Validation of Satellite and Merged Rainfall Data over Ghana, West Africa

Abstract

In regions of sparse gauge networks, satellite rainfall products are mostly used as surrogate measurements for various rainfall impact studies. Their potential to complement rain gauge measurements is influenced by the uncertainties associated with them. This study evaluates the performance of satellites and merged rainfall products over Ghana in order to provide information on the consistency and reliability of such products. Satellite products were validated with gridded rain gauge data from the Ghana Meteorological Agency (GMet) on various time scales. It was observed that the performance of the products in the country are mostly scale and location dependent. In addition, most of the products showed relatively good skills on the seasonal scale (r > 0.90) rather than the annual, and, after removal of seasonality from the datasets, except ARC2 that had larger biases in most cases. Again, all products captured the onsets, cessations, and spells countrywide and in the four agro-ecological zones. However, CHIRPS particularly revealed a better skill on both seasonal and annual scales countrywide. The products were not affected by the number of gauge stations within a grid cell in the Forest and Transition zones. This study, therefore, recommends all products except ARC2 for climate impact studies over the region.

Spatiotemporal Changes in Temperature and Precipitation in West Africa. Part I: Analysis with the CMIP6 Historical Dataset

“…The cold nights (days), TN10p (TX10p), showed a southward declining trend. This observation was confirmed by [101], which identified uniform declining trends in TN10p and TX10p over WA. Furthermore, during the period 1950-2014, the trends of cool/warm nights (TN10p/TX90p) were more significant than those of cool/warm days (TX10p/TX90p); this justifies the finding of [56], which reached the same conclusion over China.…”

“…R95p illustrated a significant positive trend in heavy rainfall near countries such as Gabon, Cameroon, the southern part of Nigeria, the northern part of Benin, Burkina Ghana, and the southern part of Mali. According to [101], it was expected that the number of consecutive dry days would be more pronounced in the northern regions than in the southern. The same analysis led to the conclusion in [102] that rainfall in the littoral zone of southern WA was more extreme than that inland.…”

Assessment of CHADFDM satellite‐based input dataset for the groundwater recharge estimation in arid and data scarce regions

“…Moreover, it was noted that the performance of the products is largely scale and geographic location dependent. Most of the presently applied products showed comparatively good skills on the seasonal scale ( R 2 > 0.90) rather than at annual scale (Atiah et al, 2020). This indicates that satellite data should be improved taking into account the type of precipitation (i.e., intensity), and for that a minimum of daily resolution is required.…”

“…Moreover, it was noted that the performance of the products is largely scale and geographic location dependent. Most of the presently applied products showed comparatively good skills on the seasonal scale (R 2 > 0.90) rather than at annual scale (Atiah et al, 2020).…”

Estimation of the return periods of maxima rainfall and floods at the Pra River Catchment, Ghana, West Africa using the Gumbel extreme value theory

“…The product can be obtained from daily to seasonal timescales and has a spatio-temporal resolution of 0.05 0.05 ∘ and 1981 to present. In Ghana, the CHIRPS product has been validated and observed to have a good agreement with station rainfall data ( Atiah et al, 2020 ). For this study, the version 2.0 (v2.0) of CHIRPS was obtained from 1981 to 2015 and used for the analysis in the spatial dynamics of maxima rainfall and return periods, and variations in CDD and CWD.…”