lidar measurements
Recently Published Documents


TOTAL DOCUMENTS

1441
(FIVE YEARS 295)

H-INDEX

59
(FIVE YEARS 8)

2022 ◽  
Vol 22 (1) ◽  
pp. 355-369
Author(s):  
Moritz Haarig ◽  
Albert Ansmann ◽  
Ronny Engelmann ◽  
Holger Baars ◽  
Carlos Toledano ◽  
...  

Abstract. Two layers of Saharan dust observed over Leipzig, Germany, in February and March 2021 were used to provide the first-ever lidar measurements of the dust lidar ratio (extinction-to-backscatter ratio) and linear depolarization ratio at all three classical lidar wavelengths (355, 532 and 1064 nm). The pure-dust conditions during the first event exhibit lidar ratios of 47 ± 8, 50 ± 5 and 69 ± 14 sr and particle linear depolarization ratios of 0.242 ± 0.024, 0.299 ± 0.018 and 0.206 ± 0.010 at wavelengths of 355, 532 and 1064 nm, respectively. The second, slightly polluted-dust case shows a similar spectral behavior of the lidar and depolarization ratio with values of the lidar ratio of 49 ± 4, 46 ± 5 and 57 ± 9 sr and the depolarization ratio of 0.174 ± 0.041, 0.298 ± 0.016 and 0.242 ± 0.007 at 355, 532 and 1064 nm, respectively. The results were compared with Aerosol Robotic Network (AERONET) version 3 (v3) inversion solutions and the Generalized Retrieval of Aerosol and Surface Properties (GRASP) at six and seven wavelengths. Both retrieval schemes make use of a spheroid shape model for mineral dust. The spectral slope of the lidar ratio from 532 to 1064 nm could be well reproduced by the AERONET and GRASP retrieval schemes. Higher lidar ratios in the UV were retrieved by AERONET and GRASP. The enhancement was probably caused by the influence of fine-mode pollution particles in the boundary layer which are included in the columnar photometer measurements. Significant differences between the measured and retrieved wavelength dependence of the particle linear depolarization ratio were found. The potential sources for these uncertainties are discussed.


2022 ◽  
Vol 15 (1) ◽  
pp. 149-164
Author(s):  
Alberto Sorrentino ◽  
Alessia Sannino ◽  
Nicola Spinelli ◽  
Michele Piana ◽  
Antonella Boselli ◽  
...  

Abstract. We consider the problem of reconstructing the number size distribution (or particle size distribution) in the atmosphere from lidar measurements of the extinction and backscattering coefficients. We assume that the number size distribution can be modeled as a superposition of log-normal distributions, each one defined by three parameters: mode, width and height. We use a Bayesian model and a Monte Carlo algorithm to estimate these parameters. We test the developed method on synthetic data generated by distributions containing one or two modes and perturbed by Gaussian noise as well as on three datasets obtained from AERONET. We show that the proposed algorithm provides good results when the right number of modes is selected. In general, an overestimate of the number of modes provides better results than an underestimate. In all cases, the PM1, PM2.5 and PM10 concentrations are reconstructed with tolerable deviations.


2021 ◽  
Author(s):  
Igor Veselovskii ◽  
Qiaoyun Hu ◽  
Albert Ansmann ◽  
Philippe Goloub ◽  
Thierry Podvin ◽  
...  

Abstract. A remote sensing method, based on fluorescence lidar measurements, that allows to detect and to quantify the smoke content in upper troposphere and lower stratosphere (UTLS) is presented. The unique point of this approach is that, smoke and cirrus properties are observed in the same air volume simultaneously. In the article, we provide results of fluorescence and multiwavelength Mie-Raman lidar measurements performed at ATOLL observatory from Laboratoire d’Optique Atmosphérique, University of Lille, during strong smoke episodes in the summer and autumn seasons of 2020. The aerosol fluorescence was induced by 355 nm laser radiation and the fluorescence backscattering was measured in a single spectral channel, centered at 466 nm of 44 nm width. To estimate smoke properties, such as number, surface area and volume concentration, the conversion factors, which link the fluorescence backscattering and the smoke microphysical properties, are derived from the synergy of multiwavelength Mie-Raman and fluorescence lidar observations. Based on two case studies, we demonstrate that the fluorescence lidar technique provides possibility to estimate the smoke surface area concentration within freshly formed cirrus layers. This value was used in smoke INP parameterization scheme to predict ice crystal number concentrations in cirrus generation cells.


2021 ◽  
Vol 2145 (1) ◽  
pp. 012053
Author(s):  
Ronald Macatangay ◽  
Worapop Thongsame ◽  
Raman Solanki ◽  
Ying-Jen Wu ◽  
Sheng-Hsiang Wang ◽  
...  

Abstract In this study, an improvement in the estimation of the mixing height is carried out by introducing a time-dependent maximum and minimum analysis altitude (TDMMAA) in the Haar wavelet covariance transform (WCT) technique applied to atmospheric light detection and ranging (LiDAR) measurements generally used in mixing height estimations. Results showed that the standard method usually overestimates the mixing height and that the proposed algorithm is more robust against clouds and residual layers in the boundary layer that generally occur in the nighttime and early morning. The TDMMAA method does have a bit of subjectivity especially in defining the analysis periods as well as the top and bottom of the analysis altitudes as it needs user experience and guidance. Moreover, the algorithm needs to be further objectively refined for automation and operational use, validated with in-situ profile measurements, and tested during different atmospheric conditions.


2021 ◽  
Author(s):  
Sonja Gisinger ◽  
Inna Polichtchouk ◽  
Andreas Dörnbrack ◽  
Robert Reichert ◽  
Bernd Kaifler ◽  
...  

2021 ◽  
Author(s):  
Lilian Loyer ◽  
Jean-Christophe Raut ◽  
Claudia Di Biagio ◽  
Julia Maillard ◽  
Vincent Mariage ◽  
...  

Abstract. The Arctic is facing drastic climate changes that are not correctly represented by state-of-the-art models because of complex feedbacks between radiation, clouds and sea-ice surfaces. A better understanding of the surface energy budget requires radiative measurements that are limited in time and space in the High Arctic (> 80° N) and mostly obtained through specific expeditions. Six years of lidar observations onboard buoys drifting in the Arctic Ocean above 83° N have been carried out as part of the IAOOS (Ice Atmosphere arctic Ocean Operating System) project. The objective of this study is to investigate the possibility to extent the IAOOS dataset to provide estimates of the shortwave (SW) and longwave (LW) surface irradiances from lidar measurements on drifting buoys. Our approach relies on the use of the STREAMER radiative transfer model to estimate the downwelling SW scattered radiances from the background noise measured by lidar. Those radiances are then used to derive estimates of the cloud optical depths. In turn, the knowledge of the cloud optical depth enables to estimate the SW and LW (using additional IAOOS measured information) downwelling irradiances at the surface. The method was applied to the IAOOS buoy measurements in spring 2015, and retrieved cloud optical depths were compared to those derived from radiative irradiances measured during the N-ICE (Norwegian Young Sea Ice Experiment) campaign at the meteorological station, in the vicinity of the drifting buoys. Retrieved and measured SW and LW irradiances were then compared. Results showed overall good agreement. Cloud optical depths were estimated with a rather large dispersion of about 47 %. LW irradiances showed a fairly small dispersion (within 5 W m−2), with a corrigible residual bias (3 W m−2). The estimated uncertainty of the SW irradiances was 4 %. But, as for the cloud optical depth, the SW irradiances showed the occurrence of a few outliers, that may be due to a short lidar sequence acquisition time (no more than four times 10 mn per day), possibly not long enough to smooth out cloud heterogeneity. The net SW and LW irradiances are retrieved within 13 W m−2.


Sign in / Sign up

Export Citation Format

Share Document