FTIR Measurements of Greenhouse Gases over Thessaloniki, Greece in the Framework of COCCON and Comparison with S5P/TROPOMI Observations

In this work, column-averaged dry-air mole fractions of carbon dioxide (XCO2), methane (XCH4) and carbon monoxide (XCO) are presented for the first time at a mid-latitude urban station, Thessaloniki, Greece, using the Bruker EM27/SUN ground-based low-resolution Fourier Transform spectrometer operated according to the requirements of the Collaborative Carbon Column Observing Network (COCCON). Two years of measurements are presented and examined for seasonal variability. The observed XCO2 levels show the expected seasonal cycle (spring maximum, late summer minimum) with a peak-to-peak amplitude of 12 ppm, with maximum values reported for winter 2021 exceeding 416 ppm. The XCH4 values are shown to increase in the second half of the year, with autumn showing the highest mean value of 1.878 ± 0.01 ppm. The XCO levels, following anthropogenic sources, show high winter and low summer values, exhibiting a rise again in August and September with a maximum value of 114 ± 3 ppb and a minimum in summer 2020 of 76 ± 3 ppb. Additionally, methane and carbon monoxide products obtained from the TROPOspheric Monitoring Instrument (TROPOMI), Sentinel-5P space borne sensor, are compared with the ground-based measurements. We report a good agreement between products. The relative mean bias for methane and carbon monoxide are −0.073 ± 0.647% and 3.064 ± 5.566%, respectively. Furthermore, a 15-day running average is subtracted from the original daily mean values to provide ΔXCO2, ΔXCO and ΔXCH4 residuals, so as to identify local sources at a synoptic scale. ΔXCO and ΔXCO2 show the best correlation in the winter (R2 = 0.898, slope = 0.007) season due to anthropogenic emissions in this period of the year (combustion of fossil fuels or industrial activities), while in summer no correlation is found. ΔXCO and ΔXCH4 variations are similar through both years of measurements and have a very good correlation in all seasons including winter (R2 = 0.804, slope = 1.209). The investigation of the X-gases comparison is of primary importance in order to identify local sources and quantify the impact of these trace gases to the deregulation of earth-climate system balance

First validation of GOME-2/MetOp Absorbing Aerosol Height using EARLINET lidar observations

he aim of this study is to investigate the potential of the Global Ozone Monitoring Experiment-2 (GOME-2) instruments, aboard the Meteorological Operational (MetOp)-A, MetOp-B and MetOp-C satellite programme platforms, to deliver accurate geometrical features of lofted aerosol layers. For this purpose, we use archived ground-based lidar data from stations available from the European Aerosol Research Lidar Network (EARLINET) database. The data are post-processed using the wavelet covariance transform (WCT) method in order to extract geometrical features such as the planetary boundary layer (PBL) height and the cloud boundaries. To obtain a significant number of collocated and coincident GOME-2 - EARLINET cases for the period between January 2007 and September 2019, 13 lidar stations, distributed over different European latitudes, contributed to this validation. For the 172 carefully screened collocations, the mean bias was found to be -0.18 ± 1.68 km, with a near-Gaussian distribution. On a station basis, and with a couple of exceptions where very few collocations were found, their mean biases fall in the ± 1 km range with an associated standard deviation between 0.5 and 1.5 km. Considering the differences, mainly due to the temporal collocation and the difference, between the satellite pixel size and the point view of the ground-based observations, these results can be quite promising and demonstrate that stable and extended aerosol layers as captured by the satellite sensors are verified by the ground-based data. We further present an in-depth analysis of a strong and long-lasting Saharan dust intrusion over the Iberian Peninsula. We show that, for this well-developed and spatially well-spread aerosol layer, most GOME-2 retrievals fall within 1 km of the exact temporally collocated lidar observation for the entire range of 0 to 150 km radii. This finding further testifies for the capabilities of the MetOp-borne instruments to sense the atmospheric aerosol layer heights.Horizon 2020 Framework Programme 654109, 87111

The evolution of synoptic ozone anomalies during the European Arctic Stratospheric Ozone Experiment in winter 1991/1992

The evolution of ozone anomalies over the middle and high latitudes of the Northern Hemisphere during the winter 1991-1992 is studied in this work. The largest monthly mean negative deviations in the middle latitudes of the Northern Hemisphere were about 10 percent in November and December, and up to 20 percent in January, February, and March over Eurasian territories, and much smaller over the Canadian sector. At the end of January, on individual days, total ozone values of 190-210 D.U. were observed over Eastern Europe and European part of Russia, that is 40-45 percent below normal. On the whole, the 1991-1992 winter was one of the most anomalous over all the period of ozone observations. Finally, an attempt is made to quantify the contribution of transport in the ozone layer changes over Europe during this period

Validation of OMI erythemal doses with multi-sensor ground-based measurements in Thessaloniki, Greece

The aim of this study is to validate the Ozone Monitoring Instrument (OMI) erythemal dose rates using ground-based measurements in Thessaloniki, Greece. In the Laboratory of Atmospheric Physics of the Aristotle University of Thessaloniki, a Yankee Environmental System UVB-1 radiometer measures the erythemal dose rates every minute, and a Norsk Institutt for Luftforskning (NILU) multi-filter radiometer provides multi-filter based irradiances that were used to derive erythemal dose rates for the period 2005–2014. Both these datasets were independently validated against collocated UV irradiance spectra from a Brewer MkIII spectrophotometer. Cloud detection was performed based on measurements of the global horizontal radiation from a Kipp & Zonen pyranometer and from NILU measurements in the visible range. The satellite versus ground observation validation was performed taking into account the effect of temporal averaging, limitations related to OMI quality control criteria, cloud conditions, the solar zenith angle and atmospheric aerosol loading. Aerosol optical depth was also retrieved using a collocated CIMEL sunphotometer in order to assess its impact on the comparisons. The effect of total ozone columns satellite versus ground-based differences on the erythemal dose comparisons was also investigated. Since most of the public awareness alerts are based on UV Index (UVI) classifications, an analysis and assessment of OMI capability for retrieving UVIs was also performed. An overestimation of the OMI erythemal product by 3–6% and 4–8% with respect to ground measurements is observed when examining overpass and noontime estimates respectively. The comparisons revealed a relatively small solar zenith angle dependence, with the OMI data showing a slight dependence on aerosol load, especially at high aerosol optical depth values. A mean underestimation of 2% in OMI total ozone columns under cloud-free conditions was found to lead to an overestimation in OMI erythemal doses of 1–5%.While OMI overestimated the erythemal dose rates over the range of cloudiness conditions examined, its UVIs were found to be reliable for the purpose of characterising the ambient UV radiation impact

The European aerosol research lidar network (EARLINET): an overview

The European Aerosol Research LIdar NETwork (EARLINET) is the first aerosol lidar network on a continental scale with the main goal to provide a comprehensive, quantitative, and statistically significant database for the aerosol distribution over Europe. Next, we present EARLINET along with the main network activities.Peer ReviewedPostprint (published version

STUDY OF THE TRANSFER OF THE SOLAR ULTRAVIOLET RADIATION IN THE PRESE- NCE OF OZONE AND AEROSOLS:MEASUREMENTS WITH THE LIDAR TECHNIQUE

ΤΟ ΑΝΤΙΚΕΙΜΕΝΟ ΤΗΣ ΔΙΑΤΡΙΒΗΣ ΕΙΝΑΙ Η ΜΕΛΕΤΗ ΤΗΣ ΔΙΑΔΟΣΗΣ ΤΗΣ ΥΠΕΡΙΩΔΟΥΣ ΗΛΙΑΚΗΣ ΑΚΤΙΝΟΒΟΛΙΑΣ ΣΤΗΝ ΑΚΤΙΝΟΒΟΛΙΑ ΤΗΣ ΓΗΣ ΚΑΙ ΤΩΝ ΠΑΡΑΓΟΝΤΩΝ ΠΟΥ ΤΗΝ ΕΠΗΡΕΑΖΟΥΝ,ΔΙΝΟΝΤΑΣ ΙΔΙΑΙΤΕΡΗ ΕΜΦΑΣΗ ΣΤΙΣ ΟΠΤΙΚΕΣ ΙΔΙΟΤΗΤΕΣ ΤΩΝ ΑΙΩΡΟΥΜΕΝΩΝ ΣΩΜΑΤΙΔΙΩΝ ΣΤΗΝ ΚΑΤΩΤΕΡΗ ΤΡΟΠΟΣΦΑΙ ΡΑ ΚΑΘΩΣ ΚΑΙ ΣΤΟΝ ΠΕΙΡΑΜΑΤΙΚΟ ΠΡΟΣΔΙΟΡΙΣΜΟ ΤΟΥΣ. ΣΥΓΚΕΚΡΙΜΕΝΑ ΣΤΗ ΔΙΑΤΡΙΒΗ ΓΙΝΕΤΑΙ ΚΑΤΑΓΡΑΦΗ ΤΩΝ ΣΗΜΑΝΤΙΚΟΤΕΡΩΝ ΜΕΘΟΔΩΝ ΓΙΑ ΤΗ ΘΕΩΡΗΤΙΚΗ ΜΕΛΕΤΗ ΤΗΣ ΔΙΑΔΟΣΗΣ ΤΗΣ ΥΠΕΡΙΩΔΟΥΣ ΗΛΙΑΚΗΣ ΑΚΤΙΝΟΒΟΛΙΑΣ, ΣΤΗ ΓΗΙΝΗ ΑΤΜΟΣΦΑΙΡΑ, ΓΙΝΕΤΑΙ ΑΤΜΟΣΦΑΙΡΑ, ΓΙΝΕΤΑΙ ΚΑΤΑΓΡΑΦΗ ΤΩ Ν ΣΗΜΑΝΤΙΚΟΤΕΡΩΝ ΠΑΡΑΓΟΝΤΩΝ ΠΟΥ ΕΠΗΡΕΑΖΟΥΝ ΤΗ ΔΙΑΔΟΣΗ ΤΗΣ UV ΚΑΘΩΣ ΚΑΙ ΘΕΩΡΗΤΙΚΕΣ ΠΡΟΣΔΙΟΡΙΣΜΟΣ ΚΑΙ ΑΞΙΟΛΟΓΗΣΗ ΤΗΣ ΣΗΜΑΝΤΙΚΟΤΗΤΑΣ ΤΟΥΣ, ΜΕ ΤΗ ΧΡΗΣΗ ΘΕΩΡΗΤΙΚΟΥ ΠΡΩΤΥΠΟΥ. ΣΤΟ ΠΛΑΙΣΙΟ ΤΗΣ ΜΕΛΕΤΗΣ ΤΩΝ ΠΑΡΑΓΟΝΤΩΝ ΠΟΥ ΕΠΗΡΕΑΖΟΥΝ ΤΗ ΔΙΑΔΟΣΗ ΤΗΣ ΑΚΤΙΝΟΒΟΛΙΑΣ ΠΑΡΟΥ ΣΙΑΖΕΤΑΙ Ο ΠΕΙΡΑΜΑΤΙΚΟΣ ΠΡΟΣΔΙΟΡΙΣΜΟΣ ΤΩΝ ΟΠΤΙΚΩΝ ΙΔΙΟΤΗΤΩΝ ΤΩΝ ΑΙΩΡΟΥΜΕΝΩΝ ΣΩΜΑΤΙΔΙΩΝ. ΧΡΗΣΙΜΟΠΟΙΩΝΤΑΣ ΤΙΣ ΠΡΩΤΕΣ ΜΕΤΡΗΣΕΙΣ ΣΤΟΝ ΕΛΛΑΔΙΚΟ ΧΩΡΟ ΠΟΥ ΒΑΣΙΖΟΝΤΑΙ ΣΤΗΜΕΘΟΔΟ LIDAR, ΚΑΘΩΣ ΚΑΙ ΦΑΣΜΑΤΙΚΕΣ ΜΕΤΡΗΣΕΙΣ ΤΗΣ ΡΟΗΣ ΤΗΣ UV ΑΚΤΙΝΟΒΟΛΙΑΣ.IN THE FIRST PART OF THE THESIS A SENSITIVITY ANALYSIS OF THE TROPOPHERIC ULTRAVIOLET AND VISIBLE (TUV) RADIATIVE TRANSFER MODEL WAS PERFORMED, BY EXAMININGTHE CHANGES IN THE CALCULATED GLOBAL AND DIRECT ULTRAVIOLET INRADIANCE AT THEEARTH'S SURFACE, DUE TO CHANGES IN THE REQUIRED INPUT PARAMETERS. IN THE SECOND PART THERE ARE PRESENTED THE AEROSOL LIDAR MEASUREMENTS IN THE LOWER TROPOSPHRERE, WHIC WERE PERFORMED IN GREECE AT SPATA-ATHENS, AGIOS EFSTRATIOS AND THESSALONIKI. IN THE LAST PART OF THE THESIS WE PRESENT T HE RESULTS FROM THECOMPARISON OF RADIATIVE TRANSFER MODEL CALCULATIONS WITH SPECIAL UV MEASUREMENTS UNDER VARIABLE AEROSOL CONDITIONS

A check-list of the Greek macrofungi including hosts and biogeographic distribution : 1. Basidiomycotina

As a preliminary step towards a more intensive research on the diversity of macromycetes in Greece, an updated check-list of the Greek mycoflora is presented together with information on the host-substrates and geographic occurrence. The data originated from a thorough literature search and the authors' field observations. In total, 58 families, 214 genera and 811 species of fungi are recorded belonging to Basidiomycetes. The systematics and nomenclature of the relative bibliography have been updated and suitably revised. The large gaps in our knowledge on the existence and distribution of higher fungi in Greece are emphasized

Air Quality in Two Northern Greek Cities Revealed by Their Tropospheric NO2 Levels

In this article, we aim to show the capabilities, benefits, as well as restrictions, of three different air quality-related information sources, namely the Sentinel-5Precursor TROPOspheric Monitoring Instrument (TROPOMI) space-born observations, the Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) ground-based measurements and the LOng Term Ozone Simulation-EURopean Operational Smog (LOTOS-EUROS) chemical transport modelling system simulations. The tropospheric NO2 concentrations between 2018 and 2021 are discussed as air quality indicators for the Greek cities of Thessaloniki and Ioannina. Each dataset was analysed in an autonomous manner and, without disregarding their differences, the common air quality picture that they provide is revealed. All three systems report a clear seasonal pattern, with high NO2 levels during wintertime and lower NO2 levels during summertime, reflecting the importance of photochemistry in the abatement of this air pollutant. The spatial patterns of the NO2 load, obtained by both space-born observations and model simulations, show the undeniable variability of the NO2 load within the urban agglomerations. Furthermore, a clear diurnal variability is clearly identified by the ground-based measurements, as well as a Sunday minimum NO2 load effect, alongside the rest of the sources of air quality information. Within their individual strengths and limitations, the space-borne observations, the ground-based measurements, and the chemical transport modelling simulations demonstrate unequivocally their ability to report on the air quality situation in urban locations

Towards an Algorithm for Near Real Time Profiling of Aerosol Species, Trace Gases, and Clouds Based on the Synergy of Remote Sensing Instruments

In this manuscript we present the concept of a novel algorithmic chain that aims to a dataset of unprecedented detail in the vertical distribution of multiple atmospheric components in near real time conditions. The analysis will be based on the following remote sensing instruments: a depolarization Raman lidar, a visible and a thermal all-sky camera, a Brewer spectrophotometer, and up to three mini DOAS/MAX-DOAS systems. Based on both individual and synergistic processing of the data collected, novel products will be made available in near real time conditions to the end users. Columnar aerosol information from the spectrophotometers will be combined with lidar data to retrieve vertical profiles of individual aerosol species. Cloud layers will be detected and classified based mainly on the synergy of the lidar and the sky cameras and a realistic 3D representation of cloud conditions around the measurement site will be produced. Lidar profiles will be implemented as a priori information for radiative transfer purposes, that are necessary in order to obtain high quality trace gases profiles from the DOAS/MAX-DOAS spectrophotometer. Fast synergistic data processing will ensure that the algorithm can be applied for near real time public data dissemination in the future