Analisis y diagnóstico de episodios de meteorología severa en el País Vasco

Informe de las Galernas del 25 Jul 1995 y 30 May 1996The atmospheric processes prior to and during the outbreak of 2 galernas (July 25, 1995 and May 30, 1996) are analyzed. Data from surface stations, meteorological satellites, the Punta Galea wind profiler radar and numerical simulations with the mesoscalar model RAMS are used. It is concluded that the origin of the classic galerna of the warm season is associated with the irruption of a cold front on the N coast of the Iberian Peninsula. This front, which in most cases is not recorded on the synoptic weather charts, is associated with the presence of a low-pressure N-to-S trough between a European anticyclone and the Azores anticyclone. The surface front is preceded by an intense Foehn on the north coast, which is clearly visible in the satellite images, and which causes high temperatures on the Basque coast during the morning. The frontal advection over the land mass of the northwestern half of the peninsula can leave precipitation on the W-coast and southern slopes of the mountains in Galicia (galerna of July 1995). However, over the sea, a relative cold marine boundary (MBL) layer is transported parallel to the coast from Galicia (with colder water) to the Basque coast (with warmer sea surface temperatures). It runs parallel to the coast and remains uncoupled from the south-westerly winds, which cross over the Cantabrian Mountains and blow above the MBL. The decoupling is caused by the temperature inversion associated with the cold advection of the MBL and the presence of the Cantabrian mountain range. On the Asturian coast, protected by the highest mountains, the cold coastal advection and solar heating of the slopes, cause sea-land and up-slope breezes (Avilés weather station). An intense convergence occurs at the top of the Cantabrian mountain range: SW winds that blow on its S slope and those from the NW associated with the combined sea and up-slope breezes. Data from the wind profiler radar at Punta Galea (Getxo) documented a galerna depth of 1,500 meters and intense winds from the SW blowing above, confirmed by numerical simulations with the RAMS mesoscale model (3 km horizontal resolution and 1 hour resolution).Direccion de Meteorología y Climatología del Gobierno Vasco, 200

Impact of the COVID-19 Lockdown in a European Regional Monitoring Network (Spain): Are We Free from Pollution Episodes?

The impact of the lockdown, during the period from March to June in 2020, upon the air quality of the Basque Country in northern Spain is analyzed. The evaluation accounts for the meteorology of the period. Daily and sub-daily analysis of aerosol and ozone records show that the territory was repeatedly affected by episodes of pollutants from outer regions. Three episodes of PM10 and ten of PM2.5 were caused by transported anthropogenic European sulfates, African dust, and wildland fires. The region, with a varied orographic climatology, shows high and diverse industrial activity. Urban and interurban road traffic of the region decreased by 49% and 53%, respectively, whereas industrial activity showed a lower reduction of 20%. Consequently, the average concentrations of NO2 in the cities during the period fell to 12.4 µg·m−3 (−45%). Ozone showed up to five exceedances of the WHOAQG for the daily maximum 8-h average in both rural and urban sites, associated with transport through France and the Bay of Biscay, under periods of European blocking anticyclones. However, averages showed a moderate decrease (−11%) in rural environments, in line with the precursor reductions, and disparate changes in the cities, which reproduced the weekend effect of their historical records. The PM10 decreased less than expected (−10% and −21%, in the urban and rural environments, respectively), probably caused by the modest decrease of industrial activity around urban sites and favorable meteorology for secondary aerosol formation, which could also influence the lower changes observed in the PM2.5 (−1% and +3% at the urban and rural sites, respectively). Consequently, in a future low NOx traffic emission scenario, the inter-regional PM and ozone control will require actions across various sectors, including the industry and common pollution control strategies.This research was funded by the Basque Government and the University of the Basque Country (GIC15/152 and GIU13/03) and by the Environment Vice-Department of the Basque Government for the measurement of biogenic volatile organic compounds in Valderejo Natural Park

Galernas: A history of coastally trapped disturbances (2003−2020) with hidden frontogenesis in the Bay of Biscay

Galerna is the term accepted for an abrupt westerly change that affects the north coast of Spain. The wind surge travels from the mid-north coast of Spain to France, generally reaching their maximum intensity at the Basque Coast, and cuts off a period of hot weather, clear skies, and calm conditions at sea. The galernas have a large history of shipwrecks and fishermen deaths. They have been characterized as coastally trapped disturbances (CTD) and their propagation, enhanced with the local formation of a micro-front, was documented to behave like a density current. Alternatively, synoptic fronts have also been reported to cause galernas, considered to be more intense than those generated by a local micro-front. In this article we have generated the first climatology (2003–2020) of these events based on an objective identification methodology. The developed Event Identification Software (EIS), based on both 10-min surface station data and hourly ERA5 reanalysis fields, together with a new Front Identification Scheme (FIS) have enabled a deeper study into the origin and development of these micro-fronts, and a more comprehensive exploration of the interaction of the oceanic fronts entering the Bay of Biscay. Our results show that the area receives an average of four to five relatively intense galernas (Vmax > 50 km h−1) per year. Their number shows a great interannual variability (from one to seven) and a marked seasonality: May and June concentrate the largest fraction (almost one episode each year) and practically no episodes in winter. They occur more frequently between noon and the late afternoon, where the most intense wind records concentrate. Very strong galernas (Vmax > 72 km h−1) have occurred in all 18 years, can happen in any month from February to November, and their monthly distribution does not show the mentioned seasonality. On the contrary, the highest rates of temperature decrease across the galerna front in the coastal stations (−∆T/0.5 h > 4 °C) do have a stronger seasonality, with May and June concentrating a relatively large number of cases with a more abrupt temperature drop. The FIS shows that most of the galernas (83.5%) have a local origin inside the Bay of Biscay, and only a few ones (16.5%) are caused by oceanic fronts initiated out of the region. The local frontogenesis is more frequently initiated by the relatively cold marine southwesterly pre-frontals preceding a parent oceanic front and blowing against the warm continentals inside the Bay of Biscay, after being ducted along the north and northwestern coast of Spain. This hidden local frontogenesis, first revealed by the FIS, seems to be enhanced by the observed lee troughing, which could have both a thermal and dynamic origin, acting simultaneously after the intense Foehn at the coastal strip, preceding the formation of the galerna front. The local front enhancement appears to be the reason for the apparent jump of the primary front, which may eventually weaken, and even disappear, as the galerna front sharpens. Even during the more occasional frontal galernas, directly caused by the westerlies or north-westerlies behind the oceanic front, their eastward propagation is more rapid over the coastal area. The front deforms in shape and may cause its characteristic unexpected/abrupt irruption. All the EIS detected galernas, even the frontal ones, are wind reversals caused by a coastally trapped marine boundary layer. The upper-level ridge over Europe, observed in all of them, seems to be a synoptic ingredient for their development, preventing the eastward propagation of Atlantic depressions and enhancing at the same time the temperature and pressure gradients between the marine and continental air masses.The authors wish to thank the Basque Government and the University of the Basque Country UPV/EHU as the source of our main financial support: GIA consolidated Research Groups (https://www.ehu.eus/es/web/gia) IT1057-16 (GIC15/152) and GIU13/03. These financing bodies have played an exclusively economic role in the study

Identification of "Galerna" events in the regional meteorological network of the Basque Country: a selection of 7 events in 2002

The analysis of the generation and development of a series of galernas has shown the presence of intense winds from the SW at relatively low altitudes, some hours before the triggering of a typical summer galerna. It is now also known that the mechanism of its generation and development includes other factors, such as the advection of a cold air mass in the marine boundary layer, which runs parallel to the coast from W to E, and a significant foehn on the coast of the Basque Country before noon. These results are contained in the report "Analysis and diagnosis of severe weather episodes in the Basque Country" (http://hdl.handle.net/10810/55032). Here, it is intended to use the meteorological data from the coastal meteorological surface stations of the region and the profiler radar of Punta Galea, located on the Basque shoreline, to establish a scheme for evaluating the capacity of a micro-front to deepen and generate a violent galerna in the Basque coast. At a synoptic level, all the galerna events in this report present a cold front over the Galician coast at noon, in addition to a characteristic configuration of the pressure centers: a depression over the west coast of Ireland and high pressures over Western Europe and Western Mediterranean, that block westerly flow over the continent (becomes more S by the western end of the anticyclone) causing larger E-W temperature differences. However, it has been proven that this configuration of the synoptic pressure centers and the position of the fronts is not sufficient for a correct assessment of galerna risk. It is also necessary to know the near frontal activity (either from a synoptic or from any other sub-synoptic front). This activity could be assessed at the local level, using the Punta Galea radar wind profiler output during a time window of several hours before the solar noon: intense SW winds (greater than 10-12 ms-1) at all the levels in the surveillance time interval are indicators of the approach of a cold front with sufficient activity to cause a galerna event. This characteristic, together with an appreciable solar activity, capable of making the boundary layer over the Basque coastal land mass sufficiently unstable (more likely between April and September) and the presence of a mass of cold air trapped to the north of the Cantabrian Mountain Range, over the sea, running parallel to the coast from W to E, are sufficient ingredients for the generation of a galerna. In this regard, it is important to highlight the fact that for the three frontal galernas, out of the seven possible analyzed events, the galerna fronts that penetrates into the Basque Country are always located ahead of the synoptic front, and the latter is not always detected in the surface stations (May 20). The temperature differences between the south-westerlies blowing ahead of the galerna front and the westerlies at the rear easily exceeds 10°C in the warm season, but the W-E thermal contrasts cannot be used only by themselves to make an adequate assessment of galerna risk: the May 24, June 16 and August 17 events are clear examples. Only the combination of the factors described and their proper monitoring could lead to a valid operational prediction.Dirección de Meteorología y Climatología del Gobierno Vasco, 200

Analysis of summer O3 in the Madrid air basin with the LOTOS-EUROS chemical transport model

Tropospheric O-3 remains a major air-quality issue in the Mediterranean region. The combination of large anthropogenic emissions of precursors, transboundary contributions, a warm and dry aestival climate, and topographical features results in severe cases of photochemical pollution. Chemical transport models (CTMs) are essential tools for studying O-3 dynamics and for assessing mitigation measures, but they need to be evaluated specifically for each air basin. In this study, we present an optimisation of the LOTOS-EUROS CTM for the Madrid air basin. Five configurations using different meteorological datasets (from the European Centre for Medium-Range Weather Forecast, ECMWF; and the Weather Research and Forecasting Model, WRF), horizontal resolution and number of vertical levels were compared for July 2016. LOTOS-EUROS responded satisfactorily in the five configurations reproducing observations of surface O-3 with notable correlation and reduced bias and errors. However, the best-fit simulations for surface O-3 were obtained by increasing spatial resolution and using a large number of vertical levels to reproduce vertical transport phenomena and the formation of reservoir layers. Using the optimal configuration obtained in the evaluation, three characteristic events have been described: recirculation (REC) episodes and northern and southern advection (NAD and SAD, respectively) events. REC events were found to produce the highest O-3 due to the reduced ventilation associated with low wind speeds and the contribution of reservoir layers formed by vertical transport of O-3 formed near the surface in the previous days of the event. NAD events, usually associated with higher wind speeds, present the lowest ground-level O-3 concentrations in the region. During SAD episodes, external contributions along with low wind speeds allow O-3 to increase considerably but not as much as in REC events because steady southerly winds disperse local emissions and hinder the formation of reservoir layers.This research has been supported by the Ministry of Economy, Industry and Competitiveness of Spain and FEDER (grant no. CGL2016-78594-R); the Department of Research, Innovation and University of the Aragon Regional Government and the European Social Fund (grant no. E23_17D); the Directorate General for Universities and Research of the Greater Madrid Region (grant no. S2013/MAE-2972); and the Ministry of Education and Science of Spain (grant no. CAS17/00108)

Lessons from the COVID-19 air pollution decrease in Spain: Now what?

We offer an overview of the COVID-19 -driven air quality changes across 11 metropolises in Spain with the focus on lessons learned on how continuing abating pollution. Traffic flow decreased by up to 80% during the lockdown and remained relatively low during the full relaxation (June and July). After the lockdown a significant shift from public transport to private vehicles (+21% in Barcelona) persisted due to the pervasive fear that using public transport might increase the risk of SARS-CoV-2 infection, which need to be reverted as soon as possible. NO2 levels fell below 50% of the WHO annual air quality guidelines (WHOAQGs), but those of PM2.5 were reduced less than expected due to the lower contributions from traffic, increased contributions from agricultural and domestic biomass burning, or meteorological conditions favoring high secondary aerosol formation yields. Even during the lockdown, the annual PM2.5 WHOAQG was exceeded in cities within the NE and E regions with high NH3 emissions from farming and agriculture. Decreases in PM10 levels were greater than in PM2.5 due to reduced emissions from road dust, vehicle wear, and construction/demolition. Averaged O3 daily maximum 8-h (8hDM) experienced a generalized decrease in the rural receptor sites in the relaxation (June–July) with -20% reduced mobility. For urban areas O3 8hDM responses were heterogeneous, with increases or decreases depending on the period and location. Thus, after canceling out the effect of meteorology, 5 out of 11 cities experienced O3 decreases during the lockdown, while the remaining 6 either did not experience relevant reductions or increased. During the relaxation period and coinciding with the growing O3 season (June–July), most cities experienced decreases. However, the O3 WHOAQG was still exceeded during the lockdown and full relaxation periods in several cities. For secondary pollutants, such as O3 and PM2.5, further chemical and dispersion modeling along with source apportionment techniques to identify major precursor reduction targets are required to evaluate their abatement potential.The present work was supported by the Spanish Ministerio para la Transición Ecológica y Reto Demográfico (17CAES010), the “Agencia Estatal de Investigación” from the Spanish Ministry of Science and Innovation (IDAEA-CSIC is a Centre of Excellence Severo Ochoa CEX2018-000794-S), FEDER funds under the project CAIAC (PID2019- 108990RB-I00), and by the Generalitat de Catalunya (AGAUR 2017 SGR41). We would like to thank the Spanish Meteorological Office (AEMET) for providing meteorological data as well as NASA for providing OMI-NO2 data. BSC co-authors acknowledge the support of the Copernicus Atmosphere Monitoring Service (CAMS), which is implemented by the European Centre for Medium-Range Weather Forecasts (ECMWF) on behalf of the European Commission, the Ministerio de Ciencia, Innovación y Universidades (MICINN) (RTI2018-099894-BI00, CGL2017-88911-R), the Agencia Estatal de Investigación (PID2019-108086RA-I00/AEI/0.13039/501100011033), the AXA Research Fund, and PRACE and RES for awarding access to Marenostrum4 based in Spain at the Barcelona Supercomputing Center. H. Petetin also acknowledges the European Union's Horizon 2020 - Research and Innovation Framework Programme under the H2020 Marie Skłodowska-Curie Actions grant agreement H2020-MSCACOFUND-2016-754433.Peer ReviewedArticle signat per 20 autors/es: Xavier Querol (a), Jordi Massagué (a, b), Andrés Alastuey (a), Teresa Moreno (a), Gotzon Gangoiti (c), Enrique Mantilla (d), José Jaime Duéguez (d), Miguel Escudero (e), Eliseo Monfort (f), Carlos Pérez García-Pandog (h), Hervé Petetin (g), Oriol Jorba (g), Víctor Vázquez (i, j), Jesús de la Rosa (k), Alberto Campos (l), Marta Muñóz (l), Silvia Monge (l), María Hervás (l), Rebeca Javato (l), María J. Cornide (l) a- Institute of Environmental Assessment and Water Research, IDAEA-CSIC, Barcelona 08034, Spain b- Department of Mining, Industrial and ICT Engineering, Universitat Politècnica de Catalunya - BarcelonaTech (UPC), Manresa 08242, Spain c- Department of Chemical and Environmental Engineering, University of Basque Country, Leioa 48940, Spain d- Centro de Estudios Ambientales del Mediterráneo, CEAM, València 46980, Spain e- Centro Universitario de la Defensa, Academia General Militar, Zaragoza 50090, Spain f- Instituto de Tecnología Cerámica ITC-UJI, Castelló 12006, Spain g- Barcelona Supercomputing Center, BSC-CNS, Barcelona 08034, Spain h- ICREA, Catalan Institution for Research and Advanced Studies, Barcelona 08010, Spain i- Department of Ecology, Faculty of Sciences, University of Málaga, 29071 Málaga, Spain j- Department of Research and Development, Coccosphere Environmental Analysis, 29120 Málaga, Spain k- Department of Geology, University of Huelva, Unidad de Investigación Associada a IDAEA-CSIC, Huelva 21819, Spain l- D.G. Calidad y Evaluación Ambiental del Ministerio de Transición Ecológica y Reto Demográfico, Madrid 28071, SpainPostprint (published version