LAGRANGIAN WIND FLUCTUATIONS AT 300 MB DERIVED FROM TRANSOSONDE DATA

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  • 1 United States Weather Bureau
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Abstract

The dependence upon frequency of the variance and cross variance of zonal-meridional and natural ageostrophic wind components is determined for twelve 300-mb transosonde flights of 60 to 130 hr duration. The main peaks in the variance of these components occur at periods near 50 hr and are assoriated with the transit time of the transosondes through long waves in the westerlies. Two of the longest flights have a secondary peak in the variance of the zonal wind component at a period of 12 hr. For fluctuations of period near 50 hr, the cross variance indicates that the zonal wind component is usually a maximum slightly upstream from the trajectory crest, and that the maximum flow towards low pressure consistently occurs near the inflection point downstream from the trajectory trough line. The evidence for inertial oscillations is inconclusive, partly due to the difficulty in resolving inertial oscillations and fluctuations associated with the but, pending the analysis of more such data, generalization is not attempted.

Abstract

The dependence upon frequency of the variance and cross variance of zonal-meridional and natural ageostrophic wind components is determined for twelve 300-mb transosonde flights of 60 to 130 hr duration. The main peaks in the variance of these components occur at periods near 50 hr and are assoriated with the transit time of the transosondes through long waves in the westerlies. Two of the longest flights have a secondary peak in the variance of the zonal wind component at a period of 12 hr. For fluctuations of period near 50 hr, the cross variance indicates that the zonal wind component is usually a maximum slightly upstream from the trajectory crest, and that the maximum flow towards low pressure consistently occurs near the inflection point downstream from the trajectory trough line. The evidence for inertial oscillations is inconclusive, partly due to the difficulty in resolving inertial oscillations and fluctuations associated with the but, pending the analysis of more such data, generalization is not attempted.

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