A new method for nocturnal aerosol measurements with a lunar photometer prototype

This paper presents the preliminary results of nocturnal Aerosol Optical Depth (τa) and Angström Exponent (α) obtained from a new lunar photometer prototype, trade name Cimel CE-318U. Due to the variation of the moon's illumination inherent to the lunar cycle, the typical Langley-plot Method used in solar photometry to calibrate these instruments cannot be applied. In this paper, we propose three different methods to carry out the lunar-photometer calibration. In order to validate the results, we have selected three events which encompass seven nights and ten days under different atmospheric conditions, including several saharan dust intrusions episodes. Method#1 is introduced in this work as a modification of the usual Langley Method.The Aeronet sunphotometer at Izana has been calibrated within ˜ AERONET-EUROPE TNA supported by the European Community – Research Infrastructure Action under the FP7 “Capacities” specific programme for Integrating Activities, ACTRIS Grant Agreement no. 262254

Recovering long-term aerosol optical depth series (1976–2012) from an astronomical potassium-based resonance scattering spectrometer

A 37-year long-term series of monochromatic aerosol optical depth (AOD) has been recovered from solar irradiance measurements performed with the solar spectrometer Mark-I, deployed at Izaña mountain since 1976. The instrument operation is based on the method of resonant scattering, which affords wavelength absolute reference and stability (long-term stability and high precision) in comparison to other instruments based purely on interference filters. However, it has been specifically designed as a reference instrument for helioseismology, and its ability to determine AOD from transmitted and scattered monochromatic radiation at 769.9 nm inside a potassium vapour cell in the presence of a permanent magnetic field is evaluated in this paper. Particularly, the use of an exposed mirror arrangement to collect sunlight as well as the Sun–laboratory velocity dependence of the scattered component introduces some important inconveniences to overcome when we perform the instrument's calibration. We have solved this problem using a quasi-continuous Langley calibration technique and a refinement procedure to correct for calibration errors as well as for the fictitious diurnal cycle on AOD data. Our results showed similar calibration errors retrieved by means of this quasi-continuous Langley technique applied in different aerosol load events (from 0.04 to 0.3), provided aerosol concentration remains constant throughout the calibration interval.The AERONET sun photometers at Izaña have been calibrated within AERONET-Europe TNA supported by the European Community-Research Infrastructure Action under the FP7 “Capacities” specific programme for Integrating Activities, ACTRIS grant agreement no. 262254. The GAW-PFR network for AOD at WMO-GAW global observatories has been implemented by the World Optical Depth Research and Calibration Center (WORCC). Mark-I operation was supported by the Spanish National Plan of Research and Development under grant no. AYA2012–17803

Assessment of nocturnal aerosol optical depth from lunar photometry at the Izaña high mountain observatory

This work involves a first analysis of the systematic errors observed in the AOD retrieved at nighttime using the Sun–sky–lunar CE318-T photometer. In this respect, this paper is a first attempt to correct the AOD uncertainties that currently affect the lunar photometry by means of an empirical regression model. We have detected and corrected an important bias correlated to the Moon's phase and zenith angles, especially at longer wavelength channels.AERONET Sun photometers at Izaña have been calibrated within the AERONET Europe TNA, supported by the European Union’s Horizon 2020 research and innovation program under grant agreement no. 654109 (ACTRIS-2)

Optical calibration facility at the Izaña Atmospheric Research Center [Póster]

Póster presentado en: 37th Annual European Meeting on Atmospheric Studies by Optical Methods, celebrado en 2010 en Valladolid.Financial supports from the Spanish MICIIN (ref.CGL2008-05939-CO3-00/CLIandCGL2009-09740) and from the GR-220 Project of the Junta de Castilla y León are gratefully acknowledged

Preliminary characterization of columnar aerosol properties (AOD-AE) at the Saharan Tamanrasset (Algeria) station [Póster]

Póster presentado en: 37th Annual European Meeting on Atmospheric Studies by Optical Methods, celebrado en 2010 en Valladolid.Financial supports from the Spanish MICIIN (ref.CGL2008-05939-CO3-00/CLIandCGL2009-09740) and from the GR-220 Project of the Junta de Castilla y León are gratefully acknowledged

Caracterización preliminar de las propiedades del aerosol en columna (EOA-EA) en la estación sahariana de Tamanrasset (Argelia)

A Cimel sun photometer has been in operation at Tamanrasset station since late 2006. In this study, more than two years of aerosol measurements have been analyzed from October 2006 to January 2009. Two parameters, aerosol optical depth (AOD) and Ångström exponent (AE), have been used for this preliminar characterization. At this station, the mean AOD is 0.25±0.15 and the mean AE is 0.48±0.23. Both time series data show a clear seasonal cycle. A dry-cool season (fall and winter time), characterized by low AOD and high AE values, and a wet-hot season (in spring-summer), with strong and frequent mineral dust storms, giving high AOD and low AE values, are observed at Tamanrasset. Both, AOD and AE values show the behaviour of a station where desert mineral dust is the prevailing aerosol defining the characteristic of the site. However a significant number of episodes with AE values around 1 together with AOD greater than 0.2 have been found, what suggests the presence of pollution derived aerosols.Financial supports from the Spanish MICIIN (ref. CGL2008-05939-CO3-00/CLI and CGL 2009-09740) and from the GR-220 Project of the Junta de Castilla y León are gratefully acknowledged

Análisis de la trazabilidad en los valores del AOD obtenidos a partir de las medidas de las redes AERONET-CIMEL y GAW-PFR durante el período 2005-2015 en el Observatorio Atmosférico de Izaña

Las dos grandes redes mundiales de fotómetros terrestres para la medida de las propiedades ópticas del aerosol en la columna atmosférica con las AERONET-CIMEL y GAW-PFR. Dado que ambas son diferentes en cuanto a tipos, características, número y localización de fotómetros utilizados, así como a metodologías, procedimientos de calibración y algoritmos de cálculo empleados en la evaluación de datos, resulta conveniente comparar los productos similares suministrados por las dos redes y así determinar en qué medida son homogéneos o equivalentes. El objetivo de este trabajo es analizar las diferencias que existen en una propiedad óptica, fundamental para conocer y caracterizar el contenido en columna de los aerosoles atmosféricos, que es el espesor óptico de aerosoles (AOD) obtenido para diferentes longitudes de onda por cada una de las dos redes. El análisis se estructura en tres capítulos. En el capítulo 1, se expone el concepto de trazabilidad y se explica en qué se basa la definición y cuáles son sus implicaciones. Posteriormente, se aplica a las series de AOD y se muestran los resultados. En el capítulo 2, se analizan las principales causas que pueden dar lugar a diferencias no trazables de AOD para cada una de las parejas de series comparadas en cada longitud de onda. Finalmente, el capítulo 3, recoge las conclusiones y recomendaciones para mejorar, en la medida de lo posible, la trazabilidad y la homogeneidad de estos productos.Los autores agradecen a PMOD/WRC y AERONET los datos proporcionados y utilizados en este trabajo así como las calibraciones de los fotómetros Cimel por parte de AERONET-Europe TNA en el marco del proyecto europeo FP7 ACTRIS nº262254. Este trabajo forma parte de las actividades del “WMO-CIMO Testbed for Aerosols and Water Vapor Remote Sensing Instruments (Izana, Spain)”

The AERONET-Europe calibration facility: access within the ACTRIS project

Comunicación presentada en: 2012 European Aerosol Conference (EAC-2012), B-WG01S2P30, celebrada del 2 al 7 de septiembre de 2012 en Granada.This work has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement N. 262254. Financial support from the Spanish Ministry of Science (MICINN) under projects with ref. CGL2009-09740, CGL2011-23413, CGL2010-09480-E and CGL2011-13085-E as well as from Junta de Castilla y León are gratefully acknowledged

Laboratorio de calibración óptica del Centro de Investigación Atmosférica de Izaña

Financial supports from the Spanish MICIIN (ref. CGL2008‐05939‐CO3‐00/CLI and CGL 2009‐ 09740) and from the GR‐220 Project of the Junta de Castilla y León are gratefully acknowledged

Detecting moisture transport pathways to the subtropical North Atlantic free troposphere using paired H2O-δD in situ measurements

We present two years of in situ measurements of water vapour (H$_{2}$O) and its isotopologue ratio (δD, the standardized ratio between H$_{2}$$^{16}$O and HD$^{16}$O), made at two remote mountain sites on Tenerife in the subtropical North Atlantic. We show that the data – if measured during night-time – are well representative for the lower/middle free troposphere. We use the measured H$_{2}$O-δD pairs, together with dust measurements and back trajectory modelling for analysing the moisture pathways to this region. We can identify four principally different transport pathways. The air mass transport from high altitudes and high latitudes shows two different scenarios. The first scenario brings dry air masses to the stations, as the result of condensation events occurring at low temperatures. The second scenario brings humid air masses to the stations, due to cross-isentropic mixing with lower-level and more humid air during transport since last condensation (LC). The third pathway is transportation from lower latitudes and lower altitudes, whereby we can identify rain re-evaporation as an occasional source of moisture. The fourth pathway is linked to the African continent, where during summer, dry convection processes over the Sahara very effectively inject humidity from the boundary layer to higher altitudes. This so-called Saharan Air Layer (SAL) is then advected westward over the Atlantic and contributes to moisten the free troposphere. We demonstrate that the different pathways leave distinct fingerprints on the measured H$_{2}$O-δD pairs