Page 1 COST 723 – Opening Workshop - ESTEC March 2004 GEO-MTR: A 2-Dimensional Multi Target Retrieval System for MIPAS/ENVISAT observations Bianca Maria Dinelli ISAC – CNR Bologna

Page 2 COST 723 – Opening Workshop - ESTEC March 2004 LIMITS of Conventional INVERSION METHODS atmospheric domain F The sampled atmosphere is assumed as perfectly stratified (Horizontal Homogeneity Assumption) F In the case of a steady platform (balloon or airplane) this assumption applies to a length of several hundreds of kilometres F In the case of satellite measurements, because of the movement of the platform, this assumption extends to a larger scale (For “along track” observations it can be 2000 km) F When pronounced horizontal gradients are present, this assumption introduces systematic errors difficult to assess

Page 3 COST 723 – Opening Workshop - ESTEC March 2004 F Atmospheric spectra recorded by a spectrometer like MIPAS contain features due to several gases and often these spectral features overlap. F The retrievals are usually operated on a single target and all the target quantities are sequentially retrieved for each limb-scanning sequence F In the sequence of the retrievals the uncertainty of the retrieved quantities acts as a systematic error source on the subsequent retrievals. F To minimize these errors we can 1. Act on the sequence of the retrievals 2. Act on the selection of the analysed spectral intervals F However, in many cases these errors are not negligible LIMITS of Conventional INVERSION METHODS target domain

Page 4 COST 723 – Opening Workshop - ESTEC March 2004 GEO-FIT rationale F The information content about a given location of the atmosphere can be gathered from all the lines of sight that cross that location F the loop of cross-talk between nearby sequences closes when the starting sequence is reached again at the end of the orbit F So all the information is exploited by merging in a simultaneous fit the observations of a complete orbit....

Page 5 COST 723 – Opening Workshop - ESTEC March 2004 GEO-FIT advantages F The retrieval grid is independent from the measurement grid, so the real horizontal resolution of satellite measurements can be studied. F Enables to exploit at its best the information content of along-track satellite limb scanning measurements F Enables to model the horizontal variability of the atmosphere (allowing for a comprehensive assessment of the impact of the horizontal homogeneity assumption)

Page 6 COST 723 – Opening Workshop - ESTEC March 2004 Multi Target Retrieval - rationale F In the sequence of the retrievals the uncertainty of the retrieved quantities acts as a systematic error source on the subsequent retrievals. F In MIPAS PDS the target quantities are sequentially retrieved F If we retrieve all the target quantities that are correlated simultaneously this error propagation may be eliminated

Page 7 COST 723 – Opening Workshop - ESTEC March 2004 MTR – advantages F the uncertainty on the initial guess of the quantities that are going to be simultaneously retrieved does not act as a source of systematic errors F the error due to the cross-talk between different target quantities is properly represented by the variance- covariance matrix of the retrieved parameters. F The selection of the spectral intervals to be used in the analysis is no longer dominated by the need to reduce the interferences among target species F the information on pressure and temperature can be gathered from the spectral features of all target species

Page 8 COST 723 – Opening Workshop - ESTEC March 2004 GEO-MTR F A new analysis system has been developed for the analysis of MIPAS nominal and special observation modes F The system is named GEO-MTR and is based on the Geofit and the Multi Target Retrieval (MTR) functionalities. F The system is developed by University of Bologna, ISAC- CNR, AOPP, LPPM, IFAC-CNR, ASPER Under ESRIN contract No /02/I-LG F The system will be delivered to ESA as open source code

Page 9 COST 723 – Opening Workshop - ESTEC March 2004 GEO-MTR functionalities F The functionalities of the new analysis system are: 1. Geofit analysis of a full orbit 2. orbit-segments analysis (in 2D), 3. single-sequence analysis F Multi Target Retrieval (MTR) of: u p,T + n VMRs (with n=1,2,…..) u p,T u n VMRs F Any combination of MTR with 1, 2, or 3 can be selected

Page 10 COST 723 – Opening Workshop - ESTEC March 2004 GEO-MTR functionalities F With the use of auxiliary files sequential retrievals can be obtained running the analysis system in sequence through a unix script F Any combination of MTR and sequential retrievals can be performed F GEO-MTR can analyze all the backward looking Sn (n=1…6) special observation modes

Page 11 COST 723 – Opening Workshop - ESTEC March 2004 F Orbit 2081 has been analysed performing GEO-MTR analysis for P,T, H 2 O and O 3 F Dedicated MWs have been produced for GEO-MTR F To speed up the retrieval the pointing information and the initial guess were the results of the L2 analysis performed by MIPAS PDS F Convergence has been reached after 2 iterations F The retrieval has also been started using IG2 profiles and L1B pointing information F Convergence has been reached after 3 iterations GEO-MTR analysis of orbit

Page 12 COST 723 – Opening Workshop - ESTEC March 2004 GEO-MTR Results Temperature

Page 13 COST 723 – Opening Workshop - ESTEC March 2004 GEO-MTR Results Pressure

Page 14 COST 723 – Opening Workshop - ESTEC March 2004 GEO-MTR Results Ozone

Page 15 COST 723 – Opening Workshop - ESTEC March 2004 GEO-MTR Results Water

Page 16 COST 723 – Opening Workshop - ESTEC March 2004 GEO-MTR vs PDS

Page 17 COST 723 – Opening Workshop - ESTEC March 2004 GEO-MTR vs PDS

Page 18 COST 723 – Opening Workshop - ESTEC March 2004 GEO-MTR vs PDS

Page 19 COST 723 – Opening Workshop - ESTEC March 2004 COMPUTING REQUIREMENTS F The computing resources needed to run GEO-MTR are examined for the showed retrieval (72 Sequences) F The time needed to perform the retrieval on the full orbit is: u 54 min 55 s on a single CPU Intel Pentium IV (2.8 GHz) u 8 min 20 s on a cluster of 8 CPU Pentium IV (2.8 GHz) F The memory required by this test case is 1.05 Gbyte (can be reduced at the expenses of code readability)

Page 20 COST 723 – Opening Workshop - ESTEC March 2004 Conclusions F A new retrieval system for MIPAS observations has been developed F The new system is capable to perform 2D analyses in Multi Target mode F It has been successfully tested on real MIPAS observations F Memory and time requirements very reasonable F The MTR functionality enables to retrieve p,T H 2 O and O 3 with lower errors than the PDS analysis system F Can perform real time processing of MIPAS observations F The code will be distributed by ESA as open source (no profit!)