Rainfall variability in Northern Tanzania in the March-May season (long rains) and its links to large-scale climate forcing

Climate Research

Faustine F. Tilya¹  Eduardo Zorita¹ 

关键词: Rainfall;    Eastern Africa;    Indian Ocean;    Monsoon;   

DOI  :  10.3354/cr020031

来源: Inter-Research Science Publishing

【 摘 要 】

ABSTRACT: Mean rainfall in Northern Tanzania is characterized by 2 annual maxima: in March-May, the long rains, and in October-December, the short rains. The interannual variability of rainfall in the March-May season and its relationshipsto large-scale fields from the NCEP/NCAR Reanalysis in the African-Indian Ocean sector were analysed. It was found that the March-May precipitation has characteristics different to that in October-December, the former being much less persistent within theseason and being associated with intraseasonally changing large-scale patterns of surface temperature, sea-level pressure and winds. March and April rainfall anomalies are linked to zonal thermal contrast between the Indian Ocean and the Eastern Africanland mass, to zonal surface winds anomalies and to vertical velocity anomalies. On the other hand, May rainfall anomalies are associated with a meridional surface temperature contrast between the Indian Ocean and the Asian continent and meridional surfacewinds anomalies, indicating a relationship to the Indian Monsoon. Local convergence seems to play a smaller role than for March anomalies. Indeed, Northern Tanzanian rainfall anomalies in May are correlated with the area-averaged Indian rainfall in thefollowing months of June, July and August. The consequences for possible statistical seasonal prediction schemes are briefly discussed.

【 授权许可】

Unknown