Ozone climatologies at 9–12 km altitude as seen by the MOZAIC airborne program between September 1994 and August 1996

Abstract

Abstract. From data collected at cruise levels by the five aircraft of the Measurement of Ozone and Water Vapor by Airbus In-Service Aircraft (MOZAIC) program during a 2-year period (September 1994 to August 1996), an accurate ozone climatology at 9-12 km altitude has been generated over the northern hemisphere (130øW -140øE; 0ø-80øN), and down to 30øS over South America and Africa. North of 35øN, the distribution is dominated by the influence of ozone-rich air of stratospheric origin; farther south, ozone-poor air from the troposphere prevails. A classification based on a threshold of 100 ppbv of ozone is used to distinguish between the stratospheric and tropospheric components and to help in interpreting the data. Seasonal variations of ozone are observed in stratospheric air (maximum in spring, minimum in winter) and in tropospheric air (maximum in summer, minimum in autumn), related to the intensities of dynamic (tropopause variations; stratosphere/troposphere exchanges) and chemical (photochemistry) processes. The tropics exhibit variations that are heterogeneous in time and space, and reflect the influences of active photochemical processes, deep convection and biomass burning emissions. Ozone concentrations decrease with latitude in both the stratosphere and troposphere. A strong vertical gradient is found in stratospheric air but not in tropospheric air, which is much more homogeneous. The integration of data over characteristic geographical areas shows smaller concentrations over the Atlantic Ocean compared to the continents; this is related to the zonal variation of the polar front and the position of ridge/trough pressure systems. IntroductionThere are still large uncertainties in the budget of atmospheric ozone, that is, in the relative importance of photochemical formation and exchanges between the stratosphere and troposphere, and in determining future ozone trends. Knowledge of the ozone distribution in the atmosphere and of the strength of its sources/sinks is required to evaluate the impact of man's activities and to forecast the long-term evolution of this important gas. without separating the stratospheric and tropospheric components, a discrimination method using an ozone threshold at 100 ppbv is discussed and applied to the data. Horizontal ozone climatologies, corresponding to integrations of data in cells 2.5 ø by 2.5 ø at the five cruise levels, are presented thereafter, and their main features are discussed as functions of several parameters (e.g., season, altitude, geographical location, photochemistry, tropopause altitude, ozone stratospheric/tropospheric components, etc.).Average ozone concentrations over 18 characteristics areas are calculated and intercompared. Finally, geographical plots and numerical panels, summarizing this 2-year MOZAIC climatology, are given in order to make these data available to the scientific community. Characteristics of MOZAIC FlightsThe five MOZAIC aircraft were progressively delivered to participating airlines (Air France, Sabena, Lufthansa, Austrian A...

Tropospheric ozone over Equatorial Africa: regional aspects from the MOZAIC data

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Tropospheric ozone climatology over Beijing: analysis of aircraft data from the MOZAIC program

“…O 3 was measured using the dual-beam UV absorption analyzer (Thermo Environment Instruments -Model 49-103), with an overall measurement precision of ±2 ppbv. The sensors were recalibrated after every 500 flight hours (Thouret et al, 1998a. More details of this program can be found on the MOZAIC website (http://mozaic.aero.obs-mip.fr/web/).…”

Classification of tropospheric ozone profiles over Johannesburg based on mozaic aircraft data

“…Traditionally, mean profiles averaged by season or year, together with some measure of variability about these means, have been analyzed. Examples of studies that have focused on constructing an ozone climatology for particular locations, include Kirchhoff et al (1991), Diab et al (1996), Fortuin and Kelder (1998), Thouret et al (1998a), Logan (1999) and Thompson et al (2003). However, computation of the mean tends to obscure the profile micro-structure because of the many counteracting influences present in the data.…”