Fabrizio Ravegnani

During the last few years UV-Vis spectrometers were developed at the FISBAT Institute and are used for application of differential optical absorption spectroscopy method to detect many atmospheric trace gases playing important roles in the stratospheric chemistry. After several test both ...

... As described in section 4.1 for NO2, also for O3 the determination of the vertical profiles is obtained with the application of the Chahine inversion algorithm to the observed SCD. The input data of the tool utilized for the retrieval of the Proc. ... [22] Kondo, Y., Mathews, AW, Solomon ...

ABSTRACT A geometrical method to determine the vertical distribution of a trace gas in the lower troposphere is presented. The technique is based on quasi-simultaneous measurements of diffuse solar radiation with spectrometric equipment observing the atmosphere from different viewing directions and a measurement of a distant lamp. Differential optical absorption spectroscopy (DOAS) algorithms are applied to retrieve the slant column densities (SCDs) of the analyzed compound. A recursive procedure involving the set of observed SCDs, the geometry of measurement, and several offline radiative transfer simulations provides the vertical profile of the target trace gas. This technique is applied to nitrogen dioxide (NO2) SCDs, and the results are compared to the output of the modeling system Gas Aerosol Modeling Evaluation System (GAMES). The correlation coefficient between the DOAS and GAMES NO2 concentration profiles is 0.7 and shows a nonnegligible variability as a function of altitude and sky conditions.

During the RECONCILE campaign in the Arctic winter 2009/10, an active Match experiment was performed sampling the same air masses up to three times during two consecutive flights of the high-altitude research aircraft M55-Geophysica from Kiruna (67.83 N, 20.42 E). The first flight was westbound and its flightpath designed to resample the air masses from the outbound leg during the

The results of investigation of NO2 pollutions on board of research aircraft Falcon (DLR, Germany) are presented. The measurements have been carried out by chemiluminescent ni- trogen dioxide analyzer developed in Central Aerological Observatory (Russia). The data of NO2 distribution have been obtained during QUANTIFY (West Europe, July 2007) and POLARCAT (Greenland, July 2008) field campaigns. NO2 measurements over Greenland during POLARCAT field campaign have been carried out using ACCENT support. Different sources of nitrogen oxides are investigated. Some aspects of nitrogen dioxide distribution and transport are considered. Chemi- cal transformation of nitrogen oxides inside ship plumes is observed and analyzed.

In-situ measurements of the HDO/H2O Isotopic ratio in the Asian Summer Monsoon trace strong convective activity Benjamin Clouser1, Clare Singer2, Sergey Khaykin3, Martina Krämer4, Alexey Lykov5, Sylvia Bucci6, Bernard Legras 6 , Stephan Borrmann 7 , Francesco Cairo 8 , Valentin Mitev 9 , Renaud Matthey 10 , Fabrizio Ravegnani 8 , Christian Rolf 4 , Alexey Ulanovsky 11 , Silvia Viciani 12 , Francesco D'Amato 12 , C Michael Volk 13 , Vladimir Yushkov 11 , Fred Stroh 4 , and Elisabeth Moyer 1

A Fast OZone ANalizer (FOZAN) was installed on board of M55-Gheophysica, a stratospheric platform able to reach an altitude of more then 20 Km. During the APE-GAIA campaign in october-november 1999 (Carli et al., this issue) the M55 aircraft performed 5 scientific flights from Ushuaia (Argentina) to the Antarctic Peninsula; most of the flights were performed in chemical depleted region, inside the polar vortex and on its boundary. FOZAN performed successfully during all flights, measuring O3 concentration along the flight path with a temporal resolution of 1 sec. The paper presents the design of the instrument and preliminary results of ozone measurements obtained during the APE-GAIA campaign.

Continuous monitoring of Raven's seaboard since 1978 has evinced high nocturnal ozone concetrations. The present study of the averaged ozone values at three monitoring stations in the summers of 1993 and 1994, when there were no significant variations in precursor emission sources or in the usual weather conditions, shows nocturnal minima generally occurring between 3 o'clock and 7 o'clock am local time in a 20-30 (mu) g/m3 range. Nocturnal values above the normal range (> 70 (mu) g/m3) has a 6% frequency and, when compared to weather conditions, occured simultaneously at all sites (spaced 5-10 km apart) and coincided with the passing of a front or a low-pressure situation.

Urban air pollution is determined as much by emission rates and source sitelocation in a given area as by chemical transformations and, to a very large extent, by meteorology. Milan, northern Italy's largest metropolitan area, is situated in the northwesternmost part of the Po Valley, being bounded by the Alps to the north and to the west and the Ligurian Apennines to the south. Because of its topography and orography, and in concomitance with the area's prevailing anticyclonic circulation, the city is marked by a persistent lack of breeze, a fact that promotes the accumulation and vertical layering over the city of gaseous pollutants. Frequent diurnal and nocturnal thermal inversions as well as fumigation phenomena lead to high pollutant concentrations at ground level and the consequent violation of air quality standards. A greater pollutant dispersion is usually associated with intense prevailing winds from northnorthwest and east. The former, known as Foehn, can determine...

ABSTRACT The use of CFCs, which are the main responsible for the ozone depletion in the upper atmosphere and the formation of the so-called "ozone hole" over Antarctic Region, was phase out by Montreal Protocol (1989). CFCs' concentration is recently reported to decrease in the free atmosphere, but severe episodes of ozone depletion in both Arctic and Antarctic regions are still occurring. Nevertheless the complete recovery of the Ozone layer is expected by about 2050. Recent simulation of perturbations in stratospheric chemistry highlight that circulation, temperature and composition are strictly correlated and they influence the global climate changes. Chemical composition plays an important role in the thermodynamic of the atmosphere, as every gaseous species can absorb and emit in different wavelengths, so their different concentration is responsible for the heating or cooling of the atmosphere. Therefore long-term observations are required to monitor the evolution of the stratospheric ozone layer. Measurements from satellite remote sensing instruments, which provide wide coverage, are supplementary to selective ground-based observations which are usually better calibrated, more stable in time and cover a wider time span. The combination of the data derived from different space-borne instruments calibrated with ground-based sensors is needed to produce homogeneous and consistent long-term data records. These last are required for robust investigations and especially for trend analysis. Here, we perform a review of the major remote-sensing techniques and of the principal datasets available to study the evolution of ozone layer in the past decades and predict future behavio

ABSTRACT Water vapour and ozone in-situ observations in the tropical tropopause layer (TTL) during the three tropical campaigns SCOUT-O3, AMMA and TroCCiNOx are reconstructed from diabatic and kinematic backtrajectories, with the reconstruction method for the tracer fields based on freeze-drying and photochemichal ozone production. The results using diabatic trajectories show that both water vapour and ozone in-situ observations can be well reconstructed from trajectories. Consequentially, in-situ observations agree with the assumption of freeze-drying due to the large-scale temperature field as the main control mechanism for water vapour and photochemical production and transport as main control mechanisms for tropical ozone. The kinematic ozone reconstruction, however, shows a large high-bias during SCOUT-O3 and a too strong variability during all campaigns, due to excessive transport of stratospheric ozone into the TTL. We conclude that kinematic reconstructions of in-situ observations are less reliable than diabatic, due to unrealistic inhomogeneities in the velocity field.

A UV/Vis DOAS spectrometer (GASCOD, Gas Analyzer Spectrometer Correlating Optical Differences) was installed at Monte Cimone station in 1993 and since then it has been measuring zenith scattered solar radiation at sunset and sunrise. During 1995 it was possible to investigate two spectral regions, about 50 nm width, centered at 365 nm and 436 nm while later we only have measurements at 436 nm available. The spectra obtained during the 1995 - 96 period have been processed with DOAS technique to obtain column amounts of NO2 and O3. The seasonal and diurnal variation of the NO2 column amounts is shown with a summer maximum (about 1.2 X 1017 mol(DOT)cm-2 for p.m. value and 6 X 1016 mol(DOT)cm-2 for a.m.) and winter minimum (about 2 X 1016 mol(DOT)cm-2 for a.m. and 5 X 1016 mol(DOT)cm-2 for p.m.). An anomalous spring increase in p.m. NO2 value during 1995 is investigated through a vertical distribution analysis. The gas profile is retrieved through a Chahine inversion algorithm applied to the slant columns measured at different solar zenith angle. In fact the air mass factor variation with solar zenith angle can be used to extract information about the gas concentration at each atmospheric layers. A consistent and frequent tropospheric increase in NO2 a.m. concentration is evident. The method and the results obtained are discussed.

. The StratoClim airborne campaign took place in Nepal from 27 July to 10 August 2017 to document the physical and chemical properties of the South Asian Upper Troposphere Lower Stratosphere (UTLS) during the Asian Summer Monsoon (ASM). In the present paper, simulations with the Meso-NH cloud-chemistry model at a horizontal resolution of 15 km are performed over the Asian region to characterize the impact of monsoon deep convection on the composition of Asian Monsoon Anticyclone (AMA) and on the formation of the Asian Tropopause Aerosol Layer (ATAL) during the StratoClim campaign. StratoClim took place during a break phase of the monsoon with an intense convective activity over south China and Sichuan. Comparisons between Brightness Temperature (BT) at 10.8 microns observed by satellite sensors and simulated by Meso-NH highlight the ability of the model to correctly reproduce the life cycle of deep convective clouds. Comparison between CO and O3 concentrations from Meso-NH and airborne observations (StratoClim and IAGOS) demonstrates that the model captures most of the observed variabilities. Nevertheless, for both gases, the model tends to overestimate the concentrations and misses some thin CO plumes related to local convective events probably because of a too coarse resolution, but the convective uplift of pollution is very well captured by the model. We have therefore focused on the impact of Sichuan convection on the AMA composition. A dedicated sensitivity simulation showed that the 7 August convective event brought large amounts of CO deep into the AMA and even across the 380 K isentropic level located at 17.8 km. This Sichuan contribution enhanced the CO concentration by ~ 15 % to reach more than 180 ppbv over a large area around 15 km height. Noteworthy, Meso-NH captures the impact of the diluted Sichuan plume on the CO concentration during a StratoClim flight south of Kathmandu highlighting its ability to reproduce the transport pathway of Sichuan pollution. According to the model, primary organic aerosol and black carbon particles originating from Sichuan are transported following the same pathway as CO. The large particles are heavily scavenged within the precipitating part of the convective clouds but remain the most important contributor to the particle mass in the AMA. Over the whole AMA region, the 7 August convective event resulted in a 0.5 % increase of CO over the 10–20 km range that lasted about 2 days. The impact of pollution uplift from three regions (India, China and Sichuan) averaged over the first 10 days of August has also been evaluated with sensitivity simulations. Even during this monsoon break phase, the results confirm the predominant role of India relative to China with respective contributions of 11 and 7 % to CO in the 10–15 km layer. Moreover, during this period a large part (35 %) of the Chinese contribution comes from the Sichuan basin alone.

The problems of the stratospheric ozone decline during the last decades is the subject of scientific efforts to discover the main factors influencing the processes leading to its disappearance. The exact understanding of chemical- physical processes in the Earth's atmosphere needs high- quality representative measurements for time-series and modeling study. The present paper deals with the problems of the polarization characteristics of DOAS instruments and the corresponding requirements for instrumental orientation relative to the scattered plane. To avoid the polarization effects upon the measurement's accuracy the instrument has to be 'unpolarized'. A fiber optic and an appropriate diffraction grating are used to do this. Experimental measurements have been carried out to check the possibility to use a fiber optic bundle for DOAS applications. The results obtained from this experiments how that the tested fiber bundles do not completely destroy the polarization st...

A comparison with coincident 03 total column measurements taken in the same Antarctic area is presented, as is another comparison performed in Italy. Also introduced is an updated model for solar zenith measurements taken from a ground-based, upward-looking GASCOD spectrometer, which was employed for the 1991-92 winter campaign at Are-Ostersund in Sweden (63.3°N, 13.1°E) during EASOE (European Arctic Stratospheric Ozone Experiment). The GASCOD can examine the spectra from 300 to 700 nm, in 50 nm steps, by movin E the spectrometer's grating. At present, it takes measurements of solar zenith radiation in the 310-342 nm range for 03 and in the 405-463 nm range for NO2.

ABSTRACT The present paper deals with the factors influencing the accuracy of the DOAS and in particularly, with the changing of the depolarization ratio of the zenith scattered radiation and related variations of the retrieved NO:! slant column. Ground based measurements caried out during 1997 and 1998 of the polarisation state of the zenith-scattered radiation and the NO2 slant columns have been obtained in 4075 Angstrom - 4640 Angstrom spectral interval. The depolarization ratio is calculated from the spectra registered with a sheet linear polarizer, inserted into the instrument. A linear regression analysis is applied to retrieve NO2 slant columns. The obtained results are analysed and discussed.