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We have constructed an atmospheric inversion framework based on TM5-4DVAR to jointly assimilate measurements of methane and δ13C of methane in order to estimate source-specific methane emissions. Here we present global emission estimates from this framework for the period 1999–2016. We assimilate a newly constructed, multi-agency database of CH4 and δ13C measurements. We find that traditional CH4-only atmospheric inversions are unlikely to estimate emissions consistent with atmospheric δ13C data, and assimilating δ13C data is necessary to derive emissions consistent with both measurements. Our framework attributes ca. 85 % of the post-2007 growth in atmospheric methane to microbial sources, with about half of that coming from the tropics between 23.5∘ N and 23.5∘ S. This contradicts the attribution of the recent growth in the methane budget of the Global Carbon Project (GCP). We find that the GCP attribution is only consistent with our top-down estimate in the absence of δ13C data. We find that at global and continental scales, δ13C data can separate microbial from fossil methane emissions much better than CH4 data alone, and at smaller scales this ability is limited by the current δ13C measurement coverage. Finally, we find that the largest uncertainty in using δ13C data to separate different methane source types comes from our knowledge of atmospheric chemistry, specifically the distribution of tropospheric chlorine and the isotopic discrimination of the methane sink.

We describe and implement a data selection algorithm aimed at identifying background atmospheric CO2 observations from in situ continuous measurements. Several selection criteria for detecting the background data have been developed and are currently used: the main objective of this work was to define a common methodology to extract the atmospheric background signal minimizing heterogeneities due to the use of different selection algorithms. The algorithm used in this study, (BaDS, Background Data Selection) was tested and optimized using data (from 2014 to 2018) from four Italian stations characterized by markedly different environmental conditions (i.e., mountain, coastal and marine): Plateau Rosa (PRS), Mt. Cimone (CMN), Capo Granitola (CGR) and Lampedusa (LMP). Their locations extend from the Alps to the central Mediterranean. The adopted algorithm proved to be effective in separating the local/regional from the background signal in the CO2 time series. About 6% of the data at LMP, 11% at PRS, 20–38% at CMN and 65% at CGR were identified as non-background. LMP and PRS can be used as reference sites for the central Mediterranean, while CMN and CGR were more impacted by regional sources and sinks. Finally, we discuss a possible application of BaDS screened data.

Detailed atmospheric and aerosol properties, and radiation measurements were carried out in summer 2013 during the Aerosol Direct Radiative Impact on the regional climate in the MEDiterranean region (ADRIMED) campaign in the framework of the Chemistry-Aerosol Mediterranean Experiment (ChArMEx) experiment. This study focusses on the characterization of infrared (IR) optical properties and direct radiative effects of mineral dust, based on three vertical profiles of atmospheric and aerosol properties and IR broadband and narrowband radiation from airborne measurements, made in conjunction with radiosonde and ground-based observations at Lampedusa, in the central Mediterranean. Satellite IR spectra from IASI are also included in the analysis. The atmospheric and aerosol properties are used as input to a radiative transfer model, and various IR radiation parameters (upward and downward irradiance, nadir and zenith brightness temperature at different altitudes) are calculated and compared with observations. The model calculations are made for different sets of dust size distribution and refractive indices, derived from observations and from the literature. The main results of the analysis are that the IR dust radiative forcing is non negligible, and strongly depends on size distribution (SD) and refractive index (RI). When calculations are made using the in situ measured size distribution, it is possible to identify the refractive index that produces the best match with observed IR irradiances and brightness temperatures (BTs). The most appropriate refractive indices correspond to those determined from independent measurements of mineral dust aerosols from the source regions (Tunisia, Algeria, Morocco) of dust transported over Lampedusa, suggesting that differences in the source properties should be taken into account. With the in situ size distribution and the most appropriate refractive index the estimated dust IR radiative forcing efficiency is +23.7 W m-2 at the surface, -7.9 W m-2 within the atmosphere, and +15.8 W m-2 at the top of the atmosphere. The use of column integrated dust SD from AERONET may also produce a good agreement with measured irradiances and BTs, but with significantly different values of the RI. This implies large differences, up to a factor of 2.5 at surface, in the estimated dust radiative forcing, and in the IR heating rate. This study shows that spectrally resolved measurements of brightness temperatures are important to better constrain the dust IR optical properties, and to obtain a reliable estimate of its radiative effects. Efforts should be directed at obtaining an improved description of the dust size distribution, its vertical distribution, and at including regionally-resolved optical properties.

We present a characterization of reactive gases (RG: O3, NO, NO2,SO2, CO) and methane (CH4) variability in the central Mediterranean basin,analyzing in situ measurements at three new permanent WMO/GAW Observatories in Southern Italy: Capo Granitola – CGR (Sicily), Lamezia Terme – LMT (Calabria) and Lecce – ECO (Apulia). At all the measurement sites, a combination of the breeze wind system (especially at CGR and LMT),PBL dynamics, anthropogenic/natural emissions, and photochemistry lead the appearance of well-defined diurnal cycles for the observed RG. According to O3/NOx variability, local emissions appeared to influence CGR and LMT (no NOx data were available for ECO during the period of study) in 4% and 20% of the hourly data, nearby sources in 39% and 40%, remote sources in 31% and 14%, while background O3/NOx were observed in 26% of cases for both the stations. Most of the background O3/NOx were observed during daytime, when offshore air masses usually affected the measurement sites. Local sources of CH4 at CGR can be related to biogenic (oxic) emissions from biomasses along the coastline, while emissions from live stocks can represent a local source of CH4 at LMT. Finally, we provide first hints about the export of O3 from Sicily/Southern Italy to the Mediterranean Sea by comparing simultaneous observations at CGR and Lampedusa (LMP), a small island in the middle of the Strait of Sicily where a WMO/GAW Regional Station is located. In summer,O3 increased by some 7 ppb for transport times lower than 48 h, while no statistical significant differences were observed for travel time longer than 48. This would suggest that photochemical O3 production occurred within air-mass travelling from CGR to LMP, but also that the central Mediterranean MBL represents a O3 sink for relatively aged air-masses.

Particulate matter with aerodynamic diameters lower than 10 µm, (PM10) aerosol samples were collected during summer 2013 within the framework of the Chemistry and Aerosol Mediterranean Experiment (ChArMEx) at two sites located north (Capo Granitola) and south (Lampedusa Island), respectively, of the main Mediterranean shipping route in the Straight of Sicily. The PM10 samples were collected with 12 h time resolutions at both sites. Selected metals, main anions, cations and elemental and organic carbon were determined. The evolution of soluble V and Ni concentrations (typical markers of heavy fuel oil combustion) was related to meteorology and ship traffic intensity in the Straight of Sicily, using a high-resolution regional model for calculation of back trajectories. Elevated concentration of V and Ni at Capo Granitola and Lampedusa are found to correspond with air masses from the Straight of Sicily and coincidences between trajectories and positions of large ships; the vertical structure of the planetary boundary layer also appears to play a role, with high V values associated with strong inversions and a stable boundary layer. The V concentration was generally lower at Lampedusa than at Capo Granitola V, where it reached a peak value of 40 ng m−3. Concentrations of rare earth elements (REEs), La and Ce in particular, were used to identify possible contributions from refineries, whose emissions are also characterized by elevated V and Ni amounts; refinery emissions are expected to display high La ∕ Ce and La ∕ V ratios due to the use of La in the fluid catalytic converter systems. In general, low La ∕ Ce and La ∕ V ratios were observed in the PM samples. The combination of the analyses based on chemical markers, air mass trajectories and ship routes allows us to unambiguously identify the large role of the ship source in the Straight of Sicily. Based on the sampled aerosols, ratios of the main aerosol species arising from ship emission with respect to V were estimated with the aim of deriving a lower limit for the total ship contribution to PM10. The estimated minimum ship emission contributions to PM10 were 2.0 µg m−3 at Lampedusa and 3.0 µg m−3 at Capo Granitola, corresponding with 11 and 8.6 % of PM10, respectively.

Long-range transport of biomass burning (BB) aerosols between North America and the Mediterranean region took place in June 2013. A large number of ground-based and airborne lidar measurements were deployed in the western Mediterranean during the Chemistry-AeRosol Mediterranean EXperiment (ChArMEx) intensive observation period. A detailed analysis of the potential North American aerosol sources is conducted including the assessment of their transport to Europe using forward simulations of the FLEXPART Lagrangian particle dispersion model initialized using satellite observations by MODIS and CALIOP. The three-dimensional structure of the aerosol distribution in the ChArMEx domain observed by the ground-based lidars (Minorca, Barcelona and Lampedusa), a Falcon-20 aircraft flight and three CALIOP tracks, agrees very well with the model simulation of the three major sources considered in this work: Canadian and Colorado fires, a dust storm from western US and the contribution of Saharan dust streamers advected from the North Atlantic trade wind region into the westerlies region. Four aerosol types were identified using the optical properties of the observed aerosol layers (aerosol depolarization ratio, lidar ratio) and the transport model analysis of the contribution of each aerosol source: (i) pure BB layer, (ii) weakly dusty BB, (iii) significant mixture of BB and dust transported from the trade wind region, and (iv) the outflow of Saharan dust by the subtropical jet and not mixed with BB aerosol. The contribution of the Canadian fires is the major aerosol source during this episode while mixing of dust and BB is only significant at an altitude above 5 km. The mixing corresponds to a 20–30 % dust contribution in the total aerosol backscatter. The comparison with the MODIS aerosol optical depth horizontal distribution during this episode over the western Mediterranean Sea shows that the Canadian fire contributions were as large as the direct northward dust outflow from Sahara.

The SPectral IMager (SPIM) facility is a laboratory visible infrared spectrometer developed to support space borne observations of rocky bodies of the solar system. Currently, this laboratory setup is used to support the DAWN mission, which is in its journey towards the asteroid 1-Ceres, and to support the 2018 Exo-Mars mission in the spectral investigation of the Martian subsurface. The main part of this setup is an imaging spectrometer that is a spare of the DAWN visible infrared spectrometer. The spectrometer has been assembled and calibrated at Selex ES and then installed in the facility developed at the INAF-IAPS laboratory in Rome. The goal of SPIM is to collect data to build spectral libraries for the interpretation of the space borne and in situ hyperspectral measurements of planetary materials. Given its very high spatial resolution combined with the imaging capability, this instrument can also help in the detailed study of minerals and rocks. In this paper, the instrument setup is first described, and then a series of test measurements, aimed to the characterization of the main subsystems, are reported. In particular, laboratory tests have been performed concerning (i) the radiation sources, (ii) the reference targets, and (iii) linearity of detector response; the instrumental imaging artifacts have also been investigated. © 2015 AIP Publishing LLC.

We wish to thank the Italian Space Agency (ASI) for funding and fully supporting the Ma_Miss experiment (ASI/INAF grant I/ 060/10/0). We also thank G.F. De Astis (INGV) for providing the Aeolian samples, and A.Frigeri for providing the red micritic limestone. We thank an anonymous reviewer for useful comments and suggestions. The Ma_Miss instrument (Mars Multispectral Imager for Subsurface Studies, Coradini et al. (2001)) is a Visible and Near Infrared miniaturized spectrometer that will observe the Martian subsurface in the 0.4-2.2 μm spectral range. The instrument will be entirely hosted within the Drill of the ExoMars-2018 Pasteur Rover: it will allow analyzing the borehole wall excavated by the Drill, at different depths, down to 2 m. The aim will be to investigate and characterize the mineralogy and stratigraphy of the shallow Martian subsurface. A series of spectroscopic measurements have been performed in order to characterize the spectral performances of the laboratory model of the instrument (breadboard). A set of six samples have been analyzed. Each sample (four volcanic rocks, a micritic limestone and a calcite) has been reduced in particulate form, ground, sieved and divided into nine different grain sizes in the range d

Results from the Ground-based and Airborne Measurements of Aerosol Radiative Forcing (GAMARF) campaign carried out at Lampedusa island in 2008 are presented. The campaign was focussed on measurements of longwave (LW) irradiance profiles up to 4 km, until now absent in the Mediterranean Sea, and to the estimation of shortwave (SW) and LW aerosol direct radiative forcings (ADRFs), using data collected by ground-based and airborne instrumentation and radiative transfer simulations. The SW and LW ADRFs have been calculated for a case of desert dust characterized by relatively large aerosol optical depth. © 2013 AIP Publishing LLC.

The Ground-based and Airborne Measurements of the Aerosol Radiative Forcing (GAMARF) campaign was carried out during spring 2008 in Lampedusa Island (Central Mediterranean). Several flights were performed by an instrumented ultralight in different atmospheric conditions. In situ measurements of aerosol size distribution vertical profiles were used together with ground-based measurements of aerosol optical depth and ÅAngström exponent to retrieve simultaneously profiles of the aerosol radiative properties and its effective refractive index. The retrieved backscattering and extinction profiles are in agreement with independent Lidar measurements, within the estimated uncertainties. This analysis suggests that in situ measurements of aerosol distribution can be used quantitatively for the determination of the aerosol optical and radiative properties. © 2013 AIP Publishing LLC.

In this study we present an intercomparison of measurements of very low water vapor column content obtained with a Ground‐Based Millimeter‐wave Spectrometer (GBMS), Vaisala RS92k radiosondes, a Raman Lidar, and an IR Fourier Transform Spectrometer. These sets of measurements were carried out during the primary field campaign of the ECOWAR (Earth COoling by WAter vapor Radiation) project which took place on the Western Italian Alps from 3 to 16 March, 2007.

The paper presents a novel methodology to retrieve the foreign-broadened water vapor continuum absorption coefficients in the spectral range 240 to 590 cm(-1) and is the first estimation of the continuum coefficient at wave numbers smaller than 400 cm(-1) under atmospheric conditions. The derivation has been accomplished by processing a suitable set of atmospheric emitted spectral radiance observations obtained during the March 2007 Alps campaign of the ECOWAR project (Earth COoling by WAter vapor Radiation). It is shown that, in the range 450 to 600 cm(-1), our findings are in good agreement with the widely used Mlawer, Tobin-Clough, Kneizys-Davies (MT_CKD) continuum. Below 450 cm(-1) however the MT_CKD model overestimates the magnitude of the continuum coefficient. (C) 2008 Optical Society of America

Observations of very low amounts of precipitable water vapor ( PWV) by means of the Ground- Based Millimeter wave Spectrometer ( GBMS) are discussed. Low amounts of column water vapor ( between 0.5 and 4 mm) are typical of high mountain sites and polar regions, especially during winter, and are difficult to measure accurately because of the lack of sensitivity of conventional instruments to such low PWV contents. The technique used involves the measurement of atmospheric opacity in the range between 230 and 280 GHz with a spectral resolution of 4 GHz, followed by the conversion to precipitable water vapor using a linear relationship. We present the intercomparison of this data set with simultaneous PWV observations obtained with Vaisala RS92k radiosondes, a Raman lidar, and an IR Fourier transform spectrometer. These sets of measurements were carried out during the primary field campaign of the Earth Cooling by Water vapor Radiation ( ECOWAR) project which took place at Breuil- Cervinia ( 45.9 degrees N, 7.6 degrees E, elevation 1990 m) and Plateau Rosa ( 45.9 degrees N, 7.7 degrees E, elevation 3490 m), Italy, from 3 to 16 March 2007. GBMS PWV measurements show a good agreement with the other three data sets exhibiting a mean difference between observations of similar or equal to 9%. The considerable number of data points available for the GBMS versus lidar PWV correlation allows an additional analysis which indicates negligible systematic differences between the two data sets.

The impact of extreme energy cosmic rays on the Earth's atmosphere is manifested by the generation of fluorescence and Cherenkov radiation: these effects constitute source fields that propagate and, once detected, provide an indirect way to deduce energy, trajectory, composition of the primary particle. Because of the relatively infrequent probability of detection of such effects at the ground, proposals have been advanced to observe them from space: one of the proposed experiments is EUSO (Extreme Universe Space Observatory). Both the generation and propagation of these fields are affected by the high variability of the atmospheric conditions: to limit the deriving uncertainties, the observations would greatly benefit by the support of adequate instrumentation to provide the status of the atmosphere at the time of detection. Thus the use of an optical radar––lidar––has been suggested to complement the EUSO capability. This paper discusses: (a) the distortion induced by different atmospheric conditions on the fluorescence and Cherenkov profiles acquired from space; (b) the lidar retrieval of the transmission and scattering characteristics of the atmosphere and the use of these data to correct the detected signals to reach a realistic assessment of the atmospheric sources and of the primary particle characteristics. The simulations are based on experimental results with regard to aerosol and cloud backscatter data, on a relatively simple transfer model and on realistic assumptions regarding the extinction to backscatter ratio.