Some Observations of the Microstructure of Dry Cold Fronts

H. C. Martin Atmospheric Environment Service, Toronto, Ontario, Canada

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Abstract

The microstructure of dry cold fronts was recorded at a coastal site. Three examples of the fine-structure of temperature and horizontal wind measured at 14 m are discussed. One example includes the refractive index fine-structure.

The frontal zone is very narrow and turbulent with the bulk of the change occurring in less than a minute. The wind freshens just prior to the arrival of the front.

Temperature and refractive index fluctuations are negatively correlated over a wide range of scales. It is suggested that if the observed low-level refractive index fine-structure is representative of this field at greater heights, the resulting radar backscattering may be sufficient to cause the line echoes observed during this study.

On two occasions unexpected warm pockets of air were present in the frontal zone. These observations are briefly discussed.

Abstract

The microstructure of dry cold fronts was recorded at a coastal site. Three examples of the fine-structure of temperature and horizontal wind measured at 14 m are discussed. One example includes the refractive index fine-structure.

The frontal zone is very narrow and turbulent with the bulk of the change occurring in less than a minute. The wind freshens just prior to the arrival of the front.

Temperature and refractive index fluctuations are negatively correlated over a wide range of scales. It is suggested that if the observed low-level refractive index fine-structure is representative of this field at greater heights, the resulting radar backscattering may be sufficient to cause the line echoes observed during this study.

On two occasions unexpected warm pockets of air were present in the frontal zone. These observations are briefly discussed.

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