:
Validation of TRMM and FEWS Satellite Rainfall Estimates with Rain Gauge Measurement over Ashanti Region, Ghana
AUTHORS:
Leonard K. Amekudzi, Marian A. Osei, Winifred A. Atiah, Jeffrey N. A. Aryee, Maureen A. Ahiataku, Emmanuel Quansah, Kwasi Preko, Sylvester K. Danuor, Andreas H. Fink
KEYWORDS:
Rain Gauge, Validation, TRMM and FEWS-RFE, DACCIWA Project, Ashanti Region
JOURNAL NAME:
Atmospheric and Climate Sciences,
Vol.6 No.4,
October
28,
2016
ABSTRACT: Satellite
rainfall estimates have predominantly been used for climate impact studies due
to poor rain gauge network in sub-Saharan Africa. However, there are limited
microscale studies within the sub-region that have assessed the performance of
these satellite products, which is the focus of the present study. This paper
therefore considers validation of Tropical Rainfall Measuring Mission (TRMM)
and Famine Early Warning System (FEWS) satellite estimates with rain gauge
measurements over Ashanti region of Ghana. First, a consistency assessment of
the two gauge data products, the Automatic Rain Gauge (ARG) and Ghana
Meteorological Agency (GMet) Standard Rain Gauge (SRG) measurements, was
performed. This showed a very good agreement with correlation coefficient of
0.99. Secondly, satellite rainfall products from TRMM and FEWS were validated
with the two gauge measurements. Validation results showed good agreement with
correlation coefficients of 0.6 and 0.7 for TRMM and FEWS with SRG, and 0.87 and
0.86 for TRMM and FEWS with ARG respectively. Probability Of Detection (POD)
and Volumetric Hit Index (VHI) were found to be greater than 0.9. Volumetric
Critical Success Index (VCSI) was 0.9 and 0.8 for TRMM and FEWS respectively
with low False Alarm Ratio (FAR) and insignificant Volumetric Miss Index (VMI).
In general, relatively low biases and RMSE values were observed. The biases
were less than 1.3 and 0.8 for TRMM and FEWS-RFE respectively. These indicate
high rainfall detection capabilities of both satellite products. In addition,
both TRMM and FEWS were able to capture the onset, peak and cessation of the
rainy season, as well as the dry spells. Although TRMM and FEWS sometimes
under/overestimated rainfall, they have the potential to be used for agricultural
and other hydro-climatic impact studies over the region. The Dynamic-Aerosol-Cloud-Chemistry
Interactions in West Africa (DACCIWA) project will provide an improved spatial
gauge network database over the study area to enhance future validation and
other climate impact studies.