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Impacts of the ENSO Modoki and other Tropical Indo-Pacific Climate-Drivers on African Rainfall.

Preethi B, Sabin TP, Adedoyin JA, Ashok K - Sci Rep (2015)

Bottom Line: However, both the El Niño flavours anomalously reduce the northern hemispheric rainfall during June-September.During boreal summer, the El Niño Modoki and canonical El Niño (positive IOD) tend to weaken (strengthen) the tropical easterly jet, and result in strengthening (weakening) and southward shift of African easterly jet.This anomalously reduces (enhances) rainfall in the tropical north, including Sahelian Africa.

View Article: PubMed Central - PubMed

Affiliation: Indian Institute of Tropical Meteorology, Pune 411008, India.

ABSTRACT
The study diagnoses the relative impacts of the four known tropical Indo-Pacific drivers, namely, El Niño Southern Oscillation (ENSO), ENSO Modoki, Indian Ocean Dipole (IOD), and Indian Ocean Basin-wide mode (IOBM) on African seasonal rainfall variability. The canonical El Niño and El Niño Modoki are in general associated with anomalous reduction (enhancement) of rainfall in southern (northern) hemispheric regions during March-May season. However, both the El Niño flavours anomalously reduce the northern hemispheric rainfall during June-September. Interestingly, during boreal spring and summer, in many regions, the Indian Ocean drivers have influences opposite to those from tropical Pacific drivers. On the other hand, during the October-December season, the canonical El Niño and/or positive IOD are associated with an anomalous enhancement of rainfall in the Eastern Africa, while the El Niño Modoki events are associated with an opposite impact. In addition to the Walker circulation changes, the Indo-Pacific drivers influence the African rainfall through modulating jet streams. During boreal summer, the El Niño Modoki and canonical El Niño (positive IOD) tend to weaken (strengthen) the tropical easterly jet, and result in strengthening (weakening) and southward shift of African easterly jet. This anomalously reduces (enhances) rainfall in the tropical north, including Sahelian Africa.

No MeSH data available.


Partial correlations between CRU seasonal rainfall and SST indices.(a–d) with EMI, (e–h) with ENSO index, (i,l) with IOBMI, (j,k) with IODMI for the seasons MAM (a,e,i), JJAS (b,f,j), OND (c,g,k) and JF (d,h,l). Correlations significant at 85%, 90% and 95% confidence level, based on Student’s t-test are shown. [Figure created using the COLA/GrADS software].
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f2: Partial correlations between CRU seasonal rainfall and SST indices.(a–d) with EMI, (e–h) with ENSO index, (i,l) with IOBMI, (j,k) with IODMI for the seasons MAM (a,e,i), JJAS (b,f,j), OND (c,g,k) and JF (d,h,l). Correlations significant at 85%, 90% and 95% confidence level, based on Student’s t-test are shown. [Figure created using the COLA/GrADS software].

Mentions: The relative impacts of Indo-Pacific drivers on the African seasonal rainfall during various seasons are explored using the partial correlation analysis between the local rainfall and SST indices (Fig. 2). Figure 2a,d (Fig. 2e,h) exhibit the impact of various phases of ENSO Modoki (canonical ENSO) evolution on the seasonal rainfall. The significant impact of the IOD (IOBM) events on the African climate during JJAS and OND seasons (MAM and JF) can be discerned from Fig. 2j,k (Fig. 2i,l). The results obtained using CRU rainfall dataset (Fig. 2) is reconfirmed using GPCP (Fig. A2) satellite estimates. A composite analysis also, in general, confirms the result (Fig. A3).


Impacts of the ENSO Modoki and other Tropical Indo-Pacific Climate-Drivers on African Rainfall.

Preethi B, Sabin TP, Adedoyin JA, Ashok K - Sci Rep (2015)

Partial correlations between CRU seasonal rainfall and SST indices.(a–d) with EMI, (e–h) with ENSO index, (i,l) with IOBMI, (j,k) with IODMI for the seasons MAM (a,e,i), JJAS (b,f,j), OND (c,g,k) and JF (d,h,l). Correlations significant at 85%, 90% and 95% confidence level, based on Student’s t-test are shown. [Figure created using the COLA/GrADS software].
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4645176&req=5

f2: Partial correlations between CRU seasonal rainfall and SST indices.(a–d) with EMI, (e–h) with ENSO index, (i,l) with IOBMI, (j,k) with IODMI for the seasons MAM (a,e,i), JJAS (b,f,j), OND (c,g,k) and JF (d,h,l). Correlations significant at 85%, 90% and 95% confidence level, based on Student’s t-test are shown. [Figure created using the COLA/GrADS software].
Mentions: The relative impacts of Indo-Pacific drivers on the African seasonal rainfall during various seasons are explored using the partial correlation analysis between the local rainfall and SST indices (Fig. 2). Figure 2a,d (Fig. 2e,h) exhibit the impact of various phases of ENSO Modoki (canonical ENSO) evolution on the seasonal rainfall. The significant impact of the IOD (IOBM) events on the African climate during JJAS and OND seasons (MAM and JF) can be discerned from Fig. 2j,k (Fig. 2i,l). The results obtained using CRU rainfall dataset (Fig. 2) is reconfirmed using GPCP (Fig. A2) satellite estimates. A composite analysis also, in general, confirms the result (Fig. A3).

Bottom Line: However, both the El Niño flavours anomalously reduce the northern hemispheric rainfall during June-September.During boreal summer, the El Niño Modoki and canonical El Niño (positive IOD) tend to weaken (strengthen) the tropical easterly jet, and result in strengthening (weakening) and southward shift of African easterly jet.This anomalously reduces (enhances) rainfall in the tropical north, including Sahelian Africa.

View Article: PubMed Central - PubMed

Affiliation: Indian Institute of Tropical Meteorology, Pune 411008, India.

ABSTRACT
The study diagnoses the relative impacts of the four known tropical Indo-Pacific drivers, namely, El Niño Southern Oscillation (ENSO), ENSO Modoki, Indian Ocean Dipole (IOD), and Indian Ocean Basin-wide mode (IOBM) on African seasonal rainfall variability. The canonical El Niño and El Niño Modoki are in general associated with anomalous reduction (enhancement) of rainfall in southern (northern) hemispheric regions during March-May season. However, both the El Niño flavours anomalously reduce the northern hemispheric rainfall during June-September. Interestingly, during boreal spring and summer, in many regions, the Indian Ocean drivers have influences opposite to those from tropical Pacific drivers. On the other hand, during the October-December season, the canonical El Niño and/or positive IOD are associated with an anomalous enhancement of rainfall in the Eastern Africa, while the El Niño Modoki events are associated with an opposite impact. In addition to the Walker circulation changes, the Indo-Pacific drivers influence the African rainfall through modulating jet streams. During boreal summer, the El Niño Modoki and canonical El Niño (positive IOD) tend to weaken (strengthen) the tropical easterly jet, and result in strengthening (weakening) and southward shift of African easterly jet. This anomalously reduces (enhances) rainfall in the tropical north, including Sahelian Africa.

No MeSH data available.