The observations acquired during the full mission of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instrument, aboard the European Space Agency Environmental Satellite (Envisat), have been analysed with version 8.22 of the Optimised Retrieval Model (ORM), originally developed as the scientific prototype of the ESA level-2 processor for MIPAS observations. The results of the analyses have been included into the MI- PAS level-2 version 8 (level2-v8) database containing atmospheric fields of pressure, temperature, and volume mixing ratio (VMR) of MIPAS main targets H2 O, O3 , HNO3 , CH4 , N2 O, and NO2 , along with the minor gases CFC- 11, ClONO2 , N2 O5 , CFC-12, COF2 , CCl4 , CF4 , HCFC-22, C2 H2 , CH3 Cl, COCl2 , C2 H6 , OCS, and HDO. The database covers all the measurements acquired by MIPAS in the nominal measurement mode of the full resolution (FR) part of the mission (from July 2002 to March 2004) and all the observation modes of the optimised resolution (OR) part (from January 2005 to April 2012). The number of species included in the MIPAS level2-v8 dataset makes it of particular importance for the studies of stratospheric chemistry. The database is considered by ESA the final release of the MIPAS level-2 products.The ORM algorithm is operated at the vertical grid coincident to the tangent altitudes of the observations or to a subset of them, spanning (in the nominal mode) the alti- tude range from 6 to 68km in the FR phase and from 6 to 70 km in the OR period. In the latitude domain, FR profiles are spaced by about 4.7o, while the OR profiles are spaced by about 3.7o. For each retrieved species, the auxiliary data and the retrieval choices are described. Each product is characterised in terms of the retrieval error, spatial resolution, and "useful" vertical range in both phases of the MIPAS mission. These depend on the characteristics of the measurements (spectral and vertical resolution of the measurements), the retrieval choices (number of spectral points in- cluded in the analyses, number of altitudes included in the vertical retrieval grid), and the information content of the measurements for each trace species. For temperature, water vapour, ozone, and nitric acid, the number of degrees of freedom is significantly larger in the OR phase than in the FR one, mainly due to the finer vertical measurement grid. In the FR phase, some trace species are characterised by a smaller retrieval error with respect to the OR phase, mainly due to the larger number of spectral points used in the analyses, along with the reduced vertical resolution. The way of handling possible caveats (negative VMR, vertical grid representation) is discussed. The quality of the retrieved profiles is assessed through four criteria, two providing information on the successful convergence of the retrieval iterations, one on the capability of the retrieval to reproduce the measurements, and one on the presence of outliers. An easy way to identify and filter the problematic profiles with the informa- tion contained in the output files is provided. MIPAS level2- v8 data are available to the scientific community through the ESA portal (https://doi.org/10.5270/EN1-c8hgqx4).

Questo documento riassume l'attività svolta nei vari WP, le azioni completate e lo stato di del progetto per il periodo di attività dal 16 giugno 2020 (RA2) al 9 giugno 2021 (RA3).

Given the definition of Software Unit (SU) as a computer program, which takes some input data and processesthem producing output data, this Technical Note (TN) provides some general guidelines to prepare the scientificand technical documentation of the different SUs developed and shared by the partners of the "FORUM Scienza"project.

In this paper, we study the retrieval of water vapor profiles from simulated FORUM measurements. We show that the bias towards the a-priori introduced by the Optimal Estimation technique can be reduced by using larger errors for the a-priori. Reducing the strength of the a-priori may, however, cause unphysical oscillations in the resulting profiles because of the ill-conditioning of the retrieval problem. An a-posteriori regularization technique, the Iterative Variable Strength method, is thus applied to reduce the amplitude of the oscillations.

Conformational variability and heterogeneity are crucial determinants of the function of biological macromolecules. The possibility of accessing this information experimentally suffers from severe under-determination of the problem, since there are a few experimental observables to be accounted for by a (potentially) infinite number of available conformational states. Several computational methods have been proposed over the years in order to circumvent this theoretically insurmountable obstacle. A large share of these strategies is based on reweighting an initial conformational ensemble which arises from, for example, molecular simulations of different qualities and levels of theory. In this work, we compare the outcome of three reweighting approaches based on radically different views of the conformational heterogeneity problem, namely Maximum Entropy, Maximum Parsimony and Maximum Occurrence, and we do so using the same experimental data. In this comparison we find both expected as well as unexpected similarities.

Questo documento riassume l'attività svolta nei vari WP, le azioni completate e lo stato di del progetto per il periodo di attività dal 19 febbraio 2020 (RA1) al 16 giugno 2020 (RA2).

The main goal of this work package is to establish a convention for the interfaces files, both between the various modules which compose the final retrieval system, and the input/output files.

MIPAS is a Fourier Transform spectrometer that measured the atmospheric limb emission spectra in the middle infrared on board the ENVISAT satellite. These measurements allowed the global monitoring of the three-dimensional (latitude, longitude and altitude) distribution of concentrations of many species, during both day and night, for 10 years, from July 2002 to April 2012. Being a limb sounding instrument, the focus of MIPAS measurements was the study of the atmosphere from the upper troposphere to the stratosphere and above, up to the mesosphere. The interest in these measurements goes beyond the end of the mission, as they can be used in long time series of data to determine changes in our planet's climate. To this purpose, it is therefore important to continue improving their quality. The quality of MIPAS L2 products depends on the quality of the L1 products, on the L2 model accuracy, on the quality of auxiliary data, particularly on spectroscopic data. For the last reanalysis of the whole MIPAS mission, a significant effort was made by the MIPAS Quality Working Group, supported by ESA, to improve both L1 and L2 processors, as well as spectroscopy, with the objectives of obtaining L2 products with increased accuracy, better temporal stability, and a larger number of retrieved species. Here we present the full mission dataset, including vertical profiles of 21 trace species plus temperature, obtained by applying the latest version of ESA L2 processor (ORM V8) to the MIPAS L1 data obtained with version 8 of the L1 processor. The impact of the improvements of both L1 and L2 processors on the quality of the L2 products is presented, as well as results of the validation against independent correlative measurements.

Riporta i principali risultati ottenuti nell'ambito del progetto: "Support to MIPAS Level 2 processor Verification and Validation - Phase F", Contratto ESA 4000112093/14/I-LG, cioe' la messa a punto del codice ORM_V8 da utilizzare per la rianalisi di livello 2 dell'intera missione di MIPAS/ENVISAT, il dataset processato, i test di verifica e di validazione dei prodotti di Livello 2 generati.

his report forms the basis for the selection of the ninth Earth Explorer mission within ESA's Earth Observation Programme. Two competing 'Fast Track' candidates, the Far-infrared Outgoing Radiation Understanding and Monitoring (FORUM) mission and the Surface ocean KInematics Multiscale (SKIM) mission. Each have each undergone a rapid and compressed Phase A feasibility study. This report covers the FORUM mission.

We developed a Self-Adapting Constraint Retrieval Scheme (SACRS) to retrieve ozone profiles from nadir infrared satellite measurements. In this algorithm, the constraint is variable in altitude and adapted automatically for each individual measurement. The algorithm is tested on synthetic observations representing the future IASI-NG satellite observations and considering either ozonesonde measurements or chemistry-transport model ozone simulations to represent the true ozone (pseudo-reality). The ozone retrievals are evaluated mainly for the troposphere with a specific focus on the lower troposphere between the surface and 6 km. Compared to a previous algorithm based on a fixed constraint retrieval scheme (FCRS), the biases, correlation and error estimates are improved with the SACRS. The bias is reduced by 40% and the correlation coefficient increases from 0.72 to 0.80. The SACRS algorithm also leads to an enhanced sensitivity in the lower troposphere with degrees of freedom for signal up to 0.83, increased by 11% compared to the FCRS. The SACRS performs especially well where current algorithms usually fail, namely for polar and tropical air masses. The bias is reduced from 8.6% to 0.5% in the troposphere (surface-9 km) when considering polar cases and from 24.4% to 10.1% in the upper troposphere - lower troposphere column (12-18 km) in the tropics.

The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) is a limb-viewing infrared Fourier transform spectrometer that operated from 2002 to 2012 onboard the ENVISAT satellite. The analysis of MIPAS measurements allows to study the temporal evolution of numerous species of interest for the study of the ozone in the stratosphere, pollutants and many green-house gases. The objective of the MIPAS Quality Working Group is to improve the quality of the MIPAS products through a fruitful collaboration among spectroscopists, Level 1, Level 2, and validation teams. A large effort has recently led to implement significant improvements in both ESA Level 1 and Level 2 processors, as well as in spectroscopic database and in some absorption cross-sections in order to improve the quality of the products. In addition to the products already present in the V7 dataset (temperature and the VMR of H2O, O3, HNO3, CH4, N2O, NO2, CFC-11, CFC-12, N2O5, ClONO2, HCFC-22, COF2, CF4, HCN and CCl4), the VMR of six additional species (OCS, CH3Cl, HDO, C2H2, C2H6, COCl2) will be provided in V8 dataset. In order to evaluate the impact of the changes in the products before full mission reprocessing, the analysis of the performances of the products of the modified L1 and L2 processors, as well as the auxiliary data, has been performed on a Diagnostic DataSet (DDS). The orbits of the DDS have been chosen in coincidence with correlative measurements for performing also a preliminary assessment of the accuracy of the products and to evaluate possible changes in the drift. With respect to V7 products, main improvements consist in a reduction of the temperature bias in the first part of the mission, a reduction of the discontinuities in CH4 and N2O time series due to daily gain upgrade, a better filtering of clouds and a better handling of horizontal inhomogeneities.The results of the assessment of the quality of MIPAS measurements will be shown, as well as the study of the temporal evolution and variability of all species. We will also investigate the spatial, seasonal, and interannual variations in the distribution of these species.

The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) is a limb-viewing infrared Fourier transform spectrometer that operated from 2002 to 2012 on board the ENVISAT satellite. The fruitful collaboration among spectroscopists, Level 1, Level 2, and validation teams in the frame of the MIPAS Quality Working Group has recently led to the implementation of significant changes in both ESA Level 1 and Level 2 processors, as well as in the spectroscopic database and in some absorption cross-sections. In addition to the products already present in V7 dataset (temperature and the VMR of H2O, O3, HNO3, CH4, N2O, NO2, CFC-11, CFC-12, N2O5, ClONO2, HCFC-22, COF2, CF4, HCN and CCl4), the VMR of six additional species (OCS, CH3Cl, HDO, C2H2, C2H6, COCl2) will be provided in V8 dataset.Among the new species, methyl chloride (CH3Cl) is of great interest in stratospheric ozone chemistry since it is the most abundant chlorine-containing gas in the troposphere and, in contrast to other relatively long-lived ozone-depleting gases, it has both natural and anthropogenic sources, with the known emission being mainly natural (tropical plants, biomass burning, the ocean, salt marshes and fungi). Since it is not controlled under the Montreal Protocol, its importance is expected to increase in the coming decades as emission controls alter the relative contributions from natural and anthropogenic halogen sources.In this paper we present a preliminary assessment of the quality of the MIPAS CH3Cl data, in terms of precision, accuracy and vertical resolution, and we investigate the spatial and seasonal variations in the distribution of CH3Cl in the upper troposphere/lower stratosphere (UTLS).

The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) is a limb-viewing infrared Fourier transform spectrometer that operated from 2002 to 2012 onboard the ENVISAT satellite. The maintenance and the upgrade of both L1 and L2 ESA processors are accomplished by the Quality Working Group, where a fruitful collaboration among Level 1, Level 2 and validation teams can be exploited. Recently both ESA L1 and L2 processors have been updated, as well as the spectroscopic database and some absorption cross-sections. In addition to the products already present in the current release (V7) of ESA MIPAS data (temperature and the VMR of H2O, O3, HNO3, CH4, N2O, NO2, CFC-11, CFC-12, N2O5, ClONO2, HCFC-22, COF2, CF4, HCN and CCl4), the VMR of six additional species (OCS, CH3Cl, HDO, C2H2, C2H6, COCl2) will be provided in V8 dataset. In preparation of V8 full mission reprocessing, three Diagnostic Datasets have been generated to check the performances of all L1, L2 processors and the new auxiliary data.The analysis of these Diagnostic Datasets and the comparison with previous full mission dataset V7 will be used to perform a first assessment of the quality of the new V8 products. In the paper special focus will be given to the new species.

New remote sensing satellite sensors for the measurements of atmospheric radiation offer the advantage of very high spectral resolution and spectral and/or spatial and temporal coverage. The analysis of these measurements often requires a forward model (FM) for the simulation of the radiation collected by the sensor. The FM should model all the processes affecting the radiance, such as absorption and scattering by molecules and particles. Despite the advancement in sensor technology, the radiative transfer solvers are almost the same since several decades. Among these, the DISORT solver is still one of the most widely used. The DISORT code was developed 30 years ago, and while the code is maintained and updated regularly, the improvements are more geared towards new features than to a revision of the original setup. While the implementation was the best possible at the time, the memory constrains and language limitations of the time are nowadays considerably changed. On the other hand there is still the need of NRT retrievals, and the computing time of the multiple scattering needed in cloudy sky conditions is still the bottleneck of the FM calculation. We modified the DISORT algorithm in three directions: 1) Language improvements. Making use of dynamical assignment and modularity of modern fortran reduces execution time. 2) Algorithm improvements. By approaching the delta-m transformation on a per-layer basis, many computations were saved, expecially when the cloud pattern does not cover all the atmospheric range. 3) Numerical analysis improvements. While these improvements do not shorten the computational time, they improve the precision of the solution of the eigenvalue sub-problems that arises in the multiple scattering calculations. The modifications in the DISORT solver produce an improvement in calculation performances of a factor 3 with respect to the original version. The new solver is named as fast-DISORT (fDISORT).

MIPAS on ENVISAT performed almost continuous measurements of atmospheric composition for approximately 10 years, from June 2002 to April 2012. ESA processor, based on the algorithm ORM (Optimized Retrieval Model), originally designed for the Near Real Time analysis, is currently used for the reanalysis of the full MIPAS mission. Version 7 of the full mission data was released in 2016, but further improvements have been recently performed in ORM V8 to be used in next full mission reanalysis. For these latest releases (V7 and V8) L1 data corrected for reducing the instrumental drift are used.TheinstrumentaldriftisduetoMIPASphotometricdetectorsnonlinearitiesthatchangewithtimeduetothe ageing of the instrument. Numerous species are retrieved from MIPAS measurements. Among them, CCl4 has been recently studied. This species has received increasing interest due to the so called "mystery of CCl4", since it was found that its atmospheric concentration at the surface declines with a rate significantly smaller than its lifetime-limited rate. Indeed there is a discrepancy between the atmospheric observations and the estimated distribution based on the reported production and consumption. MIPAS products generated with Version 7 of the L2 ESA algorithm were used to estimate CCl4 distributions, its trend, and atmospheric lifetime in the upper troposphere / lower stratosphere (UTLS) region. The trends derived by these observations between 2002 and 2012 as a function of both latitude and altitude confirm the decline of atmospheric mixing ratios, in agreement with ground based observations. Stratospheric trend derived from the MIPAS data are non-uniform, with some positive trends even being found in the middle stratosphere, mainly at high altitudes in the Southern Hemisphere. The variability in stratospheric trends reflects the impact of variability in stratospheric transport on trace gases and their temporal evolution.In addition to CCl4, some preliminary results obtained with the latest version of the processor (V8), that performs the analysis of a larger number of species and takes into account horizontal inhomogeneities, will be shown.

The largest part of the Earth's atmosphere ozone is located in the stratosphere, forming the so-called ozone layer. This layer played a key role in the development of life on Earth and still protects the planet from the most Dangerous ultraviolet radiation. After the discovery of the high ozone depletion potential of some anthropogenic origin substances (e.g. chlorofluorocarbons), some limitations in the production of the major ozone-depleting substances (ODS) have been applied with the Montreal Protocol in 1987. The reduction of the ODS concentrations in the stratosphere started in the mid-1990s and, thereafter, the stratospheric ozone layer should have started its recovery. In the attempt to detect this recovery we use the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) measurements to estimate the stratospheric ozone trend in the mission period (July 2002 - April 2012). In particular, we use MIPAS products generated with Version 7 of the Level 2 (L2v7) algorithm operated by the European Space Agency. The L2v7 data are based on the MIPAS Level 1b radiances Version 7. These radiances are calculated with an improved radiometric calibration that exploits a time-dependent non-linearity correction scheme. After this correction the residual drift of the calibration error is smaller than 1% across the entire mission, thus allowing to determine accurate trend estimates.

Atmospheric emissions of carbon tetrachloride (CCl4) are regulated by the Montreal Protocol due to its role as a strong ozone-depleting substance. The molecule has been the subject of recent increased interest as a consequence of the so-called "mystery of CCl4", the discrepancy between atmospheric observations and reported production and consumption. Surface measurements of CCl4 atmospheric concentrations have declined at a rate almost 3 times lower than its lifetime-limited rate, suggesting persistent atmospheric emissions despite the ban. In this paper, we study CCl4 vertical and zonal distributions in the upper troposphere and lower stratosphere (including the photolytic loss region, 70-20 hPa), its trend, and its stratospheric lifetime using measurements from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), which operated onboard the ENVISAT satellite from 2002 to 2012. Specifically, we use the MIPAS data product generated with Version 7 of the Level 2 algorithm operated by the European Space Agency. The CCl4 zonal means show features typical of long-lived species of anthropogenic origin that are destroyed primarily in the stratosphere, with larger quantities in the troposphere and a monotonic decrease with increasing altitude in the stratosphere. MIPAS CCl4 measurements have been compared with independent measurements from other satellite and balloon-borne remote sounders, showing a good agreement between the different datasets. CCl4 trends are calculated as a function of both latitude and altitude. Negative trends of about -10 to -15 pptv decade-1 (-10 to -30 % decade-1) are found at all latitudes in the upper troposphere-lower stratosphere region, apart from a region in the southern midlatitudes between 50 and 10 hPa where the trend is positive with values around 5-10 pptv decade-1 (15-20 % decade-1). At the lowest altitudes sounded by MIPAS, we find trends consistent with those determined on the basis of long-term ground-based measurements (-10 to -13 pptv decade-1). For higher altitudes, the trend shows a pronounced asymmetry between the Northern and Southern hemispheres, and the magnitude of the decline rate increases with altitude. We use a simplified model assuming tracer-tracer linear correlations to determine CCl4 lifetime in the lower stratosphere. The calculation provides a global average lifetime of 47 (39-61) years, considering CFC-11 as the reference tracer. This value is consistent with the most recent literature result of 44 (36-58) years.

The Optimized Retrieval Code (ORM) was originally designed to be the scientific code used as the reference for the ESA operational Near Real Time Analysis of MIPAS measurements on ENVISAT. After the end of ENVISAT mission, occurred on April 2017, this code has been adapted and improved to perform the reanalysis of the full MIPAS mission.

MIPAS on ENVISAT performed almost continuous and global measurements of atmospheric temperature and composition from June 2002 to April 2012. These data are very useful for understanding atmosphere climatology from the upper troposphere to the mesosphere, including trends in composition and variability, as a reference for middle atmosphere ozone and general circulation as well as improvement of tropospheric composition retrievals. The ESA Level 2 processor, based on the Optimized Retrieval Model (ORM), originally designed for the Near Real Time analysis and developed by an European Consortium led by IFAC, is currently improved and used for the reanalysis of the full MIPAS mission. The maintenance and the upgrade of the ESA processor are made in the frame of the MIPAS Quality Working Group, where a fruitful collaboration among Level 1, Level 2 and validation teams is exploited. This collaboration is essential to improve the accuracy of the products and their characterization. This paper is meant to describe the most recent upgrades in the MIPAS processor, in particular the full mission was recently reprocessed with L1 V7 and L2 V7 processors, containing significant improvements with respect to previous version 6, and further improvements are in preparation, that will be collected in version 8 of the ESA processor. The improvements include both L1 and L2 processors, as well as the auxiliary data. In the L1 processor the correction of the instrumental drift caused by the ageing of the detectors has been implemented in order to reduce the non negligible systematic error in the trend estimation. Furthermore, the measured daily gain instead of the weekly gain is now used for the radiometric calibration that allows to better take account for the discontinuities in the gain that occasionally occur in MIPAS band B. Improvements in the L2 processor include a different approach for retrieving atmospheric continuum, the use of an a posteriori regularization with altitude dependent constraint, a better approach for handling interfering species, a reduced bias in CFC-11, the handling of horizontal inhomogeneities and the use of ECMWF altitude/pressure relation to determine more accurate altitudes. Improvements in the auxiliary data consist in the use of microwindows with larger information content, an improved spectroscopic database and diurnally varying climatological dataset. Furthermore, additional species are provided in the new processors, leading to a total of 22 retrieved species by the L2 version 8 processor. Each of these changes has a different impact on the Level 2 products. The individual contributions, as well as the cumulative effects, will be evaluated with a comparison with previous versions of MIPAS products and corresponding results of validation. Improvements in the trend determination will also be evaluated, as well as the quality of the new retrieved species.