99 research outputs found
An update on the dynamically induced episodes of extreme low ozone values over the northern middle latitudes
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The History of Total Ozone Measurements; the Early Search for Signs of a Trend and an Update
No full textSearch for Man-Made Cirrus Contrails over Southeast Asia
No full textIn this study we examine the effect of natural perturbations on cirrus cloud cover in the tropics and we look for possible signal of cirrus contrails in tropical air traffic regions focussing on Southeast Asia, a region that has received much less attention than the well investigated North Atlantic and North American air traffic corridors. The analysis is based on the latest version of the ISCCP D2 cirrus cloud dataset and covers the period 1984 - 2000. Four parameters were examined for their relation with cirrus cloud trends: deep convective clouds from ISCCP, vertical velocities, relative humidity and air temperature at 200 mb from ECMWF/ERA40. The results show that there is a strong correlation between cirrus clouds and dynamical parameters (deep convective clouds, vertical velocities) over Southeast Asia, explaining a significant part of the tropical cirrus cloud variability. After removing seasonality, the ENSO signal becomes dominant on cirrus, on deep convective clouds and on vertical velocities over regions of the western and the eastern tropical Pacific Ocean. Over Southeast Asia, the average decrease in cirrus during the strong 1997/98 El Nino event was about 6% cloud cover or ~25% of the regional mean. In order to search for possible signal of cirrus contrails over S. E. Asia, we calculated trends in cirrus coverage over tropical regions with high air traffic after removing the ENSO effect. The results show that there is a small positive trend in cirrus clouds over the S. E. Asia air corridors during winter (+0.1% cover/decade), which is not statistically significant and is related to small positive trends in deep convective clouds. In summer, cirrus clouds are anti-correlated with deep convective clouds over this region and the trends are opposite. The negative trends in cirrus clouds, which are observed in the summer (-4.5% cover/ decade), are related to trends in dynamical and thermo-dynamical parameters. It is shown that cirrus clouds are statistically significant correlated with vertical velocities and air temperature at 200 mb (correlations of -0.7 and -0.6, respectively), explaining the highest part of the long-term variability of cirrus clouds over S. E. Asia. Over the Caribbean air corridors, on the other hand, there are significant increases in cirrus cloudiness by about 2.5% per decade in winter (99% confidence level) and 2.7% cover/ decade in the summer (95% confidence level), part of which is also related to trends in dynamical and thermo-dynamical parameters. According to our findings, it is difficult to detect possible effects of regional persistent contrails on cirrus cloud trends over the S. E. Asia air traffic corridors. This is because in winter there are not statistically significant trends in cirrus clouds and in summer trends in dynamics and thermo-dynamics mask this issue. Taking also into account that flight frequencies and fuel consumption are moderate over the tropical air traffic corridors, it makes it even more difficult to detect and quantify any possible anthropogenic effects
Search for Man-Made Cirrus Contrails over Southeast Asia
No full textIn this study we examine the effect of natural perturbations on cirrus cloud cover in the tropics and we look for possible signal of cirrus contrails in tropical air traffic regions focussing on Southeast Asia, a region that has received much less attention than the well investigated North Atlantic and North American air traffic corridors. The analysis is based on the latest version of the ISCCP D2 cirrus cloud dataset and covers the period 1984 - 2000. Four parameters were examined for their relation with cirrus cloud trends: deep convective clouds from ISCCP, vertical velocities, relative humidity and air temperature at 200 mb from ECMWF/ERA40. The results show that there is a strong correlation between cirrus clouds and dynamical parameters (deep convective clouds, vertical velocities) over Southeast Asia, explaining a significant part of the tropical cirrus cloud variability. After removing seasonality, the ENSO signal becomes dominant on cirrus, on deep convective clouds and on vertical velocities over regions of the western and the eastern tropical Pacific Ocean. Over Southeast Asia, the average decrease in cirrus during the strong 1997/98 El Nino event was about 6% cloud cover or ~25% of the regional mean. In order to search for possible signal of cirrus contrails over S. E. Asia, we calculated trends in cirrus coverage over tropical regions with high air traffic after removing the ENSO effect. The results show that there is a small positive trend in cirrus clouds over the S. E. Asia air corridors during winter (+0.1% cover/decade), which is not statistically significant and is related to small positive trends in deep convective clouds. In summer, cirrus clouds are anti-correlated with deep convective clouds over this region and the trends are opposite. The negative trends in cirrus clouds, which are observed in the summer (-4.5% cover/ decade), are related to trends in dynamical and thermo-dynamical parameters. It is shown that cirrus clouds are statistically significant correlated with vertical velocities and air temperature at 200 mb (correlations of -0.7 and -0.6, respectively), explaining the highest part of the long-term variability of cirrus clouds over S. E. Asia. Over the Caribbean air corridors, on the other hand, there are significant increases in cirrus cloudiness by about 2.5% per decade in winter (99% confidence level) and 2.7% cover/ decade in the summer (95% confidence level), part of which is also related to trends in dynamical and thermo-dynamical parameters. According to our findings, it is difficult to detect possible effects of regional persistent contrails on cirrus cloud trends over the S. E. Asia air traffic corridors. This is because in winter there are not statistically significant trends in cirrus clouds and in summer trends in dynamics and thermo-dynamics mask this issue. Taking also into account that flight frequencies and fuel consumption are moderate over the tropical air traffic corridors, it makes it even more difficult to detect and quantify any possible anthropogenic effects
Earlinet observations of the Eyjafjallajökull ash plume over Greece
No full textThe arrival of the volcanic ash plume of the Eyjafjallajökull eruption was observed over Greece almost one week after its major eruption (on April 14, 2010) with two multi-wavelength Raman lidar systems, members of the EARLINET network. Intensive lidar measurements were performed throughout the event over Thessaloniki and Athens to derive the optical properties of the ash aerosols in the troposphere. During April 21, 2010 two layers of volcanic ash were present over Thessaloniki, one around 2.5 and one around 5 km height after circulating over central Europe. The first layer was persistent but with variable thickness, while the thin layer observed at 5 km height disappeared after some hours. Later on and at higher altitudes thin layers of ash were observed between 5 and 8 km, directly associated with the volcanic eruption. The observed layer at around and 3 km was persistently observed till April 28. The volcanic ash was observed over Athens, after passing over Southern Italy, during April and May 2010, in two height regions: between 6-10 km height and between 4 km and the ground level. We found that this was directly linked to the maximum height of the emitted volcanic ash. The most intensive period for ash presence over Athens was between April 21 and 23. In most cases, ash layers were very well stratified in the form of filaments starting around 3-4 km down to 1.5 km height. Mixing of ash with locally produced aerosols was frequently observed during the measuring period resulting to enhanced PM 10 concentrations at ground level. Volcanic ash was also observed during May 10-11 and 17-19, 2010, after being transported over Spain and Northern Italy. Both over Athens and Thessaloniki Saharan dust particles were mixed with volcanic ones on certain days of May 2010, which resulted to more complicated structures of the aerosol layers observed over Greece
A 1-year remote sensing study of radiative effects of aerosol and clouds over the NE Mediterranean
No full textFour-dimensional distribution of the 2010 Eyjafjallajökull volcanic cloud over Europe observed by EARLINET
No full textThe eruption of the Icelandic volcano Eyjafjallajökull in April–May 2010 represents a "natural experiment" to study the impact of volcanic emissions on a continental scale. For the first time, quantitative data about the presence, altitude, and layering of the volcanic cloud, in conjunction with optical information, are available for most parts of Europe derived from the observations by the European Aerosol Research Lidar NETwork (EARLINET). Based on multi-wavelength Raman lidar systems, EARLINET is the only instrument worldwide that is able to provide dense time series of high-quality optical data to be used for aerosol typing and for the retrieval of particle microphysical properties as a function of altitude. In this work we show the four-dimensional (4-D) distribution of the Eyjafjallajökull volcanic cloud in the troposphere over Europe as observed by EARLINET during the entire volcanic event (15 April–26 May 2010). All optical properties directly measured (backscatter, extinction, and particle linear depolarization ratio) are stored in the EARLINET database available at http://www.earlinet.org. A specific relational database providing the volcanic mask over Europe, realized ad hoc for this specific event, has been developed and is available on request at http://www.earlinet.org. During the first days after the eruption, volcanic particles were detected over Central Europe within a wide range of altitudes, from the upper troposphere down to the local planetary boundary layer (PBL). After 19 April 2010, volcanic particles were detected over southern and south-eastern Europe. During the first half of May (5–15 May), material emitted by the Eyjafjallajökull volcano was detected over Spain and Portugal and then over the Mediterranean and the Balkans. The last observations of the event were recorded until 25 May in Central Europe and in the Eastern Mediterranean area. The 4-D distribution of volcanic aerosol layering and optical properties on European scale reported here provides an unprecedented data set for evaluating satellite data and aerosol dispersion models for this kind of volcanic events
Large-scale network based observations of a Saharan dust event across the European continent in spring 2022
No full textBetween 14 March and 21 April 2022, an extensive investigation of an extraordinary Saharan dust intrusion over Europe was performed based on lidar measurements obtained by the European Aerosol Research Lidar Network (EARLINET). The dust episode was divided into two distinct periods, one in March and one in April, characterized by different dust transport paths. The dust aerosol layers were studied over 18 EARLINET stations, examining aerosol characteristics during March and April in four different regions (M-I, M-II, M-III, and M-IV and A-I, A-II, A-III, and A-IV, respectively), focusing on parameters such as aerosol layer thickness, center of mass (CoM), lidar ratio (LR), particle linear depolarization ratio (PLDR), and Ångström exponents (ÅE). In March, regions exhibited varying dust geometrical and optical properties, with mean CoM values ranging from approximately 3.5 to 4.8 km, and mean LR values typically between 36 and 54 sr. PLDR values indicated the presence of both pure and mixed dust aerosols, with values ranging from 0.20 to 0.32 at 355 nm and 0.24 to 0.31 at 532 nm. ÅE values suggested a range of particle sizes, with some regions showing a predominance of coarse particles. Aerosol Optical Depth (AOD) simulations from the NAAPS model indicated significant dust activity across Europe, with AOD values reaching up to 1.60. In April, dust aerosol layers were observed between 3.2 to 5.2 km. Mean LR values typically ranged from 35 to 51 sr at both 355 nm and 532 nm, while PLDR values confirmed the presence of dust aerosols, with mean values between 0.22 and 0.31 at 355 nm and 0.25 to 0.31 at 532 nm. The ÅE values suggested a mixture of particle sizes. The AOD values in April were generally lower, not exceeding 0.8, indicating a less intense dust presence compared to March. The findings highlight spatial and temporal variations in aerosol characteristics across the regions, during the distinctive periods. From 15 to 16 March 2022, Saharan dust significantly reduced UV-B radiation by approximately 14% over the ATZ station (Athens, GR). Backward air mass trajectories showed that the dust originated from the Western and Central Sahara when, during this specific case, the air mass trajectories passed over GRA (Granada, ES) and PAY (Payerne, CH) before reaching ATZ, maintaining high relative humidity and almost stable aerosol properties throughout its transport. Lidar data revealed elevated aerosol backscatter (baer) and PLDR values, combined with low LR and ÅE values, indicative of pure dust aerosols.C.-A.P. acknowledges the support of the project on Strengthening human cap- ital of ACTRIS Italy Research infrastructure-PER-ACTRIS-IT (project code no. CIR01_00015, no. 2595—CUP: B58I20000220001). M.G.’s work was supported by the Hellenic Foundation for Research and Innovation (HFRI) under the 4th Call for HFRI Ph.D. Fellowships (Fellowship number: 9293). H.B., R.E., S.F.A., J.H. and A.A.F. acknowledge the funding by the German Federal Ministry of Education and Research (BMBF) under the FONA Strategy “Research for Sustainability” for the installation of the Dushanbe lidar site under the grant agreement 01LK1603A, and for ACTRIS-D under the grant agreements 01LK2001A-K and 01LK2002A-G. J.A.B.A.’s and J.A.G.’s work was sup- ported by the projects INTEGRATYON3 (PID2020-117825GB-C21 and PID2020-117825GB-C22) and ELPIS (PID2020-120015RB-I00), funded by MCIN/AEI/10.13039/501100011033 and ATMO-ACCESS (grant no.101008004). B.D.R.’s, G.G.’s, P.G.C.’s, and M.M.’s work was supported by IR0000032— ITINERIS, Italian Integrated Environmental Research Infrastructures System (D.D. no. 130/2022— CUP B53C22002150006) funded by the EU—Next Generation EU PNRR-Mission 4 “Education and Research”—Component 2: “From research to business”—Investment 3.1: “Fund for the realization of an integrated system of research and innovation infrastructures”. C.M.P. and A.R.G. were also supported by the Spanish Ministry of Science and Innovation (grant no. PID2023-149747NB-I00) and the Horizon Europe-REALISTIC project (grant no. 101086690). I.S.S. and D.M.S. acknowledge sup- port of the National Information Processing Institute of Poland (OPI-BIP) within the Smart Growth Operational Programme grant ACTRIS-Poland no. POIR.04.02.00-00-D019/20; the National Science Centre of Poland (NCN) within the Preludium 19 grant preDUST no. 2020/37/N/ST10/02682; and the Polish Fund for Science and Technology (FNiTP) grant no. 519/FNITP/115/2010.K.A.V. acknowl- edges support by the PANGEA4CalVal (grant agreement no. 101079201) funded by the European Union. E.M. acknowledges support by the Hellenic Foundation for Research and Innovation (H.F.R.I.) under the “3rd [NT1] Call for H.F.R.I. Research Projects to support Post-Doctoral Researchers” (Project Acronym: REVEAL, Project Number: 07222). Moreover, the authors acknowledge support by the European Commission under the H2020—Research and Innovation Framework Programme, H2020- INFRAIA-2020-1, ATMO-ACCESS (grant no. 101008004). The authors also acknowledge the scientific projects ACTRIS-2 under the H2020, GRASP-ACE, and ACTRIS IMP (grant no. 654109, 778349 and 871115), the NOAA Air Resources Laboratory (ARL) for the provision of the HYSPLIT transport and dispersion model, and/or the READY website (http://www.ready.noaa.gov) used in this publication. The authors .ready.noaa.gov) used in this publication. The authors also acknowledge the EAR- LINET-ACTRIS community for providing the aerosol lidar profiles utilized in this study. We partic- ularly acknowledge those members who conducted the measurements, evaluated the lidar data, and made the data available in the EARLINET database. The data set used in this study was obtained within the ACTRIS IMP H2020 GA 871115. The access to the ACTRIS infrastructure got support from ATMO-ACCESS H2020 GA 101008004. Authors gratefully acknowledge the CALIPSO satellite for the CALIOP data products obtained from the NASA Langley Research Center Atmospheric Sci- ence Data Center. The authors also acknowledge the AOD images provided by the U.S. N.Peer ReviewedArticle signat per 39 autors/es: Christina-Anna Papanikolaou, Alexandros Papayannis, Marilena Gidarakou, Sabur F. Abdullaev,Nicolae Ajtai, Holger Baars, Dimitris Balis, Daniele Bortoli, Juan Antonio Bravo-Aranda, Martine Collaud-Coen, Benedetto de Rosa, Davide Dionisi , Kostas Eleftheratos, Ronny Engelmann, Athena A. Floutsi, Jesús Abril-Gago, Philippe Goloub, Giovanni Giuliano, Pilar Gumà-Claramunt, Julian Hofer, Qiaoyun Hu, Mika Komppula, Eleni Marinou , Giovanni Martucci, Ina Mattis , Konstantinos Michailidis,Constantino Muñoz-Porcar, Maria Mylonaki, Michail Mytilinaios, Doina Nicolae, Alejandro Rodríguez-Gómez, Vanda Salgueiro,
Xiaoxia Shang, Iwona S. Stachlewska, Horat, iu Ioan Stefănie, Dominika M. Szczepanik,
Thomas Trick, Hannes Vogelmann and Kalliopi Artemis VoudouriPostprint (published version
Earlinet validation of CATS L2 product
No full textThe Cloud-Aerosol Transport System (CATS) onboard the International Space Station (ISS), is a lidar system providing vertically resolved aerosol and cloud profiles since February 2015. In this study, the CATS aerosol product is validated against the aerosol profiles provided by the European Aerosol Research Lidar Network (EARLINET). This validation activity is based on collocated CATS-EARLINET measurements and the comparison of the particle backscatter coefficient at 1064nm.Atmospheric Remote Sensin
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