Provisionally corrected surface wind data, worldwide ocean-atmosphere surface fields, and Sahelian rainfall variability

Journal Article · Fri May 01 04:00:00 EDT 1992 · Journal of Climate; (United States)

DOI:https://doi.org/10.1175/1520-0442(1992)005<0454:PCSWDW>2.0.CO;2· OSTI ID:6601823

Ward, M N ^[1]

---

1. Hadley Centre for Climate Prediction and Research, Berks (United Kingdom)

Worldwide ship datasets of sea surface temperature (SST), sea level pressure (SLP), and surface vector wind are analyzed for a July-September composite of five Sahelian wet years (1950, 1952, 1953, 1954, 1958) minus five Sahelian dry years (1972, 1973, 1982, 1983, 1984) (W - D). The results are compared with fields for a number of individual years and for 1988 minus 1987 (88 - 87); Sahelian rainfall in 1988 was near the 1951-80 normal, whereas 1987 was very dry. An extensive study of the geostrophic consistency of trends in pressure gradients and observed wind was undertaken. The results suggest, during the period 1949-88, a mean increase in reported wind speed of about 16% that cannot be explained by trends in geostrophic winds derived from seasonal mean SLP. Estimates of the wind bias are averaged for 18 ocean regions. A map of correlations between Sahelian rainfall and SLP in all available ocean regions is shown to be field significant. Remote atmospheric associations with Sahelian rainfall are consistent with recent suggestions that SST forcing from the tropical Atlantic and the other ocean basins may contribute to variability in seasonal Sahelian rainfall. It is suggested that wetter years in the Sahel are often accompanied by a stronger surface monsoonal flow over the western Indian Ocean and low SLP in the tropical western Pacific near New Guinea, and that there is increased cyclonicity over the extratropical eastern North Atlantic and northwest Europe. In the tropical Atlantic, W - D shows many of the features identified by previous authors. However, the 88-87 fields do not reflect these large-scale tropical Atlantic changes. Instead there is only local strengthening of the pressure gradient and wind flow from Brazil to Senegal. Further individual years are presented (1958, 1972, 1975) to provide specific examples.

• OSTI ID: 6601823
• Journal Information: Journal of Climate; (United States), Journal Name: Journal of Climate; (United States) Vol. 5:5; ISSN JLCLEL; ISSN 0894-8755
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540110*
AFRICA
AIR
ANNUAL VARIATIONS
ASIA
ATMOSPHERIC CIRCULATION
ATMOSPHERIC PRECIPITATIONS
AUSTRALASIA
BRAZIL
CORRELATIONS
DEVELOPING COUNTRIES
EUROPE
FLUIDS
GASES
GLOBAL ASPECTS
GUINEA
INDIAN OCEAN
ISLANDS
LATIN AMERICA
LEVELS
MONITORING
NEW GUINEA
OCEANIC CIRCULATION
PRESSURE GRADIENTS
RAIN
SEA LEVEL
SEAS
SEASONAL VARIATIONS
SENEGAL
SOUTH AMERICA
SURFACE AIR
SURFACE WATERS
TEMPERATURE MONITORING
TROPICAL REGIONS
VARIATIONS
WIND