Zonal Wind

Zonal wind is the east-west component of the horizontal wind vector, conventionally denoted u, with positive values for westerly flow toward the east. It is paired with the meridional, north-south component to resolve the full wind. Zonal-mean winds, averaged around a latitude circle, describe the general circulation: easterly trades in the tropics, westerlies in the mid-latitudes, and the jet-stream maxima. Anomalies in the equatorial zonal wind drive ENSO through the Walker circulation, and zonal wind reversals in the stratosphere define the Quasi-Biennial Oscillation. The zonal component is also the dominant term in the geostrophic balance at most latitudes.