role of the indian and atlantic oceans on the climate variability of eastern africa charles c. mutai...
TRANSCRIPT
![Page 1: ROLE OF THE INDIAN AND ATLANTIC OCEANS ON THE CLIMATE VARIABILITY OF EASTERN AFRICA Charles C. Mutai Kenya Meteorological Department P. O. Box 30259,](https://reader036.vdocuments.mx/reader036/viewer/2022062417/5515438e55034673228b5f4f/html5/thumbnails/1.jpg)
ROLE OF THE INDIAN AND ATLANTIC OCEANS ON THE CLIMATE VARIABILITY OF
EASTERN AFRICA
Charles C. Mutai
Kenya Meteorological Department
P. O. Box 30259, Nairobi Kenya
![Page 2: ROLE OF THE INDIAN AND ATLANTIC OCEANS ON THE CLIMATE VARIABILITY OF EASTERN AFRICA Charles C. Mutai Kenya Meteorological Department P. O. Box 30259,](https://reader036.vdocuments.mx/reader036/viewer/2022062417/5515438e55034673228b5f4f/html5/thumbnails/2.jpg)
CURRENT UNDERSTANDING OF EAST AFRICAN CLIMATE
• Rainfall is the climatic factor of maximum significance• Seasonal rainfall patterns related to migration of ITCZ:
long rains (MAM), short rains (S/OND)• Interannual variability of seasonal rains results from
complex interactions of forced and free atmospheric variations (OND variability stronger than MAM):SST forcing in Pacific, Atlantic and Indian (Ogallo et al. 1988; Nyenzi 1992; Ininda 1994; Mutai et al. 1988; among others)
OND rainfall positively related to ENSO Large/synoptic/meso - scale circulations; Anticyclones cyclones, easterly/westerly perturbations (Nakamura 1969; Anyamba 1984; Hastenrath et al. 1993; Okoola 1999; Mutai and Ward 2000; etc).
![Page 3: ROLE OF THE INDIAN AND ATLANTIC OCEANS ON THE CLIMATE VARIABILITY OF EASTERN AFRICA Charles C. Mutai Kenya Meteorological Department P. O. Box 30259,](https://reader036.vdocuments.mx/reader036/viewer/2022062417/5515438e55034673228b5f4f/html5/thumbnails/3.jpg)
CURRENT UNDERSTANDING OF EAST AFRICAN CLIMATE (2)
• Predictive schemes based solely on ENSO showed skill (Farmer 1988; Hutchinson 1988; KMD/DMCN; etc.)
• Anomalous SST in the Atlantic and Indian Oceans - associated with rainfall fluctuations (Reverdin et al. 1986; Flohn 1987; Nicholson and Entekhabi 1987; Webster et al. 1999; Saji et al. 1999; Black et al. 2002; among others)
• Two SSTs (of the three) predictors used by Mutai et al. (1998) largely independent ENSO ~ SST variability in the northwestern tropical Pacific - Indian Ocean and in the equatorial - tropical South Atlantic.
• GCM simulations (Goddard and Graham 1999; Latif et al. 1999) indicated strong role for the Indian Ocean SSTs in East African rainfall variability
• SST gradients in the Atlantic and Indian Ocean are currently used in monthly / seasonal climate monitoring and forecasting (KMD and DMCN)
![Page 4: ROLE OF THE INDIAN AND ATLANTIC OCEANS ON THE CLIMATE VARIABILITY OF EASTERN AFRICA Charles C. Mutai Kenya Meteorological Department P. O. Box 30259,](https://reader036.vdocuments.mx/reader036/viewer/2022062417/5515438e55034673228b5f4f/html5/thumbnails/4.jpg)
MEAN MONTHLY RAINFALL (mm) OVER EAST AFRICA, 1931-1985
“Long Rains”
“Short Rains”
0-25 25-50 50-100 100-200 > 200 mm
Nyenzi (1992)
![Page 5: ROLE OF THE INDIAN AND ATLANTIC OCEANS ON THE CLIMATE VARIABILITY OF EASTERN AFRICA Charles C. Mutai Kenya Meteorological Department P. O. Box 30259,](https://reader036.vdocuments.mx/reader036/viewer/2022062417/5515438e55034673228b5f4f/html5/thumbnails/5.jpg)
REGIONALIZATION OF E.A. RAINFALL
Indeje et al. (2000)Indeje et al. (2000)
![Page 6: ROLE OF THE INDIAN AND ATLANTIC OCEANS ON THE CLIMATE VARIABILITY OF EASTERN AFRICA Charles C. Mutai Kenya Meteorological Department P. O. Box 30259,](https://reader036.vdocuments.mx/reader036/viewer/2022062417/5515438e55034673228b5f4f/html5/thumbnails/6.jpg)
OND SST / OLR TELECONNECTIONS
X -1
![Page 7: ROLE OF THE INDIAN AND ATLANTIC OCEANS ON THE CLIMATE VARIABILITY OF EASTERN AFRICA Charles C. Mutai Kenya Meteorological Department P. O. Box 30259,](https://reader036.vdocuments.mx/reader036/viewer/2022062417/5515438e55034673228b5f4f/html5/thumbnails/7.jpg)
MAM SST/OLR TELECONNECTIONS
1951-96
1974-96
![Page 8: ROLE OF THE INDIAN AND ATLANTIC OCEANS ON THE CLIMATE VARIABILITY OF EASTERN AFRICA Charles C. Mutai Kenya Meteorological Department P. O. Box 30259,](https://reader036.vdocuments.mx/reader036/viewer/2022062417/5515438e55034673228b5f4f/html5/thumbnails/8.jpg)
OND RAINFALL-WIND TELECONNECTIONS
1974-96
![Page 9: ROLE OF THE INDIAN AND ATLANTIC OCEANS ON THE CLIMATE VARIABILITY OF EASTERN AFRICA Charles C. Mutai Kenya Meteorological Department P. O. Box 30259,](https://reader036.vdocuments.mx/reader036/viewer/2022062417/5515438e55034673228b5f4f/html5/thumbnails/9.jpg)
OND RAINFALL-WIND TELECONNECTIONS
ENSO - variance - removed
![Page 10: ROLE OF THE INDIAN AND ATLANTIC OCEANS ON THE CLIMATE VARIABILITY OF EASTERN AFRICA Charles C. Mutai Kenya Meteorological Department P. O. Box 30259,](https://reader036.vdocuments.mx/reader036/viewer/2022062417/5515438e55034673228b5f4f/html5/thumbnails/10.jpg)
CONTRIBUTION OF ATLANTIC OCEAN IN CLIMATE VARIABILITY OF EAST AFRICA
Mutai et al. (1998) developed an empirical prediction for East Africa OND rainfall based on three precursor global SST REOFs:
• SST REOF4 closely reflect the ENSO signal
• SST REOF5 - SST variance in northwestern tropical Pacific - Indian Ocean
• SST REOF2 - variability in the equatorial and tropical South Atlantic
![Page 11: ROLE OF THE INDIAN AND ATLANTIC OCEANS ON THE CLIMATE VARIABILITY OF EASTERN AFRICA Charles C. Mutai Kenya Meteorological Department P. O. Box 30259,](https://reader036.vdocuments.mx/reader036/viewer/2022062417/5515438e55034673228b5f4f/html5/thumbnails/11.jpg)
ROTATED SST PREDICTORS (Mutai et al. 1998)
SST REOF5
SST REOF4
SST REOF2
![Page 12: ROLE OF THE INDIAN AND ATLANTIC OCEANS ON THE CLIMATE VARIABILITY OF EASTERN AFRICA Charles C. Mutai Kenya Meteorological Department P. O. Box 30259,](https://reader036.vdocuments.mx/reader036/viewer/2022062417/5515438e55034673228b5f4f/html5/thumbnails/12.jpg)
OND TELECONNECTIONS WITH SEPTEMBER SST REOF2, 1974-
96
![Page 13: ROLE OF THE INDIAN AND ATLANTIC OCEANS ON THE CLIMATE VARIABILITY OF EASTERN AFRICA Charles C. Mutai Kenya Meteorological Department P. O. Box 30259,](https://reader036.vdocuments.mx/reader036/viewer/2022062417/5515438e55034673228b5f4f/html5/thumbnails/13.jpg)
PENTAD 850-hPa WIND TELECONNECTIONS
Oct-Nov 1979-96
![Page 14: ROLE OF THE INDIAN AND ATLANTIC OCEANS ON THE CLIMATE VARIABILITY OF EASTERN AFRICA Charles C. Mutai Kenya Meteorological Department P. O. Box 30259,](https://reader036.vdocuments.mx/reader036/viewer/2022062417/5515438e55034673228b5f4f/html5/thumbnails/14.jpg)
PENTAD 200-hPa WIND TELECONNECTIONS
Oct-Nov 1979-96
![Page 15: ROLE OF THE INDIAN AND ATLANTIC OCEANS ON THE CLIMATE VARIABILITY OF EASTERN AFRICA Charles C. Mutai Kenya Meteorological Department P. O. Box 30259,](https://reader036.vdocuments.mx/reader036/viewer/2022062417/5515438e55034673228b5f4f/html5/thumbnails/15.jpg)
CONTRIBUTION OF INDIAN OCEAN IN CLIMATE VARIABILITY
OF EAST AFRICAEquatorial Indian Ocean variability can be simply be computed as a multivariate measure of key variables over the west (W), East (E) and central (C) Indian Ocean basin:
IOD = (TW - TE) - (PW - PE) - UC
where T, P and U represents the SST, sea-level pressure (SLP) and near-surface zonal wind index, respectively.
![Page 16: ROLE OF THE INDIAN AND ATLANTIC OCEANS ON THE CLIMATE VARIABILITY OF EASTERN AFRICA Charles C. Mutai Kenya Meteorological Department P. O. Box 30259,](https://reader036.vdocuments.mx/reader036/viewer/2022062417/5515438e55034673228b5f4f/html5/thumbnails/16.jpg)
PENTAD COMPOSITE 850-hPa WINDS
Warm Phase ~
W. Indian Ocean
Cold Phase ~
W. Indian Ocean
![Page 17: ROLE OF THE INDIAN AND ATLANTIC OCEANS ON THE CLIMATE VARIABILITY OF EASTERN AFRICA Charles C. Mutai Kenya Meteorological Department P. O. Box 30259,](https://reader036.vdocuments.mx/reader036/viewer/2022062417/5515438e55034673228b5f4f/html5/thumbnails/17.jpg)
SURFACE WIND FIELDS - Reverdin et al. 1986
NOV 1961
Climatology
Cf. 1997
![Page 18: ROLE OF THE INDIAN AND ATLANTIC OCEANS ON THE CLIMATE VARIABILITY OF EASTERN AFRICA Charles C. Mutai Kenya Meteorological Department P. O. Box 30259,](https://reader036.vdocuments.mx/reader036/viewer/2022062417/5515438e55034673228b5f4f/html5/thumbnails/18.jpg)
• Goddard and Graham (1999) used observed SSTs 1970-92
• Latif et al. (1999) considered case of heavy rains of Dec-Jan 1997/98
• Isolated the primary control of SST anomalies in the Indian Ocean only, then in the Pacific and then in both the Indian and Pacific Oceans
• Role of Indian Ocean in climate variability over East Africa
GCM CLIMATE SIMULATIONS
![Page 19: ROLE OF THE INDIAN AND ATLANTIC OCEANS ON THE CLIMATE VARIABILITY OF EASTERN AFRICA Charles C. Mutai Kenya Meteorological Department P. O. Box 30259,](https://reader036.vdocuments.mx/reader036/viewer/2022062417/5515438e55034673228b5f4f/html5/thumbnails/19.jpg)
GCM CLIMATE SIMULATIONS - Goddard and Graham 1999
1970-92
![Page 20: ROLE OF THE INDIAN AND ATLANTIC OCEANS ON THE CLIMATE VARIABILITY OF EASTERN AFRICA Charles C. Mutai Kenya Meteorological Department P. O. Box 30259,](https://reader036.vdocuments.mx/reader036/viewer/2022062417/5515438e55034673228b5f4f/html5/thumbnails/20.jpg)
• Understanding mechanisms for Indian / Atlantic Ocean dynamics is important for East African climate
• Observational network in Indian Ocean?• Utility of satellite-derived and reanalysis
data
SUMMARY