Search

Ponencia presentada en: XII Congreso de la Asociación Española de Climatología celebrado en Santiago de Compostela entre el 19 y el 21 de octubre de 2022. [ES]Las proyecciones de extremos climáticos son esenciales para el diseño de planes estratégicos de adaptación/mitigación a los posibles efectos adversos del cambio climático. Para obtener las proyecciones de los índices de temperaturas extremas en Canarias se aplicó una metodología de downscaling dinámico. Para ello se empleó el modelo WRF con una resolución espacial de 3 km en los periodos 2030-2059 (MID) y 2070-2099 (END), y para los escenarios RCPs 4.5 y 8.5. Las condiciones iniciales se definieron mediante los modelos GFDL-ESM2M, MIROC-ESM e IPSL-CM5. Los cambios a futuro se calcularon frente al período de referencia 1980-2009 (HIS) para los índices extremos dados por el Equipo de Expertos en Detección e Índices de Cambio Climático (ETCCDI): temperaturas máxima y mínima mensual (TX y TN), máximo mensual del rango de temperatura diurna diaria (DTR), noches tropicales (TR), días cálidos (noches frías) TX90p (TN10p), índice de duración de olas de calor (WSDI) y de olas de frío (CSDI). Además, se analizaron los niveles y periodos de retorno para la temperatura máxima anual utilizando la distribución de valores extremos generalizados (GEV). [EN]Projections of climate extremes are essential data for the design of strategic plans for adaptation/mitigation to the possible adverse effects of climate change. To obtain projections of extreme temperature indices in the Canary Islands, a dynamic downscaling methodology was applied. For this purpose, the WRF modeling system was configured with a spatial resolution of 3 km, for the periods 2030-2059 (MID) and 2070-2099 (END), and the RCPs 4.5 and 8.5 scenarios. Initial conditions were defined using three models of the Coupled Model Intercomparison Project 5 (CMIP5): GFDL-ESM2M, MIROC-ESM and IPSL-CM5. Future changes were calculated against the reference period 1980-2009 (HIS). The extreme indices selected were those defined by the Expert Team on Climate Change Detection and Indices (ETCCDI): monthly maximum and minimum temperature (TX and TN), monthly maximum of the daily diurnal temperature range (DTR), tropical nights (TR), warm days (cold nights) TX90p (TN10p), warm spell duration index (WSDI) and cold spell duration index (CSDI). In addition, return levels and return periods for annual maximum temperature were analyzed using the generalized extreme value (GEV) distribution. Este trabajo fue financiado por los proyectos CGL2015-67508-R, y RTC-2017-6409-3, Ministerio de Ciencia e Innovación, España.

Ponencia presentada en: XII Congreso de la Asociación Española de Climatología celebrado en Santiago de Compostela entre el 19 y el 21 de octubre de 2022. [ES]El cambio climático supone un factor de gran incertidumbre en cuanto a la posible evolución de los niveles de aridez y de sequía. Por una parte, se prevé un aumento de la evapotranspiración y por otra, el comportamiento de la precipitación presenta importantes diferencias regionales. En este trabajo se han analizado las proyecciones de la aridez y de las futuras sequías en las Islas Canarias, en términos de frecuencia, duración y severidad, utilizando el modelo Weather Research and Forecasting (WRF) para el periodo 2070-2099, y para los escenarios Representative Concentration Pathways (RCPs) 4.5 y 8.5. Las condiciones iniciales y de contorno se definieron mediante tres modelos incluidos en el Coupled Model Intercomparison Project 5 (CMIP5): GFDL-ESM2M, MIROC-ESM e IPSL-CM5. Los cambios futuros de la aridez se obtuvieron empleando el cambio en el índice de aridez (ACI), basado en la relación entre el cambio fraccional de la evaporación potencial y de la precipitación respecto al periodo de referencia 1981-2009. En el caso de la sequía, se utilizó el índice estandarizado de precipitación (SPI) para las escalas de tiempo de 3 y 12 meses. Asimismo, se consideraron eventos de sequía extrema (eventos extremos húmedos) cuando el SPI toma valores por debajo (por encima) de -2 (2). A partir de los resultados obtenidos, podemos destacar que la aridez y los eventos de sequía extrema aumentarán a finales de siglo respecto al periodo de referencia, para ambos escenarios. [EN]Climate change is a great relevance factor in the evolution of aridity and droughts due to increase of evapotranspiration and the behavior of precipitation. In this work, we analyses climate change projections in terms of frequency, duration, and severity of future aridity and drought in the Canary Island with the Weather Research and Forecasting (WRF) model driven by some Coupled Models Intercomparison Project phase 5 (CMIP5) simulations, for the period 2070-2099 and for two Representative Concentration Pathways (RCP) scenarios (RCP4.5 and RCP8.5). Initial and boundary conditions were defined using three models of the Coupled Model Intercomparison Project 5 (CMIP5): GFDL-ESM2M, MIROC-ESM and IPSL-CM5. Aridity change index was obtained to assessment future changes of aridity, which is based on the fractional change of potential evapotranspiration and precipitation with respect to the reference period (1981-2009). To evaluate droughts, the Standardized Precipitation Index (SPI) was applied at the 3 and 12-month time scales. In addition, extreme drought (wet) events are considered when SPI is lower (higher) than -2 (2). The results show an increase of extreme aridity and drought events by the end of this century with respect to the reference period for both emission scenarios. Este estudio se ha realizado en el marco del proyecto VidDATA (RTC2019-006948-7), cofinanciado por el Programa Estatal de I+D+i Orientada a los Retos de la Sociedad del Ministerio de Ciencia e Innovación, España. Agradecemos el apoyo del Proyecto PLANCLIMAC (MAC / 3.5b / 244), el cual está financiado por el Programa INTERREG MAC 2014-2020 de la Unión Europea, cofinanciado por el Fondo Europeo de Desarrollo Regional (FEDER-FEDER).

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 authors also acknowledge the support from ACTRIS, Ministerio de Ciencia e Innovación, Spain, through the projects SYNERA (PID2020-118793GA-I00) and ePOLAAR (RTI2018-097864-BI00) and from Junta de Castilla y León (grant no. VA227P20).

El volumen 119 de 2016 de la revista EPJ Web of Conferences recoge las ponencias del 27th International Laser Radar Conference (ILRC 27) A seasonal distribution of the Lidar Ratio (LR, extinction-to-backscattering coefficient ratio) for pure Saharan dust particles has been achieved. Simultaneous MPLNET/Micro Pulse lidar measurements in synergy with AERONET sun-photometer data were collected in the Tenerife area, a Saharan dust-influenced region, from June 2007 to November 2009. Dusty cases were mostly observed in summertime (71.4 % of total dusty cases). No differences were found among the LR values derived for spring, summertime and autumn times (a rather consistent seasonally averaged LR value of 57 sr is found). In wintertime, however, a higher mean LR is derived (65 sr), associated likely with a potential contamination from fine biomass burning particles coming from Sahel area during wintertime deforestation fires period. Results, obtained from a free-tropospheric pristine station (AEMET/Izaña Observatory) under Saharan dust intrusion occurrence, provide a more realistic perspective about LR values to be used in elastic lidar-derived AOD inversion for Saharan pure dust particles, and hence in improving CALIPSO AOD retrievals. This work has been supported by the Spanish Ministerio de Economía y Competitividad (MINECO) under grant CGL2011-24891 (AMISOC project).

The mixture of mineral dust with biomass burning or urban-industrial aerosols presents significant differences in optical properties when compared to those of the individual constituents, leading to different impacts on solar radiation levels. This effect is assessed by estimating the direct radiative forcing (ΔF) of these aerosols from solar flux models using the radiative parameters derived from the Aerosol Robotic Network (AERONET). These data reveal that, in oceanic and vegetative covers (surface albedo (SA) < 0.30), the aerosol effect at the top of atmosphere (TOA) is always cooling the Earth-atmosphere system, regardless of the aerosol type. The obtained average values of ΔF range between −27 ± 15 Wm−2 (aerosol optical depth (AOD) at 0.55 μm, 0.3 ± 0.3) for mineral dust mixed with urban-industrial aerosols, registered in the East Asia region, and −34 ± 18 Wm−2 (AOD = 0.8 ± 0.4) for the mixture of the mineral dust and biomass burning particles, observed in the Central Africa region. In the intermediate SA range (0.30–0.50) the TOA radiative effect depends on the aerosol absorption properties. Thus, aerosols with single scattering albedo at 0.55 μm lower than ∼0.88 lead to a warming of the system, with ΔF of 10 ± 11 Wm−2 for the mixture of mineral dust and biomass burning. Cases with SA > 0.30 are not present in East Asia region. At the bottom of atmosphere (BOA) the maximum ΔF values are associated with the highest AOD levels obtained for the mixture of mineral dust and biomass burning aerosols (−130 ± 44 Wm−2 with AOD = 0.8 ± 0.4 for SA < 0.30). Support for this study was given by Spanish Ministry of Education and Science, projects CGL2005‐03428‐C04‐02, CGL2007‐66477‐C02‐02/CLI, PI042005/033, and CGL2008‐04740/CLI.

Comunicación presentada en: V Reunión Española de Ciencia y Tecnología de Aerosoles – RECTA 2011 celebrada del 27 al 29 de junio de 2011 en CIEMAT, Madrid.

The shortwave radiative forcing (1F) and the radiative forcing efficiency (1Feff) of natural and anthropogenic aerosols have been analyzed using estimates of radiation both at the Top (TOA) and at the Bottom Of Atmosphere (BOA) modeled based on AERONET aerosol retrievals. Six main types of atmospheric aerosols have been compared (desert mineral dust, biomass burning, urbanindustrial, continental background, oceanic and free troposphere) in similar observational conditions (i.e., for solar zenith angles between 55 and 65 ) in order to compare the nearly same solar geometry. We acknowledge to the MEC (Ministry of Education and Science, Spain) for the next supports: projects CGL2007-66477-C02-02/CLI, CGL2008-04740/CLI and CGL2010-21366-C04-01.

Comunicación presentada en: V Reunión Española de Ciencia y Tecnología de Aerosoles – RECTA 2011 celebrada del 27 al 29 de junio de 2011 en CIEMAT, Madrid.

Focusing on aerosolized matter of relevance to respiratory health, a major public health issue worldwide, we studied mineral and biological aerosol (bioaerosol) composition (TSP and PM2.5) and geographical origins during dust intrusions in the Canary Islands. Seven days’ back- ward trajectories were assessed daily during March 2004 with the ends of back trajectories being the sampling station of Iza?a (high moun- tain, 2360 m a.s.l. at the Ca?adas del Teide National Park, Tenerife island), a free troposphere site allowing characterization of dust with low influence of other pollutant sources. Scanning electron microscopy (SEM) was used to survey major types of airborne particles in the dust plumes. Control, non-intrusion conditions correspond to Atlantic oceanic middle troposphere (OMT) air masses. Of the 14 samples taken, 1 corresponded to a control (clear atmosphere conditions), and the remaining 13 to dust intrusions, with the following sources: African Dust; EAM: mixture of Europe, Africa and Oceanic; MaA: maritime aerosols. Of the air masses, 79% were directly transported to the islands from Africa, and an increase of African dust events was detected when comparing with a 52-year previous data sequence. Quartz microcristals and aggregates of quartz and platy clay were the dominant minerals identified, with marine salt and gypsum also present. Freshwater diatom tests (from two Aulacoseira species) represented the most important biogenic aerosols, although fungi and pollen were also detected. The diverse and complex mixture of respirable particles in large quantities in airborne dust, especially from nearby Sahara and from the Sahelian region, is of maximum interest for air- way pathology in the Canaries, including the highly visited highlands in Tenerife. We acknowledge to the MEC (Ministry of Education and Science, Spain) and F.E.D.E.R. founds (E.U.) for the economical support of the following projects: CGL2005-03428-C04-02, CGL2007-66477-C02-02/CLI, CGL2008- 04740 and PI042005/033.

The influence of mineral dust on ultraviolet energy transfer is studied for two different mineralogical origins. The aerosol radiative forcing ΔF and the forcing efficiency at the surface ΔFeff in the range 290–325 nm were estimated in ground-based stations affected by the Saharan and Asian deserts during the dusty seasons. UVB solar measurements were taken from the World Ozone and Ultraviolet Data Center (WOUDC) for four Asian stations (2000–04) and from the Santa Cruz Observatory, Canary Islands (2002–03), under Gobi and Sahara Desert influences, respectively. The Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol optical depth at 550 nm was used to characterize the aerosol load τ, whereas the aerosol index provided by the Total Ozone Mapping Spectrometer (TOMS) sensor was employed to identify the mineral dust events. The ΔF is strongly affected by the aerosol load, the values found being comparable in both regions during the dusty seasons. Under those conditions, ΔF values as large as −1.29 ± 0.53 W m−2 (τ550 = 0.48 ± 0.24) and −1.43 ± 0.38 W m−2 (τ550 = 0.54 ± 0.26) were reached under Saharan and Asian dust conditions, respectively. Nevertheless, significant differences have been observed in the aerosol radiative forcing per unit of aerosol optical depth in the slant path, τS. The maximum ΔFeff values associated with dust influences were −1.55 ± 0.20 W m−2 τS550−1 for the Saharan region and −0.95 ± 0.11 W m−2 τS550−1 in the Asian area. These results may be used as a benchmark database for establishing aerosol corrections in UV satellite products or in global climate model estimations. We acknowledge the MCYT (Ministry of Science and Technology, Spain) and F.E.D.E.R. foundations (E.U.) for their economic support of projects CGL2004-05984-C07-05, CGL2005-03428-C04-02, CGL2007-66477-C02-02/CLI, CGL2008-04740/CLI and PI042005/033.

Atmospheric aerosol effects on spectral global UV irradiance were evaluated during the VELETA2002 field campaign between 8 and 19 July 2002 in southeast Spain. In the first stage, seven UV spectroradiometer and six CIMEL Sun photometer measurements were carried out simultaneously, allowing them to be calibrated and intercompared. The mean ratio obtained for the global irradiance between the spectroradiometers, with regards to a reference instrument, ranges from 0.98 up to 1.04 with standard deviations that oscillate between ±0.01 and ±0.17. In particular, the two spectroradiometers used to obtain the aerosol forcing efficiencies have a ratio of 1.000 ± 0.001. The aerosol optical depth (AOD) obtained with the CIMEL Sun photometers has a standard deviation of lower than ±0.01 for all the channels. Under clear sky conditions, the diurnal aerosol forcing efficiency (DDFe) and fractional diurnal forcing efficiency (DFDFe) was calculated for two Mediterranean stations: Armilla (691 m.a.s.l.) within the boundary layer and Sabinas (2200 m.a.s.l) on the lower limit of the free troposphere and 25 km away from the first station. The DDFe values obtained at Armilla range between _2.72 ± 0.45 W m_2/t380 and _2.88 ± 0.45 W m_2/t440 and between _3.22 ± 0.61 W m_2/t380 and _3.40 ± 0.62 W m_2/t440 at Sabinas station; the DFDFe values range from _8.0 ± 1.4%/t380 to _8.6 ± 1.3%/t440 and _12.0 ± 2.3%/t380 to _12.6 ± 2.3%/t440 at the two stations, respectively. Also, an experimental aerosol transmittance factor, CT, used to obtain UV satellite derived products was found as a result of the dependence of the global irradiance with the AOD, under cloudless conditions. The average aerosol attenuation factor, h, obtained from the CT, is 6 ± 2% under weakly absorbing aerosols, with a negligible spectral dependence. This work was supported by CICYT–MCYT through the coordinated projects CGL2004-05984-C07-05 and CGL2005-03428-C04-02.

Ponencia presentada en: 1er Encuentro sobre Meteorología y Atmósfera de Canarias, celebrado en el Puerto de la Cruz, los días 12,13 y 14 de noviembre de 2003. El encuentro estuvo organizado por el Centro Meteorológico Territorial en Canarias Occidental, con la colaboración del Observatorio Atmosférico de Izaña y del Grupo de Física de la Atmósfera de la Facultad de Física (Universidad de La Laguna) El control de la capa de ozono es una de las tareas más importantes en la evaluación de los posibles riesgos producidos por la radiación UV. De igual forma, los aerosoles atmosféricos también modifican el balance de energía en el sistema, de forma directa mediante procesos de scattering y absorción de radiación, y de forma indirecta, mediante la modificación de ciclo de vida de las nubes. En este trabajo se han estudiado las posibles diferencias entre el ozono medido por el TOMS y el medido desde Tierra en presencia de aerosoles; estos vienen determinados por el índice de aerosoles, Al del TOMS. Para realizar este estudio se ha tomado una base de datos superior a 7GB, desde el 1 de Noviembre de 1978 hasta el 31 de Diciembre de 2001, correspondientes a /os datos del TOMS, y las 214 estaciones que hay repartidas por todo el planeta. El resultado obtenido para estas diferencias muestra que no existe diferencia apreciable entre los valores de 0 3 TOMS y los obtenidos desde tierra con el Al-TOMS. Este trabajo ha sido financiado por los proyectos REN2001-0609-C02/CLI y REN2000-0903-C08- 06/CLI del Ministerio de Ciencia y Tecnología.

Ponencia presentada en: 1er Encuentro sobre Meteorología y Atmósfera de Canarias, celebrado en el Puerto de la Cruz, los días 12,13 y 14 de noviembre de 2003. El encuentro estuvo organizado por el Centro Meteorológico Territorial en Canarias Occidental, con la colaboración del Observatorio Atmosférico de Izaña y del Grupo de Física de la Atmósfera de la Facultad de Física (Universidad de La Laguna) Los aerosoles atmosféricos modifican el balance de energía en el sistema Tierra-Atmósfera, jugando un papel fundamental en el forcing radiativo. De entre estos constituyentes atmosféricos cabe señalar especialmente el polvo mineral procedente de África, debido a su enorme concentración bajo determinadas situaciones climáticas. Para valorar su influencia en la transferencia de energía se han analizado /as variaciones de energía ultravioleta (UV) durante intrusiones africanas en Canarias para /os años 2000 y 2002. Se observa así como dicha variación de energía oscila entre el 3% y el 36%, dependiendo de la carga de aerosoles presente en la estación de medida. Esta carga viene representada por el índice de aerosoles del TOMS. Este trabajo ha sido financiado por las becas FP2001-0963 y FP2000-5379 asociadas a los proyectos REN2001-0609-C02/CLI y REN2000-0903-C08-06/CLI del Ministerio de Ciencia y Tecnología.

Ponencia presentada en: 1er Encuentro sobre Meteorología y Atmósfera de Canarias, celebrado en el Puerto de la Cruz, los días 12,13 y 14 de noviembre de 2003. El encuentro estuvo organizado por el Centro Meteorológico Territorial en Canarias Occidental, con la colaboración del Observatorio Atmosférico de Izaña y del Grupo de Física de la Atmósfera de la Facultad de Física (Universidad de La Laguna) El índice de aerosoles del TOMS es una herramienta muy útil para evaluar los aerosoles absorbentes en el UV. Su resolución espacial y temporal permite estimar apropiadamente el alcance global de los mismos. Para estudiar la serie temporal del Al hemos calculado la variabilidad espacial y temporal en un conjunto de cuatro píxeles centrados en el correspondiente a lzaña: píxel IZO (28.500°N, 16.875°W), píxel del SW en (27.500°N, 18.125°W), píxel del N en (29.500°N, 16.875°W) y píxel del SE en (27.500°N, 15.625°W). El promedio de la variabilidad temporal de Al es aproximadamente de O. 02±0. 58 para los cuatro píxeles y el período de estudio. Mientras que el promedio de la variabilidad espacial es: 0.06±0.28, 0.04±0.33 y 0.03±0.41, para los píxeles N, el SW y SE con respecto al píxel de IZO. Este trabajo ha sido financiado por las becas FP2001-0963 y FP2000-5379 asociadas a los proyectos REN2001-0609-C02/CLI y REN2000-0903-C08-06/CLI del Ministerio de Ciencia y Tecnología.

Ponencia presentada en: 1er Encuentro sobre Meteorología y Atmósfera de Canarias, celebrado en el Puerto de la Cruz, los días 12,13 y 14 de noviembre de 2003. El encuentro estuvo organizado por el Centro Meteorológico Territorial en Canarias Occidental, con la colaboración del Observatorio Atmosférico de Izaña y del Grupo de Física de la Atmósfera de la Facultad de Física (Universidad de La Laguna) Uno de los aspectos más importantes a la hora de estudiar la influencia de los aerosoles atmosféricos en el balance energético es parametrizar de manera adecuada sus propiedades radiativas. Para ello, necesitamos estudiar su distribución en tamaño, la ella/ se puede caracterizar a partir del radio efectivo de la misma. Para obtener esta información a partir de las medidas del sensor A VHRR, se ha comparado el radio efectivo proporcionado por el sensor MOD/S con el cociente entre los canales 1 y 2 (0. 63 y O. 82 pm respectivamente) del A VHRR demostrando que éste no es un buen parámetro para evaluar el radio efectivo. Sí se observa la posibilidad de discretizar los valores del radio efectivo en función del backscattering ratio.

We report on measurements of atmospheric transmission (ATT) and aerosol optical depth (AODT) made at three wavelengths (368, 500, and 778 nm) with a spectroradiometer placed on Tenerife (28.5°N, 16.3°W), Canary Islands. Using the National Oceanic and Atmospheric Administration (NOAA) advanced very high resolution radiometer (AVHRR) channel 1, we also measured the aerosol optical depth (AODS) and albedo over a region of the North Atlantic Ocean extending from 15°–35°N to 12°–25°W. We observe large changes in ATT and AODT when dust outbreaks pass over this region. Using all these data, we derive the asymmetry factor (g), the single-scattering albedo (ω), and the local mean AODT and we compute the direct radiative forcing ΔF attributable to mineral dust. The local radiative forcing obtained is over the ocean ΔF = −9.7 W/m2 and for the land ΔF = −4.5 W/m2 with an error of ±25%. Extending these results to global-scale averages, we obtain values of ΔF of −1.22 W/m2 over the ocean and −0.57 W/m2 over land. The forcings attributable to dust are comparable in magnitude to those reported in the literature for anthropogenic sulphate and for biomass burning aerosols. We wish to thank the Gobierno Autónomo de Canarias for its financial support by contract 4/95, the Comisi6n Interministerial de Ciencia y Tecnologia (CICYT) by contract CLI97- 0453, and the University of La Laguna by contract 1802260003. A portion of this work was carried out as part of the Atmosphere/Ocean Chemistry Experiment (AEROCE) and supported by the National Science Foundation grants ATM-9414808, ATM-9414812, and ATM- 9414846.

The role played by aerosols on UV radiative transfer in the atmosphere is very uncertain. This is especially true regarding mineral dust. To determine the sensitivity of the UV levels to the presence of this atmospheric specie, we have simulated the UV irradiance with different vertical distributions of mineral dust. We have used a discrete ordinates radiative transfer model to obtain the UV levels both at sea level and at 3000 m. We have computed the aerosol single-scattering albedo, the phase function, and the asymmetry factor by Mie scattering theory. The background aerosol profiles were taken from WCRP [1986] models, whereas the radiative properties of mineral dust have been calculated from the aerosol size distribution obtained during Saharan dust invasions at Tenerife island (28.5°N, 16.3°W). The values for aerosol optical depth assumed as input for the model calculations are 0.2 (at 550 nm) for clean background aerosols and 0.3 (at 550 nm) for the mineral dust component. From the results we can conclude that the dust vertical size distribution can affect the irradiance ratio F (with Saharan dust)/F (no Saharan dust) by 2–4%. In addition, we observe that to the same total optical depth the diffuse UV levels depend not only on the vertical dust distribution but also on the background aerosol vertical distribution. We have computed differences for the diffuse radiation fluxes of about 5% between a maritime and a continental model to the same mineral dust vertical distribution. This work has been supported by the CICYT (Comisión Interministerial de Ciencia y Tecnologia- Spanish Government) under contract CLI97-0453 and the Gobierno Autónomo de Canarias by contract 4/95.

Los aerosoles atmosféricos juegan un papel fundamental para el clima en la Tierra. Estas partículas son capaces de interactuar con la radiación procedente del Sol de forma directa, modificando la entrada de energía al sistema, e indirectamente, alterando las propiedades de las nubes. Además, dado su tamaño pueden llegar a ser importantes para la salud de las personas, especialmente en aquellas con problemas respiratorios. Se describre aquí de forma precisa toda la labor realizada para llevar a cabo el cálculo de diferentes propiedades radiactivas de los aerosoles atmosféricos, tales como el espesor óptico de aerosoles o el carácter de la distribución en tamaños de dichas partículas, a partir de las medidas realizadas desde satélite. Para ello se han desarrollado un algoritmo novedoso, a partir de los datos obtenidos por el radiómetro AVHRR de los satélites NOAA, con lo que es posible abarcar toda la región del Atlántico Norte Subtropical. Para poder estimar la precisión de las medidas realizadas desde satélite se ha llevado a cabo el desarrollo y puesta a punto de dos radiómetros terrestres. Estos equipos han sido profusamente calibrados e intercomparados con otros de su misma clase, siguiendo las pautas marcadas por organizaciones internacionales como la O.M.M. con el fin de garantizar la validez de los datos registrados.

The climate in the Canary Islands is characterized by quasi permanent stability due to the air stratification over the archipelago. This configuration of layers is composed of a low and moist layer of air that flows over an isothermal surface, mainly because of the presence of the Canary Islands current and the trade winds from NE, a layer of thermal inversion that oscillates yearly between 700 m and 1500 m, and finally a dry layer of air with a NW winds circulation almost all year. Due to this, the climate perturbations in the islands are induced by the alteration of this layer configuration and therefore, these constitute the main generators of intense rainfall in the islands. In this work, we study the synoptic configurations that produce “heavy rain” in the archipelago to classify the main causes of them, and their spatial and temporal distribution in the islands. To do this, we made a selection of dates of “heavy rain” and then, study manually the synoptic patterns that cause them, splitting the synoptic situations into three main types, Lows, Troughs, and Cutoff Lows, to create a temporal series of the precipitation data. Then, to study the spatial distribution of the rain, we separate the times series of precipitation associated with each one of the synoptic patterns by: Separation by sectors in the surroundings of the archipelago. Creation of rain zones by clustering algorithms. Pressure, geopotential height, and temperature mean anomalies, were calculated for each one of the sectors to identify the mean synoptic patterns. With this, various statistical parameters were obtained for the precipitation data, based on the sectors and rain zones, and so to study the spatial distribution of rain among the islands. The results obtained for this work show that the method developed for the study is capable of identifying the main generators of “heavy rains” and their temporal and spatial distribution, but it cannot be used to make predictions about the mean values of rainfall. In general, during the studied period, the rainfall pattern occurs throughout the winter months with no heavy rainfall events for the months from April to September. In addition, the synoptic situations with the highest number of associated dates are the Troughs, followed by the Lows, and the Cutoff Lows. Finally, the spatial distribution of “heavy rains” is highly conditioned by the orography, with the western islands registering the highest rainfall intensity values. El clima de Canarias se caracteriza por una gran estabilidad debido a la estratificaci´on del aire sobre el archipi´elago. Esta configuraci´on de capas est´a compuesta por una capa baja y h´umeda de aire que discurre sobre una superficie isot´ermica, principalmente por la presencia de la corriente de Canarias y los vientos alisios del NE, una capa de inversi´on t´ermica que oscila anualmente entre 700 m y 1500 m, y finalmente una capa de aire seco con una circulaci´on de vientos del NW casi todo el a˜no. Debido a esto, las perturbaciones clim´aticas en las islas son inducidas por la alteraci´on de esta configuraci´on y por tanto, estas constituyen las principales generadoras de precipitaci´on intensa en las islas. En este trabajo, se estudian las configuraciones sin´opticas que producen “lluvias intensas” en el archipi´elago y as´ı clasificar las principales causas de estas en las islas, as´ı como su distribuci´on espacial y temporal. Con este prop´osito, se llev´o a cabo una selecci´on de fechas de “lluvias intensas” y luego se estudi´o manualmente los patrones sin´opticos que las causan, dividiendo las situaciones en tres tipos principales, Borrascas, Vaguadas y DANAs, para crear una serie temporal de los datos de precipitaci´on. Luego, para estudiar la distribuci´on espacial de la lluvia, se separaron las series temporales de precipitaci´on asociadas a cada uno de los patrones sin´opticos mediante: Separaci´on por sectores del entorno del archipi´elago. Creaci´on de zonas de lluvia mediante algoritmos de clusterizaci´on. Se calcularon anomal´ıas medias de presi´on, altura geopotencial, y temperatura para cada uno de los sectores con el fin de identificar los patrones sin´opticos medios, y se obtuvieron diversos par´ametros estad´ısticos de los datos de precipitaci´on, en funci´on de los sectores y zonas de lluvia, para estudiar la distribuci´on de la lluvia en las islas. Los resultados obtenidos para este trabajo, muestran que el m´etodo desarrollado es capaz de identificar las principales situaciones sin´opticas generadoras de “lluvias intensas” y su distribuci´on temporal y espacial, pero no puede ser utilizado para hacer predicciones sobre los valores medios de lluvia. En general, durante el periodo estudiado, el r´egimen de lluvias ocurre a lo largo de los meses de Invierno, sin precipitaciones durante los meses de abril a septiembre. Adem´as, las situaciones sin´opticas con mayor n´umero de fechas asociadas son las Vaguadas, seguidas de las Borrascas y las DANAs. Finalmente, la distribuci´on espacial de las “lluvias intensas” est´a muy condicionada por el factor orogr´afico, siendo las islas occidentales las que registran los valores m´as altos de intensidad pluviom´etrica.

At present, the study of atmospheric aerosols has aroused great interest, especially in places where, due to their geographical location, there are many invasions. One example is the Canary Islands, which suffers episodes of desert dust from the African continent. These episodes, known as calima, affect the radiative balance and cloud formation, as well as influence human health and ecosystems. The study of desert dust intrusions has evolved over the years thanks to advances in observational methods and numerical models. In the present study, the potential of the GCMs (Global Climate Models) of the new phase of CMIP (Coupled Model Intercomparison Project), CMIP6, will be evaluated. For this purpose, the results of the simulations of these models will be compared with the observations of recent past years. In particular, the only three models that have made daily data on dust concentrations available, i.e. IPSL, GFDL and MIROC6, will be used. These three models allow us the analysis of aerosol transport and generation through simulations. For the observations, the data studied are from MERRA version 2 (Modern-Era Retrospective analysis for Research and Applications). They are obtained from the reanalysis of space-based aerosol observations. For the simulated models and the observations we worked with column dust concentrations (kg m -2 ) and in order to study the incidence of calima episodes the data associated with a focused grid point in the Canary Islands was chosen. This study begins by studying the percentile associated with the concentration corresponding to an atmospheric aerosol episode, i.e. the 60th percentile. Once the percentile was determined, using the information on dust episodes provided by Ministerio para la Transición Ecológica y el Reto Demográfico, the monthly mean column concentration, the number of days above the 60th percentile and the number of days above the 95th percentile were analysed for two periods: the historical period and the future period. The historical period is from 1980 to 2009 and the future period is divided into two, mid-century (2030-2059) and late century (2070-2099). In addition, the SSP (Shared Socioeconomic Pathways) scenarios from CMIP6 describing CO2 concentrations in the future will be used for the future period. So first of all, the monthly averages of dust column concentrations in the historical period for the three CMIP6 models and for the MERRA2 measurements are compared, which allows us to discard the IPSL model for future simulations, as its behaviour is quite far from the observed one. Then the monthly averages of dust column concentration in the future are analysed for the GFDL models in the SSP585 and SSP245 scenarios and MIROC6 in the SSP126, SSP245, SSP370 and SSP585 scenarios. Since a general increase in the monthly mean dust column concentrations is observed, the number of days above the 60th and 95th percentile is studied to determine whether this increase is due to the increased intensity of the episodes or the duration of these intrusions. For the historical period, the IPSL model does not represent the stationarity of the observations and the number of days above the 60th percentile is much higher than for the 95th percentile. Therefore, it can be said that the calima episodes were not too intense in the past. For the future, an increase in the number of days with dust intrusions is generally observed for the two selected CMIP6 models, which indicates that the increase in the monthly mean is due to the longer duration of the dust intrusions and, to a lesser extent, to the intensity. So, in order to obtain more information on this matter, this work was finalised by studying the future trends for MIROC and GFDL. A study of the trends in annual dust column concentrations shows a gradual increase, which can be associated with more dust episodes as well as with an increase in intensity. Consequently, the trend in the number of annual days of extreme events (95th percentile) was analysed for both models and an increasing behaviour was observed. However, although the increase in desert aerosol concentrations can be related to the increase in the number of these episodes, a study of the average dust concentrations for the events in each year has been carried out. From this study, which turned out not to be statistically significant, it is possible to conclude that it cannot be considered an important cause for the growth of dust concentrations. Finally, it can be concluded, in first place, that the potential of the MIROC and GFDL models is favourable and consequently they postulate to be good simulators for the future. Furthermore, the future increase in frequency and intensity of desert dust intrusions is evident, in particular for the worst-case scenario concerning CO2 concentrations. Therefore, under the initial conditions and assumptions proposed, this work reflects the worsening of the calima episodes in the Canary Islands and stimulates contributing to the slowing down of climate change.

The present work analyzes the atmospheric synoptic conditions which mainly affect rain episodes over the Canary Islands. The main aims are to assess the reliability of two databases used to determine the weather in the Canary Islands and to study the phenomenological distribution of rain episodes. To achieve these aims is especially important to keep into account 3 specific features of the Canary Islands. First, their particular location: close to the African continent in a transition area from mild to tropical temperatures affected by the North Atlantic Oscillation (NAO) and the Azores High. Second, the common weather conditions: the archipelago is considered as a dry and very stable area, having over 50 raining episodes per year on average. Third, its steep orography: altitude varies more than 3000m in less than 20km horizontally. After setting these features, a phenomenological classification is given. A total of 4 atmospheric disturbance phenomena are classified: Deep Atlantic Lows (DAL), Atlantic Surface Lows (ASL), upper Atlantic Lows (UAL) and Troughs (TRO) are the considered phenomena used to characterize the Canary Islands weather. The phenomena which are not possible to include in any of these categories are included in No detection type (ND, None). Using some online resources, such as the AEMET database ARCIM´IS, and Meteo Centre Reanalysis, a set of 104 cases of heavy rain (>30mm episodes) is analyzed to better understand the particular situations in the atmosphere. Furthermore, this type of analysis gives a reliable method to compare the further automatic classification of the phenomena. After that, the AEMET database is analyzed. This particular database shows the distribution of heavy rain (> 30mm) and all the rain (> 1mm) in the Canary Islands. These data are further used to compare the reliability of the numerical databases. Then, Spread and WRF databases are analyzed. Maps of the distribution of the above classification is shown for these two databases. First, 10 and 1mm maps, then, seasonal maps. In this way, both databases are easily compared and furthermore, it is possible to set which are the main phenomena affecting the Canary Islands and their particular location. Finally, as conclusions: the correspondence between these databases is exposed as well the most important phenomena over the Canary Islands. The correspondence between databases is particularly trustworthy. The most important phenomenon affecting the Canary Islands is DAL and it is prominent during the winter. En la presente memoria se pretende analizar las perturbaciones atmosf´ericas que dan lugar a las precipitaciones m´as importantes en las Islas Canarias. Los objetivos principales del trabajo son establecer la fiabilidad de las bases de datos para determinar los fen´omenos de precipitaciones as´ı como estudiar la distribuci´on de los episodios de lluvia. Para lograr estos objetivos es particularmente importante tener en cuenta tres caracter´ısticas de las Islas Canarias. Primero, su localizaci´on peculiar: cercanas al continente africano en una zona de transici´on de temperaturas suaves a tropicales, afectadas por la Oscilaci´on del Atl´antico Norte (NAO) y por el anticicl´on de las Azores. En segundo lugar, las condiciones clim´aticas generales: el Archipi´elago Canario est´a considerado como un ´area seca y estable, con una media de 50 episodios de lluvia al a˜no. En tercer lugar, su abrupta orograf´ıa: se alcanzan alturas de m´as de 3000 m en menos de 20 km horizontalmente. Una vez se han establecido las caracter´ısticas anteriores, se proporciona una clasificaci´on fenomenol´ogica. Dicha clasificaci´on contiene 4 casos de perturbaciones atmosf´ericas: bajas atl´anticas profundas (DAL), bajas atl´anticas en superficie (ASL), bajas atl´anticas en altura (UAL) y vaguadas (TRO). Con estos fen´omenos se pretende caracterizar esta situaci´on especial de precipitaciones en las Islas Canarias. Los episodios que no ha sido posible incluir en ninguno de los anteriores fen´omenos se han incluido en la catergor´ıa de ninguna detecci´on (ND, None). Usando recursos en l´ınea tales como la base de datos ARCIM´IS de AEMET y Meteo Centre Reanalysis, se analizan, con el fin de entender completamente las situaciones particulares de la atm´osfera para esos fen´omenos, un conjunto de 104 casos de lluvias extremas (episodios de m´as de 30 mm en alg´un punto). Adem´as, este tipo de an´alisis proporciona un m´etodo fiable para comparar la clasificaci´on autom´atica de los fen´omenos. Despu´es, se analiza la base de datos de AEMET. Usando esta base se estudian las distribuciones de lluvia extrema (> 30mm) y de la lluvia total (> 1mm). M´as tarde estos datos se usan para comparar la fiabilidad de las otras dos bases de datos. Luego, se analizan las bases de datos Spread y WRF. Se muestran mapas de estas dos bases de datos donde se indican la distribuci´on de los fen´omenos clasificados. Primero se analizan mapas de 10 y 1 mm y despu´es mapas por estaciones. De esta forma, se pueden comparar de forma clara ambas bases de datos y adem´as es posible establecer cu´ales son los fen´omenos que afectan principalmente a las Islas Canarias y d´onde est´an localizados. Finalmente, a modo de conclusiones se establece que: primero, la correspondencia entre las bases de datos es fidedigna. Segundo, el fen´omeno m´as importante durante los episodios de lluvia es DAL y la estaci´on que deja m´as lluvias es el invierno.

The rainfalls in the Canary Islands are very important for the social and economic life of their population. However, the precipitation has different influences depending on the islands or the zones: there are desert areas and very wet ones. The Alisios winds have an important influence in the humidity of the islands, especially the occidental ones, that generally have more relief than the rest. That is caused by the Azores anticyclone, which has more impact in summer months. Nevertheless, this is not the principal cause of the heavy rains in the archipelago: that is principally due to atmospheric disturbances that destroy the stability that generate these winds. In this project, the main objective is to characterize the impact of some weather types (WTs) in the precipitation of the islands making use of two different databases, WRF and SPREAD, in the period 1st January 1995 – 31st December 2004, which involves ten years of data. To achieve this goal the Principal Components Analysis will be used to determine 4 regions or components, also known as principal components (PC), using the precipitation values registered in those databases. The Jones’s equations and rules will be also applied, which define a classification method to identify different WTs depending on the pressure disturbances in a specific day. To determine this last is necessary the sea level pressure values available in NCEP/NCAR Reanalysis-1 database. To apply the PCA, a region must be defined to make possible the calculation of the PC. The chosen area is 27.025o N - 29.975o N, 13.025o W - 18.975o W (see figure 2). Each component has an associated explained variance, which is related to the corresponding amount of information. It is important to know that the calculated components will be rotated. For the determination of the WTs, another region must be defined. Now, because of the spatial resolution of NCEP/NCAR database, the zone is defined between the coordinates 20o N – 40o N, 10o W – 25oW (see figure 3). With the information that will be extracted from the results of applying the Jones’s method tables of values will be computed. The calculation of percentiles will be also applied to determine what WTs are more important for intense precipitation in the Canary Islands. After finishing all this procedure, the results will be discussed. First of all, the WTs classification has detected 1266 days of anticyclonic type (WT2), 1234 of directional types (WT1), 993 of hybrid types (WT0), 74 days of cyclonic type (WT3) and 86 days undefined (U) (see figures 18 and 19). With that, the regions obtained applying the PCA will be analysed. To do this, the percentile 95 will be studied, because it discriminates the light rains against the heavy ones: • WRF database: (see figure 6 and table 13) − W-PC1: this component is formed by Fuerteventura and Lanzarote. There, the WTs that usually cause heavy rains are the west winds (23.67 % of the accumulated precipitation in the 10 analysed years), the cyclonic type (16.56 % of the accumulated precipitation) and the northwest winds (16.41 % of the accumulated precipitation). Other WTs that are less important are the east (14.47 % of the accumulated precipitation) and the northeast winds (10.14 % of the accumulated precipitation). 4 − W-PC2: this one is formed by the north-western islands of the archipelago, except the northeast of Tenerife and La Palma. The most important WTs in this zone are the cyclonic type (30.32 % of the accumulated heavy precipitation) and the west winds (25.03 % of the accumulated precipitation). Also the east (12.86 % of the accumulated precipitation) and northeast (10.38 % of the accumulated precipitation) winds have influence. − W-PC3: this component considers the island of Gran Canaria and a part of the coast of Santa Cruz de Tenerife. In this region the cyclonic type is again very important (27.55 % of the accumulated precipitation), and also the northeast (18.72 % of the accumulated precipitation), east (18.28 % of the accumulated precipitation) and west winds (17.45 % of the accumulated precipitation). − W-PC4: the last component is formed by the northeast of La Palma and Tenerife, a region characterized by laurisilva that stands out because of its moisture. The northeast winds are now the most important WT in the region (22.00 % of the accumulated precipitation). The cyclonic type (21.18 % of the accumulated precipitation) and the west (16.40 % of the accumulated precipitation) and east winds (14.29 % of the accumulated precipitation) are also important for the rains in the zone. • SPREAD database: (see figure 13 and table 14) − S-PC1: this region includes almost all Fuerteventura, the south of Gran Canaria and some parts in the east of Tenerife. The WTs that cause the heaviest rains in this zone are the west winds (34.15 % of the accumulated precipitation) and the cyclonic type (33.01 % of the accumulated precipitation). Both WTs amount nearly two thirds of the intense rains in the region. With less prominence are the east winds (11.55 % of the accumulated precipitation). − S-PC2: this component is formed by the north-western islands, except the north and northeast of Tenerife, and the west of Gran Canaria. There, the most important WTs are the cyclonic type (35.86 % of the accumulated precipitation) and the west winds (28.27 % of the accumulated precipitation). The southwest winds have also importance (9.82 % of the accumulated precipitation), but much less than the aforementioned WTs. − S-PC3: this component considers Lanzarote and the north of Fuerteventura. Now, the west winds are so important (43.45 % of the accumulated precipitation), practically the double of the contribution of the cyclonic type (22.63 % of the accumulated precipitation). The east winds have less importance (9.98 % of the accumulate precipitation). − S-PC4: this region includes the north of the capital islands. The most important WTs are the cyclonic type (23.62 % of the accumulated precipitation) and the northwest (18.41 % of the accumulated precipitation) and west winds (15.81 % of the accumulated precipitation). The northeast (14.60 % of the accumulated precipitation) and north winds (10.36 % of the accumulated precipitation) are important too, but to a lesser extent. 5 The regions W-PC2 and S-PC1 are quite similar, and also the components W-PC4 and S-PC4 are slightly similar. Also, for both databases the cyclonic type is very important for the heavy rains in the archipelago, and the west and east winds too. In the other hand, the anticyclonic type hardly ever is the cause of intense precipitations in the Canary Islands, but the south and southeast winds have less importance than it. Finally, the northeast winds are important in the entire components calculated using WRF database, but if the SPREAD database is used, these winds have more importance in the north of the capital islands.

Este Trabajo de Fin de Grado sirve de análisis meteorológico para el conocimiento de los principales factores que afectan a la navegación (viento, ola, presión atmosférica y temperatura). Reconociendo las condiciones predominantes en la zona de navegación en estudio podemos llegar a conocer una zona de navegación, a fin de diferenciar las distintas épocas del año teniendo en cuenta los diversos factores climatológicos que caracterizan a cada una de las estaciones y así poder fabricar la derrota de una navegación óptima y segura para nuestro buque.