Seasonal and inter-annual variability of the net ecosystem CO2 exchange of a temperate mountain grassland: Effects of weather and management

摘要

In order to examine internal gravity wave characteristics we have analyzed small-scale fluctuations of normalized temperature in the Earth's stratosphere using radio occultation data. An analysis to identify the observed fluctuations as wave-induced, assuming gravity wave shear saturation, is proposed. This technique is based upon a comparison of the experimental and theoretical values of the relative amplitude threshold which is defined as the wave amplitude required for shear instability. The theoretical amplitude threshold, assuming a minimum Richardson number of 1/4, is a function of f/ω, where f and ω are inertial and intrinsic frequencies, correspondingly. The theoretical threshold values are confined from zero to unity. In the case when this criterion is satisfied for its experimental counterpart and the analyzed fluctuations are positively identified as wave-induced, then the intrinsic frequency of the monochromatic gravity wave can be determined from only a single vertical temperature (or density) profile measurement. The results of the determination of the intrinsic frequency and other characteristics of internal gravity waves are presented and discussed.