Previous: Ext. Abst. Next: Radiosonde data Up: Ext. Abst.

Introduction

Large and small-scale structures such as planetary and gravity waves are recognized to be major sources of the variability

of atmospheric long-lived trace constituents resulting in both horizontal and vertical exchanges in the atmosphere (Ehhalt et al., 1983; Pfister et al., 1986). In the case of gravity waves, Chiu and Ching (1978) first proposed an analytical estimation of the linear response of trace gases to interpret small-scale density variations of the neutral or ionospheric layer structures. For example, ozone reveals to be a good indicator of gravity wave motions in the troposphere and the stratosphere (Gruzdev and Elanskiy, 1984). But the signatures of gravity wave motions which are extracted from vertical profiles of ozone or temperature can be contaminated by those of laminar structures produced by horizontal large-scale advection. The variability of trace gases induced by gravity waves is observed to be highly correlated with perturbations of potential temperature as opposed to that of quasi-horizontal motions (Holton, 1987).

In fact, normalized perturbations of ozone mixing ratio can be simply linked to those of temperature in the linear case when gravity waves are present (Teitelbaum et al., 1996).

__ and ‘ denote the unperturbed background and perturbations, q is the potential temperature.

Eckermann et al. (1998) formalized the complete analytical response of vertical minor constituent profiles of arbitrary shape or broadly of conserved quantities to adiabatic gravity-wave displacements. Gibson-Wilde et al. (1997) observed simultaneously two small-scale structures on a vertical ozone profile around the same height range in the stratosphere. Using a relation similar to equation 1, the observed structures were identified as resulting from two processes of different nature: a synoptic-scale quasi-horizontal advection and gravity waves.

In this study, these two types of vertical short-scale structures are examined in the upper troposphere and the lower stratosphere (UT/LS) using radiosonde data at La Reunion Island (20.8 S, 55.3 E). The identification and the characterization are based on wavelet techniques (Chane-Ming et al., 2000a).