All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 74 19 14
PDF Downloads 11 1 0

Large–Circulation Anomalies Over the Tropics during 1971–72

Arthur F. KrugerNational Environmental Satellite Service, NOAA, Washington, D.C. 20233

Search for other papers by Arthur F. Kruger in
Current site
Google Scholar
PubMed
Close
and
Jay S. WinstonNational Environmental Satellite Service, NOAA, Washington, D.C. 20233

Search for other papers by Jay S. Winston in
Current site
Google Scholar
PubMed
Close
Full access

Abstract

The authors have been monitoring the large-scale circulation over the tropics since 1968 through use of operational tropical wind analyses prepared by the National Meteorological Center. Seasonal and monthly anomaly charts of the tropical circulation at 700 and 200 mb have been prepared using four-year seasonal and monthly means as a preliminary “normal” A sequence of seasonal anomaly charts is used here to describe the highly anomalous tropical circulation during the northern summer of 1972 and its antecedents. During this season the trades were weaker than “normal” over most of the Pacific with both the North and South Pacific anticyclones displaced poleward. In the upper troposphere the anomalous flow was anticyclonic over the Central Pacific reflecting the weakness of the mid-oceanic troughs north and south of the equator. From the eastern Pacific eastward across the Atlantic, Africa, and the Indian Ocean the flow at upper levels north of the equator was westerly relative to normal, signifying a notable reduction in the strength of the summertime “monsoon” easterlies over Africa and the Indian Ocean. The evolution of these striking circulation anomalies from a substantially different initial state a year earlier and their association with sea-surface temperature variations over the equatorial Pacific are discussed.

Abstract

The authors have been monitoring the large-scale circulation over the tropics since 1968 through use of operational tropical wind analyses prepared by the National Meteorological Center. Seasonal and monthly anomaly charts of the tropical circulation at 700 and 200 mb have been prepared using four-year seasonal and monthly means as a preliminary “normal” A sequence of seasonal anomaly charts is used here to describe the highly anomalous tropical circulation during the northern summer of 1972 and its antecedents. During this season the trades were weaker than “normal” over most of the Pacific with both the North and South Pacific anticyclones displaced poleward. In the upper troposphere the anomalous flow was anticyclonic over the Central Pacific reflecting the weakness of the mid-oceanic troughs north and south of the equator. From the eastern Pacific eastward across the Atlantic, Africa, and the Indian Ocean the flow at upper levels north of the equator was westerly relative to normal, signifying a notable reduction in the strength of the summertime “monsoon” easterlies over Africa and the Indian Ocean. The evolution of these striking circulation anomalies from a substantially different initial state a year earlier and their association with sea-surface temperature variations over the equatorial Pacific are discussed.

Save