We present the analysis of the strongest North African desert dust (DD) intrusion that occurred over the Iberian Peninsula (IP) during the last decade, as registered by modern remote sensing techniques like Sun photometry. This event took place from 22 July to 3 August 2004. The most relevant features of this exceptional event, originated over the Saharan desert, were its great intensity and duration. We focus on the columnar aerosol properties measured by the AERONET‐Cimel photometers at El Arenosillo (southwest) and Palencia (north‐center) stations. Aerosol optical depth (AOD) reached a maximum of 2.7 at El Arenosillo during 22 July and 1.3 at Palencia on 23 July, with the Ånsgtröm exponent values near zero during the AOD peaks. In addition, PM10 concentration levels are also reported at various sites of the IP in order to establish the impact of this intrusion, reaching daily values as high as 200 μg/m³ and peaks near 600 μg/m³ in an hourly basis. The interest of this special event is increased because of the mixing with smoke particles from concurrent forest fires in the IP. Features of the columnar volume particle size distribution and derived microphysical parameters, the single scattering albedo, and a reliable estimation of the radiative forcing under these extreme conditions are also reported. Complementary information, as air mass back trajectories, synoptic charts, images, and AOD maps of satellite sensors (SeaWIFS, MODIS) together with NAAPS prognostic model, is used in the analysis in order to draw a detailed scenario of this dust‐smoke event over the IP.

Routine aerosol measurements are carried out at El Arenosillo station (37.1°N, 6.7°W), in Huelva (Spain), since February 2000 with a Cimel Sun photometer included in the AERONET network. This station, located in the coast of the southwestern Iberian Peninsula, is an appropriate site for the detection and characterization of desert dust aerosols arriving from North Africa. The aerosol database allows us to make an inventory of desert dust events over 6 years corresponding to the period 2000–2005. The inventory is based on threshold values for the aerosol optical depth (AOD) and Ångström exponent, the analysis of the size distributions, a manual inspection, and the use of air mass back trajectories as complementary information. This inventory shows the presence of desert aerosols 65 d yr⁻¹ (18% of days), although there are significant differences among years. Desert dust events have a mean duration of 4 days, with mean AOD (440 nm) of 0.31 and mean Ångström exponent of 0.66. The desert dust episodes are more frequent in February, March, and the summer months. During autumn, winter, and April the episodes are less frequent. This seasonal pattern of the desert events influences the AOD at El Arenosillo, which presents an analogous seasonal pattern. Because of the desert events, AOD levels increase 28% at 440 nm and 48% at 870 nm. Desert dust intrusions have been also catalogued according to four basic meteorological scenarios. The analysis of the desert inventory has made it possible to establish an automatic method for the detection of the desert dust intrusions over the Iberian Peninsula with Sun photometer data. Finally, a classification of air masses (based on back trajectories) has been compared with the occurrence of desert dust intrusions.

The aim of the present work is to carry out a detailed analysis of columnar microphysical properties obtained from Cimel sun-photometer measurements in the Southwest of Spain within the frame of the Aerosol Robotic Network (AERONET) – Iberian Network for aerosol measurements (RIMA). AERONET level 2 inversion products are analysed, in particular the particle size distribution together with their associated microphysical parameters for both fine and coarse modes: volume concentration, effective radius and the fine mode volume fraction. This work complements previous works based on aerosol optical depth (AOD) and the Ångström exponent (AE) for a global characterization of atmospheric aerosol in this area of southwestern Spain. The analysed dataset spans between February 2000 and October 2008. Time series and statistical analysis has been carried out for these parameters in order to assess their typical values and seasonality together with their relationships with the AOD and AE. Mean values of volume particle concentration are 0.06±0.07 μm³ μm⁻² for total, 0.019±0.015 μm³ μm⁻² for fine and 0.04±0.06 μm³ μm⁻² for coarse mode; mean effective radii are 0.40±0.19 μm for total, 0.14±0.02 μm for fine and 1.96±0.41 μm for coarse mode. The most relevant features are the clear bimodality of the volume particle size distribution, with a slight dominance of the coarse mode in the overall climatology given the prevailing atmospheric conditions at the site (coastal marine). There is a clear prevalence of the coarse mode in summer months plus September and March, in coincidence with the occurrence of desert dust intrusions and highest AOD values. During desert dust outbreaks, the particle size distribution is practically monomodal with strong prevalence of the coarse mode which also shows a shift of the modal radius toward lower values. The size particle predominance defines the characteristic of the site and it has been analysed under two different parameters: the Ångström exponent and the fine mode volume fraction Vf/Vt. We investigated the relationship between them and also their relationship with the effective radius of the size distribution.

The volcanic eruption of Cumbre Vieja (La Palma Island, Spain), started on 19 September 2021 and was declared terminated on 25 December 2021. A complete set of aerosol measurements were deployed around the volcano within the first month of the eruptive activity. This paper describes the results of the observations made at Tazacorte on the west bank of the island where a polarized micro-pulse lidar was deployed. The analyzed two-and-a-half months (16 October–31 December) reveal that the peak height of the lowermost and strongest volcanic plume did not exceed 3 km (the mean of the hourly values is 1.43 ± 0.45 km over the whole period) and was highly variable. The peak height of the lowermost volcanic plume steadily increased until week 11 after the eruption started (and 3 weeks before its end) and started decreasing afterward. The ash mass concentration was assessed with a method based on the polarization capability of the instrument. Two days with a high ash load were selected: The ash backscatter coefficient, aerosol optical depth, and the volume and particle depolarization ratios were, respectively, 3.6 (2.4) Mm⁻¹sr⁻¹, 0.52 (0.19), 0.13 (0.07) and 0.23 (0.13) on 18 October (15 November). Considering the limitation of current remote sensing techniques to detect large-to-giant particles, the ash mass concentration on the day with the highest ash load (18 October) was estimated to have peaked in the range of 800–3200 μg m⁻³ in the lowermost layer below 2.5 km.

Aerosol optical depth (AOD) using different instruments during three short and intensive campaigns carried out from 1999 to 2001 at El Arenosillo in Huelva, Spain, are presented and compared. The specific aim of this study is to determine the level of agreement between three different instruments running in operational conditions. This activity, however, is part of a broader objective to recover an extended data series of AOD in the UV range obtained from a Brewer spectroradiometer. This instrument may be used to obtain AOD at the same five UV wavelengths used during normal operation for ozone content determination. As part of the validation of the Brewer AOD data, a Cimel sun photometer and another spectroradiometer, a Li-Cor 1800, were used. A detailed comparison of these three instruments is carried out by means of near-simultaneous measurements, with particular emphasis on examining diurnal AOD variability. Absolute AOD uncertainties range from 0.02 for the Cimel to 0.08 for the Brewer, with intermediate values for the Li-Cor 1800. All data during the comparison are in reasonable agreement, when taking into account the different performance characteristics of each instrument. The comparison also demonstrates current deficiencies in the Brewer data and thus the difficulty to determine AOD values with low errors.