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Within the frame of the project CONCERNING (COmpact RamaN lidar for Atmospheric CO2 and ThERmodyNamic ProfilING), we investigated the feasibility and the limits of a ground-based Raman lidar system dedicated to the measurement of CO2 profiles. The performance of the lidar system was evaluated through a set of numerical simulations. The possibility of exploiting both CO2 Raman lines of the ν1:2ν2 resonance was explored. An accurate quantification of the contribution of the Raman O2 lines on the signal and other (e.g., aerosol, absorbing gases) disturbance sources was carried out. The signal integration over the vertical and over time required to reach a useful signal to noise ratio both in day-time and night-time needed for a quantitative analysis of carbon dioxide sources and sinks was evaluated. The above objectives were obtained developing an instrument simulator software consisting of a radiative transfer model able to simulate, in a spectrally resolved manner, all laser light interaction mechanisms with atmospheric constituents, a consistent background signal, and all the devices present in the considered Raman lidar experimental setup. The results indicate that the simulated lidar system, provided to have a low overlap height, could perform measurements on the low troposphere (

The University of Basilicata, in cooperation with ISMAR-CNR, deployed two compact Raman lidars, namely the system CONCERNING and the system MARCO, in Southern France in the frame of the “Water Vapor Lidar Network Assimilation (WaLiNeAs)” experiment. WaLiNeAs, primarily funded by the “French National Research Agency” (ANR), is an international field experiment aimed at studying extreme precipitation events and improving their predictability through the assimilation of water vapour profile measurements from a network of Raman lidar systems into mesoscale numerical models. The experiment has a specific geographical focus on Southern France. The measurement strategy implies the exploitation of seven Raman lidars along the Mediterranean coasts of Spain and France, capable to provide real-time measurements of water vapour mixing ratio profiles over a three-month period starting on October 1st, 2022.CONCERNING (COmpact RamaN lidar for Atmospheric CO2 and ThERmodyNamic ProfilING), developed in the frame of a cooperation between University of Basilicata, ISMAR-CNR and University of Rome, is a compact and transportable Raman lidar system designed for long-term all-weather continuous operation, capable to perform high-resolution and accurate carbon dioxide and water vapour mixing ratio profile measurements, together with temperature and multi-wavelength (355, 532 and 1064 nm) particle backscattering/extinction/depolarization profile measurements. The system relies on a 45-cm diameter Newtonian telescope and on a diode-pumped Nd:Yag laser source, capable of emitting pulses at the three traditional wavelengths of this laser source(355, 532 and 1064 nm), with a single pulse energy at 355 nm of 110 mJ and an average emitted power of 11 watts, based on a pulse repetition frequency of 100 Hz.MARCO (Micropulse Atmospheric Optical Radar for Climate Observations) is also a compact and easily transportable Raman lidar system, developed around a high- frequency laser source (20 kHz), capable to perform 24/7 high-resolution and accurate CO2 and water vapour mixing ratio profile measurements, together with temperature and single-wavelength (355 nm) particle backscattering/extinction/depolarization measurements. In the frame of WaLiNeAs, as a result of the restrictions imposed by air traffic authority in the use of the visible and infrared laser radiation, only the 355 wavelength was exploited in CONCERNING, the temperature channel was not available in MARCO, while the CO2 channels, not needed for the purposes of WaLiNeAs, were temporarily deactivated in both systems.Both systems have been recently designed and developed and WaLiNeAs represents the first international field deployment for both. CONCERNING was deployed at the University of Toulon in La Garde (Lat.: 43.136040 N, Long.: 6.011650 E, Elev.: 65 m, with continuous measurements since 29 September 2022, i.e. over more than 100 days up to now), while MARCO, was deployed at the Direction de Services Techniques in Port-Saint-Louis-du-Rhône, Camargue (Lat.: 43.392570 N, Long.: 4.813480 E, Elev.: 5 m, with continuous measurements since 19 October 2022, i.e. over more than 80 days up to now). At the time of the submission of this abstract, both system are still operational with a tbc date for the stop of the operation of 31 January 2023. Preliminary results from these two systems will be illustrated and discussed during the Conference.

Introduction: The comprehension and interpretation of VIS-IR spectra from space missions to Solar System rocky bodies is generally based on the qualitative/quantitative comparison with standard laboratory datasets [1,2,3,4], i.e. spectra often acquired in laboratory at room pressure/temperature, so dominated by water bands [5]. We developed the new laboratory setup CAPSULA (Chamber for Analogues of Planetary Surfaces Laboratory), consisting of an environmental chamber equipped with a FTIR spectrometer to acquire spectra of planetary analogues in various conditions. The chamber allows to obtain (i) high vacuum (-6 mb); (ii) high (>1000K) and cryogenic T (Setup description: The CAPSULA setup is hosted at INAF-IAPS C-Lab laboratory (fig.1). It is constituted by (i) a Bruker Fourier Transform Infrared (FTIR) spectrometer, equipped with an MCT and DLaTGS detectors and (ii) a large high vacuum chamber 50x60 cm, in which the samples to be analyzed are placed. The chamber and the spectrometer are coupled by means of optical fiber bundles, each composed by seven 200/260-mm core/cladding fibers. Although the FTIR detectors are sensitive up to 20 µm, currently the fibers, in Indium Fluoride Glass, allow the signal to be transmitted in the 0.35-5.5 µm range. The illumination spot on the sample (at angle of 30°) and the collection spot (at 0°) are 3N4 heaters, placed just below copper sampleholders cups, allows to heat samples up to 1073K in high vacuum. A liquid He compressor connected to a cold head within the chamber permits to cool down the samples at cryogenic temperatures below 80K.Preliminary tests and measurements: As preliminary activity the optical fibers have been extensively characterized in the laboratory in terms of spectral transmission, in the 0.35-5.5-µm range, resulting in an average transmission of at least 80% for each fiber.With the aim of starting to test the setup, preliminary spectral measurements have been performed on a powder sample of ammoniated montmorillonite (NH4-SCa3) [6,7] (fig.2). The sample, in the form of 1 µm) and NIR source spectrum cut-off (3 mbar), then at 5, 4, 3 mbar and down to 10-6 mbar. Each spectrum (both reference and sample) is acquired by doing 512 scans with the FTIR interferometer, which takes about 2’. During this time the pressure changed very slowly, i.e. by less than 5%. It can be seen how dehydration proceeds during the pumping, as seen by the decrease of H2O bands at 1.5, 2 and 3 µm. Correspondingly absorption features due to NH4+ become clearly visible (1.55, 2.1-2.2, 3.1 and 3.25 µm) (fig.3). Future work:We are currently testing the different subsystems of the setup (cooling/heating system) and working on several upgrades of the experimental system, including the extension of the spectral range in the mid-IR (above 5 µm) through the use of mirrors. We are in parallel starting to carry out scientific measurements on analogues of different planetary rocky objects (Mars, Ceres) with the current setup.References: [1] De Sanctis M.C. et al. (2015), Nature Letter 528, 241-244. [2] Elkins-Tanton L.T., et al.: (2016) XLVII LPSC, abstract #1631. [3] Hamilton V.E., et al. (2019) Nature Astronomy. [4] Kitazato K., et al. (2019), Science, 364, 272-275. [5] Beck P., et al. (2018) Icarus 313, 124–138. [6] Ferrari M., et al. (2019) Icarus. [7] De Angelis S., et al. (2021), JGR:Planets, V.126, Is.5, e2020JE006696.Acknowledgements: The CAPSULA project has been funded in the framework of ASI-INAF Announcement of Opportunity in 2018 for Solar System studies, with a two years grant. We acknowledge financial contribution from the Agreement ASI-INAF n.2018-16-HH.0.

The Arctic region is showing the most intense warming of the globe, because of different regional feedback mechanisms. Both observed and projected warming rates reach a maximum in the autumn and winter seasons (Bintanja and Krikken, 2016), when the Arctic surface energy budget is dominated by longwave radiation. Indeed, due to the seasonal variation of the of shortwave radiation, the longwave radiation plays a key role in the Arctic, where the annual total Downward Longwave Irradiance (DLI) is usually more than twice as large as the annual downward shortwave irradiance. Nevertheless, surface longwave irradiance measurements in the Arctic are particularly scarce, and satellite retrievals of surface radiation budget based on satellite data are notoriously problematic at high latitudes.High resolution observations of DLI, surface temperature, water vapour surface partial pressure and column amount, zenith sky IR radiance and vertical temperature profile derived by a microwave radiometer are routinely carried out at the Thule High Arctic Atmospheric Observatory (THAAO, 76.5 N, 68.8 W), in North Eastern Greenland (https://ofcsg2dvf1.dwd.de/fmlurlsvc/?fewReq=:B:JVs5MjYzOSV1PjEtMyVqZz4zMjkzMiVwamRtYnd2cWY+MTVnMjJiYmU6ZztgZ2dlYDBiNWVnO2U1NjtiNmE6OjtgNTcwNGBnMSV3PjI1NjEzOjI2NTslcmpnPjE3OkJJUDtOMzI1NDM3LjE3OkJJUDtNMzI1NDM3JXFgc3c+UHdmZWJtLVRiYGhmcUNndGctZ2YlYD43OiVrZ28+Mw==&url=https%3a%2f%2fwww.thuleatmos-it.it%2f ). In the frame of the CLouds And Radiation in the Arctic and Antarctica (CLARA2) project, a celiometer has been installed in November 2019 with the aim of strengthening the cloud observational capability at the Observatory already including, among the other instruments, upward- and downward-looking pyranometers and pyrgeometers operating at THAAO since July 2016.Preliminary statistical results for cloud base altitude, cloud depth, liquid water path (LWP), temperature profiles and presence/intensity of temperature inversion at THAAO will be shown. Analysis on the relationship between LWP and IR downward irradiance and radiance in cloudy and clear sky is also presented.ReferencesBintanja, R., Krikken, F. Magnitude and pattern of Arctic warming governed by the seasonality of radiative forcing. Sci Rep 6, 38287 (2016). https://ofcsg2dvf1.dwd.de/fmlurlsvc/?fewReq=:B:JVs5MjYzOSV1PjEtMyVqZz4zMjkzMiVwamRtYnd2cWY+MjRnOzY0ZjQ3Ojc1ZTAwNDM2NWAxYjE1NTVmNzo3N2YwYDAyNDRnMyV3PjI1NjEzOjI2NTslcmpnPjE3OkJJUDtOMzI1NDM3LjE3OkJJUDtNMzI1NDM3JXFgc3c+UHdmZWJtLVRiYGhmcUNndGctZ2YlYD42MSVrZ28+Mw==&url=https%3a%2f%2fdoi.org%2f10.1038%2fsrep38287

Boreal fires have increased during the last years and are projected to become more intense and frequent as a consequence of climate change. Wildfires produce a wide range of effects on the Arctic climate and ecosystem, and understanding these effects is crucial for predicting the future evolution of the Arctic region. This study focuses on the impact of the long-range transport of biomass-burning aerosol into the atmosphere and the corresponding radiative perturbation in the shortwave frequency range. As a case study, we investigate an intense biomass-burning (BB) event which took place in summer 2017 in Canada and subsequent northeastward transport of gases and particles in the plume leading to exceptionally high values (0.86) of Aerosol Optical Depth (AOD) at 500 nm measured in northwestern Greenland on 21 August 2017. This work characterizes the BB plume measured at the Thule High Arctic Atmospheric Observatory (THAAO; 76.53∘N, 68.74∘W) in August 2017 by assessing the associated shortwave aerosol direct radiative impact over the THAAO and extending this evaluation over the broader region (60∘N–80∘N, 110∘W–0∘E). The radiative transfer simulations with MODTRAN6.0 estimated an aerosol heating rate of up to 0.5 K/day in the upper aerosol layer (8–12 km). The direct aerosol radiative effect (ARE) vertical profile shows a maximum negative value of −45.4 Wm−2 for a 78∘ solar zenith angle above THAAO at 3 km altitude. A cumulative surface ARE of −127.5 TW is estimated to have occurred on 21 August 2017 over a portion (∼3.1×106 km2) of the considered domain (60∘N–80∘N, 110∘W–0∘E). ARE regional mean daily values over the same portion of the domain vary between −65 and −25 Wm−2. Although this is a limited temporal event, this effect can have significant influence on the Arctic radiative budget, especially in the anticipated scenario of increasing wildfires.

Measurements of downwelling shortwave (SW) and longwave (LW) irradiance were carried out on an oceanographic buoy close to the island of Lampedusa (Italy), in the central Mediterranean Sea. Irradiance measurements on the buoy were acquired at high time resolution together with the radiometer pitch and roll angles. The measurements carried out during 2016 have been compared with ground-based observations made at the Lampedusa Atmospheric Observatory, about 15 km northeast of the buoy. The radiometers were compared before and after deployment on the buoy and are traceable to the World Radiometric Reference scale. The SW measurements were corrected for the thermal offset. A small bias (measurements over the sea are smaller than on land) of about −2 W m−2 is found in the daily mean SW, and a moderate bias of +6.2 W m−2 (irradiance over the sea is larger than on land) is found in the LW. Similar biases are found when instantaneous measurements obtained with horizontal radiometers, clean domes, and cloud-free conditions are selected, suggesting that impacts of the moving platform and poor dome cleaning are minor at this site. The effect of the mean tilt angle was also investigated. Deviations in the hourly mean SW irradiance are on the order of 20% for a mean offset of 4° with respect to the solar zenith angle; the effect of tilt angle on LW irradiance appears to be negligible. Radiative transfer calculations show that the observed biases may be ascribed to the differences in the instrument altitude (through radiation absorption, scattering, and emission by the atmospheric constituents in the lowest atmospheric layers) and in the SW surface albedo.

Extended and intense wildfires occurred in Northern Canada and, unexpectedly, on the Greenlandic West coast during summer 2017. The thick smoke plume emitted into the atmosphere was transported to the high Arctic, producing one of the largest impacts ever observed in the region. Evidence of Canadian and Greenlandic wildfires was recorded at the Thule High Arctic Atmospheric Observatory (THAAO, 76.5°N, 68.8°W, www.thuleatmos-it.it) by a suite of instruments managed by ENEA, INGV, Univ. of Florence, and NCAR. Ground-based observations of the radiation budget have allowed quantification of the surface radiative forcing at THAAO. Excess biomass burning chemical tracers such as CO, HCN, H2CO, C2H6, and NH3 were measured in the air column above Thule starting from August 19 until August 23. The aerosol optical depth (AOD) reached a peak value of about 0.9 on August 21, while an enhancement of wildfire compounds was detected in PM10. The measured shortwave radiative forcing was -36.7 W/m2 at 78° solar zenith angle (SZA) for AOD=0.626.MODTRAN6.0 radiative transfer model (Berk et al., 2014) was used to estimate the aerosol radiative effect and the heating rate profiles at 78° SZA. Measured temperature profiles, integrated water vapour, surface albedo, spectral AOD and aerosol extinction profiles from CALIOP onboard CALIPSO were used as model input. The peak aerosol heating rate (+0.5 K/day) was reached within the aerosol layer between 8 and 12 km, while the maximum radiative effect (-45.4 W/m2) is found at 3 km, below the largest aerosol layer.The regional impact of the event that occurred on August 21 was investigated using a combination of atmospheric radiative transfer modelling with measurements of AOD and ground surface albedo from MODIS. The aerosol properties used in the radiative transfer model were constrained by in situ measurements from THAAO. Albedo data over the ocean have been obtained from Jin et al. (2004). Backward trajectories produced through HYSPLIT simulations (Stein et al., 2015) were also employed to trace biomass burning plumes.The radiative forcing efficiency (RFE) over land and ocean was derived, finding values spanning from -3 W/m2 to -132 W/m2, depending on surface albedo and solar zenith angle. The fire plume covered a vast portion of the Arctic, with large values of the daily shortwave RF (< -50 W/m2) lasting for a few days. This large amount of aerosol is expected to influence cloud properties in the Arctic, producing significant indirect radiative effects.

The radiative effects of clouds and their microphysical structure in Polar regions are still object of large uncertainty, that contribute to determine the large inaccuracies of climate model in the representation of clouds and their effects.In the frame of the CLouds And Radiation in the Arctic and Antarctica (CLARA2) project, a celiometer has been installed in November 2019 at the Thule High Arctic Atmospheric Observatory, THAAO, an international infrastructure located in proximity of Thule Air Base (76.5°N, 68.8°W), Greenland (http://www.thuleatmos-it.it/) with the aim of strengthening the cloud observational capability at the Observatory already including, among the other instruments, a microwave profiler and upward- and downward-looking pyranometers and pyrgeometers operating since July 2016.CLARA2 should have contributed to the YOPP 2020 Arctic Special Observing Period (SOP) in February-March with intensive measurements of the atmospheric vertical structure by means of a microwave profiler, a celiometer and daily radiosoundings, but the arrival of the COVID19 prevented the involved researchers to carry out the field campaign at THAAO. Nonetheless the automatic measurements were collected regularly also during the 2020 SOP.The temporal evolution of the cloud’s presence and characteristics during the two months SOP will be presented and discussed in terms of meteorological conditions, broadband surface radiation fluxes, cloud’s geometrical characteristics, phase and liquid water path.

The Mediterranean basin is considered a global hot-spot region for climate change and air-quality. CO2 is the single most-important anthropogenic greenhouse gas (GHG) in the atmosphere, accounting approximatively for ∼63% of the anthropogenic radiative forcing by long-lived GHG. According to Le Quérée et al. (2018), the increasing of the atmospheric CO2 mixing ratios in the global atmosphere is driven by fossil fuel and cement production.In order to reduce GHG emissions and taking into account the needs for economy and society development, schemes of regulation and emission trading have been adopted at international, national, and city levels. The implementation of these regulation, to achieve the goal successfully, needs scientific evidence and information provided on consistent datasets. In the last year, efforts are dedicated to set up harmonized reference networks at difference scales (WMO/GAW, AGAGE, ICOS).In this work, we analysed a set of continuous long-term measurements of CO2 carried out at 4 atmospheric observatories in Italy belonging to the WMO/GAW network and spanning from the Alpine region to central Mediterranean Sea: Plateau Rosa (western Italian Alps, 3480 m a.s.l.), Mt. Cimone (northern Apennines, 2165 m a.s.l.), Capo Granitola (southern Sicily coastline) and Lampedusa Island. Mt. Cimone is also a “class-2” ICOS station, while Plateau Rosa and Lampedusa are in the labelling process. Starting time of GHG observations range from 1979 for Mt. Cimone to 2015 for Capo Granitola. Due to their different locations and ecosystems, they provide useful hints to investigate CO2 variability on different latitudinal and altitudinal ranges in the Mediterranean basin and to study of natural and anthropogenic-related processes able to affect the observed variability.The study addresses primarily differences in daily and seasonal cycles at the different sites, and implemented a procedure to identify background conditions called BaDSfit (Background Data Selection for Italian stations; Trisolino et al., submitted). This methodology was originally used at Plateau Rosa station (Apadula, 2019) and it is based on the Mauna Loa data selection method (Tans and Thoning, 2008). BaDSfit consist of three steps and an optimization of the procedure was carried out with a sensitivity study. Marked differences among the daily cycles at the various sites exist. The effect of the data selection on the seasonal and diurnal cycle and long-term evolution is investigated. The BaDSfit lead to a more coherent diurnal and seasonal evolution of the different datasets, is able to identify background condition and allows the separation of local/regional scale from large scale phenomena in the CO2 time series.

International audience; The SPectral Imager (SPIM) facility is a laboratory VIS-IR spectrometer developed to support spaceborne observations of rocky bodies of the solar system. Currently, this laboratory setup is used to support the Dawn NASA mission and to support the 2018 ExoMars mission in the spectral investigation of Martian subsurface. Specifically, for this mission, a selection of relevant Mars analogue materials has been characterized and stored in the International Space Analogue Rockstore (ISAR), hosted in Orléans, France. In this investigation, two volcanic rock samples from the ISAR collection were analyzed. These two samples were chosen because of their similarity in mineralogical composition and age with Martian basalts and volcanic sands. Moreover, volcanic sands are particularly interesting because they can contain fossils of primitive life forms. The analysis of data collected by SPIM resulted in good agreement with the mineralogical phases detected in these two samples by mineralogical and petrographical techniques, demonstrating the effectiveness of the high spatial and spectral resolution of SPIM for identifying and for mapping different mineralogical species on cut rock and mineral samples.

Ship traffic, population, infrastructure development, and mining activities are expected to increase in the Arctic due to its rising temperatures. This is expected to produce a major impact on aerosol composition. Metals contained in atmospheric particles are powerful markers and can be extremely helpful to gain insights on the different aerosol sources. This work aims at studying the sources of metals in the Arctic aerosol sampled at the Thule High Arctic Atmospheric Observatory (THAAO; Greenland, 76.5°N 68.8°W). Due to the particular composition of Greenlandic soils and to properties of other sources, it was possible to find several signatures of natural and anthropogenic aerosols transported from local and long-range regions. Arctic haze (AH) at Thule builds up on long-range transported aerosol mainly from Canada and Nord America. From a chemical standpoint, this aerosol is characterized by a high concentration of sulfate, Pb, As and Cd and by a La/Ce ratio larger than 1. The Ti/Al and Fe/Al ratios in the AH aerosol are lower (Ti/Al = 0.04 w/w; Fe/Al = 0.79 w/w) than for local aerosol (Ti/Al = 0.07 w/w; Fe/Al = 0.89 w/w). Conversely, aerosol arising from coastal areas of South-West Greenland is characterized by a high concentration of V, Ni, and Cr. These metals, generally considered anthropogenic, arise here mainly from natural crustal sources. In some summer samples, however, the V/Ni ratio becomes larger than 3. In particular, cases displaying this characteristic ratio, as also shown by backward trajectories, are associated with sporadic transport to Thule of ship aerosol from ships passing through Baffin Bay and arriving to Thule during summer. Although further measurements are necessary to confirm the discussed results, the analysis carried out in this work on a large number of metals sampled in coastal Greenland aerosol is unprecedented.

New calculations of the relative optical air mass function are made over the 0°–87° range of apparent solar zenith angle θ, for various vertical profiles of background aerosol, diamond dust and thin cirrus cloud particle extinction coefficient in the Arctic and Antarctic atmospheres. The calculations were carried out by following the Tomasi and Petkov (2014) procedure, in which the above-mentioned vertical profiles derived from lidar observations were used as weighting functions. Different sets of lidar measurements were examined, recorded using: (i) the Koldewey-Aerosol-Raman Lidar (KARL) system (AWI, Germany) at Ny-Ålesund (Spitsbergen, Svalbard) in January, April, July and October 2013, (ii) the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite-based sensor over Barrow (Alaska), Eureka (Nunavut, Canada) and Sodankylä (northern Finland), and Neumayer III, Mario Zucchelli and Mirny coastal stations in Antarctica in the local summer months of the last two years, (iii) the National Institute of Optics (INO), National Council of Research (CNR) Antarctic lidar at Dome C on the Antarctic Plateau for a typical “diamond dust” case, and (iv) the KARL lidar at Ny-Ålesund and the University of Rome/National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA) lidar at Thule (northwestern Greenland) for some cirrus cloud layers in the middle and upper troposphere. The relative optical air mass calculations are compared with those obtained by Tomasi and Petkov (2014) to define the seasonal changes produced by aerosol particles, diamond dust and cirrus clouds. The results indicate that the corresponding air mass functions generally decrease as angle θ increases with rates that are proportional to the increase in the pure aerosol, diamond dust and cirrus cloud particle optical thickness.

JIRAM is an imager/spectrometer on board the Juno spacecraft bound for a polar orbit around Jupiter. JIRAM is composed of IR imager and spectrometer channels. Its scientific goals are to explore the Jovian aurorae and the planet's atmospheric structure, dynamics and composition. This paper explains the characteristics and functionalities of the instrument and reports on the results of ground calibrations. It discusses the main subsystems to the extent needed to understand how the instrument is sequenced and used, the purpose of the calibrations necessary to determine instrument performance, the process for generating the commanding sequences, the main elements of the observational strategy, and the format of the scientific data that JIRAM will produce.

In remote marine areas, biogenic productivity and atmospheric particulate are coupled through dimethylsulfide (DMS) emission by phytoplankton. Once in the atmosphere, the gaseous DMS is oxidized to produce H2SO4 and methanesulfonic acid (MSA), both species can affect the formation of cloud condensation nuclei. This study analyses eight years of biogenic aerosol evolution and variability at two Arctic sites: Thule (76.5&deg, N, 68.8&deg, W) and Ny &Aring, lesund (78.9&deg, N, 11.9&deg, E). Sea ice plays a key role in determining the MSA concentration in polar regions. At the beginning of the melting season, in April, up to June, the biogenic aerosol concentration appears inversely correlated with sea ice extent and area, and positively correlated with the extent of the ice-free area in the marginal ice zone (IF-MIZ). The upper ocean stratification induced by sea ice melting might have a role in these correlations, since the springtime formation of this surface layer regulates the accumulation of phytoplankton and nutrients, allowing the DMS to escape from the sea to the atmosphere. The multiyear analysis reveals a progressive decrease in MSA concentration in May at Thule and an increase in July August at Ny &Aring, lesund. Therefore, while the MSA seasonal evolution is mainly related with the sea ice retreat in April, May, and June, the IF-MIZ extent appears as the main factor affecting the longer-term behavior of MSA.

The seasonal evolution of the tropospheric aerosol vertical distribution and of its optical properties is investigated using lidar and multi-filter rotating shadow-band radiometer (MFRSR) measurements collected throughout the period 2006–2009 in the urban environment of Rome. The evolution of the aerosol distribution is studied also in relation to long range transport of dust. Hybrid Single-Particle Lagrangian Integrated Trajectory model backward trajectories are used to identify possible aerosol sources in remote regions. Aerosol optical depth at 500 nm, τ, and Angstrom exponent, α, are derived from MFRSR measurements. The Angstrom exponent generally displays relatively high values, indicating the predominance of fine particle over the entire column. The average optical depth at 500 nm and Angstrom exponent over the whole period are 0.18 ± 0.09 and 1.12 ± 0.39, respectively. Cases affected by Saharan dust (class 1) are separated from those not influenced by dust (class 0) by using backward trajectories. The average values of τ and α are 0.17 ± 0.08 and 1.17 ± 0.36 for class 0, respectively, and 0.22 ± 0.09 and 0.95 ± 0.46 for class 1. About 214 days of lidar measurements are selected for the analysis. The aerosol vertical distribution is influenced by dust events that induce a marked seasonal behaviour. Desert dust generally reaches higher altitudes than other aerosol types; the maxima altitudes are observed during Spring and Summer, when the monthly average altitude exceeds 5 km. The annual average occurrence of desert dust is 27%, with maxima in Spring and in the first part of Summer. The decrease in the dust event frequency observed in winter months is mainly linked to the seasonal behaviour of the synoptic circulation in the Mediterranean. According to the back-trajectories aerosols are primarily observed below 3 km altitude throughout the year when classified as not affected by desert dust. The extinction coefficient vertical profiles for the two classes show largest differences during Spring and Summer. The extinction for non-dust profiles decreases monotonically with altitude throughout the year, except in Summer. Conversely, the aerosol extinction coefficient shows a relative minimum at the lowest sounded altitude, always except in winter, for class 1 cases. A winter maximum of the aerosol is evidently present in winter in the lower troposphere. Using the MFRSR optical depth and the lidar profiles, the lidar ratio was derived. The overall average lidar ratio is 58 sr.

The Raman lidar system BASIL was operational in Achern (Black Forest) between 25 May and 30 August 2007 in the framework of the Convective and Orographically-induced Precipitation Study (COPS). The system performed continuous measurements over a period of approx. 36 h from 06:22 UTC on 1 August to 18:28 UTC on 2 August 2007, capturing the signature of a severe Saharan dust outbreak episode. The data clearly reveal the presence of two almost separate aerosol layers: a lower layer located between 1.5 and 3.5 km above ground level (a.g.l.) and an upper layer extending between 3.0 and 6.0 km a.g.l. The time evolution of the dust cloud is illustrated and discussed in the paper in terms of several optical parameters (particle backscatter ratio at 532 and 1064 nm, the colour ratio and the backscatter Angstrom parameter). An inversion algorithm was used to retrieve particle size and microphysical parameters, i.e., mean and effective radius, number, surface area, volume concentration, and complex refractive index, as well as the parameters of a bimodal particle size distribution (PSD), from the multi-wavelength lidar data of particle backscattering, extinction and depolarization. The retrieval scheme employs Tikhonov’s inversion with regularization and makes use of kernel functions for randomly oriented spheroids. Size and microphysical parameters of dust particles are estimated as a function of altitude at different times during the dust outbreak event. Retrieval results reveal the presence of a fine mode with radii of 0.1–0.2 μm and a coarse mode with radii of 3–5 μm both in the lower and upper dust layers, and the dominance in the upper dust layer of a coarse mode with radii of 4–5 μm. Effective radius varies with altitude in the range 0.1–1.5 μm, while volume concentration is found to not exceed 92 μm3 cm−3. The real and imaginary part of the complex refractive index vary in the range 1.4–1.6 and 0.004–0.008, respectively.

The vertical profile of Saharan dust in the atmosphere is generally characterized by a large aerosol concentration in the mid troposphere, differently from the climatological distribution of other types of particles, that show a peak at the surface and a rapid decrease with height. Saharan dust is also characterized by particles of relatively large size of irregular shape, and variable values of the single scattering albedo (the ratio between radiation scattering and extinction). The dust's peculiar vertical distribution is expected to produce an effect on the calculation of the direct aerosol radiative forcing at the surface and at the top of the atmosphere. This effect is investigated by comparing estimates of aerosol direct visible radiative forcing at the surface and at the top of the atmosphere for dust vertical profiles measured in the Mediterranean, and for the climatological profile. The radiative forcing is estimated by means of an accurate radiative transfer model, and for the ocean surface. The sensitivity of the results on the solar zenith angle, aerosol optical depth, and aerosol absorption is also investigated. The aerosol radiative forcing at the surface shows a very small dependency on the aerosol vertical profile. At the top of the atmosphere, the radiative forcing is weakly dependent on the vertical profile (up to 10% variation on the daily average forcing) for low absorbing particles; conversely, it shows a strong dependency (the daily radiative forcing may vary up to 100%) for absorbing particles. The top of the atmosphere visible radiative forcing efficiency produced by dust having single scattering albedo

The Raman lidar system BASIL was operational in Achern (Supersite R, Lat: 48.64° N, Long: 8.06° E, Elev.: 140 m) in the frame of the Convective and Orographically‐induced Precipitation Study. BASIL operated continuously over a period of approx. 36 hours from 06:22 UTC on 1 August to 18:28 UTC on 2 August 2007, to cover IOPs 13 a‐b. In this timeframe the signature of a severe Saharan dust outbreak episode was captured. An inversion algorithm was used to retrieve particle size distribution parameters, i.e., mean and effective radius, number, surface area, and volume concentration, and complex refractive index, as well as the parameters of a bimodal particle size distribution, from the multi‐wavelength lidar data of particle backscattering and extinction. The inversion method employs Tikhonov’s inversion with regularization. Size distribution parameters are estimated as a function of altitude at different times during the dust outbreak event. Retrieval results reveal the dominance in the upper dust layer of ...

During the Convective and Orographically‐induced Precipitation Study (COPS), lidar dark bands were observed by the Univ. of BASILicata Raman lidar system (BASIL) on several IOPs and SOPs (among others, 23 July, 15 August, 17 August). Dark band signatures appear in the lidar measurements of particle backscattering at 355, 532 and 1064 nm and particle extinction at 355 and 532 nm, as well as in particle depolarization measurements. Lidar data are supported by measurements from the University of Hamburg cloud radar MIRA 36 (36 GHz), the University of Hamburg dual‐polarization micro rain radars (24.1 GHz) and the University of Manchester Radio UHF clear air wind profiler (1.29 GHz). Results from BASIL and the radars are illustrated and discussed to support in the comprehension of the microphysical and scattering processes responsible for the appearance of the lidar dark band and radar bright band.

The Raman lidar system BASIL was deployed in Achern (Supersite R, Lat: 48.64° N, Long: 8.06° E, Elev.: 140 m) in the frame of the Convective and Orographically‐induced Precipitation Study. On 20 July 2007 a frontal zone passed over the COPS region, with a Mesoscale Convective System (MCS) imbedded in it. BASIL was operated continuously during this day, providing measurements of temperature, water vapour, particle backscattering coefficient at 355, 532 and 1064 nm, particle extinction coefficient at 355 and 532 nm and particle depolarization at 355 and 532 nm. The thunderstorm approaching determined the lowering of the anvil clouds, which is clearly visible in the lidar data. A cloud deck is present at 2 km, which represents a mid‐level outflow from the thunderstorm/MCS. The mid‐level outflow spits out hydrometeor‐debris (mostly virga) and it is recycled back into it. The MCS modified the environment at 1.6–2.5 km levels directly (outflow) and the lower levels through the virga/precipitation. Wave structur...

Aerosol optical properties have been measured on the island of Lampedusa (35.5°N, 12.6°E) with sevenband multifilter rotating shadowband radiometers (MFRSRs) and a CE 318 Cimel sunphotometer (part of the AERONET network) since 1999. Four different MFRSRs have operated since 1999. The Cimel sunphotometer has been operational for a short period in 2000 and in 2003-2006 and 2010-present. Simultaneous determinations of the aerosol optical depth (AOD) from the two instruments were compared over a period of almost 4 years at several wavelengths between 415 and 870 nm. This is the first longterm comparison at a site strongly influenced by desert dust and marine aerosols and characterized by frequent cases of elevated AOD. The datasets show a good agreement, with MFRSR underestimating the Cimel AOD in cases with low Angström exponent; the underestimate decreases for increasing wavelength and increases with AOD. This underestimate is attributed to the effect of aerosol forward scattering on the relatively wide field of view of the MFRSR. An empirical correction of the MFRSR data was implemented. After correction, the mean bias (MB) between MFRSR and Cimel simultaneous AOD determinations is always smaller than 0.004, and the root mean square difference is ≤0.031 at all wavelengths. The MB between MFRSR and Cimel monthly averages (for months with at least 20 days with AOD determinations) is 0.0052. Thus, by combining the MFRSR and Cimel observations, an integrated long-term series is obtained, covering the period 1999-present, with almost continuous measurements since early 2002. The long-term data show a small (nonstatistically significant) decreasing trend over the period 2002-2013, in agreement with independent observations in the Mediterranean. The integrated Lampedusa dataset will be used for aerosol climatological studies and for verification of satellite observations and model analyses. © 2015 Optical Society of America.

Combined measurements of diffuse-to-global radiation ratio and global spectral irradiances in the UV are used to derive cosine-corrected UV irradiances and aerosol optical depth (AOD). The diffuse-to-global radiation ratio is used first in the cosine correction of the global irradiance, then to calculate absolutely calibrated direct irradiances. The Beer-Lambert law is applied to derive the UV AOD using independent measurements of the extraterrestrial solar flux. The AOD can be derived with an uncertainty of about 0.03 at 60 degrees solar zenith angle. The method was applied to measurements obtained with two UV multifilter rotating shadowband radiometers (UV-MFRSRs) and a MK III Brewer spectrophotometer on the Island of Lampedusa in the Central Mediterranean during two periods of 2002 and 2004. The derived AOD at 318 and 332 nm was compared with UV AOD measured at 318, 320, and 368 nm with different techniques. The retrieved AOD, combining MFRSR and Brewer measurements, is in good agreement with the optical depth derived with the other methods.

International audience; The main objective of this work is to provide accurate error estimates for the different water vapour profiling sensors based on an intensive inter-comparison effort. The inter-comparison, performed in the framework of COPS--Convective and Orographically-induced Precipitation Study (01 June-31 August 2007), involves airborne and ground-based water vapour lidar systems, radiosondes with different humidity sensors, GPS and Microwave radiometers (MWR). Simultaneous and co-located data from different sensors are used to compute relative bias and root-mean square (RMS) deviations as a function of altitude