The detection of post-monsoon tropospheric ozone variability over south Asia using IASI data
- Resource Type
- Authors
- E. Le Flochmoën; Marco Matricardi; E. Pavelin; Jean-Pierre Cammas; Brice Barret; Bastien Sauvage
- Source
- Atmospheric Chemistry and Physics, Vol 11, Iss 18, Pp 9533-9548 (2011)
Atmospheric Chemistry and Physics
Atmospheric Chemistry and Physics, European Geosciences Union, 2011, 11, pp.9533-9548. ⟨10.5194/acp-11-9533-2011⟩
Atmospheric Chemistry and Physics, 2011, 11, pp.9533-9548. ⟨10.5194/acp-11-9533-2011⟩
- Subject
- Atmospheric Science
Ozone
010504 meteorology & atmospheric sciences
Correlation coefficient
Subtropics
010501 environmental sciences
Atmospheric sciences
01 natural sciences
law.invention
010309 optics
Troposphere
lcsh:Chemistry
chemistry.chemical_compound
law
0103 physical sciences
Tropospheric ozone
0105 earth and related environmental sciences
[PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph]
lcsh:QC1-999
chemistry
lcsh:QD1-999
13. Climate action
Climatology
Radiosonde
Environmental science
Tropical cyclone
Bay
lcsh:Physics
- Language
- English
- ISSN
- 1680-7324
1680-7316
The ozone (O3) variability over south Asia during the 2008 post-monsoon season has been assessed using measurements from the MetOP-A/IASI instrument and O3 profiles retrieved with the SOftware for a Fast Retrieval of IASI Data (SOFRID). The information content study and error analyses carried out in this paper show that IASI Level 1 data can be used to retrieve tropospheric O3 columns (TOC, surface-225 hPa) and UTLS columns (225–70 hPa) with errors smaller than 20%. Validation with global radiosonde O3 profiles obtained during a period of 6 months show the excellent agreement between IASI and radiosonde for the UTLS with correlation coefficient R > 0.91 and good agreement in the troposphere with correlation coefficient R > 0.74. For both the UTLS and the troposphere Relative Standard Deviations (RSD) are lower than 23%. Comparison with in-situ measurements from the MOZAIC program around Hyderabad demonstrates that IASI is able to capture the TOC inter and intra-seasonal variability in central India. Nevertheless, the agreement is mitigated by the fact that the smoothing of the true O3 profiles by the retrieval results in a reduction of the TOC variability detected by IASI relative to the variability observed by in situ instruments. The post-monsoon temporal variability of the vertical profile of O3 around Hyderabad has been investigated with MOZAIC observations. These observations from airborne instruments show that tropospheric O3 is steadily elevated during most of the studied period with the exception of two sharp drops following the crossing of tropical storms over India. Lagrangian simulations with the FLEXPART model indicate that elevated O3 concentrations in the middle troposphere near Hyderabad are associated with the transport of UTLS air-masses that have followed the Subtropical Westerly Jet (SWJ) and subsided over northern India together with boundary layer polluted air-masses transported from the Indo-gangetic plain by the north-easterly trades. Low O3 concentrations result from the uplift and westward transport of pristine air-masses from the marine boundary layer of the Bay of Bengal by tropical storms. In order to extend the analysis of tropospheric O3 variability to the whole of south Asia, we have used IASI-SOFRID O3 data. We show that IASI O3 data around Hyderabad were able to capture the fast variability revealed by MOZAIC. Furthermore, their spatio-temporal coverage demonstrates that the behaviour of tropospheric O3 observed near Hyderabad extended over most of central and south India and part of the Bay of Bengal. This result highlights the ability of the IASI sensor to capture fast changes in chemical composition related to dramatic tropical weather conditions.