scholarly journals Lidar Depolarization Ratio of Atmospheric Pollen at Multiple Wavelengths

2020 ◽  
Author(s):  
Stephanie Bohlmann ◽  
Xiaoxia Shang ◽  
Ville Vakkari ◽  
Elina Giannakaki ◽  
Ari Leskinen ◽  
...  
Keyword(s):  
Wavelength Dependence ◽  
Depolarization Ratio ◽  
Ambient Conditions ◽  
Pollen Concentrations ◽  
Multiple Wavelengths ◽  
Pollen Mixture ◽  
Atmospheric Pollen ◽  
Total Pollen ◽  
Pollen Number ◽  
Depolarization Ratios

Abstract. Lidar observations during the pollen season 2019 at the European Aerosol Research Lidar Network (EARLINET) station in Kuopio, Finland were analyzed in order to optically characterize atmospheric pollen. Previous studies showed the detectability of non-spherical pollen using depolarization ratio measurements. We present lidar depolarization ratio measurements at three wavelengths of atmospheric pollen in ambient conditions. In addition to the depolarization ratio detected with the multiwavelength Raman polarization lidar PollyXT at 355 and 532 nm, depolarization measurements of a co-located HALO Photonics Streamline Doppler lidar at 1565 nm were utilized. During a four days period of high birch (Betula) and spruce (Picea abies) pollen concentrations, unusually high depolarization ratios were observed within the boundary layer. Detected layers were investigated regarding the share of spruce pollen to the total pollen number concentration. Daily mean particle depolarization ratios of the pollen layers on the day with the highest spruce pollen share are 0.10 ± 0.02, 0.38 ± 0.23 and 0.29 ± 0.10 at 355, 532 and 1565 nm, respectively. Whereas on days with lower spruce pollen share, depolarization ratios are lower with less wavelength dependence. This spectral dependence of the depolarization ratios could be indicative of big, non-spherical spruce pollen. The depolarization ratio of pollen particles was investigated by applying a newly developed method and assuming a backscatter-related Ångström exponent of zero. Depolarization ratios of 0.44 and 0.16 at 532 and 355 nm for the birch and spruce pollen mixture were determined.

scholarly journals Lidar depolarization ratio of atmospheric pollen at multiple wavelengths

2021 ◽  
Vol 21 (9) ◽  
pp. 7083-7097
Author(s):  
Stephanie Bohlmann ◽  
Xiaoxia Shang ◽  
Ville Vakkari ◽  
Elina Giannakaki ◽  
Ari Leskinen ◽  
...  
Keyword(s):  
Wavelength Dependence ◽  
Depolarization Ratio ◽  
Ambient Conditions ◽  
Air Sampler ◽  
Pollen Concentrations ◽  
Multiple Wavelengths ◽  
Pollen Mixture ◽  
Atmospheric Pollen ◽  
Total Pollen ◽  
Depolarization Ratios

Abstract. Lidar observations during the pollen season 2019 at the European Aerosol Research Lidar Network (EARLINET) station in Kuopio, Finland, were analyzed in order to optically characterize atmospheric pollen. Pollen concentration and type information were obtained by a Hirst-type volumetric air sampler. Previous studies showed the detectability of non-spherical pollen using depolarization ratio measurements. We present lidar depolarization ratio measurements at three wavelengths of atmospheric pollen in ambient conditions. In addition to the depolarization ratio detected with the multiwavelength Raman polarization lidar PollyXT at 355 and 532 nm, depolarization measurements of a co-located Halo Doppler lidar at 1565 nm were utilized. During a 4 d period of high birch (Betula) and spruce (Picea abies) pollen concentrations, unusually high depolarization ratios were observed within the boundary layer. Detected layers were investigated regarding the share of spruce pollen to the total pollen number concentration. Daily mean linear particle depolarization ratios of the pollen layers on the day with the highest spruce pollen share are 0.10 ± 0.02, 0.38 ± 0.23 and 0.29 ± 0.10 at 355, 532 and 1565 nm, respectively, whereas on days with lower spruce pollen share, depolarization ratios are lower with less wavelength dependence. This spectral dependence of the depolarization ratios could be indicative of big, non-spherical spruce pollen. The depolarization ratio of pollen particles was investigated by applying a newly developed method and assuming a backscatter-related Ångström exponent of zero. Depolarization ratios of 0.44 and 0.16 at 532 and 355 nm for the birch and spruce pollen mixture were determined.

scholarly journals Characterization of atmospheric pollen with active remote sensing

2021 ◽  
Author(s):  
◽  
Stephanie Bohlmann ◽  
Keyword(s):  
Lower Troposphere ◽  
Wavelength Dependence ◽  
Forest Site ◽  
Depolarization Ratio ◽  
Additional Information ◽  
Lidar Measurements ◽  
Atmospheric Pollen ◽  
Pollen Distribution ◽  
532 Nm ◽  
Depolarization Ratios

Atmospheric pollen is a well-known health threat causing allergy-related diseases. As a biogenic aerosol, pollen also affects the climate by directly absorbing and scattering solar radiation and by acting as cloud condensation or ice nuclei. A good understanding of pollen distribution and transport mechanisms is needed to evaluate the environmental and health impacts of pollen. However, pollen observations are usually performed close to ground and vertical information, which could be used to evaluate and improve pollen transport models, is widely missing. In this thesis, the applicability of lidar measurements to detect pollen in the atmosphere is investigated. For this purpose, measurements of the multiwavelength Raman polarization lidar PollyXT at the rural forest site in Vehmasmäki (Kuopio), Eastern Finland have been utilized. The depolarization ratio was identified to be the most valuable optical property for the detection of atmospheric pollen, as nonspherical pollen like pine and spruce pollen causes high depolarization ratios. However, detected depolarization ratios coincide with typical values for dusty mixtures and additional information such as backward trajectories need to be considered to ensure the absence of other depolarizing aerosols like dust. To separate pollen from background aerosol, a method to estimate the optical properties of pure pollen using lidar measurements was developed. Under the assumption that the Ångström exponent of pure pollen is zero, the depolarization ratio of pure pollen can be estimated. Depolarization ratios for birch and pine pollen at 355 and 532 nm were determined and suggested a wavelength dependence of the depolarization ratio. To further investigate this wavelength dependence, the possibility to use depolarization measurements of Halo Doppler lidars (1565 nm) was explored. In the lower troposphere, Halo Doppler lidars can provide reasonable depolarization values with comparable quality to PollyXT measurements. Finally, measurements of PollyXT and a Halo StreamLine Doppler lidar were used to determine the depolarization ratio at three wavelengths. A wavelength dependence of the particle depolarization ratio with maximum depolarization at 532 nm was found. This could be a characteristic feature of non-spherical pollen and the key to distinguish pollen from other depolarizing aerosol types.

scholarly journals Depolarization and lidar ratios at 355, 532, and 1064 nm and microphysical properties of aged tropospheric and stratospheric Canadian wildfire smoke

2018 ◽  
Vol 18 (16) ◽  
pp. 11847-11861 ◽  
Author(s):  
Moritz Haarig ◽  
Albert Ansmann ◽  
Holger Baars ◽  
Cristofer Jimenez ◽  
Igor Veselovskii ◽  
...  
Keyword(s):  
Wavelength Dependence ◽  
Particle Radius ◽  
Depolarization Ratio ◽  
Particle Volume ◽  
Wildfire Smoke ◽  
Smoke Particles ◽  
Microphysical Properties ◽  
532 Nm ◽  
Tropospheric Layer ◽  
Depolarization Ratios

Abstract. We present spectrally resolved optical and microphysical properties of western Canadian wildfire smoke observed in a tropospheric layer from 5–6.5 km height and in a stratospheric layer from 15–16 km height during a record-breaking smoke event on 22 August 2017. Three polarization/Raman lidars were run at the European Aerosol Research Lidar Network (EARLINET) station of Leipzig, Germany, after sunset on 22 August. For the first time, the linear depolarization ratio and extinction-to-backscatter ratio (lidar ratio) of aged smoke particles were measured at all three important lidar wavelengths of 355, 532, and 1064 nm. Very different particle depolarization ratios were found in the troposphere and in the stratosphere. The obviously compact and spherical tropospheric smoke particles caused almost no depolarization of backscattered laser radiation at all three wavelengths (<3 %), whereas the dry irregularly shaped soot particles in the stratosphere lead to high depolarization ratios of 22 % at 355 nm and 18 % at 532 nm and a comparably low value of 4 % at 1064 nm. The lidar ratios were 40–45 sr (355 nm), 65–80 sr (532 nm), and 80–95 sr (1064 nm) in both the tropospheric and stratospheric smoke layers indicating similar scattering and absorption properties. The strong wavelength dependence of the stratospheric depolarization ratio was probably caused by the absence of a particle coarse mode (particle mode consisting of particles with radius >500 nm). The stratospheric smoke particles formed a pronounced accumulation mode (in terms of particle volume or mass) centered at a particle radius of 350–400 nm. The effective particle radius was 0.32 µm. The tropospheric smoke particles were much smaller (effective radius of 0.17 µm). Mass concentrations were of the order of 5.5 µg m−3 (tropospheric layer) and 40 µg m−3 (stratospheric layer) in the night of 22 August 2017. The single scattering albedo of the stratospheric particles was estimated to be 0.74, 0.8, and 0.83 at 355, 532, and 1064 nm, respectively.

scholarly journals Investigation of diurnal patterns in vertical distributions of pollen in the lower troposphere using LIDAR technique

2012 ◽  
Vol 12 (12) ◽  
pp. 31187-31204 ◽  
Author(s):  
Y. M. Noh ◽  
H. Lee ◽  
D. Mueller ◽  
K. Lee ◽  
D. Shin ◽  
...  
Keyword(s):  
Turbulent Transport ◽  
Lower Troposphere ◽  
Pollen Concentration ◽  
Depolarization Ratio ◽  
Concentration Data ◽  
High Pollen ◽  
Diurnal Patterns ◽  
Pollen Concentrations ◽  
Vertical Distributions ◽  
Depolarization Ratios

Abstract. The diurnal patterns in pollen vertical distributions in the lower troposphere were investigated by the LIDAR remote sensing technique. Meteorological and pollen concentration data was measured at the surface using a Burkard 7 day recording volumetric spore sampler. An aerosol extinction coefficient and depolarization ratio of 532 nm was obtained from LIDAR measurements in spring (4 May–2 June) 2009 in Gwagnju, Korea. Depolarization ratios from 0.08 to 0.14 were observed only in daytime (09:00–17:00 local time (LT)) during high pollen concentration days from 4 to 9 May. Vertical distributions in the depolarization ratio with time showed a specific diurnal pattern. Depolarization ratios, which varied from 0.08 to 0.14, were measured near the surface in the morning. High depolarization ratios were detected even up to 2.0 km between 12:00 and 14:00 LT but subsequently were observed only close to the surface after 17:00 LT. Low values of depolarization ratios (≤ 0.05) were detected after 18:00 LT until next morning. During the measurement period, the daily variations in the high depolarization ratios close to the surface showed good agreement with those in surface pollen concentrations, which implies that high depolarization ratios can be attributed to high pollen concentrations. The diurnal characteristics in high values of depolarization ratios were closely associated with turbulent transport, which can be caused by increasing temperature and wind speed and decreasing relative humidity. Continuously measured diurnal and vertical characteristics of pollen data can be further used to enhance the accuracy of the pollen-forecasting model via data assimilation studies.

scholarly journals Análisis del contenido aeropolínico estival en la provincia de Málaga

2001 ◽  
Vol 26 ◽  
pp. 89-98
Author(s):  
Marta Recio ◽  
M. Mar Trigo ◽  
Silvia Docampo ◽  
Baltasar Cabezudo
Keyword(s):  
Airborne Pollen ◽  
Summer Season ◽  
Palabras Clave ◽  
Low Concentrations ◽  
Pollen Content ◽  
Pollen Types ◽  
Pollen Concentrations ◽  
Atmospheric Pollen ◽  
Annual Total ◽  
Total Pollen

RESUMEN. Análisis del contenido aeropolínico estival en la provincia de Málaga. En el presente trabajo se realiza un estudio del contenido polínico de la atmósfera de la provincia de Málaga durante cl periodo estival (Julio-Septiembre) tomando los registros obtenidos durante los últimos años en varias localidades de la provincia: Málaga (1992-1999), Estepona (1995-1997), Antequera (1998-1999) y Nerja (2000). En general, durante estos tres meses se recoge sólo entre el 3 y el 6% del polen anual, estando el espectro aeropolínico estival de Málaga representado básicamente por 14 tipos polínicos: Eucalyptus, Castanea, Parkinsotzia, Cannabis, Apiaceae, Ligustrum, Chenopodiaceae-Amaranthaceae, Palmae, Compositae, Artemisia, Typha, Cyperaceae, Poaceae y U rticaceae. Los tipos que alcanzan mayores concentraciones son Eucalyptus, Chenopodiaceae-Amaranthaceae y Poaceae. El resto de los taxa citados aparecen en concentraciones muy bajas. Determinados taxa presentan concentraciones más elevadas en determinadas estaciones de muestreo: Castanea y Compositae en Antequera, Palmae y Parkinsonia en Málaga, y Artemisia en Nerja. La evolución a lo largo de los tres meses muestra, en general, dos tipos de tendencia: una descendente de Julio a Agosto (presente en todos los tipos polínicos estudiados, excepto en Artemisia y Palinae, y en todas las zonas estudiadas) y otra ascendente, de Agosto a Septiembre, de pequeña intensidad, aunque muy acusada para los dos tipos anteriores y para Chenopodiaceae-Amaranthaceae y Cotnpositae. La mayoría de los tipos polínicos estudiados tienen sus máximos diarios en primavera, estación del año con mayor concentración polínica en el sur de Europa, excepto Eucalyptus, Castanea, Parkinsonia y Cannabis, que generalmente lo tienen en verano, y que alcanzaron máximos históricos relevantes: Eucalyptus en 1994 (112 granos/111 3), Castanea en 1997 (233 granos/m 3), Cannabis en 1998 (28 granos/m 3).Palabras clave. Acrobiología, polen, verano, turismo, alergia, Málaga, sur de España.ABSTRACT. Analysis of the summer airborne pollen contera in the province of Malaga. In this work, a study about the atmospheric pollen content during the period July-September has been carried out in the province of Malaga. The study was made taking the data obtained during the last years in several localities of the province: Malaga (1992-1999), Estepona (1995-1997), Antequera (1998-1999) and Nerja (2000). In general, just between 3 and 6% of the annual total pollen were collected during those three months, the airborne pollen spectrum being represented by 14 pollen types: Eucalyptus, Castanea, Parkinsonia, Cannabis, Apiaceae, Ligustrum,Chenopodiaceae-Amaranthaceae, Palmae, Compositae, Artemisia,Typha, Cyperaceae, Poaceae y Urticaceae. During the period studied, the pollen types that reached highest concentrations were Eucalyptus, Chenopodiaceae-Amaranthaceae and Poaceae while the rest of the cited taxa were detected at very low concentrations. Some taxa present higher concentrations at determined sampling stations: Costana(' and Compositae in Antequera, Palmae and Parkin.s. onia in Malaga, and Artemisia in Ncrja. The evolution along the summer season shows, in general, two trends. The first one, in which the pollen concentrations are decreasing from July to August, is present in all the taxa and localities studied, except in Artemisia and Palmae. The other one, in which the pollen concentrations lightly increase from August to September, is present in the former two pollen types but also in Chenopodiaceae- Amarantliaceae and Compositae. Most of the pollen types studied reach their maximum daily peaks in spring (season in which the pollen concentrations are highest in southern Europe) except Eucalyptus, Castanea, Parkinsonia and Cannabis, that generally presented them in summer. These taxa reached notable maximum daily concentrations values: Eucalyptus in 1994 (112 grains/m 3), Castanea in 1997 (233 grains/ in3), Cannabis in 1998 (28 grains/m 3).Key words. Aerobiology, pollen, summer, tourism, allergy, Malaga, southern Spain.

scholarly journals Airborne pollen observations using a multi-wavelength Raman polarization lidar in Finland: characterization of pure pollen types

2020 ◽  
Author(s):  
Xiaoxia Shang ◽  
Elina Giannakaki ◽  
Stephanie Bohlmann ◽  
Maria Filioglou ◽  
Annika Saarto ◽  
...  
Keyword(s):  
Optical Properties ◽  
Airborne Pollen ◽  
Pollen Grains ◽  
Wavelength Dependence ◽  
Depolarization Ratio ◽  
Mean Values ◽  
Pollen Types ◽  
Pine Pollen ◽  
Significant Wavelength ◽  
532 Nm

Abstract. We present a novel algorithm for characterizing the optical properties of pure pollen particles, based on the depolarization values obtained in lidar measurements. The algorithm was first tested and validated through a simulator, and then applied to the lidar observations during a four-month pollen campaign from May to August 2016 at the European Aerosol Research Lidar Network (EARLINET) station in Kuopio (62°44′ N, 27°33′ E), in Eastern Finland. Twenty types of pollen were observed and identified from concurrent measurements with Burkard sampler; Birch (Betula), pine (Pinus), spruce (Picea) and nettle (Urtica) pollen were most abundant, contributing more than 90 % of total pollen load, regarding number concentrations. Mean values of lidar-derived optical properties in the pollen layer were retrieved for four intense pollination periods (IPPs). Lidar ratios at both 355 and 532 nm ranged from 55 to 70 sr for all pollen types, without significant wavelength-dependence. Enhanced depolarization ratio was found when there were pollen grains in the atmosphere, and even higher depolarization ratio (with mean values of 25 % or 14 %) was observed with presence of the more non-spherical spruce or pine pollen. The depolarization ratio at 532 nm of pure pollen particles was assessed, resulting to 24 ± 3 % and 36 ± 5 % for birch and pine pollen, respectively. Pollen optical properties at 1064 nm and 355 nm were also estimated. The backscatter-related Ångström exponent between 532 and 1064 nm was assessed as ~ 0.8 (~ 0.5) for pure birch (pine) pollen, thus the longer wavelength would be better choice to trace pollen in the air. The pollen depolarization ratio at 355 nm of 17 % and 30 % were found for birch and pine pollen, respectively. The depolarization values show a wavelength dependence for pollen. This can be the key parameter for pollen detection and characterization.

scholarly journals The characterization of Taklamakan dust properties using a multi-wavelength Raman polarization lidar in Kashi, China

2020 ◽  
Author(s):  
Qiaoyun Hu ◽  
Haofei Wang ◽  
Philippe Goloub ◽  
Zhengqiang Li ◽  
Igor Veselovskii ◽  
...  
Keyword(s):  
Fine Particles ◽  
Depolarization Ratio ◽  
Taklamakan Desert ◽  
Multi Wavelength ◽  
Lidar Ratio ◽  
Linear Depolarization Ratio ◽  
Dust Events ◽  
532 Nm ◽  
Depolarization Ratios

Abstract. The Taklamakan desert is an important dust source for the global atmospheric dust budget and a cause of the dust weather in Eastern Asia. The characterization of the properties and vertical distributions of Taklamakan dust in the source region is still very limited. To fill this gap, the DAO (Dust Aerosol Observation) was conducted in Kashi, China in 2019. Kashi site is about 150 km to the west rim of the Taklamakan desert and is strongly impacted by desert dust aerosols, especially in spring time, i.e. April and May. Apart from dust, fine particles coming from local anthropogenic emissions or/and transported aerosols are also a non-negligible aerosol component. In this study, we provide the first profiling of the 2α + 3β + 3δ lidar profiles of Taklamakan dust based on a multi-wavelength Raman polarization lidar. Four cases, including two Taklamakan dust events (Case 1 and 2) and two polluted dust events (Case 3 and 4) are presented. The lidar ratio in the Taklamakan dust outbreak is found to be 51 ± 8–56 ± 8 sr at 355 nm and 45 ± 7 sr at 532 nm. The particle linear depolarization ratios are about 0.28 ± 0.04–0.32 ± 0.05 at 355 nm, 0.35 ± 0.05 at 532 nm and 0.31 ± 0.05 at 1064 nm. The observed polluted dust is commonly featured with reduced particle linear depolarization ratio and enhanced extinction and backscatter Angstrom exponent. In Case 3, the lidar ratio of polluted dust is about 42 ± 6 sr at 355 nm and 40 ± 6 sr at 532 nm. The particles linear depolarization ratios decrease to about 0.25, with a weak spectral dependence. In Case 4, the variability of lidar ratio and particle linear depolarization ratio is higher than in Case 3, which reflects the complexity of the nature of mixed pollutant and the mixing state. The results provide the first reference for the characteristics of Taklamakan dust measured by Raman lidar. The data could contribute to complementing the dust model and improving the accuracy of climate modeling.

Atmospheric pollen concentrations in Antalya, South Turkey

Aerobiologia ◽  
2014 ◽  
Vol 31 (1) ◽  
pp. 99-109 ◽  
Author(s):  
Aycan Tosunoglu ◽  
Mustafa Kemal Altunoglu ◽  
Adem Bicakci ◽  
Ozkan Kilic ◽  
Taner Gonca ◽  
...  
Keyword(s):  
Pollen Concentrations ◽  
Atmospheric Pollen

Measurement of Depolarization Ratios in the Raman Spectra of Powdered Crystalline Solids

1971 ◽  
Vol 49 (4) ◽  
pp. 671-674 ◽  
Author(s):  
D. W. Johnson ◽  
D. Sutton
Keyword(s):  
Refractive Index ◽  
Liquid Medium ◽  
Sodium Sulfate ◽  
Barium Nitrate ◽  
Vibrational Modes ◽  
Crystalline Solids ◽  
Depolarization Ratio ◽  
Surrounding Liquid ◽  
Do So ◽  
Depolarization Ratios

The change in apparent depolarization ratio as a function of the refractive index of the surrounding liquid medium has been measured for the Raman active vibrational modes of powdered crystalline barium nitrate and sodium sulfate. This method provides an accurate measurement of the refractive index and depolarization ratios for barium nitrate, but fails to do so for sodium sulfate due to birefringent effects. The general applications of this technique for determining depolarization ratios of powdered crystalline solids are discussed.

scholarly journals Near-surface and columnar measurements with a micro pulse lidar of atmospheric pollen in Barcelona, Spain

2016 ◽  
Vol 16 (11) ◽  
pp. 6805-6821 ◽  
Author(s):  
Michaël Sicard ◽  
Rebeca Izquierdo ◽  
Marta Alarcón ◽  
Jordina Belmonte ◽  
Adolfo Comerón ◽  
...  
Keyword(s):  
Airborne Pollen ◽  
Correlation Coefficients ◽  
Vertical Motion ◽  
Surface Concentration ◽  
Correlation Study ◽  
Near Surface ◽  
Pollen Types ◽  
Pollen Concentrations ◽  
Micro Pulse Lidar ◽  
Depolarization Ratios

Abstract. We present for the first time continuous hourly measurements of pollen near-surface concentration and lidar-derived profiles of particle backscatter coefficients and of volume and particle depolarization ratios during a 5-day pollination event observed in Barcelona, Spain, between 27 and 31 March 2015. Daily average concentrations ranged from 1082 to 2830 pollen m−3. Platanus and Pinus pollen types represented together more than 80 % of the total pollen. Maximum hourly pollen concentrations of 4700 and 1200 m−3 were found for Platanus and Pinus, respectively. Every day a clear diurnal cycle caused by the vertical transport of the airborne pollen was visible on the lidar-derived profiles with maxima usually reached between 12:00 and 15:00 UT. A method based on the lidar polarization capabilities was used to retrieve the contribution of the pollen to the total aerosol optical depth (AOD). On average the diurnal (09:00–17:00 UT) pollen AOD was 0.05, which represented 29 % of the total AOD. Maximum values of the pollen AOD and its contribution to the total AOD reached 0.12 and 78 %, respectively. The diurnal means of the volume and particle depolarization ratios in the pollen plume were 0.08 and 0.14, with hourly maxima of 0.18 and 0.33, respectively. The diurnal mean of the height of the pollen plume was found at 1.24 km with maxima varying in the range of 1.47–1.78 km. A correlation study is performed (1) between the depolarization ratios and the pollen near-surface concentration to evaluate the ability of the former parameter to monitor pollen release and (2) between the depolarization ratios as well as pollen AOD and surface downward solar fluxes, which cause the atmospheric turbulences responsible for the particle vertical motion, to examine the dependency of the depolarization ratios and the pollen AOD upon solar fluxes. For the volume depolarization ratio the first correlation study yields to correlation coefficients ranging 0.00–0.81 and the second to correlation coefficients ranging 0.49–0.86.

Sign in / Sign up

Export Citation Format

Share Document