Physical and optical aerosol properties at the Dutch North Sea coast based on AERONET observations

International audienceSun photometer measurements at the AERONET station at the North Sea coast in The Hague (The Netherlands) provide a climatology of optical and physical aerosol properties for the area. Results are presented from the period January 2002 to July 2003. For the analysis and interpretation these data are coupled to chemical aerosol data from a nearby station of the Dutch National Air Quality Network. This network provides PM10 and black carbon concentrations. Meteorological conditions and air mass trajectories are also used. Due to the location close to the coast, the results are strongly dependent on wind direction, i.e. air mass trajectory. In general the aerosol optical properties are governed by industrial aerosol emitted form various industrial, agricultural and urban areas surrounding the site in almost all directions over land. For maritime air masses industrial aerosols are transported from over the North Sea, whereas very clean air is transported from the NW in clean polar air masses from the North Atlantic. In the winter the effect of the production of sea salt aerosol at high wind speeds is visible in the optical and physical aerosol data. In these cases fine and coarse mode radii are similar to those reported in the literature for marine aerosol. Relations are derived between the Ångström coefficients with both the fine/coarse mode fraction and the ratio of black carbon and PM10

Physical and optical aerosol properties at the Dutch North Sea coast

International audienceSun photometer measurements at the AERONET station at the North Sea coast in The Hague (The Netherlands) provide a climatology of optical and physical aerosol properties for the area. Results are presented from the period January 2002 to July 2003. For the analysis and interpretation these data are coupled to chemical aerosol data from a nearby station of the Dutch National Air Quality Network. This network provides PM10 and black carbon concentrations. Meteorological conditions and air mass trajectories are also used. Due to the location close to the coast, the results are strongly dependent on wind direction, i.e.~air mass trajectory. In general the aerosol optical properties are governed by industrial aerosol emitted form various industrial, agricultural and urban areas surrounding the site in almost all directions over land. For maritime air masses industrial aerosols are transported from over the North Sea, whereas very clean air is transported from the NW in clean polar air masses from the North Atlantic. In the winter the effect of the production of sea salt aerosol at high wind speeds is visible in the optical and physical aerosol data. In these cases fine and coarse mode radii are similar to those reported in the literature for marine aerosol. Relations are derived between the Ångström coefficients with both the fine/coarse mode fraction and the ratio of black carbon and PM10

Analysis of the influence of solar activity and atmospheric factors on Be-7 air concentration by seasonal-trend decomposition

7Be air concentrations were measured at the Universitat Politecnica de Valencia campus (in the east of Spain) during the period 2007e2014. The mean values of monthly 7Be concentrations ranged from 2.65 to 8.11 mBq/m3, showing significant intra and interannual variability. A seasonal-trend decomposition methodology was applied to identify the trend-cycle, seasonal and irregular components of the 7 Be time series. The decomposition model makes it possible to estimate the influence of solar activity and atmospheric factors on the independent components, in order to find the different sources of 7Be variability. The results show that solar activity is a factor with a high inverse influence on the trend cycle pattern of 7Be variability. Solar radiation, temperature and relative humidity are positive influential factors on the seasonal 7Be variation with a regular pattern over the years. Finally, the irregular component presents a significant negative correlation with precipitation and wind speed parameters, which have an irregular behavior over the years and seasons.This study has been supported partially by the REM program of the Nuclear Safety Council SRA/2071/2015/227.06 of Spain. We are also grateful to the UPV's weather station and the AEMET service for providing the atmospheric information used in this study.Bas Cerdá, MDC.; Ortiz Moragón, J.; Ballesteros Pascual, L.; Martorell Alsina, SS. (2016). Analysis of the influence of solar activity and atmospheric factors on Be-7 air concentration by seasonal-trend decomposition. Atmospheric Environment. 145:147-157. https://doi.org/10.1016/j.atmosenv.2016.09.027S14715714

The EOF method applied to approximate the atmospheric aerosol PSD

Examples of the approximation of the aerosol size distributions with EOFs are given here by using data from a set of 2449 aerosol size distribution profiles measured during the Rough Evaporation Duck (RED) experiment that took place off Oahu, Hawaii, from 26 August to 15 September 2001. The measurements are discussed in detail by, for example, Kusmierczyk-Michulec J and van Eijk 2006. Each size distribution from this data set is a vector with 25 components corresponding respectively to particle diameters of 0.25, 0.27, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.5, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, and 15 μm. The particle diameter is defined here as the equivalent spherical diameter

Ångström coefficient as an indicator of the atmospheric aerosol type for a well-mixed atmospheric boundary layer: Part 1: Model development

The physical and optical properties of an atmospheric aerosol mixture depend on a number of factors. The relative humidity influences the size of hydroscopic particles and the effective radius of an aerosol mixture. In consequence, values of the aerosol extinction, the aerosol optical thickness and the Ångström coefficient are modified. A similar effect is observed when the aerosol composition changes. A higher content of small aerosol particles causes the effective radius of an aerosol mixture to decrease and the Ångström coefficient to increase. Both effects are analysed in this paper. The parameters of the size distribution and the type of components used to represent natural atmospheric aerosol mixtures are based on experimental data. The main components are sea-salts (SSA), anthropogenic salts (WS, e.g. NH4HSO4, NH4NO3, (NH4)2SO4), organic carbon (OC) and black carbon (BC). The aerosol optical thickness is modelled using the external mixing approach. The influence of relative humidity on the optical and physical properties of the following aerosol mixtures is investigated: (SSA&WS), (SSA&OC), (SSA&BC), (SSA, WS&OC) and (WS, OC&BC). It is demonstrated that the Ångström coefficient can be used as a rough indicator of the aerosol type

Aerosol optical thickness retrieval over land and water using Global Ozone Monitoring Experiment (GOME) data

An algorithm for the retrieval of the aerosol optical thickness over land and over water from Global Ozone Monitoring Experiment (GOME) data is presented. The cloud fraction in the GOME pixels is determined using the Fast Retrieval Scheme for Clouds From the Oxygen A Band (FRESCO) algorithm. Surface contributions to the top of atmosphere reflectance are determined from the GOME surface reflectance database. The aerosol retrieval algorithm uses lookup tables that were created using the radiative transfer model 6S. The algorithm allows retrieving the aerosol types characterized by Angstrom coefficients in the range from -0.1 to 2.8; i.e., the range of values observed by the AERONET ground-based measurements. Validation of the algorithm done using the AERONET Sun photometer data for 12 sites in Europe and Africa, for the year 1997, shows very good agreement. The correlation coefficient between the satellite retrieval and AERONET data for the wavelength of 440 nm is 97%, and for 670 nm it is 94%. Validation of the algorithm for the year 2000 was done for a few sites with similar results. The algorithm has been successfully tested over an island influenced by Saharan dust (i.e., Cape Verde, 16oN, 22oW and over a site located near the Saharan desert (i.e., Bondoukoui, 11oN, 3oW). For other sites located near the Saharan desert such as Bidi Bahn (14oN, 2oW) and Banizombou (13oN, 2oE), the agreement was very good at 440 nm. The algorithm has not been tested over other bright surfaces such as ice-covered regions. Examples of the spatial distribution of the aerosol optical thickness over Europe, north Africa, and the North Atlantic for the year 1997 and 2000 are presented

Influence of aerosols on off-axis laser detection capabilities

The radiation coming from a laser which operates in the coastal zone can be detected not only when a detector is placed in front of the laser beam but also when it is located outside the main beam direction. The reason is that in a real detection scheme the power collected by a detector not only comes from direct radiation but also from other radiation sources, like port scattering, aerosol scattering and background radiation. Their relative contributions depend on many factors, i.e. laser features, collecting optics features, meteorological conditions, etc. An important contributor is aerosol scattering and its intensity depends on the aerosol composition and particle density. It was found that more humid conditions cause a decrease in the direct radiation and an increase in the diffuse component. This effect depends on the contribution of hygroscopic and non-hygroscopic aerosols. In the marine-continental atmosphere, represented by a mixture of sea-salts (SSA), anthropogenic salts (WS) and organic carbon (OC), a change in relative humidity from 80% to 95% can change the result for the predicted irradiance level on the sensor by more than a factor of three. Dust-like (DL) particles produce much stronger scatter irradiance than other aerosol types, independently of the off-axis distance

The influence of sea-salt aerosols on the atmospheric extinction over the Baltic and the north seas.

The results of spectral aerosol optical thickness measurements at the Polish coast (Sopot, Hel) carried out in the period from July 1997 up to May 1999 are presented. The empirical orthogonal function (EOF) method applied to aerosol optical thickness spectra allowed to distinguish three aerosol advections, associated with wind direction sectors: 290}303, 30}703, and 80}2803, corresponding to three main aerosol types: maritime or mixed (continental}maritime), continental, and the modi"ed version of the continental aerosol type. The discrepancies between oceanic and the Baltic maritime aerosol type are investigated in terms of sea-salt aerosols size distributions including the North Sea experimental measurements. 2000 Elsevier Science Ltd