Abstract
Observed rainfall data of the National Meteorological Service of Guinea (NMS) exhibit that synoptic station usually records the largest rainfall amount in Guinea. Only few studies have been done on this rainfall peak observed in Conakry. This work better analyses the atmospheric dynamics leading to rainfall particularity. Using NMS data from 1981 to 2010, the monthly contribution and mean seasonal cycle of each station has been done. These findings of the study show that between July and August (rainfall season peak), the coastline particularly Conakry records the largest amount of rainfall. Using Era Interim data for the common period (1981-2010), we also investigate the rainfall dynamics in the lower level (1000 hPa - 850 hPa) from precipitable water, divergence, and moisture flow transport. There is a west and southwest moisture flow transport explained by a strong moisture convergence in the coastal region (Lower-Guinea). Furthermore, values of precipitable water in the same region are found, in agreement with the high moisture flow transport gradient. These incoming flow (west and south-west) undergo a return by blocking’s Kakoulima range (foehn effect) and Fouta Djallon massif to initiate convection clouds on the Guinean coast. These processes enhance a convergence of moisture associated with orographic origin convection. This has an important effect by increasing the rainfall amount in Conakry.
Highlights
In West Africa, deep convection exhibits important variability by convective mesoscale systems, and by local thunderstorms or smaller convective systems [1]
Considering the two sus-mentioned, we consider the JJASO season third section, we focus on precipitable water vapor (Pwv) during the JJASO season
The analysis of rainfall climatology on West Africa over the period 1981-2010 are consistent with the work of Manetsa et al, (2011) [10] which make over the 1951-2002
Summary
In West Africa, deep convection exhibits important variability by convective mesoscale systems (squall lines), and by local thunderstorms or smaller convective systems [1]. It is often associated with East African Waves [2]. The tropical convective clouds often evolve into organized clusters with anvils blending in a single mesoscale cloud [3]. They have a fundamental importance for the earth’s climate especially for its radiative energy balance [4]. Rainfall comes largely from water vapor condensation in the atmosphere [9]
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