Changes in the West Africa Monsoon Precipitation Extremes during ENSO developing Phases

IF 1.6 4区地球科学 Q4 METEOROLOGY & ATMOSPHERIC SCIENCES Atmosphere-Ocean Pub Date : 2023-05-02 DOI:10.1080/07055900.2023.2202656

Sacré Régis Mailly Didi, Moussa Diakhaté, A. Diedhiou

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Abstract

ABSTRACT A 37-year record of rainfall gridded data covering West Africa and a Global Sea Surface Temperature (SST) dataset are used to investigate the remote influence of SST anomalies in the Equatorial Pacific on the interannual variability of West Africa’s extreme rainfall indices over the period 1981–2018. The top five (5) years with the strongest and weakest peak of Niño3.4 SST monthly anomalies are selected, and May-to-September (MJJAS) composite anomalies of the total and extreme rainfall indices are performed. Results reveal that Equatorial Pacific SST’s impacts on daily rainfall intensity are generally more robust than that on their frequency. The significant changes in the mean zonal atmospheric circulation associated with the SST lead to significant dynamic and thermodynamic changes that affect the West African monsoon system locally. During El Niño (La Niña) years, (i) a weakening (strengthening) of the Tropical Easterly Jet (TEJ), (ii) a strengthening (weakening), and southward (northward) shift position of the African Easterly Jet (AEJ), and (iii) a decrease (increase) of the monsoon flow are noted. These changes in the atmospheric circulation prevent (encourage) a supply of moisture, resulting in a reduction (increase) in extreme precipitation observed across West Africa. Equatorial eastern Pacific warming (cooling) is also shown to lead to stable (unstable) atmospheric conditions over West Africa that block (generate) the development of convective systems.

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来源期刊

Atmosphere-Ocean 地学-海洋学

CiteScore

2.50

自引率

16.70%

发文量

审稿时长

>12 weeks

期刊介绍： Atmosphere-Ocean is the principal scientific journal of the Canadian Meteorological and Oceanographic Society (CMOS). It contains results of original research, survey articles, notes and comments on published papers in all fields of the atmospheric, oceanographic and hydrological sciences. Arctic, coastal and mid- to high-latitude regions are areas of particular interest. Applied or fundamental research contributions in English or French on the following topics are welcomed: climate and climatology; observation technology, remote sensing; forecasting, modelling, numerical methods; physics, dynamics, chemistry, biogeochemistry; boundary layers, pollution, aerosols; circulation, cloud physics, hydrology, air-sea interactions; waves, ice, energy exchange and related environmental topics.