TITLE:
The Impacts of Topography on Spatial and Temporal Rainfall Distribution over Rwanda Based on WRF Model
AUTHORS:
Didier Ntwali, Bob Alex Ogwang, Victor Ongoma
KEYWORDS:
Topography, Seasonal Rainfall, Rwanda, WRF Model
JOURNAL NAME:
Atmospheric and Climate Sciences,
Vol.6 No.2,
March
1,
2016
ABSTRACT: The
impact of topography on heavy rainfall during two rain seasons was investigated
in order to explain their mechanisms on rainfall distribution over Rwanda.
Weather Research and Forecasting (WRF-ARW) model was used to study two
historical cases of heavy rainfall which took place over Rwanda during two rain
seasons, March to May (MAM) and September to December (SOND), from April 7 to
9, 2012 (for MAM) and from October 29 to 31, 2012 (during SOND). The control
experiment was done with actual topography, whereas sensitivity experiment was
carried out with topography reduced by half. Results show that rainfall
distribution over Rwanda significantly changes when topography is reduced. The
reduction in topography leads to a decrease in rainfall amounts in both MAM and
SOND seasons, with varying magnitudes. This reveals the importance of orography
in determining rainfall amounts and distribution over the region. The
accumulated rainfall amount from WRF underestimate or overestimate rain gauge
stations data by region and by season, but there is good agreement especially
in altitude below 1490 m and above 1554 m during April and October
respectively. The results may motivate modelling carters to further improve
parameterization schemes in the mountainous regions.