An analysis of 1 year of tropospheric vertical soundings of ozone at the island of Reunion (21°S, 55°E) is presented. High values of ozone concentration are observed in the troposphere above the inversion level that caps the marine boundary layer (MBL) during the September to November period, concomitant with active biomass burning in the southeastern African continent and Madagascar. Tongues (prominences of higher values) of enhanced ozone are apparent on vertical profiles obtained during this period, and backward trajectories from tongue levels are generally traced back to these zones of intense burning. Profiles of high and almost constant ozone mixing ratio in the whole troposphere above the MBL are also obtained during this season and could not be traced back to a definite origin. Conversely, during January to March, MBL compounds and humidity are convected in the whole troposphere, and tropospheric ozone is very low. The seasonal variation of integrated tropospheric ozone is large, up to 30 Dobson units (DU) and the tropospheric contribution to total columnar ozone could be high, up to 50–55 DU. This seasonal variation is well correlated with total ozone mapping spectrometer (TOMS) data, anticorrelated with integrated water content, and approximately follows, with a small time lag, the seasonal fire activity in the southeastern Africa. Data from Reunion are in accord with equivalent results from Ascension Island (8°S, 15°W), Brazzaville (Congo; 4°S, 15°E) and Natal (Brazil; 6°S, 35°W), corroborate satellite observations, and suggest that the concentration of tropospheric ozone in the tropics is governed by the coupling of photochemical and dynamical processes.

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A direct investigation focussed on the vicinity of the interface of bubble populations generated by different breaking wave fields in a wind-water simulation facility is presented. Bubble size spectrum over a diameter range 60 # < d < 3000 #, obtained from a laser-based single-particle technique is given for different depths in the vicinity of the interface and different conditions of wave age and wind. Selfconsistent results are obtained if the dimensionless depth z* = z/H1/3, where Hi/3 is the significant wave height, is used and two partly overlapping zones are apparent: (1) next to the surface the spectral shape is found to be invariant, and the global bubble concentration decreases rapidly with depth and (2) at lower levels the concentration of small bubbles is roughly constant, and the slope of the size spectrum increases with depth. Distributions of time intervals between bubble arrivals in the sampling volume and bubble speed estimations obtained from bubble time of residence in this volume further suggest bubble clusters in the upper zone that fade out in the lower zone. In addition, bubble concentration is found to increase very rapidly at a given depth with wind speed and more rapidly for large bubbles than for small ones. Bubble cluster, speed, and size distribution variations with depth furnish evidence for the identification of the upper zone with a generation zone and the lower with a dispersion zone. Bubbles generated by breaking waves control, through aer-Johnson andCooke, 1979; Medwin, 1970] and extrapolations osol generation [Blanchard and Woodcock, 1980] or the en-using empirical rules based on these measurements. Investihancement of gas exchanges [-Merlivat and Mernery, 1983; gations about bubbles and ambient noise in the ocean Kerrnan, 1984; Monaban and Spillane, 1984], a large number •Farrner and Lemon, 1984] or about ocean-atmosphere gas of physical [-Coantic, 1980], chemical [Quinn et al., 1975], and transfer •Merlivat and Mernery, 1983] use the empirical rules biological [Blanchard and Syzdek, 1972] ocean-atmosphere derived by Wu [1981], mainly the assumption of an invariant transfer fluxes. The immediate vicinity of the interface being decisive for aerosol generation and gas exchange [Kitaigorodskii, 1984], bubble population characteristics in this zone appear as determinant for these processes and the resulting transfer fluxes. Relative contributions of jet and film droplets to aerosol production, for example, depend critically on bubble distribution in the vicinity of the interface [Cipriano and Blanchard, 1981]. However, due to the very large size and concentration ranges of bubbles generated by breaking waves, the random and violent motion of the interface, diphase occurrences, and the persistent evolution at sea of the significant parameters, bubble measurements are scarce and very reduced in the vicinity of the interface. The situation is aggravated for theoretical investigations: (1) only few measurements, obtained in different and not precisely defined experimental conditions, a...

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