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 Optical characterization of pure pollen types using a multi-wavelength Raman polarization lidar

2020 ◽  
Vol 20 (23) ◽  
pp. 15323-15339 ◽  
Author(s):  
Xiaoxia Shang ◽  
Elina Giannakaki ◽  
Stephanie Bohlmann ◽  
Maria Filioglou ◽  
Annika Saarto ◽  
...  
Keyword(s):  
Optical Properties ◽  
Wavelength Dependence ◽  
Depolarization Ratio ◽  
Mean Values ◽  
Angstrom Exponent ◽  
Pollen Types ◽  
Pine Pollen ◽  
Ångström Exponent ◽  
532 Nm ◽  
Ångstrom Exponent

Abstract. We present a novel algorithm for characterizing the optical properties of pure pollen particles, based on the depolarization ratio values obtained in lidar measurements. The algorithm was first tested and validated through a simulator and then applied to the lidar observations during a 4-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. With a Burkard sampler, 20 types of pollen were observed and identified from concurrent measurements, with birch (Betula), pine (Pinus), spruce (Picea), and nettle (Urtica) pollen being the most abundant, contributing more than 90 % of the 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. An enhanced depolarization ratio was found when there were pollen grains in the atmosphere, and an even higher depolarization ratio (with mean values of 0.25 or 0.14) was observed with the presence of the more non-spherical spruce or pine pollen. Under the assumption that the backscatter-related Ångström exponent between 355 and 532 nm should be zero for pure pollen, the depolarization ratio of pure pollen particles at 532 nm was assessed, resulting in 0.24±0.01 and 0.36±0.01 for birch and pine pollen, respectively. Pollen optical properties at 1064 and 355 nm were also estimated. The backscatter-related Ångström exponent between 532 and 1064 nm was assessed to be ∼0.8 (∼0.5) for pure birch (pine) pollen; thus the longer wavelength would be a better choice to trace pollen in the air. Pollen depolarization ratios of 0.17 and 0.30 at 355 nm 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 Detection and characterization of birch pollen in the atmosphere using a multiwavelength Raman polarization lidar and Hirst-type pollen sampler in Finland

2019 ◽  
Vol 19 (23) ◽  
pp. 14559-14569 ◽  
Author(s):  
Stephanie Bohlmann ◽  
Xiaoxia Shang ◽  
Elina Giannakaki ◽  
Maria Filioglou ◽  
Annika Saarto ◽  
...  
Keyword(s):  
Birch Pollen ◽  
Pollen Grains ◽  
Forest Site ◽  
Depolarization Ratio ◽  
Atmospheric Conditions ◽  
Mean Values ◽  
Air Sampler ◽  
Pollen Types ◽  
High Concentrations ◽  
532 Nm

Abstract. We present the results of birch pollen characterization using lidar and in situ measurements based on a 11 d pollination period from 5 to 15 May 2016 at the European Aerosol Research Lidar Network (EARLINET) station in Vehmasmäki (Kuopio; 62∘44′ N, 27∘33′ E), Finland. The ground-based multiwavelength Raman polarization lidar PollyXT performed continuous measurements at this rural forest site and has been combined with a Hirst-type volumetric air sampler, which measured the pollen type and concentration at roof level (4 m). The period was separated into two parts due to different atmospheric conditions and detected pollen types. During the first period, high concentrations of birch pollen were measured with a maximum 2 h average pollen concentration of 3700 grains m−3. Other pollen types represented less than 3 % of the total pollen count. In observed pollen layers, the mean particle depolarization ratio at 532 nm was 10±6 % during the intense birch pollination period. Mean lidar ratios were found to be 45±7 and 55±16 sr at 355 and 532 nm, respectively. During the second period, birch pollen was still dominant, but a significant contribution of spruce pollen was observed as well. Spruce pollen grains are highly nonspherical, leading to a larger mean depolarization ratio of 26±7 % for the birch–spruce pollen mixture. Furthermore, higher lidar ratios were observed during this period with mean values of 60±3 and 62±10 sr at 355 and 532 nm, respectively. The presented study shows the potential of the particle depolarization ratio to track pollen grains in the atmosphere.

scholarly journals Detection and characterization of birch pollen in the atmosphere using multi-wavelength Raman lidar in Finland

2019 ◽  
Author(s):  
Stephanie Bohlmann ◽  
Xiaoxia Shang ◽  
Elina Giannakaki ◽  
Maria Filioglou ◽  
Annika Saarto ◽  
...  
Keyword(s):  
Birch Pollen ◽  
Pollen Grains ◽  
Mean Value ◽  
Forest Site ◽  
Depolarization Ratio ◽  
Atmospheric Conditions ◽  
Raman Lidar ◽  
Pollen Types ◽  
Multi Wavelength ◽  
532 Nm

Abstract. We present the results of birch pollen characterization using lidar measurements based on a 11-day period of birch pollination from 5 to 15 May 2016 at the European Aerosol Research Lidar Network (EARLINET) station in Vehmasmäki (Kuopio, 62°44′ N, 27°33′ E), Finland. The ground-based multi-wavelength Raman lidar PollyXT performed continuous measurements at this rural forest site and has been combined with a Hirst-type volumetric air sampler which measured the pollen type and concentration on roof level (4 m). The period was separated into two parts due to different atmospheric conditions and detected pollen types. During the first period, high concentrations of birch pollen were measured with a maximum two-hour average pollen concentration of 3700 grains/m³. Other pollen types represented less than 3 % of the total pollen count. In observed pollen layers, the mean particle depolarization ratio at 532 nm was 10 ± 6 % during the intense birch pollination period. Mean lidar ratios were found to be 45 ± 7 and 55 ± 16 sr at 355 and 532 nm, respectively. During the second period, birch pollen was still dominant but a significant contribution of spruce pollen was observed. Spruce pollen grains are highly non-spherical, leading to a larger mean depolarization ratio of 26 ± 7 % of the birch-spruce pollen mixture. Furthermore, higher lidar ratios were observed during this period with a mean value of 60 ± 3 and 62 ± 10 sr at 355 and 532 nm, respectively. The presented study shows the potential of the particle depolarization ratio to track pollen grains in the atmosphere.

scholarly journals Airborne measurements of aerosol optical properties related to early spring transport of mid-latitude sources into the Arctic

2010 ◽  
Vol 10 (11) ◽  
pp. 5011-5030 ◽  
Author(s):  
R. A. de Villiers ◽  
G. Ancellet ◽  
J. Pelon ◽  
B. Quennehen ◽  
A. Schwarzenboeck ◽  
...  
Keyword(s):  
Optical Properties ◽  
The Arctic ◽  
Depolarization Ratio ◽  
Aerosol Optical Properties ◽  
Accumulation Mode ◽  
Color Ratio ◽  
Aerosol Sources ◽  
Aerosol Backscatter ◽  
532 Nm

Abstract. Airborne lidar and in-situ measurements of the aerosol properties were conducted between Svalbard Island and Scandinavia in April 2008. Evidence of aerosol transport from Europe and Asia is given. The analysis of the aerosol optical properties based on a multiwavelength lidar (355, 532, 1064 nm) including volume depolarization at 355 nm aims at distinguishing the role of the different aerosol sources (Siberian wild fires, Eastern Asia and European anthropogenic emissions). Combining, first aircraft measurements, second FLEXPART simulations with a calculation of the PBL air fraction originating from the three different mid-latitude source regions, and third level-2 CALIPSO data products (i.e. backscatter coefficient 532 nm,volume depolarization and color ratio between 1064 and 532 nm in aerosol layers) along the transport pathways, appears a valuable approach to identify the role of the different aerosol sources even after a transport time larger than 4 days. Optical depth of the aerosol layers are always rather small (<4%) while transported over the Arctic and ratio of the total attenuated backscatter (i.e. including molecular contribution) provide more stable result than conventional aerosol backscatter ratio. Above Asia, CALIPSO data indicate more depolarization (up to 15%) and largest color ratio (>0.5) for the northeastern Asia emissions (i.e. an expected mixture of Asian pollution and dust), while low depolarization together with smaller and quasi constant color ratio (≈0.3) are observed for the Siberian biomass burning emissions. A similar difference is visible between two layers observed by the aircraft above Scandinavia. The analysis of the time evolution of the aerosol optical properties revealed by CALIPSO between Asia and Scandinavia shows a gradual decrease of the aerosol backscatter, depolarization ratio and color ratio which suggests the removal of the largest particles in the accumulation mode. A similar study conducted for a European plume has shown aerosol optical properties intermediate between the two Asian sources with color ratio never exceeding 0.4 and moderate depolarization ratio being always less than 8%, i.e. less aerosol from the accumulation mode.

scholarly journals Vertical variation of optical properties of mixed Asian dust/pollution plumes according to pathway of airmass transport over East Asia

2015 ◽  
Vol 15 (3) ◽  
pp. 3381-3413 ◽  
Author(s):  
S.-K. Shin ◽  
D. Müller ◽  
K. H. Lee ◽  
D. Shin ◽  
Y. J. Kim ◽  
...  
Keyword(s):  
Optical Properties ◽  
Asian Dust ◽  
Optical Characteristics ◽  
Vertical Position ◽  
Depolarization Ratio ◽  
Dust Pollution ◽  
Transport Time ◽  
Lidar Measurements ◽  
The Mean ◽  
532 Nm

Abstract. We use five years (2009–2013) of multiwavelength Raman lidar measurements at Gwangju, Korea (35.10° N, 126.53° E) for the identification of changes of optical properties of East Asian dust in dependence of its transport path over China. Profiles of backscatter and extinction coefficients, lidar ratios, and backscatter-related Ångström exponents (wavelength pair 355/532 nm) were measured at Gwangju. Linear particle depolarization ratios were used to identify East Asian dust layers. We used backward trajectory modelling to identify the pathway and the vertical position of dust-laden air masses over China during long-range transport. Most cases of Asian dust events can be described by the emission of dust in desert areas and subsequent transport over highly polluted regions of China. The Asian dust plumes could be categorized into two classes according to the height above ground in which these plumes were transported: (I) the dust layers passed over China at high altitude levels until arrival over Gwangju, and (II) the Asian dust layers were transported near the surface and the lower troposphere over industrialized areas before they arrived over Gwangju. We find that the optical characteristics of these mixed Asian dust layers over Gwangju differ in dependence of their vertical position above ground over China and the change of height above ground during transport. The mean linear particle depolarization ratio was 0.21 ± 0.06 (at 532 nm), the mean lidar ratios were 52 ± 7 sr at 355 nm and 53 ± 8 sr at 532 nm, and the mean Ångström exponent was 0.74 ± 0.31 in case I. In contrast, plumes transported at lower altitudes (case II) showed low depolarization ratios, and higher lidar ratio and Ångström exponents. The mean linear particle depolarization ratio was 0.13 ± 0.04, the mean lidar ratios were 63 ± 9 sr at 355 nm and 62 ± 8 sr at 532 nm, respectively, and the mean Ångström exponent was 0.98 ± 0.51. These numbers show that the optical characteristics of mixed Asian plumes are more similar to optical characteristics of urban pollution. We find a decrease of the linear depolarization ratio of the mixed dust/pollution plume in dependence of transport time if the pollution layer travelled over China at low heights, i.e., below approximately 3 km above ground. In contrast we do not find such a trend if the dust plumes travelled at heights above 4 km over China. We need a longer time series of lidar measurements in order to determine the change of optical properties of dust with transport time in a quantitative way.

scholarly journals Observation of Long-Range Dust Transport from Mesopotamia and Arabian Peninsula Toward Tehran, Iran

2019 ◽  
Vol 99 ◽  
pp. 02006 ◽  
Author(s):  
Hossein Panahifar ◽  
Hamid Reza Khalesifard
Keyword(s):  
Optical Properties ◽  
Particulate Matter ◽  
Arabian Peninsula ◽  
Urban Pollution ◽  
Depolarization Ratio ◽  
Dust Transport ◽  
Linear Depolarization Ratio ◽  
Dust Events ◽  
Aerosol Types ◽  
532 Nm

Continuous vertically resolved aerosol measurements using lidar were performed in Tehran, Iran. Lidar results has been used in combination with particulate matter monitoring, synoptic meteorology observa- tion as well as satellite-based measurements. The aerosol types are classified by their optical properties. The volume linear depolarization ratio (VLDR) at 532 nm lies mostly between 0:05-0:10. These results show that mostly urban pollution mixed with particles are present in the atmosphere above Tehran. During dust events, the VLDR at 532 nm lies between 0:20-0:35.

scholarly journals Land-Use and Height of Pollen Sampling Affect Pollen Exposure in Munich, Germany

Atmosphere ◽  
2020 ◽  
Vol 11 (2) ◽  
pp. 145 ◽  
Author(s):  
Jesús Rojo ◽  
Jose Oteros ◽  
Antonio Picornell ◽  
Franziska Ruëff ◽  
Barbora Werchan ◽  
...  
Keyword(s):  
Airborne Pollen ◽  
Pollen Grains ◽  
Ground Level ◽  
Large Area ◽  
Dispersal Capacity ◽  
Pollen Types ◽  
Pollen Concentrations ◽  
Pollen Sources ◽  
Poaceae Pollen ◽  
The City

Airborne pollen concentrations vary depending on the location of the pollen trap with respect to the pollen sources. Two Hirst-type pollen traps were analyzed within the city of Munich (Germany): one trap was located 2 m above ground level (AGL) and the other one at rooftop (35 m AGL), 4.2 km apart. In general, 1.4 ± 0.5 times higher pollen amounts were measured by the trap located at ground level, but this effect was less than expected considering the height difference between the traps. Pollen from woody trees such as Alnus, Betula, Corylus, Fraxinus, Picea, Pinus and Quercus showed a good agreement between the traps in terms of timing and intensity. Similar amounts of pollen were recorded in the two traps when pollen sources were more abundant outside of the city. In contrast, pollen concentrations from Cupressaceae/Taxaceae, Carpinus and Tilia were influenced by nearby pollen sources. The representativeness of both traps for herbaceous pollen depended on the dispersal capacity of the pollen grains, and in the case of Poaceae pollen, nearby pollen sources may influence the pollen content in the air. The timing of the pollen season was similar for both sites; however, the season for some pollen types ended later at ground level probably due to resuspension processes that would favor recirculation of pollen closer to ground level. We believe measurements from the higher station provides a picture of background pollen levels representative of a large area, to which local sources add additional and more variable pollen amounts.

The importance of being the first pollen in the strobili of Scots pine

2008 ◽  
Vol 38 (12) ◽  
pp. 2976-2980 ◽  
Author(s):  
Saila Varis ◽  
Arja Santanen ◽  
Anne Pakkanen ◽  
Pertti Pulkkinen
Keyword(s):  
Pinus Sylvestris ◽  
Scots Pine ◽  
Pollen Grains ◽  
Seed Orchard ◽  
Pollen Grain ◽  
Seed Orchards ◽  
Pollination Experiments ◽  
Seed Crop ◽  
Pollen Types ◽  
Pine Pollen

Timing of pollen arrival may affect the level of seeds fertilized by pollen from outside seed orchards, especially in seed orchards of Scots pine ( Pinus sylvestris L.) established in southern Finland with stock from northern populations. We performed sequential pollination experiments with Scots pine pollen collected from seed orchard clones originating from southern and northern Finland and recipient strobili in clones originating from southern Finland. When southern pollen was introduced first, seeds were sired equally by northern and southern genotypes. When northern pollen was introduced first, northern genotypes were found in 75% of the resulting seeds. When both pollen types were introduced at the same time, the resulting seed crop was split almost equally between northern and southern genotypes. These results do not unconditionally support the idea that the first pollen grain in the pollen chamber always fertilizes the ovum; instead, they suggest a more complex way of competition between pollen grains.

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 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.

Sign in / Sign up

Export Citation Format

Share Document