Browsing by Author "Aryee, J. N. A."

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    Development of high spatial resolution rainfall data for Ghana
    (International Journal of Climatology, 2018-08-25) Aryee, J. N. A.; Amekudzi, L. K.; Quansah, E.; Klutse, N. A. B.; Atiah, W. A.
    Various sectors of the country’s economy – agriculture, health, energy, among others – largely depend on climate information, hence availability of quality climate data is very essential for climate-impact studies in these sectors. In this paper, a monthly rainfall database (GMet v1.0) has been developed at a 0.5∘ × 0.5∘ spatial resolution, from 113 Ghana Meteorological Agency (GMet) gauge network distributed across the four agro-ecological zones of Ghana, and spanning a 23-year period (1990–2012). The datasets were frst homogenized with quantile-matching adjustments and thereafter, gridded at a spatial resolution of 0.5∘ × 0.5∘ using Minimum Surface Curvature with tensioning parameter, allowing for comprehensive spatial felds assessment on the developed dataset. Afterwards, point-pixel validation was performed using GMet v1.0 against gauge data from stations that were earlier excluded due to large datagaps. This proved the reliability of GMet v1.0, with high and statistically signifcant correlations at 99% confdence level, and relatively low biases and rmse. Furthermore, GMet v1.0 was compared with GPCC and TRMM rainfall estimates, with both products found to adequately mimick GMet v1.0, with high correlations which are signifcant at 99% confdence level, low biases and rmse. In addition, the ratio of 90th – percentile provided fairly similar capture of extremes by both TRMM and GPCC, in relation to GMet v1.0. Finally, based on annual rainfall totals and monthly variability, k-means cluster analysis was performed on GMet v1.0, which delineated the country into four distinct climatic zones. The developed rainfall data, when offcially released, will be a useful product for climate impact and further rainfall validation studies in Ghana.
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    Overview of surface to near‑surface atmospheric profles over selected domain during the QWeCI project
    (Meteorology and Atmospheric Physics, 2018-07-04) Aryee, J. N. A.; Amekudzi, L.K.; Atiah, W. A.; Osei, M. A.; Agyapong, E.
    Assessing the evolution of surface to near-surface atmospheric fuxes is key to improving our understanding of their interactions, while further advancing climate applications. In this paper, an overview of the diurnal to seasonal evolution of some surface to near-surface atmospheric fuxes, coupled with their interactions, have been provided. Fluxes of downwelling and upwelling radiation (SW↓, SW↑, LW↓, LW↑), soil heat fux (ΔH), relative humidity (RH), rainfall (RR) and surface air temperature (T), measured from two diferent locations (Owabi and KNUST) and at a temporal resolution of 10 min, encompassing the quantifying weather and climate impact (QWeCI) Project period (2011–2013), were used to assess their relationship on diurnal to seasonal scales. First, diurnal assessments of the various profles were performed. These provided information on the relatively active daytime, with the earth surface exposed to substantial SW↓, initiating rising and sinking thermals which subsequently increased T and ΔH, with reductions in RH until few hours after midday, beyond which a reversal was observed. Also, ΔH from the vegetative terrain (Owabi) was found to be directed into the surface at daytime, and released from the sub-surface layer back into the atmosphere at night time, compensating the energy loss by LW↑ from the surface. Furthermore, rainfall (RR) in both locations were found to be generally convective and occurring mostly between 1500 GMT and 2300 GMT. The relationship between net radiation (RN) and RR is presently statistically unclear, although rainfall peaks were found to be occurring at low RN and relatively warmer T, accompanied by high RH. Thereafter, seasonal assessments were performed to capture the monthly-averaged diurnal variabilities in the measured surface to near-surface parameters. These showed heightened daytime T, ΔH and RN, coupled with relatively low RH within the dry seasons, and more reduced profles within the monsoon season. Additionally, countrywide assessments were performed using ERA-5 datasets which showed similarities with the in situ data. However, convective rains over the domain were not fully resolved in ERA-5. Nonetheless, the fndings of this study are essential to understanding surface energy balance processes in tropical, humid climates, which is important for various climate-impact modeling applications and policy formulations over the region.