TITLE:
On the Differences in the Intraseasonal Rainfall Variability between Western and Eastern Central Africa: Case of 25 - 70-Day Oscillations
AUTHORS:
Alain Tchakoutio, Armand Nzeukou
KEYWORDS:
Rainfall, Intraseasonal Variability, Central Africa, EOF Analysis
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.4 No.7,
July
28,
2016
ABSTRACT: The
intraseasonal timescale is critical in Central Africa, because the resources of
the region are highly rainfall dependent. In this paper, we use 1DD GPCP
rainfall product to investigate the differences in the space-time structures of
the 25 - 70-day intraseasonal variability of rainfall, over the Western Central
Africa (WCA) and the Eastern Central Africa (ECA), with different climate features.
The results of Empirical Orthogonal Functions (EOFs) analysis have shown that
the amount of variance explained by the leading EOFs is greater in ECA (58.4%)
than in WCA (49.8%). For both WCA and ECA, the power spectra of the Principal
Components (PCs) peaked around 40 days, indicating a MJO signal. The
seasonality of ISO is evident, but this seasonality is much noticeable in ECA
where almost 80% of the total yearly ISO power occurs during November-April
season, against only around 60% for WCA. Moreover, the lagged cross
correlations computed between WCA and ECA PCs time series showed that most of
the WCA PCs led ECA PCs time series with a timescale of 8 - 12 days, revealing
that the eastward propagation could potentially be the relationship between WCA
and ECA modes. The interannual variations in the ISO activity are weak in WCA,
when compared with ECA where the signal exhibits larger interannual variations,
quite linked with ENSO.