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A comprehensive characterisation of atmospheric aerosols in the subtropical eastern North Atlantic has been carried out using long-term ground-based Aerosol Robotic NETwork (AERONET) photometric observations over the period 2005–2020 from a unique network made up of four stations strategically located from sea level to 3555 m on the island of Tenerife. This site can be considered a sentinel for the passage of airmasses going to Europe from Africa, and therefore the aerosol characterisation performed here adds important information for analysing their evolution during their path toward Northern Europe. Two of these stations (Santa Cruz de Tenerife – SCO – at sea level and La Laguna – LLO – at 580 m a.s.l.) are located within the marine atmospheric boundary layer (MABL), and the other two (Izaña – IZO – at 2373 m a.s.l. and Teide Peak – TPO – at 3555 m a.s.l.) are high mountain stations within the free troposphere (FT). Monthly climatology of the aerosol optical depth (AOD), Ångström exponent (AE), aerosol concentration, size distribution and aerosol optical properties has been obtained for the MABL and FT. Measurements that are quite consistent across the four sites have been used to categorise the main atmospheric scenarios, and these measurements confirm an alternation between predominant background conditions and predominant dust-loaded Saharan air mass conditions caused by seasonal dust transport over the subtropical North Atlantic. Background conditions prevail in the MABL and FT for most of the year, while dust-laden conditions dominate in July and August. The MABL under background conditions appears as a well-mixed layer with a low aerosol concentration (the volume concentration, VolCon, ranges from 0.02 ± 0.01 to 0.04 ± 0.02 µm3 µm−2), a predominance of coarse-mode marine aerosols (the effective radius, Reff, changes from 1.60 ± 0.19 to 1.91 ± 0.34 µm), and a volume contribution of the fine-mode fraction Vf/Vt . The clean FT is characterised by remarkably low aerosol loading and a predominant impact of fine-mode aerosols throughout the year (Vf/Vt has a maximum value of 0.93 ± 0.13), with an average Reff of 0.16 ± 0.02 µm. However, under dust-laden conditions and mainly in summer, we observe a predominance of coarse-mode aerosols with maximum VolCon values of 0.26 ± 0.23 µm3 µm−2 for the MABL and 0.16 ± 0.12 (0.06 ± 0.05) µm3 µm−2 for IZO (TPO), and a similar and quite consistent fine-mode fraction of 0.12 ± 0.03 in the vertical within the MABL and FT. Similarities in micro-physical and optical intensive aerosol properties confirm that the Saharan Air Layer (SAL) is a well-mixed layer in terms of the particulate composition. An estimation of the difference in the aerosol loading in the 1 km layer between IZO and TPO (in terms of VolCon and AOD) is performed in this study, and this shows that aerosol loading at IZO is double that at TPO, but they have similar fine-mode fractions, effective radii and intensive optical properties. The long-term trend analysis at SCO shows a significant negative trend in the fine-mode AOD between 2005 and 2020 (−1.8 ± 0.5) × 10−5 yr−1, which might be linked to the large reduction in oil-refining SO2 emissions from the SCO refinery in 2012.

A comprehensive characterization of atmospheric aerosols in the Subtropical Eastern North Atlantic has been carried out using long-term ground-based Aerosol Robotic NETwork (AERONET) photometric observations from a unique network made up of four stations strategically located from the sea level to 3555 m height on the island of Tenerife over the period 2005–2020. This site is can be considered a sentinel of the passage of airmass going to Europe from Africa and therefore the aerosol characterization performed here adds important information to analyse their evolution during the path toward Northern Europe. Two of these stations (Santa Cruz de Tenerife –SCO- at sea level and La Laguna –LLO- at 580 m asl) are located within the Marine Boundary Layer 5 (MBL) and the other two (Izana –IZO- at 2373 m asl and Teide Peak –TPO- at 3555 m asl) are high mountain stations within the Free Troposphere (FT). Monthly climatology of Aerosol Optical Depth (AOD), Angstrom Exponent (AE), aerosol concentration, size distribution, and aerosol optical properties has been obtained for the MBL and FT. Quite consistent measurements at the four sites have been used to categorise the main atmospheric scenarios confirming the predominance of the alternating background to dust-loaded Saharan air mass conditions seasonally affecting the sites as a result of the seasonal dust transport over the Subtropical North Atlantic. Background conditions prevail in the MBL and FT most of the year while dust-laden conditions dominate in July and August. The MBL under background conditions appears as a well-mixed layer with low aerosol concentration (volume concentration, VolCon, ranging from 0.02±0.01 to 0.04±0.02 μm3 · μm−2) with a predominance of coarse mode marine aerosols (effective radius, Re ff, changing from 1.60±0.19 to 1.91±0.34 μm) and fine mode fraction < 0.35. The clean FT has been characterised by remarkably low aerosol loading and a predominant impact of fine mode aerosols throughout the year (V f / V t with a maximum value of 0.93±0.13) with an average Re ff of 0.16±0.02 μm. However, under dust-laden conditions, we observe the predominance of coarse mode aerosols, mainly in summer, with maximum VolCon values of 0.26±0.23 μm3 · μm−2 for MBL and 0.16±0.12 (0.06±0.05) μm3 · μm−2 for IZO (TPO) and a similar and quite consistent fine mode fraction of 0.120.03 in the vertical within MBL and FT. Similarities in micro-physical and optical intensive aerosol properties confirm the Saharan Air Layer (SAL) as a well-mixed layer in terms of the particulate composition. An estimation of the difference in the aerosol loading in the 1-km layer between IZO and TPO (in terms of VolCon and AOD) is performed in this study, showing that aerosol loading at IZO is double that of TPO but with similar fine mode fraction, effective radius and optical intensive properties. The long-term trend analysis at SCO shows a negative significant trend in the fine AOD mode between 2005 and 2020 (-1.8±0.5) ·10−5 yr−1, which might be linked to the large reduction of oil refining SO2 emissions at SCO refinery in 2012.

The objective is to derive methane (CH4) emissions of the metropolitan city Madrid Spain from the CH4 enhancements seen by the space-borne and the ground-based instruments. This study applies satellite-based measurements from the TROPOspheric Monitoring Instrument (TROPOMI) and the Infrared Atmospheric Sounding Interferometer (IASI) together with measurements from the ground-based COllaborative Carbon Column Observing Network (COCCON) instruments. In 2018, a two-week field campaign for measuring the atmospheric concentrations of greenhouse gases was performed in Madrid in the framework of Monitoring greenhousE Gas EmIssions of Madrid city (MEGEI-MAD) project. Five COCCON instruments were deployed at different locations around the Madrid city center enabling the observation of total column averaged CH4 mixing ratios (XCH4). Using available wind data, the differences between CH4 columns observed at these locations allow to estimate the emissions emerging from the surrounded area. In addition, based on the dominating wind direction in the Madrid region, we calculate the difference of the satellite data maps for two opposite wind regimes (northeast – southwest, NE – SW). In the following, we refer to the resultant signal as the wind-assigned anomaly. We use TROPOMI tropospheric nitrogen dioxide (NO2) observations as a test to verify our method of wind-assigned anomaly and its implementation, taking advantage of the much better detectability of the plume due to the short lifetime and low background concentrations of NO2. Pronounced bipolar plumes are found along NE and SW wind direction, which implies that our method of wind-assigned anomaly is working as expected. The wind-assigned TROPOMI XCH4 anomaly shows much weaker symmetric plumes than NO2 due to the long lifetime of CH4 and in consequence a high accumulated background of CH4 in the atmosphere. The wind-assigned plume method is also applied to the tropospheric and upper tropospheric/stratospheric column averaged CH4 mixing ratio products (in the following referred to as TXCH4 and UTSXCH4) derived from a-posteriori merged Infrared Atmospheric Sounding Interferometer (IASI) profile and TROPOMI total column data. Based on the NE and SW wind fields, we developed a simple plume model locating the source at three waste disposal sites east of Madrid for CH4. As CH4 emission strength we estimate 7.4 × 1025 ± 6.4 × 1024 molec s−1 from the TROPOMI XCH4 data and 7.1 × 1025 ± 1.0 × 1025 molec s−1 from the TROPOMI&IASI merged TXCH4 data. The COCCON observations indicate a weaker CH4 emission strength of around 3.7 × 1025 molec s−1 from local source (near to the Valdemingómez waste plant) in accordance with observations in a single day and. All emission rates estimated from the different observations are significantly larger than the emission rates provided via the official Spanish Register of Emissions and Pollutant Sources.

High-resolution Fourier transform infrared (FTIR) solar observations are particularly relevant for climate studies, as they allow atmospheric gaseous composition and multiple climate processes to be monitored in detail. In this context, the present paper provides an overview of 20 years of FTIR measurements taken in the framework of the NDACC (Network for the Detection of Atmospheric Composition Change) from 1999 to 2018 at the subtropical Izaña Observatory (IZO, Spain). Firstly, long-term instrumental performance is comprehensively assessed, corroborating the temporal stability and reliable instrumental characterization of the two FTIR spectrometers installed at IZO since 1999. Then, the time series of all trace gases contributing to NDACC at IZO are presented (i.e. C2H6, CH4, ClONO2, CO, HCl, HCN, H2CO, HF, HNO3, N2O, NO2, NO, O3, carbonyl sulfide (OCS), and water vapour isotopologues H162O, H182O, and HD16O), reviewing the major accomplishments drawn from these observations. In order to examine the quality and long-term consistency of the IZO FTIR observations, a comparison of those NDACC products for which other high-quality measurement techniques are available at IZO has been performed (i.e. CH4, CO, H2O, NO2, N2O, and O3). This quality assessment was carried out on different timescales to examine what temporal signals are captured by the FTIR records, and to what extent. After 20 years of operation, the IZO NDACC FTIR observations have been found to be very consistent and reliable over time, demonstrating great potential for climate research. Long-term NDACC FTIR data sets, such as IZO, are indispensable tools for the investigation of atmospheric composition trends, multi-year phenomena, and complex climate feedback processes, as well as for the validation of past and present space-based missions and chemistry climate models. The Izaña FTIR station has been supported by the German Bundesministerium für Wirtschaft und Energie (BMWi) via DLRunder grants 50EE1711A and by the Helmholtz Society via the research program ATMO. In addition, this research was funded by the European Research Council under FP7/(2007-2013)/ERC Grant agreement nº 256961 (project MUSICA), by the Deutsche Forschungsgemeinschaft for the project MOTIV (GeschaFTIRzeichen SCHN 1126/2-1), by the Ministerio de Economía y Competitividad from Spain through the projects CGL2012-37505 (project NOVIA) and CGL2016-80688-P (project INMENSE), and by EUMETSAT under its Fellowship Programme (project VALIASI).

El Centro Regional de Calibración Brewer para Europa (RBCC-E) en colaboración con el Área de Instrumentación e Investigación Atmosférica del Instituto Nacional de Técnica Aeroespacial (INTA), con el apoyo del programa de Vigilancia de la Atmósfera Global (VAG) de la Organización Meteorológica Mundial (OMM) y la acción COST EUBREWNET ES1207 organizaron la 12.ª campaña europea de intercomparación. En esta campaña, el RBCC-E transfirió al resto de instrumentos participantes su propia calibración absoluta de aparatos de medición de ozono obtenida mediante el método Langley en el Observatorio de Izaña. En la intercomparación participaron un total de 20 espectrofotómetros Brewer de nueve países. Estas campañas de intercomparación, que cuentan con una gran cantidad de instrumentos participantes, ofrecen una visión general del estado actual de las mediciones de ozono realizadas por la red Brewer europea. Los instrumentos se compararon con la referencia del RBCC-E, el Brewer#185, para la medición de ozono y con el patrón de referencia europeo de la unidad QASUME del Centro Radiométrico Mundial (CRM) para la medición de radiación UV.

Editado por Alberto Redondas y Stoyka Netcheva El Centro Regional de Calibración Brewer para Europa (RBCC-E) en colaboración con el Área de Instrumentación e Investigación Atmosférica del Instituto Nacional de Técnica Aeroespacial (INTA), con el apoyo del programa de Vigilancia de la Atmósfera Global (VAG) de la Organización Meteorológica Mundial (OMM) y la acción COST EUBREWNET ES1207 organizaron la 12.ª campaña europea de intercomparación. En esta campaña, el RBCC-E transfirió al resto de instrumentos participantes su propia calibración absoluta de aparatos de medición de ozono obtenida mediante el método Langley en el Observatorio de Izaña. En la intercomparación participaron un total de 20 espectrofotómetros Brewer de nueve países. Estas campañas de intercomparación, que cuentan con una gran cantidad de instrumentos participantes, ofrecen una visión general del estado actual de las mediciones de ozono realizadas por la red Brewer europea. Los instrumentos se compararon con la referencia del RBCC-E, el Brewer#185, para la medición de ozono y con el patrón de referencia europeo de la unidad QASUME del Centro Radiométrico Mundial (CRM) para la medición de radiación UV.

Editado por Alberto Redondas y Stoyka Netcheva The twelfth European Brewer Intercomparison Campaign was organized by the Regional Brewer Calibration Center for Europe (RBCC-E) in collaboration with the “Area of Instrumentation and Atmospheric Research Area” of Instituto Nacional de Tecnica Aeroespacial (INTA), with the support of the Global Atmosphere Watch (GAW) Programme of the World Meteorological Organization (WMO) and the EUBREWNET ES1207 COST Action. Alongside the campaign, the ATMOZ (Traceability of Atmospheric Total Ozone) project workshop took place at the station. In addition, this event was also used as a demonstration exercise of the calibration methodologies and error assessment developed by the project (Gröbner et al., 2018).

Ponencia presentada en: XXXV Jornadas Científicas de la AME y el XIX Encuentro Hispano Luso de Meteorología celebrado en León, del 5 al 7 de marzo de 2018. En noviembre del 2003 y bajo el amparo de la Organización Mundial Meteorología (OMM) y el Programa para la Observación Global de la Atmósfera (GAW) se estableció el Centro de calibración Regional Brewer para Europa (RBCC-E) en el Observatorio Atmosférico de Izaña (IZO) perteneciente a la Agencia Estatal de Meteorología. El RBCC-E es la referencia europea lo que le permite utilizar sus observaciones para calibrar estos Brewers. El RBCC-E organiza intercomparaciones anuales, que alternan su sede entre la estación de Radiosondeo El Arenosillo (Huelva) perteneciente al Instituto Nacional de Técnica Aeroespacial (INTA) y el Observatorio Atmosférico de Arosa (Suiza) operado por Meteoswiss. La XII Campaña de calibración se realizó en El Arenosillo entre los días del 29 de mayo al 7 de Junio, 2017. En esta campaña participaron más de 20 Brewers pertenecientes a 11 organizaciones tanto servicios meteorológicos nacionales como instituciones privadas. Además, se pudo realizar una calibración espectral en el rango ultravioleta gracias a la participación de la referencia estándar viajera QASUME perteneciente al centro de calibración Mundial para ultravioleta (WCC-UV). En este trabajo se presenta una visión general del estado inicial y final de la calibración del Brewer#102, indicando los principales parámetros que han sido tenidos en cuenta en su calibración: lámpara estándar, corrección de filtros, resultados del test de dispersión y transferencia de la nueva ETC (Constante extra-terrestre). También, y debido a que el instrumento es un Brewer de monocromador simple se calculó su corrección por stray light.

Total ozone column can be measured using Brewer sprectrophotometers which are calibrated periodically in inter- comparison campaigns with respect to a reference instrument. In 2003 the Regional Brewer Calibration Centre for Europe (RBCC-E) was established at the Izaña Atmospheric Research Centre (Canary Islands, Spain) and from 2011 it has transferred its own calibration mainly to other European Brewers using the Brewer #185 as reference instrument. The RBCC-E organizes regular inter-comparisons which are held annually alternating between Arosa (Switzerland) and El Arenosillo (Spain). This work is focused on showing the stability of the measurements of the RBCC-E Triad (Brewers #157, #183 and #185) made in the Izaña Atmospheric Observatory during the period 2005–2016. In order to study the long-term precision of the RBCC-E Triad, it must be taken into account that each Brewer performs a large number of measurements every day and, hence, it be- comes necessary to calculate a representative value of all of them. This value was calculated from methods previously used to study the long-term behaviour of the World Reference and Arosa Triads. Applying their procedures in our triad allows us to compare the three instruments. In this way, the difference between the values calculated for each Brewer and the triad mean was analyzed. In daily averages, applying the procedure used for the World Triad Reference, the RBCC-E Triad presents a relative standard deviation mean equal to 0.41 % (σ157 = 0.362 %, σ183 = 0.453 % and σ185 = 0.428 %). In opposite, using the procedure of the Arosa Triad, the RBCC-E presents a relative standard deviation around at σ = 0.5 %. In monthly averages, the method of the World Triad Reference give a relative standard deviation of 0.33 %, 0.34 % and 0.23 % for Brewers #157, #183 and #185, respectively (0.3 % in mean). Whereas, the procedure of the Arosa Triad gives a monthly values 0.3 %. In this work, two ozone datasets are analyzed: the first included all the ozone measurements available while the second only includes the simultaneous measurements of all three instruments. Furthermore, in this paper we also describe the Langley method used in the RBCC-E Triad to calculate the Extra-terrestrial constant (ETC), which is the necessary first step to ozone retrieval. Finally, the short-term, or intraday, stability is also studied to identify the effect of the solar zenith angle on the accuracy of the RBCC-E Triad.

Ponencia presentada en: XXXV Jornadas Científicas de la AME y el XIX Encuentro Hispano Luso de Meteorología celebrado en León, del 5 al 7 de marzo de 2018. Los espectrofotómetros Brewers tienen como principal tarea medir la columna total de ozono (TOC). Estos instrumentos son calibrados respecto a instrumentos de referencia viajeros como el Brewer #017, operado por IOS y calibrado frente a la triada de Canadá o, más reciente, con respecto al Brewer #185 que forma parte de la Triada del Centro de Calibración Regional Brewer para Europa (RBCC-E) situado en el Observatorio Atmosférico de Izaña y perteneciente a la Agencia Estatal de Meteorología (AEMET). En este trabajo se pretende, en primer lugar, mostrar cómo es el ciclo anual del ozono estratosférico en las Islas Canarias, indicando su período de máxima y mínima concentración y, en segundo lugar, mostrar el grado de acuerdo entre las medidas de ozono llevadas a cabo por los tres instrumentos, Brewer #157, #183 y #185 que forman la triada RBCC-E. En este sentido, y teniendo en cuenta que cada Brewer realiza a lo largo del día un elevado número de observaciones, se visto adecuado calcular su valor medio. En este trabajo se han empleado dos conjuntos de datos para evaluar el grado de acuerdo entre los tres instrumentos. El primer conjunto de datos incluye todas las medidas hechas por los Brewers mientras el segundo sólo considera las medidas que de manera simultánea han sido realizadas por los tres instrumentos. Los resultados indican que este segundo conjunto de datos muestra una mejor estimación del acuerdo existente entre los tres Brewers. No obstante, ambos conjuntos indican que la desviación entre los valores medios diarios de los tres Brewers #157, #183 y #185 que forman la RBCC-E es ~0.5%.

The high spatial and temporal variability of aerosols make networks capable of measuring their properties in near real time of high scientific interest. In this work we present and discuss results of an aerosol optical depth algorithm to be used in the European Brewer Network, which provides data in near real time of more than 30 spectrophotometers located from Tamanrasset (Algeria) to Kangerlussuaq (Greenland). Using data from the Brewer Intercomparison Campaigns in the years 2013 and 2015, and the period in between, plus comparisons with Cimel sunphotometers and UVPFR instruments, we check the precision, stability, and uncertainty of the Brewer AOD in the ultraviolet range from 300 to 320 nm. Our results show a precision better than 0.01, an uncertainty of less than 0.05, and a stability similar to that of the ozone measurements for well-maintained instruments. We also discuss future improvements to our algorithm with respect to the input data, their processing, and the characterization of the Brewer instruments for the measurement of aerosols.