Origin of Satellites and G-B SAOZ/NDACC total ozone measurement differences in the tropics
Résumé
All satellites total ozone (TOC) measurements available from SBUV, OMI-T, OMI-D, OMI-CCI, GOME-CCI, GOME2-CCI, SCIAMACHY-CCI, NPP and IASI, since 2004 until 2015 are compared to those provided by the UV-Vis Ground-Based SAOZ/NDACC spectrometer at two tropical stations, Bauru in the continental South Eastern Brazil and Reunion Island in the Indian Ocean. The comparison shows systematic differences between all satellites and SAOZ TOC of different amplitude between the stations although the instruments and the data processing are identical. Indeed, the SAOZ TOC is always larger in Bauru and the difference SAT-SAOZ displays a seasonal variation of larger amplitude there than in Reunion. But importantly also, a long-term SAOZ TOC increase by 2-3 % (6-9 DU) is observed between 2001 and 2015 in Bauru only and not in Reunion as well as in any of the other SAOZ stations.
The Bauru larger TOC and the seasonal variations reported by SAOZ are consistent with the known larger tropospheric ozone there, due to both lightning NOx (LNOx) ozone production at 12-15 km altitude in Dec-Mar and ozone formation in the lower troposphere following biomass burning during the dry season in Aug-Oct. The 2-3% ozone increase since 2001 not seen by the satellites is consistent with the biomass burning increase in Brazil following the deforestation of the area for increasing agricultural production. The ozone increase in the low troposphere is confirmed by the MOZAIC/IAGOS in situ commercial aircraft measurements in the Sao Paolo area. Shown in the presentation will be the series of Satellites-SAOZ TOC in Bauru and Reunion, the differences between the two stations and a discussion of the possible origin of the difference between Satellites and SAOZ reporting.