Step-like temperature fluctuations associated with inverted ramps in a stable surface layer

Abstract

Ensemble averages of temperature before and after step-like temperature fluctuations reveal the presence of inverted ramps in a stable surface layer. Normalized frequency of upward steps increases with increasing stability, whereas normalized magnitude of the temperature step decreases with stability and becomes constant at about R i = 1. These results suggest that the significance of temperature steps increases as stability increases. In moderate stability, the temperature pattern shows a gradual decrease after an upward step, which can be called a time-inverted ramp. Descending air and large downward heat flux are observed in a time-inverted ramp, suggesting a contribution from an ordered motion in wind. On the other hand, the temperature steps are related to gravity waves in strong stability.