Further case studies of tropical atlantic surface atmospheric and oceanic patterns associated with sub-Saharan drought

Journal Article · Fri May 01 00:00:00 EDT 1992 · Journal of Climate; (United States)

DOI:https://doi.org/10.1175/1520-0442(1992)005<0476:FCSOTA>2.0.CO;2· OSTI ID:6890342

Lamb, P J ^[1]; Peppler, R A ^[2]

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1. Univ. of Oklahoma, Norman (United States)
2. Illinois State Water Survey, Champaign (United States)

Sub-Saharan West Africa (10[degrees]20[degrees]N) receives rainfall from westward-propagating disturbance lines that have their base within and receive most of their moisture from the low-level, wedge-shaped, southwest monsoonal flow off the tropical Atlantic. This paper identifies the tropical Atlantic surface atmospheric and oceanic patterns that accompany drought in sub-Saharan West Africa. Patterns for the four driest years since 1940 are compared with counterparts for the wettest of the last 20 years and 60-year average fields. The key results for the rainy season of three of the four severe sub-Saharan drought years 1972, 1977, 1984 duplicate those obtained earlier. They include (i) a distinctive basinwide sea surface temperature (SST) anomaly pattern (positive departures to the south of[similar to] 10[degrees]N; negative departures between 10[degrees]- 25[degrees]); (ii) a concomitant southward displacement (relative to the 1911-70 mean) of the zone of maximum SST by 250-500 km; (iii) the North (South) Atlantic subtropical high extending farther (less) equatorward than in the 60-year mean; and (iv) associated southward displacements (by 200-350 km) of the near-equatorial pressure trough, wind direction discontinuity between Northern and Southern hemisphere trades, and zones of maximum rainfall frequency and total cloud amount. Very deficient sub-Saharan rainy seasons tend to coincide with the southwesterly surface monsoonal flow. Only the SST patterns of the aforementioned results show evidence of evolving during preceding seasons. This indicates the potential for tropical Atlantic SST to provide the basis for the prediction of sub-Saharan rainy season quality several months in advance. These results were not characteristic of the other extremely deficient sub-Saharan rainy season investigated (1983) or the nondrought rainy season studied for comparative purposes (1975).

• OSTI ID: 6890342
• Journal Information: Journal of Climate; (United States), Vol. 5:5; ISSN 0894-8755
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
AFRICA
DROUGHTS
MONSOONS
ATLANTIC OCEAN
ATMOSPHERIC CIRCULATION
ANNUAL VARIATIONS
ATMOSPHERIC PRESSURE
FORECASTING
MOISTURE
OCEANIC CIRCULATION
RAIN
SEAS
SEASONAL VARIATIONS
SOUTHERN HEMISPHERE
SURFACE AIR
TEMPERATURE MONITORING
TROPICAL REGIONS
WIND
AIR
ATMOSPHERIC PRECIPITATIONS
DISASTERS
EARTH PLANET
FLUIDS
GASES
MONITORING
PLANETS
STORMS
SURFACE WATERS
VARIATIONS
540110*