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Temporal evolution of vertical profiles of r, RH and β aer at 355 nm from RALMO lidar on 7 September 2017.
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This study focuses on the analysis of aerosol hygroscopicity using remote sensing techniques. Continuous observations of aerosol backscatter coefficient (βaer), temperature (T) and water vapor mixing ratio (r) have been performed by means of a Raman lidar system at the aerological station of MeteoSwiss at Payerne (Switzerland) since 2008. These mea...
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Context 1
... I corresponds to 7 September 2017. The temporal evolution of r, RH and β aer at 355 nm in the lower troposphere (0-5 km a.s.l.) is shown in Fig. 3 for this day. According to the aerosol measurements (lowest panel), low clouds were present at around 1.6 km (a.g.l.) during the first part of the day (until 12:00 UTC). After that, two clear aerosol layers can be identified, the atmospheric boundary layer (ABL) and a strong lofted aerosol layer located between 2 and 4 km (a.g.l.) ...
Context 2
... at around 14:00 UTC. It is interesting to remark how within the ABL the intensity of the aerosol backscatter signal was stronger at the top of this layer even when a strong mixing was expected at the central hours of the day (between 13:00 and 17:00 UTC). However, a larger homogeneity was observed for the same layer in the r measurements (Fig. 3, upper panel), indicating that the convective processes were strong enough to produce a wellmixed ABL in that time interval. The third element that can help to understand the observed variations in the backscatter signals is the RH measurements (central panel). From that plot, we can observe how the intensification observed in β aer is well ...
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Citations
... The advantages of active remote sensing systems are multiple: they provide high vertical and temporal resolutions, they preserve the ambient conditions (no humidification or dehydration is applied on the sample), they can measure under RHs close to saturation. In the literature the aerosol hygroscopic enhancement has been measured more often on the backscatter coefficient derived from lidar (Feingold and Morley, 2003;Fernández et al., 2015;Granados-Muñoz et al., 2015;Haarig et al., 2017;Lv et al., 2017;Navas-Guzmán et al., 2019;Chen et al., 2019;Pérez-Ramírez et al., 2021) and ceilometer (Bedoya-Velásquez et al., 2019) measurements than on the extinction coefficient derived from lidar measurements (Veselovskii et al., 2009;Dawson et al., 2020). Some intents to work on the attenuated backscatter coefficient derived from ceilometers were performed by Haeffelin et al. (2016) to help track the activation of aerosols into fog or low-cloud droplets. ...
... Moreover, for all cases, back trajectories at layer maximum and minimum altitudes (h min and h max ) were also calculated with the HYbrid Single-Particle Lagrangian Integrated Trajectory (HYS-PLIT) model (Stein et al., 2015) for verifying that all the aerosols inside the layer have the same origin. Such criteria have been applied by other authors (Granados-Muñoz et al., 2015;Navas-Guzmán et al., 2019;among others). ...
This paper presents the estimation of the hygroscopic growth parameter of atmospheric aerosols retrieved with a multi-wavelength lidar, a micro-pulse lidar (MPL) and daily radiosoundings in the coastal region of Barcelona, Spain. The hygroscopic growth parameter, γ, parameterizes the magnitude of the scattering enhancement in terms of the backscatter coefficient following Hänel parameterization. After searching for time-colocated lidar and radiosounding measurements (performed twice a day, all year round at 00:00 and 12:00 UTC), a strict criterion-based procedure (limiting the variations of magnitudes such as water vapor mixing ratio (WMVR), potential temperature, wind speed and direction) is applied to select only cases of aerosol hygroscopic growth. A spectral analysis (at the wavelengths of 355, 532 and 1064 nm) is performed with the multi-wavelength lidar, and a climatological one, at the wavelength of 532 nm, with the database of both lidars. The spectral analysis shows that below 2 km the regime of local pollution and sea salt γ decreases with increasing wavelengths. Since the 355 nm wavelength is sensitive to smaller aerosols, this behavior could indicate slightly more hygroscopic aerosols present at smaller size ranges. Above 2 km (the regime of regional pollution and residual sea salt) the values of γ at 532 nm are nearly the same as those below 2 km, and its spectral behavior is flat. This analysis and others from the literature are put together in a table presenting, for the first time, a spectral analysis of the hygroscopic growth parameter of a large variety of atmospheric aerosol hygroscopicities ranging from low (pure mineral dust, γ <0.2) to high (pure sea salt, γ > 1.0) hygroscopicity. The climatological analysis shows that, at 532 nm, γ is rather constant all year round and has a large monthly standard deviation, suggesting the presence of aerosols with different hygroscopic properties all year round. The annual γ is 0.55 ± 0.23. The height of the layer where hygroscopic growth was calculated shows an annual cycle with a maximum in summer and a minimum in winter. Former works describing the presence of recirculation layers of pollutants injected at various heights above the planetary boundary layer (PBL) may explain why γ, unlike the height of the layer where hygroscopic growth was calculated, is not season-dependent. The subcategorization of the whole database into No cloud and Below-cloud cases reveals a large difference of γ in autumn between both categories (0.71 and 0.33, respectively), possibly attributed to a depletion of inorganics at the point of activation into cloud condensation nuclei (CCN) in the Below-cloud cases. Our work calls for more in situ measurements to synergetically complete such studies based on remote sensing.
... close to saturation. In the literature the aerosol hygroscopic enhancement has been measured more often on the backscatter coefficient derived from lidar (Feingold and Morley, 2003;Fernández et al., 2015;Granados-Muñoz et al., 2015;Haarig et al., 2017;Lv et al., 2017;Navas-Guzmán et al., 2019;Chen et al., 2019;Pérez-Ramírez et al., 2021) and ceilometer (Bedoya-65 Velásquez et al., 2019) measurements than on the extinction coefficient derived from lidar measurements (Veselovskii et al., 2009;Dawson et al., 2020). Some intents to work on the attenuated backscatter coefficient derived from ceilometers were performed by Haeffelin et al. (2016) to help tracking the activation of aerosols into fog or low-cloud droplets. ...
... aerosol size due to water uptake and not to changes in the aerosol composition or concentration in the analysed layer. Such criteria have been applied by other authors (Granados-Muñoz et al., 2015;Navas-Guzmán et al., 2019;among others). ...
... All these results from independent studies are consistent with the classification presented in this paper. The singular spectral behaviour of 85% or observed in our study below 2 km was reported, although with smaller 260 values, byNavas-Guzmán et al. (2019) between 355 and 1064 nm for a mixture of biomass burning and rural aerosols and byPérez-Ramírez et al. (2021) between 355, 532 and 1064 nm for sulfates and organics. Given the little literature on the subject, it is difficult at this point to attribute the decrease of 85% with increasing wavelength to one type of aerosols or another. ...
This paper presents the estimation of the hygroscopic growth parameter of atmospheric aerosols retrieved with a multi-wavelength lidar, a micro pulse lidar and daily radiosoundings in the coastal region of Barcelona, Spain. The hygroscopic growth parameter, γ, parametrizes the magnitude of the scattering enhancement in terms of the backscatter coefficient following Hänel parametrization. After searching for time co-located lidar and radiosoundings measurements, a strict criterion-based procedure (limiting the variations of magnitudes such as water vapor mixing ratio, potential temperature, wind speed and direction) is applied to select only cases of aerosol hygroscopic growth. A spectral analysis (at the wavelengths of 355, 532 and 1064 nm) is performed with the multi-wavelength lidar, and a climatological one, at the wavelength of 532 nm, with the database of both lidars. The spectral analysis shows that below 2 km (regime of local pollution and sea salt) γ decreases with increasing wavelengths. This behaviour can be attributed to the aerosol size: the smaller the aerosol, the more hygroscopic. Above 2 km (regime of regional pollution and residual sea salt) the values of γ at 532 nm are nearly the same than below 2 km, and its spectral behaviour is flat. This analysis and others from the literature are put together in a table presenting, for the first time, a spectral analysis of the hygroscopic growth parameter of a large variety of atmospheric aerosol hygroscopicities going from low (pure mineral dust, γ 1.0) hygroscopicity. The climatological analysis shows that, at 532 nm, γ is rather constant all year round and has a large monthly standard deviation suggesting the presence of aerosols with different hygroscopic properties all year round. The annual γ is 0.55 ± 0.23. The height of the hygroscopic layers shows an annual cycle with a maximum in summer and a minimum in winter. Former works describing the presence of re-circulation layers of pollutants injected at various heights above the PBL may explain why γ, unlike the height of the hygroscopic layers, is not season-dependent. The sub-categorization of the whole database into No cloud and Below-cloud cases reveals a large difference of γ in autumn between both categories (0.71 and 0.33, respectively), possibly attributed to a depletion of inorganics at the point of activation into cloud condensation nuclei in the Below-cloud cases. Our work calls for more in-situ measurements to synergetically complete such studies based on remote sensing.
... Without tackling turbulence-scale resolution, which is the prerogative of heavier systems like the Raman lidars of the University of Hohenheim , the University of Basilicata (Di Girolamo et al., 2017), or ARTHUS (Atmospheric Raman Temperature and Humidity Sounder, Lange et al., 2019), there is a need for field-deployable instruments capable of fulfilling the breakthrough requirements set by the World Meteorological Organization in terms of accuracy on atmospheric temperature and humidity in the low troposphere (WMO, 2017). Lidar profiles have proven beneficial for numerical weather prediction (NWP) models (e.g., Adam et al., 2016;Fourrié et al., 2019), the study of dynamic processes in the planetary boundary layer (PBL) (e.g., Behrendt et al., 2015), or interactions between water vapor and aerosols (e.g., Navas-Guzmán et al., 2019). But to obtain the absolute accuracies demanded here, especially that of 1 • C or less on temperature, the required accuracy on the lidar channel ratios and their calibration is extremely stringent, and the sources of systematic error are seldom discussed in the literature (Behrendt and Reichardt, 2000;Simeonov et al., 1999;Whiteman et al., 2012). ...
Lidars using vibrational and rotational Raman scattering to continuously
monitor both the water vapor and temperature profiles in the low and middle
troposphere offer enticing perspectives for applications in weather prediction
and studies of aerosol–cloud–water vapor interactions by simultaneously deriving
relative humidity and atmospheric optical properties. Several
heavy systems exist in European laboratories, but only recently have they been
downsized and ruggedized for deployment in the field. In this paper, we
describe in detail the technical choices made during the design and
calibration of the new Raman channels for the mobile Weather and Aerosol Lidar
(WALI), going over the important sources of bias and uncertainty on the water
vapor and temperature profiles stemming from the different optical elements
of the instrument. For the first time, the impacts of interference filters and
non-common-path differences between Raman channels, and their mitigation, in particular are
investigated, using horizontal shots in a homogeneous
atmosphere. For temperature, the magnitude of the highlighted biases can be
much larger than the targeted absolute accuracy of 1 ∘C
defined by the WMO (up to 6 ∘C bias below 300 m
range). Measurement errors are quantified using simulations and a number of
radiosoundings launched close to the laboratory. After de-biasing, the
remaining mean differences are below 0.1 g kg−1 on water vapor and
1 ∘C on temperature, and rms differences are consistent with
the expected error from lidar noise, calibration uncertainty, and horizontal
inhomogeneities of the atmosphere between the lidar and radiosondes.
... Based on the lidar studies, it has been shown that coarse and giant particles are ubiquitous in Saharan dust export regions and are radiatively significant over the Sahara (Ryder et al., 2019). Hygroscopicity studies in relation to dust are of importance (Hara et al., 2018;Navas-Guzmán et al., 2019;Wu et al., 2020). Finally, real-time lidar studies of the dust-cloud interaction are possible (Huang et al., 2017), especially impact of mineral dust on cloud formation (Weger et al., 2018) and new particle formation (Miffre et al., 2019) is of importance. ...
On June 29–30, 2019, the Barcelona Dust Forecast Center with Non‐hydrostatic Multiscale Model (NMMB/BSC‐Dust) and the Navy Aerosol Analysis and Prediction System forecasted huge amounts of mineral dust over Poland. The Hybrid Single Particle Lagrangian Integrated Trajectory model confirmed uniquely fast (120 hr) long‐range air‐mass transport form North Africa to Poland. This remarkable dust event was observed using lidar at the Aerosol, Clouds and Trace Gases Research InfraStructure site in Warsaw, Central Poland; the only site equipped with Raman‐Mie polarization water vapor lidar in East‐Central Europe. The excellent capabilities of PollyXT lidar allowed to obtain an impressive number of 31 full sets of aerosol optical properties profiles, which enabled study of dust properties evolution on a rare hourly scale. The analyses were completed with the separation of fine and coarse mode dust particles form non‐dust particles using the POlarization‐LIdar PHOtometer Networking algorithm. Huge amount of an exceptionally pure mineral dust from Sahara measured in the free troposphere was characterized by a gradually decreasing coarse dust fraction (76%–21%) with a peak of fine dust fraction (67%) and particle linear depolarization ratio (26%) in the middle of the event. Within the boundary layer, a local urban dust mixed with pollution was observed with fine mode dust particles dominating (44%) and lower particle linear depolarization ratio (7.4%). The influx of pure mineral dust has been unique to this geographical region and will therefore be a reference point for future research and comparative studies.
... Although scientists have conducted a lot of researches on aerosol optical properties and their influencing factors, the influence of water vapor on aerosol optical properties remains one of the largest sources of uncertainty in climate models (IPCC, 2013;Yabuki et al., 2016). The absorption of water by aerosols at higher humidity leads to the changes in the shape and size of aerosol particles (hygroscopic growth) (Bedoya-Velásquez et al., 2018;Liu et al., 2020a), which can further affect aerosol direct and indirect radiation effects (Kuang et al., 2016;Navas-Guzmán et al., 2019;Piens et al., 2016). Using the RH profile from radiosonde and aerosol physical properties profile retrieved from Raman lidar to quantitatively study the influence of humidity on aerosol in the troposphere can reduce the uncertainty of previous studies (e.g., Qiu and Shu, 2017) using CALIPSO (Cloud-Aerosol Lidar Infrared Pathfinder Satellite Observation) data to a certain extent. ...
As a key component in the atmosphere, the increase in water vapor content can aggravate air pollution by promoting hygroscopic growth and secondary formation of aerosols. In this study, water vapor mixing ratio (WVMR) profiles retrieved from Raman lidar at night in Shanghai were used to evaluate the accuracy of a maintained microwave radiometer (MWR) and reanalysis datasets (ERA5 from ECMWF and MERRA-2 from NASA). The relative humidity (RH) profiles from radiosonde and reanalysis datasets were used to explore the influence of humidity vertical distributions on aerosol physical properties and secondary formation. There was a large WVMR difference between MWR and Raman lidar, with a mean bias (MB) and a root mean square error (RMSE) being 2.47 g/kg and 3.29 g/kg, respectively. However, the WVMR from ERA5 and MERRA-2 showed excellent agreement (correlation coefficients were both 0.94, N=11288 and 3619, respectively) with that from Raman lidar and high accuracy especially MERRA-2, which are more suitable for meteorological and climatic applications than MWR. It was found that RH had a significant effect on the vertical distribution of aerosol extinction coefficient (AEC). Aerosol hygroscopic growth caused by high RH resulted in an obvious enhancement of AEC at 355 nm below 610 m in summer. As a good indicator for determining contribution of aerosol secondary formation, large ratios of PM2.5 to CO (PM2.5/CO > 0.08) corresponded to high nitrogen oxidation ratios (NOR), sulfur oxidation ratios (SOR), and also high RH below 800 m during nighttime in winter, suggesting that RH and its vertical distribution played an important role in the aerosol secondary formation. The RH was high in the vertical direction when nitrate and sulfate mainly come from the secondary formation (NOR > 0.1 or SOR > 0.1), and in contrast to nitrate, the secondary formation for sulfates tended to depend on higher RH (> 70%), which indicated that more stringent measures for nitrogen oxides emission reduction should be implemented in Shanghai to reduce the pollution of secondary aerosols in the future.
... The combination of lidar with other meteorological measurements is ideal for answering questions about the vertically resolved aerosol hygroscopicity but requires the assumption of well-mixed conditions to isolate aerosol hygroscopicity from other aerosol processes (Wulfmeyer and Feingold, 2000;Feingold and Morley, 2003). This technique has been widely used for backscattering lidars (e.g., Granados-Muñoz et al., 2015;Haeffelin et al., 2016;Lv et al., 2017;Zhao et al., 2017;Fernández et al., 2018;Bedoya-Velasquez et al., 2018Navas-Guzmán et al., 2019;Dowson et al., 2020). However, to obtain information on how aerosol hygroscopicity affects the aerosol microphysical properties with altitude requires the application of inversion algorithms that use at least measurements of aerosol extinction (α) at two wavelengths (typically 355 and 532 nm) and of backscattering (β) at three wavelengths (typically at 355, 532 and 1064 nm). ...
This work focuses on the characterization of vertically resolved aerosol
hygroscopicity properties and their direct radiative effects through a
unique combination of ground-based and airborne remote sensing measurements
during the Column and Vertically
Resolved Observations Relevant to Air Quality (DISCOVER-AQ) 2011 field campaign in the Baltimore–Washington DC metropolitan area. To that end, we combined aerosol measurements
from a multiwavelength Raman lidar located at NASA Goddard Space Flight
Center and the airborne NASA Langley High Spectral Resolution Lidar-1 (HSRL-1) lidar system. In situ
measurements aboard the P-3B airplane and ground-based Aerosol Robotic Network – Distributed Regional Aerosol Gridded
Observational Network (AERONET-DRAGON)
served to validate and complement quantifications of aerosol hygroscopicity
from lidar measurements and also to extend the study both temporally and
spatially. The focus here is on 22 and 29 July 2011,
which were very humid days and characterized by a stable atmosphere and
increasing relative humidity with height in the planetary boundary layer
(PBL). Combined lidar and radiosonde (temperature and water vapor mixing
ratio) measurements allowed the retrieval of the Hänel hygroscopic
growth factor which agreed with that obtained from airborne in situ
measurements and also explained the significant increase of extinction and
backscattering with height. Airborne measurements also confirmed aerosol
hygroscopicity throughout the entire day in the PBL and identified sulfates
and water-soluble organic carbon as the main species of aerosol particles.
The combined Raman and HSRL-1 measurements permitted the inversion for
aerosol microphysical properties revealing an increase of particle radius
with altitude consistent with hygroscopic growth. Aerosol hygroscopicity
pattern served as a possible explanation of aerosol optical depth increases
during the day, particularly for fine-mode particles. Lidar measurements
were used as input to the libRadtran radiative transfer code to obtain
vertically resolved aerosol radiative effects and heating rates under dry
and humid conditions, and the results reveal that aerosol hygroscopicity is
responsible for larger cooling effects in the shortwave range (7–10 W m−2
depending on aerosol load) near the ground, while heating rates
produced a warming of 0.12 K d−1 near the top of PBL where aerosol
hygroscopic growth was highest.
... The integrated SW values show similar patterns on both days with an increase from minimum values at the surface (~ 0.05 K/day) to maximum values near the top of the PBL where the differences between ambient and dry conditions are maximized (~0.12 K/day) and associated again with aerosol hygroscopic growth. These 905 positive HRs for the SW region agree with other studies (Mallet et al., 2008;Lemaitre et al., 2010;Perrone et al., 2012;Meloni et al., 2015;Granados-Muñoz et al., 2019) although the aerosol types in this study are different. ...
This work focuses on the characterization of vertically-resolved aerosol hygroscopicity properties and their direct radiative effects through a unique combination of ground-based and airborne remote sensing measurements during the DISCOVER-AQ 2011 field campaign in the Washington D.C. – Baltimore metropolitan area. To that end, we combined measurements from a multiwavelength Raman lidar located at NASA Goddard Space Flight Center and the airborne NASA Langley HSRL-1 lidar system. In-situ measurements on board the P-3B airplane and ground-based AERONET-DRAGON served to validate and complement quantifications of aerosol hygroscopicity from lidar measurements and also to extend the study both temporally and spatially. The focus here is on the 22nd and 29th of July, 2011 which were very humid days and characterized by a stable atmosphere and increasing relative humidity with height in the planetary boundary layer (PBL). Combined lidar and radiosonde measurements allowed the retrieval of the Hänel hygroscopic growth factor which agreed with that obtained from airborne in-situ measurements, and also explained the significant increase of extinction and backscattering with height. Airborne measurements also confirmed aerosol hygroscopicity throughout the entire day in the PBL and identified sulfates and water soluble organic carbon as the main species of aerosol particles. The combined Raman and HSRL-1 measurements permitted the inversion for aerosol microphysical properties revealing an increase of particle radius with altitude consistent with hygroscopic growth. Aerosol hygroscopicity was identified as the main reason to explain aerosol optical depth increases during the day, particularly for fine mode particles. Lidar measurements were used as input to the libRadtram radiative transfer code to obtain vertically-resolved aerosol radiative effects and heating rates under dry and humid conditions, and the results reveal that aerosol hygroscopicity is responsible for larger cooling effects in the shortwave range (7–10 W/m2 depending on aerosol load) near the ground, while heating rates produced a warming of 0.12 K/day near the top of PBL where aerosol hygroscopic growth was highest.
... Among the most significant causes of this uncertainty is the high variability in space and time in the aerosol's concentration, composition and optical properties. Remotesensing instruments, such as light detection and ranging (lidar) systems, represent an optimal tool for the monitoring of altitude-resolved aerosol optical coefficients (backscatter and extinction), especially in the planetary boundary layer (PBL) (e.g., Amiridis et al., 2005;Navas-Guzmán et al., 2013). Lidar networks like EARLINET (https://www.earlinet.org, ...
... Aerosol backscatter coefficient measurements from RALMO were recently used to characterize hygroscopic growth during mineral dust and smoke events (Navas-Guzmán et al., 2019). Here we derive the RALMO β aer at 355 nm from the ratio between the elastic and inelastic signal, as described in Navas-Guzmán et al. (2019). The CHM 15K NIMBUS (hereafter CHM15K) ceilometer is a single-wavelength elastic-backscatter lidar manufactured by Lufft, Germany (Lufft, 2019), installed in Payerne since 2012, and a member of E-PROFILE. ...
... 2), which describes the spectral dependency of β aer between two wavelengths (λ 0 and λ) as a function of the Ångström exponent (AE) at every altitude level (z i ). The AE is an intensive property of the aerosol that, under certain assumptions on the particle's size distribution, can be used as a semi-quantitative indicator of particle size (e.g., Njeki et al., 2012;Navas-Guzmán et al., 2019). Through Eq. ...
Remote-sensing measurements by light detection and ranging (lidar)
instruments are fundamental for the monitoring of altitude-resolved aerosol
optical properties. Here we validate vertical profiles of aerosol
backscatter coefficient (βaer) measured by two independent lidar
systems using co-located balloon-borne measurements performed by Compact
Optical Backscatter Aerosol Detector (COBALD) sondes. COBALD provides
high-precision in situ measurements of βaer at two wavelengths
(455 and 940 nm). The two analyzed lidar systems are the research Raman
Lidar for Meteorological Observations (RALMO) and the commercial CHM15K
ceilometer (Lufft, Germany). We consider in total 17 RALMO and 31 CHM15K
profiles, co-located with simultaneous COBALD soundings performed throughout
the years 2014–2019 at the MeteoSwiss observatory of Payerne (Switzerland).
The RALMO (355 nm) and CHM15K (1064 nm) measurements are converted to 455 and 940 nm, respectively, using the Ångström exponent profiles
retrieved from COBALD data. To account for the different receiver field-of-view (FOV) angles between the two lidars (0.01–0.02∘) and COBALD
(6∘), we derive a custom-made correction using Mie-theory
scattering simulations. Our analysis shows that both lidar instruments
achieve on average a good agreement with COBALD measurements in the boundary
layer and free troposphere, up to 6 km altitude. For medium-high-aerosol-content measurements at altitudes below 3 km, the mean ± standard
deviation difference in βaer calculated from all considered
soundings is −2 % ± 37 % (−0.018 ± 0.237 Mm−1 sr−1 at 455 nm) for RALMO−COBALD and +5 % ± 43 %
(+0.009 ± 0.185 Mm−1 sr−1 at 940 mm) for CHM15K−COBALD. Above 3 km altitude, absolute deviations generally decrease, while
relative deviations increase due to the prevalence of air masses with low
aerosol content. Uncertainties related to the FOV correction and spatial- and
temporal-variability effects (associated with the balloon's drift with
altitude and different integration times) contribute to the large standard
deviations observed at low altitudes. The lack of information on the aerosol
size distribution and the high atmospheric variability prevent an accurate
quantification of these effects. Nevertheless, the excellent agreement
observed in individual profiles, including fine and complex structures in
the βaer vertical distribution, shows that under optimal
conditions, the discrepancies with the in situ measurements are typically
comparable to the estimated statistical uncertainties in the remote-sensing
measurements. Therefore, we conclude that βaer profiles measured
by the RALMO and CHM15K lidar systems are in good agreement with in situ
measurements by COBALD sondes up to 6 km altitude.
... However PM concentration increased, which could be a result of transported aerosols accumulation, and naturally, the observed backscatter coefficient increased. To examine the specific relation between RH and lidar measurement, a more advanced lidar can be used which also measures humidity profiles [48,56]. ...
... However PM concentration increased, which could be a result of transported aerosols accumulation, and naturally, the observed backscatter coefficient increased. To examine the specific relation between RH and lidar measurement, a more advanced lidar can be used which also measures humidity profiles [48,56]. Figure 17. ...
Ground-based lidars and ceilometers are widely used for dust and volcanic ash observation around the world. This is particularly interesting in Iceland where high-altitude dust events occur frequently during strong wind conditions and volcanic eruptions. To explore the possible application of such technologies in Iceland for monitoring dust events, we used a combination of Doppler wind lidars with depolarization channels, ceilometers, and other instruments, to monitor two dust events that occurred in Iceland during summer 2019. We applied a verified ceilometer data processing procedure with customized local corrections and developed a new procedure to process Doppler lidar data for aerosols measurements. Both lidar and ceilometer observations can be used to detect the dust layer and reveal the temporal and vertical distribution of dust aerosols in Iceland. The depolarization ratio measurements indicate that the weather conditions, e.g., relative humidity, could have a significant impact on lidar measurements. We conclude that using Doppler wind lidar and ceilometer measurements to monitor volcanic and sedimentary aerosols is possible and may be used to provide important information to the scientific community.
... InSwitzerland, Balin et al. (2004) present the observations from a PRR lidar at the Jungfraujoch alpine station, with which measurements of relative humidity have been achieved combining PRR measurements of temperature with simultaneous water vapour mixing ratio measurements from a vibrational Raman channel. Nowadays, the Raman Lidar for Meteorological Observation (RALMO) at the Payerne EARLINET station is capable of providing continuous measurements of meteorological variables(Dinoev et al. 2013;Mahagammulla Gamage et al. 2019) and allows joint studies of the coupled cycles of aerosols and water vapour(Navas Guzmán et al. 2019). In Germany, PRR lidars have been developed since the beginning of the 2000s(Behrendt et Reichardt 2000;Behrendt, Nakamura, et Tsuda 2004), with a focus on meteorological and turbulent ...
... Le résultat est un coefficient dont la valeur est donnée en légende.Des analyses restent à mener pour étudier si un accroissement en taille de l'aérosol est observé, pour le cas d'étude discuté. Sous l'hypothèse d'une nature d'aérosols et d'une concentration homogène dans la zone étudiée, les mesures continues du WALI permettront d'étudier par télédétection l'hygroscopicité sur des périodes prolongées, comme ce qui est fait par exemple parNavas-Guzmán et al. (2019). ...
... À haute résolution temporelle et verticale, ce type de mesures permet d'étudier des phénomènes de microphysique des aérosols difficilement observables. C'est pourquoi des systèmes lidar permettant de mesurer simultanément les propriétés optiques des aérosols, la température et le rapport de mélange de vapeur d'eau voient le jour(Navas Guzmán et al. 2019;Lange, Behrendt, et Wulfmeyer 2019). Ces instruments permettent l'accès à la mesure de l'humidité relative, un important facteur de modification du rôle des aérosols dans l'atmosphère(Randriamiarisoa et al. 2006; Raut et Chazette 2008). ...
Les cycles couplés des aérosols, de la vapeur d’eau et des nuages sont à l’heure actuelle un domaine de recherche dynamique au cœur d’enjeux climatiques et météorologiques. Une meilleure compréhension des interactions entre ces différents cycles atmosphériques doit permettre de mieux appréhender les processus conduisant à des évènements météorologiques extrêmes et également de diminuer les incertitudes des projections climatiques, en grande partie liées aux interactions aérosols – nuages. Contribuant à ces efforts, les travaux présentés dans cette thèse sont fondés sur l'analyse d'observations expérimentales de terrain autour d’un instrument de télédétection émergent. Il s’agit d’un lidar Raman météorologique transportable capable de mesurer simultanément la température thermodynamique, le contenu en vapeur d'eau et les propriétés optiques des aérosols, dans la colonne atmosphérique. Cet instrument, développé au LSCE et nommé WALI, permet des observations continues dans la basse et moyenne troposphère avec une précision et des résolutions verticale et temporelle en adéquation avec les objectifs de ruptures énoncés par l’OMM. En premier lieu, le bilan de liaison de la chaîne d’acquisition de la température basée sur la spectroscopie Raman rotationnelle, nouvellement implémentée sur le lidar, a été obtenu à l’aide d’une modélisation directe – inverse. Les premières mesures de température par lidar, conduites durant une période très contrastée en température marquée par l’occurrence d’une vague de froid, ont permis une comparaison avec les sorties de modèles de prévisions météorologiques à méso-échelle (AROME/Météo-France) et globale (ERA5/ECMWF) et l'instrument IASI embarqué sur les satellites de la série METOP. Lors d’une configuration météorologique hivernale analogue ayant induit des épisodes de pollution majeurs en Île-de-France, un suivi des propriétés optiques des aérosols a été effectué. Enfin, une campagne de mesure multi-instruments incluant un volet aéroporté a été conduite aux abords du lac d’Annecy, avec une stratégie originale couplant la télédétection et l'observation in situ. Elle a permis une analyse préliminaire du cycle de l'eau dans un environnement montagneux complexe, incluant les liens entre la vapeur d'eau atmosphérique, les nuages, les aérosols et le lac. Le lidar Raman météorologique s’avère être un outil idoine pour étudier ces processus.
