Impact of a priori information on IASI ozone retrievals and trends
Abstract
The IASI sensor documents atmospheric water vapor, temperature and composition since 2007. The Software for a Fast Retrieval of IASI Data (SOFRID) has been developped to retrieve O3 and CO profiles from IASI in near-real time on a global scale. Information content analyses have shown that IASI enables the quantification of O3 independently in the troposphere, the UTLS and the stratosphere. Validation studies have demonstrated that the daily to seasonal variability of tropospheric and UTLS O3 was well captured by IASI especially in the tropics. IASI-SOFRID retrievals have also been used to document the tropospheric composition during the Asian monsoon and participated to determine the O3 evolution during the 2008-2016 period in the framework of the TOAR project. Nevertheless, IASI-SOFRID O3 is biased high in the UTLS and in the tropical troposphere and the 8 years O3 trends from the different IASI products are significantly different from the O3 trends from UV-Vis satellite sensors (e.g. OMI)..SOFRID is based on the Optimal Estimation Method that requires a priori information to complete the information provided by the measured thermal infrared radiances. In SOFRID-O3 v1.5 used in TOAR the a priori consists of a single O3 profile and associated covariance matrix based on global O3 radiosoundings. Such a global a priori is characterized by a very large variabilty and does not represent our best kowledge of the O3 profile at a given time and location. Furthermore it is biased towards the northern hemisphere middle latitudes. We have therefore implemented the possibility to use dynamical a priori data in SOFRID and performed experiments using O3 climatological data and MLS O3 analyses. We will present O3 distributions and comparisons with O3 radiosoundings from the different SOFRID-O3 retrievals. We will in particular assess the impact of the use of different a priori data upon the O3 biases and trends during the IASI period.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFM.A51F2128B
- Keywords:
-
- 0322 Constituent sources and sinks;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0345 Pollution: urban and regional;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0365 Troposphere: composition and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0368 Troposphere: constituent transport and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE