Tropospheric ozone climatology at two Southern Hemisphere tropical/subtropical sites, (Reunion Island and Irene, South Africa) from ozonesondes, LIDAR, and in situ aircraft measurements

Abstract

Abstract. This paper presents a climatology and trends of tropospheric ozone in the Southwestern Indian Ocean (Reunion Island) and South Africa (Irene and Johannesburg). This study is based on a multi-instrumental dataset: PTU-O 3 ozonesondes, DIAL LIDAR and MOZAIC airborne instrumentation.The seasonal profiles of tropospheric ozone at Reunion Island have been calculated from two different data sets: ozonesondes and LIDAR. The two climatological profiles are similar, except in austral summer when the LIDAR profiles show greater values in the free troposphere, and in the upper troposphere when the LIDAR profiles show lower values during all seasons. These results show that the climatological value of LIDAR profiles must be discussed with care since LIDAR measurements can be performed only under clear sky conditions, and the upper limit of the profile depends on the signal strength.In addition, linear trends have been calculated from ozonesonde data at Reunion and Irene. Considering the whole tropospheric column, the trend is slightly positive for Reunion, and more clearly positive for Irene. Trend calculations have also been made separating the troposphere into Correspondence to: G. Clain (gaelle.clain@univ-reunion.fr) three layers, and separating the dataset into seasons. Results show that the positive trend for Irene is governed by the lower layer that is affected by industrial pollution and biomass burning. On the contrary, for Reunion Island, the strongest trends are observed in the upper troposphere, and in winter when stratosphere-troposphere exchange is more frequently expected.

Interrelated variations of O<sub>3</sub>, CO and deep convection in the tropical/subtropical upper troposphere observed by the Aura Microwave Limb Sounder (MLS) during 2004–2011

“…Holton et al, 1995;James et al, 2003, and references therein) and is consistent with previous sonde and lidar observations (e.g. Clain et al, 2009). …”

“…1 to 4), with ozone values generally largest in spring (and summer over the north Atlantic, 10Nb and 11Nb) in each hemisphere, as noted previously (e.g. Clain et al, 2009). This reflects seasonality in stratospheric influence at these latitudes (e.g.…”

Climatology and comparison of ozone from ENVISAT/GOMOS and SHADOZ/balloon-sonde observations in the southern tropics

“…SHADOZ datasets are well known and increasingly used for climatological studies (Lamsal et al, 2004;McPeters et al, 2007), variability studies (Logan et al, 2003;Witte et al, 2008) or comparison studies (Liu et al, 2006;Sivakumar et al, 2007), for case studies such as ozone isentropic transport in the lower stratosphere (Semane et al, 2006;Bencherif et al, 2007), and for trend analyses (Clain et al, 2009).…”

Tropospheric ozone profiles by DIAL at Maïdo Observatory (Reunion Island): system description, instrumental performance and result comparison with ozone external data set

“…-and the LIO3T lidar (Baray et al, 1999Clain et al, 2009Vérèmes et al, 2016), dedicated to the observation of tropospheric O 3 (as well as aerosols from the free troposphere up to the lower stratosphere).…”