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The Po valley (Italy) is one of the most polluted regions in Europe. High NO2 concentrations are often found due to industrial and urban activities and its particular geographical position. However, MAX-DOAS instruments, compliant to the Fiducial Reference Measurements for Ground-Based DOAS (FRM4DOAS) standards were not present in the Po Valley. At the beginning, the purpose of the IDEAS-QA4EO “DOAS-BO: Towards a new FRM4DOAS site in the Po valley" WPs (contract funded by ESA-ESRIN n. 4000128960/19/I-NS) was to fill this gap exploiting TROPOGAS, a custom-built spectrometer developed at CNR-ISAC institute. For this reason, we evaluated its performances and the synergies with in-situ and satellite data during a measurement campaign on the CNR-ISAC roof (Bologna). TROPOGAS was then supposed to be involved in another campaign at BAQUNIN supersite (Rome) to assess the synergies with the Pandora#117 instrument. However, since CNR-ISAC bought a new instrument (SkySpec-2D) compliant to FRM4DOAS requirements, in the frame of an Italian project, we decided to: first, assess the synergy between SkySpec-2D and TROPOGAS, during a measurement campaign in Bologna, and second, move the SkySpec-2D to Rome for the measurement campaign in BAQUNIN against Pandora#117. The results of all the campaigns involve the retrieved NO2Vertical Column Densities (VCDs).

This document reports the activities performed in the frame of the WPs 2250-2.1, 2250-2.2 and 2251-2.3 of the “WPs 2250-2251: DOAS-BO: Towards a new FRM4DOAS - compliant site” project.The WPs 2250-2.1, 2250-2.2 and 2251-2.3 of the project are mainly centred on the measurement campaign performed in Bologna at the Istituto di Scienze dell’Atmosfera e del Clima - Consiglio Nazione delle Ricerche (ISAC-CNR) with the TROPOspheric Gas Analyzer Spectrometer (TROPOGAS) instrument and reporting the obtained results in the light of the exploitation of synergies with in-situand satellitemeasurements.&nbsp

This document is the report of the activities performed in the frame of WP 2251-3 of the IDEAS-QA4EO WPs-2250-2251 “DOAS-BO: Towards a new FRM4DOAS-compliant site’’. The WP 2251-3 is centered on the inter-comparison campaign performed at La Sapienza University in Rome, part of the BAQUNIN supersite. In May 2021, the ISAC-CNR institute acquired (in the frame of a national funded project “Programma biennale degli investimenti del CNR”) a new MAX-DOAS system, the SkySpec-2D. This system took part in several FRM4DOAS inter-comparison campaigns (e.g., CINDI) and full fills all the FRM4DOAS requirements. The SkySpec-2D final destination is the San Pietro Capofiume (BO) “Giorgio Fea” ISAC-CNR observatory in the Po Valley. Due to its full compliance with FRM4DOAS requirements and its more advanced technology, we decided to use the SkySpec-2D instrument instead of the TROPOGAS for the BAQUNIN campaign. However, before traveling to Rome, the SkySpec-2D was employed in an inter-comparison campaign with the TROPOGAS instrument in Bologna, in order to compare the performances of the two MAX-DOAS systems in the same conditions. In this report, we briefly describe the SkySpec-2D system and report the results of the Bologna and BAQUNIN inter-comparison campaigns.

This document is the report of the activities performed in the frame of the two first WPs (WP2250-1.1 and WP2250-1.2) of the “WPs-2250-2251: DOAS-BO: Towards a new FRM4DOAS-compliant site” project.WP2250-1.1 and WP2250-1.2 of the project are mainly centred on the review of the available literature on best practices for DOAS and MAX-DOAS stations and data processing and the assessment of the TROPOspheric Gas Analyzer Spectrometer (TROPOGAS) performances, compliances and not with respect to requirements identified by the FRM4DOAS network.&nbsp

著者人数: 18名, 形態: カラー図版あり, Number of authors: 18, Physical characteristics: Original contains color illustrations, Accepted: 2018-06-01, 資料番号: PA1810006000

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.

We report the results of the validation, long term stability and homogeneity analysis of the AIRWAVE dataset. It consists in atmospheric water vapour total column (TCWV) retrieved using the measurements from the two Thermal InfraRed (TIR) channels of the Along Track Scanning Radiometer (ATSR) instrument series, on board the European Space Agency's ERS-1, ERS-2 and ENVISAT satellites. The retrieval scheme, named Advanced InfraRed WAter Vapour Estimator (AIRWAVE - Casadio et al., 2015), uses the instrument physical characteristics,in combination with advanced radiative transfer models and a sea surface spectral emissivity database. The retrievals therefore do not require algorithm tuning or adjustments to independent water vapour datasets. The use of the dual view capability of the ATSR-type instruments, allows for the accurate and precise day-time and night-time retrievals of cloud free TCWV over oceans. This new physical algorithm can be readily extended to dual view radiometers similar to ATSR, such as the upcoming Sea and Land Surface Temperature Radiometer (SLSTR) instrument on the European Copernicus Sentinel-3 satellite series. The global validation of AIRWAVE TCWV, spanning from 1991 to 2012, is carried out using the WMO soundings located on islands or close to coasts. Validation results will be critically analysed and discussed. Inter-comparisons with the Remote Sensing Systems Special Sensor Microwave Imager (RSS SSM/I) and ECMWF ERA-Interim total water vapour column products have been carried out and results are discussed in detail Finally, the consistency and homogeneity of the AIRWAVE TCWV data across the three ATSRs are analysed and discussed.

The AIRWAVE (Advanced Infra-Red WAter Vapour Estimator) algorithm has been developed for the retrieval of TCWV from the measurements of the Along Track Scanning Radiometer (ATSR) missions. The first version of the algorithm makes use of the TIR channels of ATSR-like instruments, exploiting the dual viewing geometries to infer the TCWV over the sea. When applied to the whole ATSR missions (ATSR-1, ATSR-2 and AATSR) it produced TCVW in good agreement with the results obtained by the Special Sensor Microwave/Imager (SSM/I) and radiosondes. The algorithm makes use of a set of tabulated parameters. In the first version of the algorithm, these parameters were fixed along the whole globe, and were calculated as a weighted average of the ones for Tropical and Mid-Latitude scenarios. We have updated the algorithm with a new set of parameters that improve the performances at all latitudes. The new sets of parameters were calculated accounting for the four seasons and atmospheric state (e.g. Tropical, Mid-Latitude and Polar conditions in January, April, July and October). We computed the new set of parameters with a Radiative Transfer forward Model (RTM) that was specifically developed to simulate ATSR radiances. We have also exploited the RTM to evaluate the impact of atmospheric and surface conditions (e.g. atmospheric temperature and water vapour profiles, HNO3, CO2, CFCs amount, Sea Surface Temperature (SST)) and instrument viewing angles on the calculated parameters. Since each of the simulated conditions produce a different set of retrieval parameters, we had to solve how automatically chose the most suitable ones to be used in each case. The choice is now performed through the use of a Neural Network (NN) that was trained using the above mentioned parameters over a set of radiances simulated with the RTM code and ECMWF temperature, pressure and water vapour profiles. Here we present the results of the application of the updated AIRWAVE algorithm to a subset of ATSR data and evaluate the performances with respect to the ones of the original version.

We present the results of the algorithm modeling the horizontal gradients in the ESA retrieval of MIPAS data ORM v8.

The Along Track Scanning Radiometer series has a long and glorious history, the ATSR instruments being known to be well calibrated, stable, and characterized by relatively high spatial resolution. After the premature departure of ENVISAT (April 2012), the ATSR community started looking into Level 1 interesting features that had not been in the focus for many years. In this context, ESA initiated a small project, called "ATSR Long Term Stability" (ALTS), in the framework of the Long Term Data Preservation programme. The aim of this project is to start looking into some ATSR characteristics from innovative perspectives. The ALTS consortium (TELESPAZIO-VEGA, CNR-ISAC, RHEA, EOSense, SERCO) put together a team of very critical and motivated researchers, never before involved in ATSR studies but with recognized international experience in other fields of remote sensing. A number of issues which up to now have had minor impact on the baseline mission objective of SST retrieval have been investigated, such as: 1) the geolocation and the nadir-forward view collocation quality 2) the radiometric calibration stability (all channels) 3) the (official) cloud mask reliability 4) the documentation availability across the whole instrument series (technical notes, scientific articles, project deliverables ...) In the first two years of ALTS, the investigations led to interesting advances (e.g. a new water vapour retrieval), or to the development of new tools (e.g. transformation from "gridded" to "ungridded" Level 1 products). The extensive work on the radiometric calibration is now producing its results. It should be emphasised that improvements of any aspect of Level 1 products could improve the quality of existing algorithm retrievals or facilitate the development of new products. In this contribution, we will provide details on ALTS achievements, demonstrating the paramount importance of the revision of "old" data for future perspectives, and on the possible outlooks.

Total Column Water Vapour (TCWV) global distribution is a key parameter for climate analysis and weather monitoring. We have designed a new algorithm that enables an accurate and precise estimate of Total Column Water Vapour (TCWV) using the Thermal Infra-Red (TIR) channels of all the Along Track Scanning Radiometer (ATSR) series of instruments. The new algorithm, called Advanced Infra-Red Water Vapour Estimator (AIRWAVE) has been developed in the frame of the ESA contract 'ATSR Long Term Stability (ALTS)' in the optic of a better exploitation of the (A)ATSR instruments and can be easily adapted to work with the Sea and Land Surface Temperature Radiometer (SLSTR) on board the Copernicus Sentinel 3. The retrieval method does not require any tuning or adjustments to independent water vapour datasets and is based on: 1) calculations from a radiative transfer model that was specifically developed to simulate ATSR radiances, 2) informations on instrumental parameters, 3) sea surface spectral emissivity. AIRWAVE exploits the simultaneous use of forward and nadir measurements in the Thermal Infra-Red channels on ocean cloudfree scenes to produce day-time and night-time TCWVs. In order to process the whole ATSR missions (1991-2012), the AIRWAVE prototype processor (AIRWAVE-PP) has been designed and integrated in the ESA GRID environment (GPOD). AIRWAVE-PP decodes each (A)ATSR Level 1 orbit file selecting sea and cloud-free radiances, retrieves TCWV at two different spatial resolution (1x1 km2 and 0.25°x0.25°) and exports the results into NetCDF-CF files and PNG quick-look plots. The physical derivation of the AIRWAVE retrieval method and its implementation will be presented. Preliminary results of the inter-comparisons between ATSR and Special Sensor Microwave/Imager (SSM/I) coincident TCWVs will be shown.

The exploitation of the synergy between infrared and mm-wave limb sounding measurements is one of the key strength of the scientific payload proposed for the PREMIER mission candidate to the Core Missions of ESA Earth Explorer 7. As part of the preparatory activities of PREMIER, the PremierEx campaign was conducted in the Arctic region (Kiruna, Sweden) with the high altitude research aircraft M-55 Geophysica in March 2010. In this work, we discuss the synergistic use of MARSCHALS and MIPAS-STR data acquired during the Premier Ex scientific flight conducted on March 10, 2010 by using an innovative approach to the problem of atmospheric data fusion. We compare the quality of synergistic and individual retrieval products and present our conclusions on the potential of combined exploitation of the information associated to infrared and mm-wave limb observations of the UTLS. The cloud coverage (low clouds in the first part, no clouds in the central part and high tropospheric clouds at the end) observed along the flight provided representative test cases to evaluate the synergy in three different cloudy scenarios.

A key issue in assessing climate change is the precise knowledge of distributions and variability of Total Column Water Vapour (TCWV). We developed a novel algorithm, named Advanced Infra-Red WAter Vapour Estimator (AIRWAVE), for the retrieval of TCWV form Along Track Scanning Radiometer (ATSR) missions measurements. The retrieval method does not require any tuning or adjustments to independent water vapour datasets and is based on: 1) calculations from a radiative transfer model that was specifically developed to simulate ATSR radiances, 2) informations on instrumental parameters, 3) sea surface spectral emissivity. AIRWAVE has been applied to ocean cloud-free ATSR radiances in the Thermal Infra-Red channels (11 and 12 microns) and exploits the simultaneous use of forward and nadir measurements. It allows for accurate and precise day-time and night-time TCWV retrievals as shown by preliminary inter-comparisons between ATSR and Special Sensor Microwave/Imager (SSM/I) coincident TCWVs. The algorithm was developed for ATSR-like instruments having channels in the TIR and exploiting dual viewing geometries. The Sea and Land Surface Temperature Radiometer (SLSTR), on board the European Copernicus Sentinel 3, fully satisfies these requirements. AIRWAVE can, therefore, be applied to SLSTR measurements to retrieve TCWV. Here we discuss the physical derivation of the AIRWAVE retrieval method and present preliminary calculations (based on available instrument characteristics) for the application of AIRWAVE to SLSTR measurements.

The Advanced Infra-Red Water Vapour Estimator, or AIRWAVE, is a novel algorithm developed by CNR and ESA for the accurate and precise estimate of ocean/cloud-free Total Column Water Vapour (TCWV). The algorithm is based on the exploitation of Thermal Infra-Red channels of the ATSR-like instruments, such as SLSTR on board Sentinel 3, in combination with advanced radiative transfer models and a sea surface spectral emissivity database. In particular, the simultaneous use of forward and nadir measurements minimise the impact of changes in sea surface temperature and in atmospheric radiation on the quality of retrieved TCWV for all illumination conditions (day and night). The AIRWAVE-PP prototype processor has been designed and integrated in the ESA GRID environment (GPOD) for testing purposes, and for the bulk processing of the ATSR missions (1991-2012). It is written in Python 2.7, and based on standard Python libraries, such as Numpy and Matplotlib. The BEAT-CODA software is used for the decoding of ESA Level 1 data format. The tool's logical operation flow can be summarised as follows: 1) ATSR Level 1 product decoding and pre-processing; 2) sea and cloud-free data screening using L1 product flags; 3) brightness temperature to radiance conversion; 4) TCWV retrieval at 1x1 km2 and 0.25°x0.25° spatial resolution; 5) exporting of TCWV results into NetCDF-CF (Climate Forecast) file products. The NetCDF-CF convention has been adopted in order to facilitate the readability of dataset by means of freely available software. For each ATSR orbit file, AIRWAVE-PP produces two outputs: a) NetCDF-CF file containing the TCWV data; b) a PNG file (image) showing the TCWV vs. latitude plot (quick-look), the latter used for a fast check on the quality of the retrieval. The AIRWAVE-PP implementation will be discussed in detail, along with the preliminary results of the ATSR vs. SSM/I TCWV inter-comparison exercise.