Anomalous Wind Circulation Observed during 1997/98 El Niño Using Indian MST Radar

Abstract

Unique facility of measuring vertical winds using Indian mesosphere?stratosphere?troposphere (MST) radar along with horizontal winds enables the study of the atmospheric circulation over Gadanki, India. Several important features are noted while analyzing the wind field. A tropical easterly jet stream of 35 m s?1 strength is seen around 16 km during monsoon season. Relatively strong jetlike northward motion (southerlies) of 5?7 m s?1 is seen around 14 km during winter months. These two maxima in zonal and meridional wind patterns, even though they differ in strength greatly, occur in two contrasting seasons. Downward motion combined with upper-level northward and lower-level southward motion observed during winter in normal years indicates the signature of tropical Hadley circulation over the study region. During the 1997/98 El Niño event, however, an anomalous pattern of winds is seen and Hadley circulation is observed to be weakened.